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Modelling the thermodynamic performance of a concentrated solar power plant with a novel modular air-cooled condenser
... This model was later modified for use with wavyfinned tubes [7]. The asymptotic-composite modelling approach has been shown to be relatively accurate in predicting the behavior of straight-finned rectangular tube heat exchangers [8,9]. The tube considered in [8,9] had roughly similar dimensions to those of the current study and was investigated for a mechanical draft ACC application. ...
... The asymptotic-composite modelling approach has been shown to be relatively accurate in predicting the behavior of straight-finned rectangular tube heat exchangers [8,9]. The tube considered in [8,9] had roughly similar dimensions to those of the current study and was investigated for a mechanical draft ACC application. The methodology is yet to be applied to a wavy-finned flattube specifically. ...
... [7] compared their model to extensive data from the literature and report root mean square errors of 25 -35 % on friction factor and 10 -25 % for Colburn j-factor. Moore et al. [9] considered a straight-finned rectangular tube with asymptotic transition between developing and fully developed laminar flow ( < 2000). They give asymptotic-composite expressions for and Nusselt number ( ) with empirical exponents = 2 and 1.5 respectively. ...
Wavy-finned, flat-tube heat exchangers are used in industrial applications for their relatively low frictional pressure drops and high heat transfer coefficients. Originally developed for mechanical draft systems, these heat exchangers are now finding application in natural draft (buoyancy driven) systems (e.g. in natural draft air-cooled condensers (NDACCs)). In the context of these natural draft systems, careful consideration of finned tube configuration (notably fin configuration) is warranted due to the juxtaposition of pressure drop (resistance) and heat transfer coefficient (which contributes to motive potential) in these tubes and the sensitivity of the overall system performance to these parameters. This study presents and validates a three-dimensional computational fluid dynamics model of a wavy-finned flat ACC tube employing the transitional 𝑘 − 𝜔 SST turbulence model in Ansys Fluent 2023 R1. The numerical results are validated against experimental data and shown to correlate well in terms of both thermal and hydraulic performance prediction over the full flow range considered (Reynolds numbers of 400 to 2000 , encompassing laminar and transitional flow). Two semi-empirical finned tube models are considered and shown to be inaccurate for the specific tube considered. A full-factorial analysis of fin spacing, fin thickness, wavy amplitude and wavy wavelength identifies fin spacing and wavy amplitude as the most significant factors, and wavy wavelength is highlighted as an interesting parameter.
... However, in addition to the water-saving advantages, the use of air as the cooling medium awards power plants much greater locational flexibility, as the constraint of having to be near a water source to service a wet-cooled condenser is lifted. ACCs are therefore particularly complementary to concentrated solar power (CSP) technologies which typically find application in arid regions where water is scarce (Moore et al., 2014). From this viewpoint, ACCs are championed as a potential contributor to assisting in achieving renewable energy targets, such as those outlined in the EU's Strategic Energy Tech (SET) plan (Moore et al., 2014). ...
... ACCs are therefore particularly complementary to concentrated solar power (CSP) technologies which typically find application in arid regions where water is scarce (Moore et al., 2014). From this viewpoint, ACCs are championed as a potential contributor to assisting in achieving renewable energy targets, such as those outlined in the EU's Strategic Energy Tech (SET) plan (Moore et al., 2014). ...
... These aspects are promoting the use of ACCs, but they remain an unpopular option of heat sink in thermoelectric power plants (Moore et al., 2014). The reluctance of industry to adopt ACCs as the preferred choice of cooling method justifies the need for continued efforts to lessen the undesirable aspects that are stalling their widespread adoption. ...
A numerical investigation into computational fluid dynamic (CFD) fan modelling techniques and the effectiveness of perimeter windscreens as a wind effect mitigation measure for air-cooled condensers (ACCs) that find application in the thermoelectric power industry. Results suggest that the windscreens mostly hinder fan row performance; however, a beneficial offering is attainable at high wind speeds for tall ACCs. The results also show that current implicit fan models limit the quantitative accuracy of CFD ACC analysis at high wind speeds.
... To mitigate against this, there have been a number of proposed modifications to the basic ACC design. Moore et al. [4] and Butler and Grimes [5] presented a novel modular design, with variable speed controllable fans to respond to variations in ambient air temperature. Chen et al. [6] proposed a vertical arrangement of ACCs to mitigate against wind effects. ...
... The basic form of the ACHEx consisted of a heat exchanger core, and a bank of variable speed axial fans. A four row staggered arrangement of annular-finned round tubes constituted the heat exchanger core, with the aerodynamic and thermal characteristics of the tube bundle quantified in studies by Moore et al. [4] and O'Donovan and Grimes [17]. The modular nature of the ACHEx design is such that the number of heat exchanger units (modules) can be tailored for a particular application. ...
... whereṁ a is the mass flow rate of air, which was varied by switching any of the six fans on or off, in an effort to maintain a constant T s value. The overall heat transfer coefficient, U , for the ACC was determined through a thermal resistance network analysis, where the air-side heat transfer coefficient was calculated from a form of Nusselt number model originally presented by Teertstra et al. [19], which was subsequently adopted, modified, and validated through measurements on an ACC by Moore et al. [4]. The steam-side heat transfer coefficient was calcu-lated from the robust correlation of Shah [20]. ...
This paper presents the essentials of low temperature thermal storage (LTTS), a novel technique whereby thermal energy storage is employed to achieve sub-ambient condensation in air-cooled Rankine cycle power plants. It summarises work which was undertaken to explore the potential and the range of application of LTTS. The technology is most effective at geographical locations with large average daily temperature ranges, and high summertime temperatures. Hourly normal temperature data was sourced for five potential deployment sites, which provided a representative sample of different climate types. A steam turbine, a condenser, an air-cooled heat exchanger, and a chilled water thermal energy storage tank formed the LTTS configuration – a techno-economic model of which was developed to simulate system behaviour. The size of the air-cooled heat exchanger, the fan speed of the air-cooled heat exchanger, and the hours of charge, discharge, and bypass of the thermal energy storage tank were all modelled as variables to determine the effects of component sizes and operating patterns. LTTS performance was benchmarked by comparison with a direct air-cooled condenser model. Results presented in this paper include daily plant output, annual power output, and payback period. This study shows that LTTS can deliver all the advantages of dry-cooling, without suffering the usual performance degradations. The inherent flexibility of LTTS allows for configurations to be customised to exploit the prevailing site climate, and capitalise on the local power demand pattern. There are also clear indications that, in suitable climatic settings, LTTS outperforms traditional air-cooled thermal power plants by offering up to 10% additional generating capacity. Coupled to this are payback periods as short as 2.5 years, ensuring LTTS can be considered a viable alternative to current air-cooling strategies.
... Additionally, the fins possess wavy corrugations characterised by amplitude (A w ) and wavelength (λ w ). Wavy amplitudes in the literature range from 0 (flat) to 2.5 mm [6,11]. However, greater amplitudes are typically associated with excessive frictional losses [12,13]. ...
... Q adj = e fQ asim (10) where the finned surface effectiveness (e f ) is calculated using (11)(12)(13). ...
Wavy-finned flattened tube heat exchangers are used in large-scale industrial direct dry cooling systems (air-cooled condensers, or ACCs) due to their relatively high air-side heat transfer and low pressure drop characteristics. Attempts at optimizing these tubes through geometry manipulation, for specific applications (e.g. in natural draft systems), requires careful consideration of the typical trade-off between enhancing heat transfer (benefit) and increasing pressure loss (detriment) across a range of relevant flow conditions. A validated parametric numerical (CFD) model
is developed Ansys Fluent 2023 R1. The model employs the transitional 𝑘 − 𝜔 SST turbulence model along with common tube modelling approaches from literature. The numerical model is used to generate thermal and hydraulic performance data, in the form of Colburn j-factor and apparent friction factor, as a function of relevant fin geometric parameters (fin spacing, fin thickness, wavy wavelength and amplitude) and flow conditions covering laminar and transitional flow (500 ≤ 𝑅𝑒 ≤ 4000). A sensitivity analysis identifies fin spacing and wavy amplitude as the most important geometric parameters. A reduced order model is generated using
a response surface analysis of the numerical data. Conditioned geometric power law correlations are presented for quantifying the thermohydraulic behaviour of a wavy finned flattened air-cooled condenser tube as a function of fin spacing and wavy
amplitude over a relevant flow range. Good accuracy is achieved with RMSE / R2 of 7.38 / 95.9% and 9.01 / 96.6% for Colburn j-factor and apparent friction factor respectively.
