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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 effecti...
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This paper aims to explore an efficient, cost-effective, and water-saving seasonal cold energy storage technique based on borehole heat exchangers to cool the condenser water in a 10 MW solar thermal power plant. The proposed seasonal cooling mechanism is designed for the areas under typical weather conditions to utilize the low ambient temperature...
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... Dry cooling is more capital intensive than water cooling, costing approximately 1.5-8 times more within the temperature ranges and operating conditions shown in Figure 7 a) & d). These findings align with what has been reported in the thermal power industry literature [53,71,72]. Furthermore, the cost of cooling per kgH2 is lower for evaporative cooling than for dry cooling (Figure 7 b) & e)), especially for ambient air temperatures exceeding 40 o C and stack operating temperatures close to 60 o C. ...
... p Further, the nondimensional entity NTU is quantified using Equation (23). 35,36 3.1.4.11 | Gross surface area ...
... In Equation (25), h and R f " refer to the heat convection coefficient (W m −2 K −1 ) and fouling factor (0.0002) (m 2 KW −1 ) at the outer (o) and inner side (i) of the HE's tube. 36 The heat convection coefficients for the inner and outer sides of the heat exchanger tube are determined using the Dittus-Boelter and Hilpert correlations owing to forced convection heat transfer. 37 ...
In the COVID‐19 pandemic, control of airborne virus transmission is exceptionally challenging as it is attached to suspended particles in the air and stays for an extended time. Air contaminated with airborne viruses holds a substantial risk for household transmission. In this study, a novel thermal treatment system is modeled based on porous heating for the decontamination of airborne SARS‐Cov‐2. The model includes an air heating domain, insulated chamber, buffer tank and heat exchanger. The airborne SARS‐Cov‐2 is decontaminated when passing through a porous heat pipe and the insulated chamber for an anticipated dwelling period of more than 5 min at 105°C and further stored in a buffer tank for natural cooling. The obligatory decontaminated air is allowed in the residential space under ambient conditions passing through a heat exchanger. The numerical investigation of the porous pipe model at different L/D ratios with altered porosities aims to establish the best‐performing porous domain. Besides this, the buffer tank is intended to maintain buffer storage of the treated air and significant natural cooling before passing to the heat exchanger. A solar PV module is proposed to meet the prerequisite energy requirements of the equipped devices.
... Numerous experimental correlations have been proposed to predict the heat transfer performance of air in classical tube types [6][7][8], including circular tube [9] and rounded corner triangular duct [10], etc. Nevertheless, most of the former experimental data are obtained at relatively low surface temperature and heat flux [11][12][13], and they have uncertainty to extend into the range of high temperature and flux that is of interest in many current engineering applications. ...
... The averaged heat flux implemented on the test section is expressed as q = Q/πDL (11) in which the heating power is calculated by Eq. (6). Based on the above parameters, the Reynolds number and Nusselt number can be obtained and their relationship can be summarized. ...
Air is widely utilized as working fluid in heat exchangers with high heat flux and high temperature, and the empirical correlations for predicting local and total heat transfer coefficients are indispensable for thermal design and optimization of the heat exchange applications. Experimental investigation on heat transfer characteristics of high temperature air in round tube is conducted. The experimental system is designed and constructed. The data processing method for obtaining wall temperature and heat transfer coefficient is introduced. The measured local and total heat transfer coefficients are compared with the widely adopted correlations, including Taylor’s correlation and Gnielinski’s correlation. The suggested empirical correlations obtained from the experimental data are presented, which may contribute to the design of heat exchangers concerning with high temperature air.
... In the current power generation industry, the combined cycle power plant (CCPP) is the most energy-efficient technology for fossil-fuel-based power generation, and its deployment has increased in the last few decades [1]. One major factor that influences the overall performance of the combined cycle power plant is the condition of the bottoming steam cycle turbine outlet, which is dependent on the cooling effectiveness of the steam condenser [2,3]. The steam condenser is primarily responsible for the heat rejection by thermally interacting with a heat sink (mainly air and/or water) at a lower temperature [4]. ...