... The installation of air-cooled condensers (ACC) in thermoelectric power plants has increased significantly in the past few decades, and this trend is projected to grow in future [10][11][12]. The dry cooling systems offer potential environmental benefits by the ability to achieve over 90% savings in water resources and plant sitting flexibility [12,13]. Typically, the capital and operations costs of the ACC system are comparatively higher than that for the wet cooling system, because it requires larger heat exchangers and fan power owing to the poor heat transfer properties of air. ...
... Vel a1 (13) where V a1 (m 3 /s) is the volume flow rate of air flowing through the cooling tower; ρ a1 (kg/m 3 ) is the average air density assumed to be constant; Vel a1 (m/s) is airflow velocity and A a1 (m 2 ) is the cross-sectional area. ...
For combined-cycle power plants, the two most dominant steam condenser cooling options are the wet-cooling tower and the air-cooled (dry) systems. The wet cooling system is commonly installed on plants located in areas with available water sources, while the dry system is typically preferred in areas where water is scarce. However, owing to the increasing regulations on water conservation, water usage costs and improvements on cooling system designs, a new approach is required for the optimal selection of plant cooling systems, incorporating site climatic conditions, amongst other considerations. This study presents a comparative techno-economic analysis of a steam turbine cycle with wet-and dry-cooling systems for five typical tropical locations in Nigeria with different climatic conditions and water usage costs. The results show that in the hot (ambient temperatures >33 • C) and dry regions (relative humidity <65%) namely Sahel, Sudan, and Guinea savannah, the plant with wet cooling generated more net power outputs with lower life-cycle costs, operating and maintenance costs than with dry cooling. Thus, for these three regions, the wet cooling system is the best option. But for the Tropical Rainforest and Coastal zones with low ambient temperatures (≤31 • C) and high relative humidity values (≥76%), the performance and cost implications of the plant with dry cooling was more favourable due to lower system sizes and costs requirements. Parametric investigations revealed that high ambient temperature increased the size and costs requirements of air-cooled systems while relative humidity significantly influenced the total power consumption of water-cooled systems.
... The cold air opens an interesting area of research in relation to marine WHRS which is the use of an air condenser unit 2 instead of the typical seawater condenser unit. In a land-based system some of the strengths of aircooled condenser units are its low cost and reduction in water requirement [22,23]. For the ship case in the Arctic using air as a coolant, in addition to the aforementioned performance benefits, the effects of seawater bio-fouling may be eliminated and, depending on the location of the heat exchanger, requiring less corrosion-resistant materials since seawater is not directly in contact with the heat exchanger material [24,25]. ...
... This decision also made sense from the overall heat transfer coefficient (U) point of view since air is flowing in the section of the condenser unit that offers the largest contact area which is beneficial when having a low convective heat transfer coefficient (h*). The finned tube condenser unit was made of aluminium with five tube rows with a rotated square layout with a constant transverse pitch (p t ) of 83 mm [22]; the working fluid flowing inside the tubes had a maximum speed of 15 m/s. The governing equation for the heat transfer across a surface using the condenser unit's desuperheating section (ds) shown in Fig. 8 was given by: ...
As Arctic sea ice coverage declines it is expected that marine traffic could increase in this northern region due to shorter routes. Navigating in the Arctic offers opportunities and challenges for waste heat recovery systems (WHRS). Lower temperatures require larger heating power on board, hence a larger demand for waste heat usage, to cover services and maintaining on board spaces temperatures. However, a lower heat rejection temperature increases the WHRS thermal efficiency. The air temperature for the Arctic route selected is colder than that of the seawater, opening the opportunity of having air as coolant. This paper explores the use of two different coolants, air and seawater, for an organic Rankine cycle (ORC) unit using the available waste heat in the scavenge air system of a container ship navigating in Arctic Circle. Using a two-step single objective optimisation process, detailed models of air and seawater heat exchangers are evaluated as the WHRS condensers. The results suggest that an ORC unit using R1233zd(E) as its working fluid coupled with seawater as its coolant is the preferable option to reduce CO2 emissions. Using the ambient air as the coolant while a less effective option could be cheaper to install.
... The overall heat transfer coefficient U considering the effects of convective resistance and conductive resistance is evaluated by Eq. (23) in Ref. [40] where U is overall heat transfer coefficient and A is area across which heat is transferred. ...
... The concept of levelized cost of electricity is used by various authors to account for lifetime, operational cost, and investment costs as whole for the production of electricity [14,40,12]. The levelized cost of electricity is given by Eqs. ...
This article compares the part-load operation of air cooled and cooling tower based low-medium temperature geothermal Organic Rankine Cycle (ORC) systems installed at different geographical locations. Working fluid R245fa was compared with a newer competitor R1233zde for thermo-economic performance, environment-friendly and efficient system integration. Monthly averaged, weather data is used to simulate ambient conditions of Ulsan, London, Vegas and Kuala Lumpur. Mathematical models for condenser part load operation were formulated for both air cooled and mechanical draft wet cooling tower based systems. Numerical study and experimental validation was performed for the condenser when wet cooling tower based system was investigated. The ORC system design was optimized for maximum power output to grid and operational control optimization was performed on the heat sink to achieve maximum power output at different ambient or off-design conditions. Economic analysis was performed by comparing the capital investment/kW and levelized cost of electricity (LCOE) over the lifetime of the system. Based on the economic analysis, the results reveal that R1233zde has potential to replace R245fa working fluid when the source temperature is higher (around 145 °C). Cooling tower based system are preferable for hot dry regions while air-cooled systems can be implemented with R1233zde for Ulsan and London.
... Liqreina and Qoaider (2014) compared the values of the annual mean overall efficiency, water consumption, and levelized cost of energy for the dry-and wet-cooled steam Rankine cycle-based CSP plants. Moore et al. (2014) performed the technoeconomic comparison between different designs of Table 4 Properties of commonly used high-temperature oils and molten salts (Gil et al. 2010;Tian and Variations in optimal turbine inlet pressure with turbine inlet temperature, design radiation, plant size, and various modifications of Rankine cycle air-cooled condensers for CSP plants. A novel air-cooled condenser has also been proposed, which can be installed in a modular scale to reduce installation costs (Moore et al. 2014). ...
... Moore et al. (2014) performed the technoeconomic comparison between different designs of Table 4 Properties of commonly used high-temperature oils and molten salts (Gil et al. 2010;Tian and Variations in optimal turbine inlet pressure with turbine inlet temperature, design radiation, plant size, and various modifications of Rankine cycle air-cooled condensers for CSP plants. A novel air-cooled condenser has also been proposed, which can be installed in a modular scale to reduce installation costs (Moore et al. 2014). Butler and Grimes (2014) studied the effect of wind on the performance and design of a modular air-cooled condenser for CSP plants. ...
Concentrated solar power (CSP) plant is an emerging technology among different renewable energy sources. Parabolic trough collector (PTC)-based CSP plant, using synthetic or organic oil as a heat-transfer fluid, is the most advanced technology. About 87 % of the operational capacities of CSP plants worldwide are based on PTC technology. Direct steam-generating linear Fresnel reflector (LFR) systems have been developed as a cost-effective alternative to PTC systems. Line-focusing concentrating solar collectors (PTC and LFR), with single-axis tracking, are simple in design and easy to operate. Prior to the detailed design of a CSP plant, it is necessary to finalize type of the solar field, type of the power-generating cycle, overall plant configuration, sizing of the solar field and the power block, etc. The optimal design of a CSP plant minimizes the levelized cost of energy for a given site. In this paper, a detailed review of important design parameters which affect the design of line-focusing concentrating solar collector-based power plants is presented. This includes parameters for solar collector field design, receiver, heat-transfer fluid, thermal energy storage, power-generating cycle, sizing and configuration of the plant, etc. This review may provide a reference for designing CSP plants. Future research directions are also identified.
... In order to alleviate deficiencies associated with current ACCs, a modular aircooled condenser (MACC) is proposed. It has been shown through previous studies by O'Donovan and Grimes [10], Moore et al. [11] and Butler and Grimes [12] that this design has the potential to maximise plant output and minimise parasitic losses. However, a factor which could inhibit the performance of the MACC, or any ACC for that matter, is the pressure losses associated with the two-phase condensing flow of steam through the tube bundle. ...
... From Table 2, it can be seen that the number of tubes, N t , and number of tube rows, N r , varied during testing. This was mainly due to the fact that aerodynamic characterisation tests, carried out in a separate study by Moore et al. [11], necessitated the reduction in the number of tubes from the original 183 to 122. Therefore, by maintaining the same total flow rate in the MACC module, the flow rate per tube increased. ...
... The accuracy and applicability of Equation (6) has been validated through pressure drop measurements carried-out on the MACC prototype in a separate study by Moore et al. [21]. Plotting the system resistance curve from Equation (6) with the fan curves from Equations (1) and (2) generates a series of operating points, from which the flow rate through the heat exchanger can be determined. ...
... The accuracy and applicability of Equation (12) has been validated through heat transfer measurements carried out on the MACC module, given in [21] ...
Diminishing fossil fuel reserves and a growing collective environmental awareness has led to the development of alternative methods of power generation such as Concentrated Solar Power (CSP). Although almost all existing CSP plants currently use water-cooled condensers, limited water supplies in the designated desert regions for such power plants, the high costs associated with providing cooling water and environmental considerations will all restrict the future use of water-cooled condensers. Air-cooled condensers (ACCs) are therefore proposed, despite evidence to suggest that they suffer from significant inefficiencies [1]. It has been suggested that a modular design, addressed in this paper, could offer solutions to issues with current ACC technologies. To fully characterise the modular ACC design it is necessary to quantify the steam-side characteristics. A series of tests were performed under vacuum conditions representative of an operational condenser. The condenser vacuum was measured for a series of incremental fan rotational speeds, to determine both the qualitative and quantitative relationship between fan speed and condenser pressure. Results indicate that for a given steam mass flow rate, the condenser pressure decreases with increasing fan rotational speed. Furthermore, the choice of vacuum pump, used to displace air leakages, was shown to have a significant influence on the steam-side response. Larger displacement-capacity vacuum pumps permit lower condenser pressures. The steam condensation pressure drop through the condenser tubes was also measured. Results for the measured pressure drop revealed a large level of momentum recovery, which is not uncommon in steam condensation processes. Experimental frictional pressure drops were determined and these compared favourably with certain two-phase frictional pressure drop correlations. In particular, the Lockhart & Martinelli correlation was found to be most capable of predicting the frictional pressure drop trends encountered during testing. The large level of agreement between the measurements and predictions provide confidence in future use of the Lockhart & Martinelli correlation to predict frictional pressure losses.
... The accuracy and applicability of Equation (6) has been validated through pressure drop measurements carried-out on the MACC prototype in a separate study by Moore et al. [21]. Plotting the system resistance curve from Equation (6) with the fan curves from Equations (1) and (2) generates a series of operating points, from which the flow rate through the heat exchanger can be determined. ...
... The accuracy and applicability of Equation (12) has been validated through heat transfer measurements carried out on the MACC module, given in [21]. ...
... The steam-side research has provided significant insight into flow regimes [9], void fraction [10,11], pressure drop [11][12][13], and heat transfer coefficient (HTC) [14]. From these results, experimentally-validated models have been developed for void fraction [15], pressure drop [12], HTC [16], and capacity [15,17] during co-current condensation in flattened-tube aircooled condensers. ...
Experimental results for counter-flow steam condensation in a 5.7 m-long air-cooled condenser tube with a flattened-tube cross section are presented. The tube is inclined at upward inclination angles from 0.5° to 40°, with both the vapor inlet and liquid outlet at the lower end of the tube. The effect of inclination angle on flow regimes, void fraction, capacity and heat transfer coefficient is presented. In addition, a water-cooled test section provides local steam-side heat transfer coefficient along the tube circumference at increased accuracy to that determined in the air-cooled test section. The range of condensation pressures tested is 88–120 kPa and all tests have a mass flux of less than 4.2 kg m⁻² s⁻¹. Stratified flow is found for nearly all conditions and locations in the condenser. Flooding of this stratified condensate layer is found for tube inclination angles of 5° and lower. This flooding is found to reduce the condenser capacity. The results are compared to those for co-current flow in the same condenser tube. Capacity is found to be unaffected by the flow configuration (counter-flow vs. co-current) when flooding does not occur. Steam-side heat transfer coefficient is also found to be unaffected by flow configuration for all conditions tested.
... Moore et al. [12] investigated a novel modular design of the ACC for the use in concentrated solar power plants (CSP). The authors carried out a set of experiments, which were used for the validation of correlations for the prediction of the thermal and aerodynamic behaviour of the ACC. ...
Many economic and environmental restrictions have resulted in the growth of dry cooling technology.
The air-cooled condenser (ACC), which can be used in power plants and other facilities, represents a way
toward the minimisation of the water footprint. In the paper, a semi-empirical computational tool
devised for the design and thermal assessment of the ACC is introduced. In comparison to commonly
used CFD-based models, the presented tool is computationally effective and inexpensive. The model is
based on a control-volume computational grid, which is coupled with three sub-models for the solution
of steam-side, air-side, and fan-related phenomena. A number of empirical correlations collected in the
literature review were incorporated in the model. Besides the underlying functionality, which includes
the determination of the steam condensation capacity, the model allows for the consideration of
advanced physical phenomena such as the condensate glut control and the influence of air in the steam
to the condensation process. The comparison of the model with datasheets from manufacturers of ACCs
as well as with experimentally gained data from a municipal solid waste incineration plant demonstrates
that the semi-empirical model is a fast and accurate tool applicable for the design and thermal assessment
of the ACC.
... Q yr e , is the electricity produced in = yr n, in units of kWh. r d is the plant discount rate applied throughout the plant lifetime, assumed here as 6% ( Moore et al., 2014). ...
The receiver in a concentrated solar power (CSP) tower system accounts for a considerable proportion of plant capital costs, and its role in converting radiant solar energy into thermal energy affects the cost of generated electricity. It is imperative to utilize a receiver design that has a high thermal efficiency, excellent mechanical integrity, minimal pressure drop, and low cost in order to maximize the potential of the CSP system. In the present work, thermal, mechanical, and hydraulic models are presented for a liquid tubular billboard receiver in a representative CSP plant. A liquid sodium heat transfer fluid as well as a number of receiver configurations of heat transfer area, tube diameter, and tube material have been analysed. The thermal analysis determines tube surface temperatures for an incident heat flux, thereby allowing for the calculation of thermal losses and efficiency. The mechanical analysis is carried out to establish creep deformation and fatigue damage that the receiver may undergo through a life service. The hydraulic analysis is concerned with calculating the required pumping power for each configuration. Results show that thermal efficiency increases for a decreasing heat transfer area, however reducing receiver area comes at the penalty of increasing tube surface temperatures and thermal stresses. The selection of tube diameter is critical, with small diameters yielding the greatest thermal efficiency and mechanical life, however the increased pressure drop reduces the overall plant efficiency due to a necessary increase in pumping power. The optimum receiver configuration is established by finding an appropriate trade-off between thermal performance, service life, pressure drop, and material costs, by using the levelized cost of electricity (LCOE) as the objective function. The analysis highlights necessary trade-offs required to optimise the design of a solar receiver.
... Besides the aforementioned accessory devices, some new configurations of ACCs are also recommended, which have a great advantage over the existing ones. Moore et al. [20] investigated a modular configured air-cooled condenser incorporated with low speed axial flow fans, which can be pre-assembled and allows the off-design operation of condenser. Instead of the large-scale axial flow fans, Butler and Grimes [21] proposed the modular aircooled condenser with a small axial flow fan array and investigated the wind effects. ...
The thermo-flow performances of air-cooled condensers (ACCs) are basically deteriorated under wind conditions, so it is of great concerns to propose the measures against the adverse wind effects on air-cooled condensers. In this work, a novel reconstruction of ACCs combined the V-frame condenser cells with the induced axial flow fans, and a modified layout of the novel ACCs for a specific wind direction are proposed based on the direct dry cooling system in a 2 × 600 MW power plant. The CFD approach with a validation is applied to the performance investigation of the novel ACCs. The variable fields, mass flow rate, inlet air temperature and turbine back pressure for both the conventional and novel layouts of ACCs under different wind conditions are obtained and compared. The results show that the mass flow rates of the novel ACCs increase conspicuously compared with the conventional ACCs both in the absence and presence of winds. The flow distortions through the induced axial flow fans are greatly restrained and the inlet air temperature of the novel ACCs decreases, which lead to the improved thermo-flow performances of ACCs and reduced turbine back pressure of power generating unit.
... Consequently, ACC research has focused almost entirely on increasing the local air-side transport performance (Sohal and O'Brien, 2001;He et al., 2010;Odabaee and Hooman, 2011;Herrault et al., 2012) or modeling systems under varying operating and ambient conditions (Pieve and Salvadori, 2011;Moore et al., 2014). However, results from the present investigation indicate that steam-side thermal resistance may be more significant than originally reported. ...