... Over time, the wet-cooling system had been the preferred cooling system for combined cycle power plants with many installations across the globe. The major attraction of the wet cooling system is their comparatively low capital costs and flexibility to achieve low steam turbine outlet temperatures with enhanced net power output owing to the excellent heat transfer properties of the water [2,3,8]. However, the major drawback of the wet cooling system is that it consumes an enormous amount of water. ...
... The present study is focused on the heat rejection section of the combined cycle plant, thus limiting the analyses to the steam turbine output, steam condensation and cooling processes. From the literature survey, it has been established that the state of the above-mentioned processes determines the efficiency of the Rankine cycle power plant, as well as the heat rejection rate [2]. ...
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.
With countries proposing the goal of carbon neutrality, the clean transformation of energy structure has become a hot and trendy issue internationally. Renewable energy generation will account for the main proportion, but it also leads to the problem of unstable electricity supply. At present, large-scale energy storage technology is not yet mature. Improving the flexibility of coal-fired power plants to suppress the instability of renewable energy generation is a feasible path. Thermal energy storage is a feasible technology to improve the flexibility of coal-fired power plants. This article provides a review of the research on the flexibility transformation of coal-fired power plants based on heat storage technology, mainly including medium to low-temperature heat storage based on hot water tanks and high-temperature heat storage based on molten salt. The current technical difficulties are summarized, and future development prospects are presented. The combination of the thermal energy storage system and coal-fired power generation system is the foundation, and the control of the inclined temperature layer and the selection and development of molten salt are key issues. The authors hope that the research in this article can provide a reference for the flexibility transformation research of coal-fired power plants, and promote the application of heat storage foundation in specific coal-fired power plant transformation projects.
Thermal power plants are required to enhance operational flexibility to ensure the power grid stability with the increasing share of intermittent renewable power. Integrating thermal energy storage is a potential solution. This work proposes a novel system of molten salt thermal storage based on multiple heat sources (i.e., high-temperature flue gas and superheated steam) integrated within a coal-fired power plant. To evaluate the performance of the thermal energy storage system, simulation models were established, and exergy analysis was conducted. Results show that the integration of molten salt thermal storage achieves the synergistic improvement of operational flexibility and thermal efficiency of the thermal power system. When the boiler keeps steady combustion, the minimum power load decreases from 30% to 14.51% of the rated load during the charging process because of the integration of the thermal energy storage system. To decrease the power load of the coal-fired power plant, the surplus heat is stored in the thermal storage system to be used later. The equivalent round-trip efficiency of the thermal energy storage system is up to 85.17%, which is achieved by the appropriate match between the heat sources and the thermal storage media.
A new type of hybrid suspension comprising microencapsulated phase change material (MEPCM) spheres and graphene oxide (GO) nanoplatelets is proposed. The dispersion stability of the MEPCM/GO suspension was guaranteed by precisely adjusting the density of the MEPCM particles, which had n-heptadecane as the core and hexanediol diacrylate polymer as the shell. The MEPCM particles with excellent monodispersity were fabricated successfully using a co-flowing microfluidic method. The micromorphology of the hybrid MEPCM/GO suspension, measured using a transmission electron microscope, showed that the MEPCM particles and GO nanoplatelets were dispersed uniformly in the base fluid without aggregation. The high dispersity and stability of the hybrid MEPCM/GO suspension provide basic conditions for regulating its thermo-physical properties. Thermal conductivity, specific heat capacity, and viscosity were measured using a laser-flash analysis device, a differential scanning calorimeter, and a rotational rheometer, respectively. The effects of the concentrations of the MEPCM particles and GO nanoplates were investigated. Results showed that enhanced thermal conductivity and specific heat capacity were achieved for the hybrid MEPCM/GO suspension. This advantage of the hybrid suspension became increasingly obvious as the MEPCM and GO concentrations increased. The viscosity of the hybrid MEPCM/GO suspension changed only slightly with the GO concentration, whereas it increased with the MEPCM concentration, and thus showed a relatively good rheological property. The proposed hybrid MEPCM/GO suspension with enhanced thermo-physical properties possesses immense potential for use as a novel working fluid for high-efficiency heat transfer.