Conventional power plant condensers operate at unsustainably high cooling water consumption rates (2 – 28 m³ MWh⁻¹). Dry air-cooled condensers (ACCs) can enable reduced water consumption in power plants. However, ACCs are rarely employed because of the substantial decreases in condenser performance and power plant efficiencies compared to wet-cooled systems. ACC studies typically focus on air-side transport, assuming that the effects of steam-side pressure drop and thermal resistance are small. The objective of the present investigation is to scrutinize this assumption – quantifying the influence of steam-side effects on ACC operation. A detailed model of a representative ACC is formulated. Model results demonstrate that condensation heat transfer and pressure drop are poorly characterized at ACC operating conditions. Predicted power plant efficiency varies by 0.7% with different condensation heat transfer models. Additionally, predicted plant efficiencies vary depending on which pressure drop correlation is employed. The differences are exacerbated at low steam saturation pressures (∼4 kPa), where the cycle efficiencies range from 36.0% and 37.7% between different pressure drop correlations. Results from this study indicate that both steam side and air-side effects must be considered to improve ACC performance. Some methods for enhancing in-tube condensation are mentioned, and future ACC research needs are discussed.
... The third approach, experimental study, focuses on the performance characterization of a scaled, similar single tube, tube banks or tube systems [20], e.g., experimental investigation of different enhanced fin structures [21], the performance characterization of a novel air-cooling condenser [22]. Experiment investigation can usually offer much reliable performance data for real application; however, it is generally quite expensive, laborious, and can hardly be employed to guide plant operation. ...
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... 따라서 single-low fin tube가 적용된 ACC 성능향상을 위한 많은 연구가 진행되어 왔다. Zhang et al. [3] Fig. 1 (a) Single-low fin tube [1] , (b) ACC cell [1] , (c) Power plant condenser unit with ACC cells [ 공기 측 열전달 계수는 Teertstra [12] 가 제시한 방법을 적용하여 계산하였으며 Moore et al. [7] 은 Teertstra [12] 의 계산방법이 ACC 관 내측의 건도변화는 Fig. 2(b) 이는 Fig. 5(b)에 잘 나타나 있다. Fig. 5 6 The effect of air temperature on the average temperature difference between water and air 보여준다. ...
A numerical study was conducted to calculate the cooling capacity variation of a power plant ACC (air-cooled condenser) caused by changes in operating conditions. A numerical model was developed using the {\varepsilon}-NTU and finite volume method, containing 100 elements for a single low fin tube. The model was validated through a comparison of cooling capacity between the simulated values and manufacturer`s data. Even though simple assumptions and previously presented heat transfer correlations were applied to the model, the prediction error was 1.9%. The simulated variables of the operating conditions were air velocity, air temperature, and mass flux. The analysis on the variation of thermal resistance along the tube showed that the water side thermal resistance was higher than the air side thermal resistance at the downstream end of the tube, indicating that the ACC capacity could be increased by applying technology to enhance in-tube flow condensation heat transfer.
... Recently, various novel constructions of air-cooled condensers are proposed, which have many advantages over the traditional air-cooled condensers. O'Donovan et al. [21][22][23] presented a novel modular air-cooled condenser mainly used in solar or thermoelectric power plants, which can be pre-assembled with small controlled axial flow fans. Butler and Grimes [24] studied the wind effect on the modular air-cooled condenser and proposed the optimal condenser configuration. ...
Ambient winds are generally unfavorable to the thermo-flow performances of air-cooled condensers in power plants. More emphases are placed to weaken the negative effects of ambient winds, but no layout alternative of air-cooled condensers is considered. In this work, a novel vertical arrangement of air-cooled condensers is proposed on the basis of a 2 × 600 MW direct dry cooling power plant, which can weaken the adverse wind effects and utilize the wind power to improve the cooling capacity of air-cooled condensers. By means of the CFD simulation and experimental validation, the flow and temperature fields of cooling air for the vertically arranged air-cooled condensers at ambient winds are obtained. The mass flow rate, inlet air temperature and turbine back pressure are computed and compared with the traditional air-cooled condensers. The results show that the flow rate of the novel air-cooled condensers increases conspicuously compared with the current ones both in the absence and presence of winds. In the wind directions of 60° and 90°, the off-axis flow distortions of axial flow fans are greatly weakened and the average inlet air temperature of the novel air-cooled condensers is reduced and almost equals the ambient temperature. The thermo-flow performances of the air-cooled condensers are improved, thus the turbine back pressure is reduced by the novel layout of air-cooled condensers.
... Some studies [9][10][11][12][13][14][15][16][17][18][19][20] were interested to the explorations and comparisons between the different technologies adopted for CSP plants such as towers, linear Fresnel and parabolic trough solar collectors. Moreover, others authors studied the main components of CSP plant from different approaches and proposed some designs and suggestions to improve the overall performances of theses installations [21][22][23][24][25][26][27]. Beside, several studies [28][29][30][31][32][33][34][35][36] have investigated the potential and the opportunities to built CSP plants in different country around the word. ...
In this paper, the potentials of solar resources and the suitable factors for the deployment of concentrated
solar power CSP in Tunisia were presented. This study was done in the framework of the enerMENA
project which aims to prepare the ground towards a sustainable realization of CSP power plants in the
North Africa and Middle-East countries. Moreover, the electrical interconnection between Tunisia and
Italy and the opportunity of the exploitation of renewable energy sources such as CSP plants in North
Africa by European countries, were discussed. In addition, solar radiations data and weather parameters
values delivered by a specific network of solar radiation and weather data installed in the Tataouine
region at the south of Tunisia, were discussed from the angle offitting with CSP technology. Besides,
simulations of 50 MW parabolic trough solar power plant based on the solar radiation and climatic data
delivered by the installed station were performed. The energetic and economic performances of the
Tunisian simulated plant were compared with a reference CSP plant Andasol in Spain. The results prove
that Tunisia has very important solar resources suitable for the CSP deployment such as the direct solar
radiation DNI. Even, the total annual production of electricity generated from the simulated field of
Tataouine exceeds that of the plant of Andasol in Spain by an amount of 1793 MWhe. However, the total
investment cost is more important in the case of Tataouine station in Tunisia. A concentrated solar power
project becomes economically competitive in Tunisia when the majority of the plant components such
the collectors structure, the mirrors and the storage system should be manufactured locally in Tunisia to
minimize the transport fees and by the way create jobs and enhances the local industry to investigate in
thisfield.
&2015 Elsevier Ltd. All rights reserved
The aerodynamic behavior of the fans array of the direct air-cooled condenser is different from that of a single fan because of the interaction effect between fans and the influence of wind. In this paper, a scale-down fan array experimental platform with measurement of the airflow and ambient wind speed is established to study the fan array partition schemes and cluster effect. The divisional cluster factors are obtained by experiment and generalized by random forest regression. The dynamic models of the condenser backpressure are introduced by the moving-boundary method. To achieve transient performance, a divisional control strategy for the direct air-cooled condenser is realized by MPC-PID cascade control. The simulation result shows that the fan power consumption is reduced by 14.7% compared to the existing control strategy. Furthermore, the wind speed disturbance is quickly suppressed cascade control.
Selection of condenser cooling technology can affect the financial as well as technical viability of concentrating solar power (CSP) plants. Detailed comparative assessment of three cooling technologies, i.e., wet, dry, and hybrid, is therefore desirable so as to facilitate selection of optimum cooling technology for the plant. Despite the high efficiency of wet cooling technology, considering the fact that the potential plant locations are generally in arid regions suffering from water scarcity, it is imperative to explore and consider other water conserving condenser cooling options. A review and comparison of technical, economic, and environmental aspects of the three condenser cooling technologies for CSP plants have been presented. Adoption of dry or hybrid technology as against wet cooling technology may lead to reduced thermal performance and increased parasitic power requirement resulting in the high cost of electricity generation. However, the same also results in reduced cooling water requirement up to 92% and thus increase the potential of solar thermal power generation considerably as sites in arid areas can also be utilized.
The choice of condenser cooling option for concentrating solar power (CSP) plants is likely to affect their techno-economic feasibility. In view of this, an attempt has been made to assess relative techno-economics and net life cycle CO2-eq emissions mitigation (LCCM) potential for 50 MW nominal capacity wet-cooled and dry-cooled parabolic trough solar collector (PTSC) and dry-cooled solar power tower (SPT) based CSP plants with 6.0 hours of thermal energy storage for two potential locations in India. It was observed that though dry cooling is likely to save significant amount of water (∼92%) in PTSC based plants, the same shall result in higher capital cost, higher performance penalty and higher parasitic power requirements leading to around 20% higher levelized cost of electricity (LCOE) as compared to wet-cooled PTSC based plants. It was also observed that the dry-cooled SPT based plants shall be able to deliver up to 4.5% higher annual electricity output and LCOE is also likely to be lowered by 13% than wet-cooled PTSC based plants. Considering emissions embodied and emissions associated with water transport/extraction from the source and water treatment, the estimation of LCCM from the PTSC and SPT based CSP plants have also been undertaken.
The frozen phenomenon is unfavorable for the direct air-cooled condensers (DACCs) in a very cold area. The effect of crosswind on frozen phenomena in DACCs at the representative 2 × 350 MW thermal power units was investigated numerically. Results showed that when the crosswind velocity was 4 m·s⁻¹, the number of frozen air-cooled units reached a maximum of six. The increase of vortex range in the air-cooled unit was one of the important reasons to restrain the formation of frozen phenomena at a crosswind velocity from 4 m·s⁻¹ to 12 m·s⁻¹. The frozen phenomena in the DACC disappeared when the crosswind velocity was 12 m·s⁻¹. As the crosswind velocity continued to increase to 28 m·s⁻¹, the frozen region mainly appeared at the position of column 1 row 4, where the airflow rate was the maximum and the inlet air temperature was the minimum among all air-cooled units. This phenomenon occurred because there existed a relatively high-pressure zone near the inlet of each frozen air-cooled unit. In addition, although the frozen area increased from one-third of the air-cooled unit surface to half with the crosswind velocity from 20 m·s⁻¹ to 28 m·s⁻¹, the flow characteristics and the size of vortices in the air-cooled unit were similar in the above two crosswind conditions. Therefore, the key influencing factor became the airflow rate and the inlet air temperature of the air-cooled units under strong crosswind conditions. This study has important guiding significance for the antifreezing design and operation of DACCs.
In addition to traditional project management objectives (cost, time, scope and quality, among others), it is now necessary to include a global sustainability objective in all projects, regardless of their nature and scale. The processes for managing this objective may include sub-processes for optimising the sustainability of some or all of the project’s deliverables. In this paper an integrated optimisation technique was applied to optimise the design of a shell and tube heat exchanger (STHE) by taking into account economic, social and environmental indicators. A case study previously analysed in the literature, although with different objectives and scope, was considered for such a purpose. Diverse sets of weights were defined for the environmental impacts, as well as two additional cases. In the first one, all the indicators where assessed in a linear way. Non-linearities were studied in the second one. Both non-nature-inspired (exhaustive search and Monte Carlo simulation) and nature-inspired (Particle Swarm Optimisation, Crow Search Algorithm and Non-dominated Sorting Genetic Algorithm-II) optimisation techniques were used to solve the problem. The results were presented and discussed in depth. The findings show the necessity of applying these kinds of methodologies in the design of energy systems and, in particular, STHEs.
Unlike conventional power plants based on fossil fuels, which are generally erected in the coastal regions, where water resource availability is not a critical limitation, concentrating solar power (CSP) plants are usually installed in desert zones where there is a lack of water resources. In this regard, the main aim of the present study is to investigate the effects of deploying dry cooling option on the techno-economic performances of a solar tower power plant (STPP), in terms of energetic and exergetic yields, as well as total investment cost, net present value, and levelized cost of electricity.
The obtained results show considerable drops in energy and exergy yields of the simulated plant with integrated dry cooling system compared to the one with the classic wet cooling mode. Furthermore, there are clear increases in the investment cost, as well as the levelized cost of electricity in the first plant. However, the main advantage of integrating dry system to solar tower power plants is to reduce its annual water consumption by almost 94.40%. The importance of this study is to define the main additions and shortcomings of using dry cooling system in solar thermal power plants, and which stage of the process needs to be improved.
To change an increasing trend of energy consumption, many counties have turned to solar thermal energy as a solution. Without greenhouse gas emissions, solar thermal power stations may play a vital role in the energy industry because they have a potential to produce electricity for 24 h per day. The goal of this study is to select solar thermal power stations from three regions (i.e., the United States, Spain and the other nations) throughout the world and to identify which region most efficiently produces solar thermal power energy. To measure their efficiencies, we use data envelopment analysis as a method to examine the performance of these power stations. Our empirical results show that the United States currently fields the most efficient solar thermal power stations. This study also finds that parabolic trough technology slightly outperforms the other two technologies (i.e., heliostat power tower and linear Fresnel reflector), but not at the level of statistical significance. In addition to the proposed efficiency assessment, we incorporate a new way of finding a possible existence of congestion. The phenomenon of congestion is separated into output-based and input-based occurrences. Output-based congestion implies a capacity limit (e.g., difficulties in transmission, voltage control and dispatch scheduling) in a grid network between generation and end users. Input-based congestion occurs when generators use “uncontrollable inputs” (e.g., sunlight hours). Renewable energy sources, such as solar thermal power, are indeed important for our future sustainability. However, this needs performance assessment on generation and transmission through which electricity generated by renewable energy is conveyed to end users. Such a holistic assessment, including both efficiency measurement and congestion identification, serves as a major component in evaluating and planning renewable energy generation.
A numerical simulation was presented to investigate condensation performance of core tubes in air-cooled condenser (ACC). The simulation had been performed in three iso-sectional tubes varying pattern from flat, oval to round. The local heat transfer coefficient (HTC) under the changes of tube inclination angle (β), vapor saturated temperature (Ts), vapor-inlet velocity (U), and sub-cool temperature (ΔTcool) was illustrated to verify the influence of these factors on heat performance of each individual tube. Meanwhile, the comparison on overall heat-flow characteristics among three tubes was also carried out. Regardless of the tube pattern, it was shown that a large β in 0–30°, a high Ts in 316–342 K, and a great U in 103–195 m/s effectively enhanced the local HTC, but a high ΔTcool in 2–8 K reduced it. A nearly twofold increase in Nusselt number was achieved by the round tube compared to flat and oval tubes in a negligible raise of friction coefficient, meanwhile the flat and oval tubes had very close value of performance evaluation criteria. This study highlighted the tube pattern effect to thermal-hydraulic development on the vapor-side of an ACC finned tube system.
In order to save more energy and quicken the load change speed of air-cooled steam condenser units, the closed-loop optimized control on the fan speed is proposed and its realization is worth making intensive study. In this regard, the study presents the static and dynamic models of air-cooled steam condenser, and the characteristics of turbine power output affected by fan speed. Then, the structure of closed-loop control on fan speed is designed. Furthermore, two optimized methods on condenser pressure based on fan speed control are separately discussed: the optimum condenser pressure is solved by the genetic algorithm to save more energy, and the condenser pressure regulation is combined with traditional boiler-turbine coordinated control to accelerate the load response. Case study in our paper proves that the fan speed optimization can significantly improve the unit load-following capability, and furthermore unit coal consumption has been significantly reduced when the unit operating in a stable load condition.
For enough cooling air flowing through the finned tube heat exchangers, the performance of the forced draught fans are always pivotal for the final characteristics of the air-cooled steam condenser (ACSC) as well as the power station. Hence, it is necessary to optimize the fan operation for a superior performance. In this paper, a previous numerical model is designated to execute the impact analysis from the blade angle regulation for forced draught fans with different positions on the performance of the air-cooled system at the prevailing wind angle of β=22.5°. The simulation results indicate the fan volumetric effectiveness, heat transfer rate and the related equilibrium back pressure are influenced significantly once the fan blade angle is regulated. Compared with the design case, it is found that a maximum elevation of net power, 17.76MW, is obtained for the fan array case when the wind speed is vm=2m·s⁻¹. Furthermore, it is found that the windward and peripheral case almost have a same effect to raise the net power of the power plant.
The Λ-frame air-cooled condenser (ΛACC) is widely applied by people, but it is also the main reason of the uneven distribution of internal air flow and temperature field in the air-cooled condenser (ACC). In order to solve these problems and make the air-cooled unit running more economically, safely and efficiently, heat transfer characteristics of new types of ACC are researched, which is of significance for improving traditional direct air cooling technology. Taking the 600MW unit model of a thermal power plant as the comparative object, innovation is made to change the heat transfer surface of Λ-frame into truncated cone-shaped. By means of the numerical simulation, the relationship between the flow and heat transfer characteristics and the top baffle porosity of the truncated cone-shaped air-cooled condenser (TCACC) is studied, and the optimal baffle porosity for heat transfer and safety is got. Then, the effect of the shapes of baffle on the heat transfer characteristics of the TCACC is studied, and the shapes of which are optimized. Comparisons for a series of ACCs in different fan inlet air volumes and temperatures are made, and the optimized ACC is obtained for heat transfer and safety finally. All these we have done are going to provide some significant theory evidence for improving of direct air cooling technology.
In view of the critical suction effect of the forced draught fans in the air-cooled steam condenser (ACSC), it is momentous to investigate and optimize the fan mode to acquire a better synthetical performance of the power plant. A verified numerical model of a 2×600MW power plant [1] is specified to discuss the influence from the different rotating speed regulation schemes on the performance of the air-cooled power plant at the design wind angle of β=22.5°. It is found that as a result of the rotating speed regulation of the forced draught fans, the improvement for the performance of the air-cooled power plant arise. It is concluded that the rotating speed regulation for the whole fan array should be proposed because the maximum net power elevation compared to the design case is applicable at all the appointed wind speeds for the fan array case.
An analytical method is presented to evaluate the air flow rate required in an air-cooled heat exchanger used in a propane pre-cooling cycle operating in an LNG (liquefied natural gas) plant. With variable ambient air inlet temperature, the air flow rate is to be increased or decreased so as to assure and maintain good performance of the operating air-cooled heat exchanger at the designed parameters and specifications. This analytical approach accounts for the variations in both heat load and ambient air inlet temperature. The ambient air inlet temperature is modeled analytically by simplified periodic relations. Thus, a complete analytical method is described so as to manage the problem of determining and accordingly regulate, either manually or automatically, the flow rate of air across the finned tubes of the air-cooled heat exchanger and thus, controls the process fluid outlet temperature required for the air-cooled heat exchangers for both cases of constant and varying heat loads and ambient air inlet temperatures. Numerical results are obtained showing the performance of the air-cooled heat exchanger of a propane cycle which cools both NG (natural gas) and MR (mixed refrigerant) streams in the LNG plant located at Damietta, Egypt. The inlet air temperature variation in the summer time has a considerable effect on the required air mass flow rate, while its influence becomes relatively less pronounced in winter.
The layout of an air-cooled steam condenser (ACSC) has a great impact on a power plant’s operation. This is owed to the fact that the performance of the condenser and subsequently of the whole power plant is strongly affected by meteorological conditions. Hence, it is of great significance to determine the optimal design of wind angle that gives a higher performance for an air-cooled power plant. This study applies an existing numerical model in order to investigate the wind angle’s impact on the performance of an air-cooled steam condenser, as well as on the whole power plant. Moreover, the optimal design of wind angle is obtained based on the corresponding sensitivity analysis. Finally, the benefit to the power plant’s performance at the optimal-design wind angle is calculated through the comparison with the actual design values at a wind angle of β=22.5°. The obtained results show that the net power and thermal efficiency can be improved by amplitudes of 1.2 and 0.37%, respectively, at the wind angle of β=90°, which should be proposed as the design wind angle for air-cooled power plants.
The thermal performance of single-row heat exchangers is generally considered to be inferior to multi-row heat exchangers. It is therefore desirable to optimize the former; especially for those cases which cannot accommodate an alternative. In this study, the heat transfer performance of a single-row circular-finned tube heat exchanger was investigated experimentally under elevated disturbance levels. Specifically, grid-generated turbulence (GGT)-the characteristics of which had been measured beforehand with a hot-wire anemometer-was applied to a clean-flow benchmark case and measurements taken at the heat exchanger outlet. It was shown that when the grid is positioned appropriately, a mean enhancement (in global Nusselt number) of up to 11% can be achieved. Flow visualizations revealed the flow structures responsible for the increase in heat transfer.
The largest source of energy loss in ships is found in the propulsion system. This study focuses on the concept of managing waste heat energy from the exhaust gases of the main engine. Using waste heat recovery systems (WHRSs) to make shipping more efficient represents a good area of opportunity for achieving the shipping industry's green objectives. Organic Rankine cycles have been applied in land-based systems before, showing improvements in performance when compared with the traditional Rankine cycle. As marine environmental rules requiring greener vessels and engine thermal efficiency continue to increase, thus reducing the available energy in the exhaust, organic Rankine cycle WHRSs become a more attractive option.The proposed WHRS was modelled using MATLAB for a typical ship installation with a slow speed diesel engine and a WHRS installed after the steam boiler in the exhaust gas system. The energy recovered from the exhaust gas flow is transformed via the thermodynamic cycle – coupled with a generator – into electricity, which helps to cover the ship's demand. The MATLAB code found the highest electric power output, hence the maximum fuel and CO2 emission savings possible, by v varying the WHRS HP. Water and four organic fluids were considered and their performance was compared over a range of different engine operating conditions. A representative ship operating profile and a typical marine generator were used to measure CO2 emission reductions. The implications of having flammable organic fluids on board are also briefly discussed. This work demonstrates that a simple organic Rankine cycle can be more effective than a steam cycle for the same engine operating conditions.
Diminishing fossil fuel reserves and a growing collective environmental awareness has led to the development of alternative methods of power generation such as Concentrated Solar Power (CSP). Although almost all existing CSP plants currently use water-cooled condensers, limited water supplies in the designated desert regions for such power plants, the high costs associated with providing cooling water and environmental considerations will all restrict the future use of water-cooled condensers. Air-cooled condensers (ACCs) are therefore proposed, despite evidence to suggest that they suffer from significant inefficiencies [1]. It has been suggested that a modular design, addressed in this paper, could offer solutions to issues with current ACC technologies. To fully characterise the modular ACC design it is necessary to quantify the steam-side characteristics. A series of tests were performed under vacuum conditions representative of an operational condenser. The condenser vacuum was measured for a series of incremental fan rotational speeds, to determine both the qualitative and quantitative relationship between fan speed and condenser pressure. Results indicate that for a given steam mass flow rate, the condenser pressure decreases with increasing fan rotational speed. Furthermore, the choice of vacuum pump, used to displace air leakages, was shown to have a significant influence on the steam-side response. Larger displacement-capacity vacuum pumps permit lower condenser pressures. The steam condensation pressure drop through the condenser tubes was also measured. Results for the measured pressure drop revealed a large level of momentum recovery, which is not uncommon in steam condensation processes. Experimental frictional pressure drops were determined and these compared favourably with certain two-phase frictional pressure drop correlations. In particular, the Lockhart & Martinelli correlation was found to be most capable of predicting the frictional pressure drop trends encountered during testing. The large level of agreement between the measurements and predictions provide confidence in future use of the Lockhart & Martinelli correlation to predict frictional pressure losses.
In this work, a parametric optimization analysis of various innovative modular air-cooled condenser systems is carried out in order to identify the optimum system configuration and size to be used as the cooling system in a 50MWe parabolic trough concentrated solar power (CSP) plant. The optimization analysis is conducted individually on a total of 17 different configurations and on a total of 8 different condenser sizes for each configuration. The results identify the optimum air cooled condenser configuration and size that can achieve the minimum CSP plant electricity unit cost.
Analytical models are developed for the average heat transfer rate in forced convection-cooled, slotted fin heat sinks. These models for the upper and lower bounds can be used to investigate the effects of slot size and placement on heat sink performance. Exper- imental measurements are performed for a variety of slot configurations over a range of Reynolds numbers, and these data are compared with the proposed an- alytical models. An approximate model is proposed that predicts the experimental results for the average heat transfer rate to within a 12% RMS difference. NOMENCLATURE A = channel surface area, m2 Aa = approach flow cross section area, m2 Ao = heat sink flow cross section area, m2
This paper describes a test apparatus and method of analysis used for the accurate determination of the basic heat-transfer and flow-friction characteristics of compact heat-exchanger surfaces. The experimental accuracy is discussed and the results of test of a typical louvered-plate-fin heat-exchanger surface are included to illustrate the quality of data obtainable. It is hoped that the experience presented here may lead to a standardization of test methods so that more accurate design data will be forthcoming.
Heat-transfer and flow-friction design data are presented for flow normal to circular tube bundles for the Reynolds-number range, 500 to 20,000 (based on tube diameter). Six staggered circular tube patterns and one in-line arrangement were tested. Tentative correlations are presented for the staggered arrangements allowing interpolation of the test results to obtain design data partially covering a transverse pitch-ratio range from 1.25 to 2.50, and a longitudinal pitch-ratio range from 0.75 to 1.50. Data also are provided so that the influence of the number of tube rows on the mean coefficient may be estimated accurately. These results are of interest in applications involving small-diameter tubes and low-density fluids, as, for example, the gas-turbine regenerator. They supplement the high Reynolds-number data of Pierson, Huge, and Grimison, and the low Reynolds-number viscous-flow-range data of Bergelin, Colburn, et al., by providing needed information for the intermediate range. A transient-test technique was employed in obtaining these data. Several tests employing a conventional steady-state technique also were made to demonstrate the validity of the transient method. The advantages and limitations of the transient method are considered in detail.
One of the methods used to fulfill application requirements in the design of finned-tube gas coolers for industrial use more adequately is to vary the spacing of the tubes. In the past there has been very little information available on the effect of tube spacing on cooler performance. This paper covers the results of a series of tests made to determine the effect of tube spacing on the pressure drop and the heat-transfer coefficient of air flowing across a bank of helically finned tubes. The tests covered a wide range of tube spacings, both at right angles to air flow and between rows in the direction of air flow. All tests were made on staggered tube rows. The tests showed that tube spacing has a marked effect on air pressure drop, but a negligible effect on the air-side heat-transfer coefficient. The number of fins per linear inch of tube had a similar effect. Baffles in the spaces at the ends of short tube rows were found to be beneficial in minimizing edge effects, the improvement in heat transfer gained by their use more than compensating for the increase in air pressure drop.
In this study, the heat transfer and friction correlation of a single row heat exchanger with helically finned tubes are experimentally determined. The transversal tube pitch was parametrically varied. A detailed description of the test rig and the data reduction procedure is given. A thorough uncertainty analysis was performed to validate the results. The proposed heat transfer correlation can describe 95% of the data within ±11% and shows a 4.49% mean deviation. The friction correlation predicts 95% of the data within ±19% with a mean deviation of 6.84%. The new correlations show the same trend as most correlations from open literature, but none of the literature correlations are able to accurately predict the results of this study.
Integrating TES (thermal energy storage) in a CSP (concentrating solar power) plant allows for continuous operation even during times when solar irradiation is not available, thus providing a reliable output to the grid. In the present study, the cost and performance models of an EPCM-TES (encapsulated phase change material thermal energy storage) system and HP-TES (latent thermal storage system with embedded heat pipes) are integrated with a CSP power tower system model utilizing Rankine and s-CO2 (supercritical carbon-dioxide) power conversion cycles, to investigate the dynamic TES-integrated plant performance. The influence of design parameters of the storage system on the performance of a 200 MWe capacity power tower CSP plant is studied to establish design envelopes that satisfy the U.S. Department of Energy SunShot Initiative requirements, which include a round-trip annualized exergetic efficiency greater than 95%, storage cost less than $15/kWht and LCE (levelized cost of electricity) less than 6 ¢/kWh. From the design windows, optimum designs of the storage system based on minimum LCE, maximum exergetic efficiency, and maximum capacity factor are reported and compared with the results of two-tank molten salt storage system. Overall, the study presents the first effort to construct and analyze LTES (latent thermal energy storage) integrated CSP plant performance that can help assess the impact, cost and performance of LTES systems on power generation from molten salt power tower CSP plant.
Limited water supplies in arid regions that have abundant solar resources eliminates the use of water as a feasible means of cooling condensers in a Concentrated Solar Power (CSP) plant condenser. This has triggered the need to optimise existing air-cooled condenser technology, which is currently extremely inefficient. This paper aims to investigate the influence of various fan parameters on the performance of a cross-flow heat exchanger. The study first focuses on the effect of varying the distance between the fan and the heat exchanger in order to establish if uniform airflow distributions can be achieved with acceptable axial spacing between the fan and the heat exchanger. This was achieved by mapping the velocity field at the outlet from the heat exchanger by means of a Particle Image Velocimetry (PIV) analysis. The analysis was carried out for two air flow scenarios; the fan mounted at the inlet to the heat exchanger (forced draught) and the fan mounted at the outlet of the heat exchanger (induced draught). An investigation into the effect of fan speed on velocity distribution was also carried out. The measurements which are presented show that uniform velocity distributions can be achieved with relatively small fan to heat exchanger spacing for the case of the induced draught, whilst for the forced draft, although increasing the fan to heat exchanger spacing resulted in increased flow uniformity, the flow was still highly non uniform at fan to heat exchanger spacing of up to 1.4 times the fan tip radius. The measurements also showed little effect of fan speed on normalised velocity distribution. Combining the fore mentioned measurements with an analytical calculation technique, the heat flux per unit area across the heat exchanger was calculated. The results highlight the limitations on heat transfer in various regions of the heat exchanger in both flow scenarios. These measurements and calculations will facilitate designers of air cooled heat exchangers in achieving the minimum fan to heat exchanger spacing which gives no further increase in total heat transfer.
The use of air cooled condensers in power generation is increasing in many arid regions of the world. The classical A-frame condenser design is implemented in most new installations despite significant empirical evidence that such designs suffer from poor efficiencies and weather effects, and therefore provide significant scope for improvements. An inefficient condenser results in higher back pressure on the turbine, over-sized condensers and increased fan power. This paper addresses the flow distribution from an air cooled condenser for a ∼400MW gas and steam power plant. The results indicate that the flow patterns from the large scale fans results in a severe inhomogeneous distribution of cooling on the condenser fins. These region of high and low velocity are closely related to the outlet flow pattern from the fans, where in the hub region the air mass flow rate is reduced, while in the tip region it is increased. These measurements provide an excellent basis for both understanding the existing deficiencies of the A-frame designs and moreover provide direction for improved designs in the future.
The application of uncertainty analysis (UA) methods to experimental programs is discussed in an introduction for advanced undergraduate and graduate students of engineering and the physical sciences. Chapters are devoted to experimental errors and uncertainty; statistical considerations in measurement uncertainties; general UA methods for experiment planning; detailed UA methods for experiment design; problems due to variable but deterministic bias errors, digital/analog conversion, and instrument dynamic response; the debugging and execution of experiments; and data analysis and the reporting of results. The propagation of errors into an experimental result is examined in detail in an appendix. 56 refs.
This paper evaluates the effect of the geometry pattern used in the equivelocity layout on the thermal hydraulic performance of a bank of high-finned tubes of the type used in air-cooled heat exchangers. Wind tunnel tests show a decrease in both the Colburn and friction factors for this layout compared with the traditional equilateral arrangement. In particular, test results show an average decrease of 19% in heat transfer coefficient and of 36% in pressure drop between the two layouts, compared on the basis of face velocity. The current literature correlations, which are available only for geometries with lower finning factors, predict an increase in both Colburn and friction factors for the same geometry. It is also shown that for high-finned tubes in this layout the Colburn and friction factors do not change significantly after the third row of tubes. A comparison with data for an expanded transverse pitch layout is included.
The primary objective of this experimental investigation is to determine the influence that different fan and heat exchanger characteristics as well as the plenum chamber geometry have on the flow losses in the plenum chamber of a forced draught air-cooled heat exchanger (ACHE). The effect of air flow maldistribution on the heat exchanger thermal performance is also investigated. A series of model tests are conducted employing different fans and heat exchangers. It is found that there is a critical minimum distance between the outlet of the fan and the heat exchanger. The heat exchanger loss coefficient and its inlet geometry have a relatively strong influence on plenum losses as well as on the air velocity distribution at the outlet of the heat exchanger. Other variables, including the position of the fan in the fan casing, fan-to-heat exchanger area ratio and fan characteristics, have a lesser effect on plenum performance. A plenum chamber recovery coefficient is defined and expressed in terms of measured parameters. This coefficient can be employed in the design of practical ACHEs. It is further found that air flow maldistribution only has a small influence on the heat exchanger thermal performance.
Exergetic analysis is without any doubt a powerful tool for developing, evaluating and improving an energy conversion system. In the present paper, two different cooling technologies for the power cycle of a 50MWe solar thermal power plant are compared from the exergetic viewpoint. The Rankine cycle design is a conventional, single reheat design with five closed and one open extraction feedwater heaters. The software package GateCycle is used for the thermodynamic simulation of the Rankine cycle model. The first design configuration uses a cooling tower while the second configuration uses an air cooled condenser. With this exergy analysis we identify the location, magnitude and the sources or thermodynamic inefficiencies in this thermal system. This information is very useful for improving the overall efficiency of the power system and for comparing the performance of both technologies.
The analysis of visual patterns of flow distribution in finned tube banks with individual fins permits the Reparation of major factors affecting heat transfer and pressure drop. A flow model and governing dimensionless variables are established on the basis of this analysis and similarity with heat transfer phenomena in channels. Heat transfer and friction factor correlations are recommended for crossflow over staggered tube banks with plain and segmented fins in the range of Reynolds numbers Reh = 300−10,000. Correlation coefficients are evaluated using original and published experimental data. The correlations correspond with most of the available test data within 10%.
This third edition is an update of the second edition published in 1964. New data and more modern theoretical solutions for flow in the simple geometries are included, although this edition does not differ radically from the second edition. It contains basic test data for eleven new surface configurations, including some of the very compact ceramic matrices. Al dimensions are given in both the English and the Systeme International (SI) system of units.
This is a remarkable new reference and text that will cover the analysis and design of heat exchangers, detailing major new research and practical advances in the field. Topics considered include heat exchangers, planning, appropriate technology, design, engineering, and research programs.
Tests are described on a pilot plant simulating an air-cooled heat exchanger that can be operated in both the induced-draft and forced-draft modes. Heat transfer coefficients in the induced-draft mode were well correlated, for greater than six rows, by the Briggs and Young correlation; for smaller numbers of rows, a new correlation is presented. In the forced-draft mode, however, none of the literature correlations fit the data and two new correlations (for more than six rows and for less than six rows, respectively) are presented. Data were also obtained for pressure drop and these are compared with existing correlations. Two new pressure-drop correlations are presented for the forced-draft mode.
The effect of nonuniform (or maldistributed) inlet airflow and temperature on the thermal performance of cross-flow air-cooled heat exchangers, with both fluids unmixed, and taking into consideration differences in performance characteristics of individual tube rows, is addressed in this article. The latter may be due to different fin pitches or other geometric variations or row effects due to changes in air turbulence. Downstream tube rows in such a multirow tube bundle experience higher performance reductions than the tube row at the air inlet. A nonuniform air velocity distribution to a tube row leaves the row with a distorted temperature profile. This temperature nonuniformity increases as the air passes through subsequent tube rows, and causes the downstream rows to be progressively less effective. The present analysis is used to evaluate the performance of the individual tube rows and ultimately the entire bundle. Velocity distributions which have been measured on air-cooled heat exchanger models are employed in the analysis in order to determine to what extent airflow maldistribution reduces exchanger performance. It is found that maldistribution occurring in well-designed air-cooled heat exchangers reduces the thermal performance by only a few percent.
The expression Y = (1 + Zn)1/n where Y and Z are expressed in terms of the solutions for asymptotically large and small values of the independent variable is shown to be remarkably successful in correlating rates of transfer for processes which vary uniformly between these limiting cases. The arbitrary exponent n can be evaluated simply from plots of Y versus Z and Y/Z versus 1/Z. The expression is quite insensitive to the choice of n and the closest integral value can be chosen for simplicity. The process of correlation can be repeated for additional variables in series. Illustrative applications are presented only for flow, conduction, forced convection, and free convection, but the expression and procedure are applicable to any phenomenon which varies uniformly between known, limiting solutions.
Recent accelerated development of science and technology has revealed a number of new problems in the field of heat transfer of tubes in cross flow. The fast growth of the chemical and power industries and the emergence of some new branches of engineering caused an increased interest in heat transfer in flows of viscous fluids at higher Prandtl and Reynolds numbers. This chapter focuses on important problems of heat transfer and the hydraulic drag of tubes, and in particular, with the heat transfer of single tubes, banks of tubes, and systems of tubes in cross flow. The chapter also discusses the influence of the physical properties of fluids on heat transfer. Extensive experimental data is analyzed and banks of tubes of various arrangements and a single tube in cross flow in the range of Prandtl number from 0.7 to 500 and that of Reynolds number from 1 to 2 x l06 are investigated. Furthermore, heat transfer is considerably influenced by the flow regime around the tube, while flow past banks of tubes is one of the most complicated problems of practical importance. Knowledge of these processes enables more extensive studies of heat transfer.
A study is reported of the potential performance of dry cooling on power generation. This is done in the context of a generic trough solar thermal power plant. The commercial power plant analysis code GateCycle is applied for this purpose. This code is used to estimate typical performance of both wet and dry cooling options. Then it is configured to estimate the performance of ideal wet and dry cooling options. The latter are defined as the condenser temperature being at the ambient wet bulb temperature or dry bulb temperature, respectively. Yearly power production of a solar power plant located in Las Vegas is presented for each of the cooling options. To move further toward approaching the possible improvement in dry cooling, the impact of a high-performance heat exchanger surface is evaluated. It is found that higher efficiency generation compared to current dry cooling designs is definitely possible. In fact the performance of these types of systems can approach that of wet cooling system units.
The present study focuses on the data reduction method to obtain the air-side performance of fin-and-tube heat exchangers. The data reduction methodology for air-side heat transfer coefficients in the literature is not based on a consistent approach. This paper recommends standard procedures for dry surface heat transfer in finned-tube heat exchangers having water on the tube-side. Inconsistencies addressed include the ε-NTU relationships, calculation of the tube-side heat transfer coefficient, calculation of fin efficiency, and whether entrance and exit loss should be included in the reduction of friction factors. Use of the recommended standardized methodology will provide more meaningful data for use in the development of correlations, or for performance comparison purposes.
http://deepblue.lib.umich.edu/bitstream/2027.42/8196/5/bad7597.0001.001.pdf http://deepblue.lib.umich.edu/bitstream/2027.42/8196/4/bad7597.0001.001.txt
An analytical model is presented that predicts the average heat
transfer rate for forced convection air cooled plate fin heat sinks for
use in the design and selection of heat sinks for electronics
applications. Using a composite solution based on the limiting cases of
fully-developed and developing flow between isothermal parallel plates,
the average Nusselt number can be calculated as a function of the heat
sink geometry and fluid velocity. The resulting model is applicable for
the full range of Reynolds number, 0.1<Reb*<100, and
accurately predicts the experimental results to within an RMS difference
of 2.1%
The specification and design of heat sinks for electronic
applications is not easily accomplished through the use of conventional
thermal analysis tools because “optimized” geometric and
boundary conditions are not known a priori. A procedure is presented
that allows the simultaneous optimization of heat sink design parameters
based on a minimization of the entropy generation associated with heat
transfer and fluid friction. All relevant design parameters for plate
fin heat sinks, including geometric parameters, heat dissipation,
material properties and flow conditions can be simultaneously optimized
to characterize a heat sink that minimizes entropy generation and in
turn results in a minimum operating temperature. In addition, a novel
approach for incorporating forced convection through the specification
of a fan curve is integrated into the optimization procedure, providing
a link between optimized design parameters and the system operating
point. Examples are presented that demonstrate the robust nature of the
model for conditions typically found in electronic applications. The
model is shown to converge to a unique solution that gives the optimized
design conditions for the imposed problem constraints
Heat transfer an flow resistance correlation for helically finned and staggered tube banks in cross flow
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Heat exchangers: design and theory source book; 1974. pp. 559e84. Hemisphere, Washington DC.
Pressure drop of air flowing across triangular pitch banks of finned tubes
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Robinson KK, Briggs DE. Pressure drop of air flowing across triangular pitch banks of finned tubes. Chem Eng Prog Symp Ser 1963;62(64): 177e83.
Heat transfer and friction characteristics of some compact heat-exchanger surfaces part 1-test system and procedure. Trans ASME
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Kays WM, London AL. Heat transfer and friction characteristics of some compact heat-exchanger surfaces part 1-test system and procedure. Trans ASME; 1954.
Study: levelized cost of electricity
- Ise Fraunhofer
Fraunhofer ISE. Study: levelized cost of electricity. Renewable Energy Technologies http://www.ise.fraunhofer.de/en/publications/studies/cost-of-electricity;
November 2013.
Analysis of laminar convection-heat transfer in the entrance region of flat rectangular ducts e NACA technical note 3331
- E M Sparrow
Sparrow EM. Analysis of laminar convection-heat transfer in the
entrance region of flat rectangular ducts e NACA technical note 3331;
1955.
Flow and fan e principles of moving air through ducts. 2 nd ed
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Berry CH. Flow and fan e principles of moving air through ducts. 2 nd ed. New
York: The Industrial Press; 1963.
The development and verification of a novel modular air cooled condenser for enhanced concentrated solar power generation e MACCSol, EC contract no
- Eu
www.drycooledcsp.eu (The development and verification of a novel modular
air cooled condenser for enhanced concentrated solar power generation e
MACCSol, EC contract no. 256797).
Steam-side characterisation of a modular air-cooled condenser
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O'Donovan A, Grimes R, Walsh E, Moore J and Reams N. Steam-side characterisation of a modular air-cooled condenser, Proc ASME IMECE 2012, Houst
TX, USA.