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Components of VRF systems.  

Components of VRF systems.  

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The use of a variable refrigerant flow (VRF) is being specified as an alternative solution to centralize HVAC systems in domestic building. This manuscript presents a comprehensive description of the configuration for the indoor and outdoor units of a multi-split VRF system. A case study of a hotel in Amman, Jordan was implemented. The suitable ind...

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... load demand. Nowadays, VRF technology uses an inverter-driven scroll compressor to derive more indoor units from one outdoor unit. The inverter-driven scroll compressors has a capability of changing its speed to keep track of the variations in the total cooling/heating load by measuring the suction gas pressure mounted on the con- densing unit. Fig. 2 shows a schematic VRF ...

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... Such deep waste heat recovery techniques are quite appropriate for combined cooling (air conditioning as a widespread version [1,2]), trigeneration or integrated energy systems [3,4], as well as for transport applications [5,6]: railway [7,8] and marine [9,10]. They are promising to be implemented into other technologies to decrease harmful particles in exhaust gases from marine ICE to compensate for a reduction in efficiency of engines [11] when applying refrigeration and jet technologies [12]. ...
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... There has been gradual development of HVAC systems from complete building to individual zones independent of other zones in the same building. Such systems (called as "multi-split air conditioning systems") focuses on zone specific comfort management, the overall comfort conditions increase significantly at the same time reducing the energy consumption from the zones in which heating is not required [110][111][112]. ...
... 18: ASHP-VRF system with multiple indoor units[110]. ...
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Low cost smart sensors, intelligent controllers, and IoT systems constitute key components to develop smart buildings. These smart systems produce optimal control strategies by continuous analysis of building performance. Two major parameters are controlled in the building: occupants’ comfort and heating or cooling load consumption optimization. For such intelligent controllers applications, it is essential to have building model with high performance accuracy and computational efficiency. The existing building models range from complete analytical to fully data-driven and hybrid models. The analytical model is extremely complex to model and computationally inefficient, whereas the data-driven models require a large amount of data. However, in the case of data unavailability, application of datadriven models become impossible. This work presents, hybrid modeling for heat transfer dynamics of the building using lumped parameter thermal network modeling technique. An efficient building model is developed by having proper structural knowledge of low-order model and identifying its parameter values. Simplified low-order systems are developed using 2nd order thermal network models with optimal thermal resistors and capacitors value.In order to determine the low-order model parameter values, a specific approach is proposed using a stochastic particle swarm optimization. This method provides a significant approximation of the parameters when compared to the reference model whilst allowing low-order model to achieve 40% to 50% computational efficiency than the reference analytical model.Furthermore, extensive simulations are carried out to evaluate the proposed simplified model with a more advanced complex solar gains model and identified parameters value. The developed simplified model is afterward validated with measured data from a case study building where the achieved results clearly show a high degree of accuracy compared to the actual data. Finally, an MPC controller is applied for the same case study building for thermal comfort optimization. Simulation results demonstrate the significance of the MPC controller in handling the constraints, multi-objective control, and producing optimal control strategy. The energy optimization results of the MPC have shown 31% of energy consumption reduction compared to a conventional controller.
... The main reasons that make the vehicular thermal environments of highly non-uniform and asymmetric environments and make it a totally different from those in a domestic building are (Ruzic 2011;Alahmer and Alsaqoor 2018): (i) the interior passenger compartment is small compared with the number of occupants; (ii) the rapid change of climatic parameters as changing of a vehicle to the sun orientation; (iii) the complexity of the interior of passenger compartment; (iv) the percentage glazing portion compared to cab surface; (v) the location of a passenger inside a car to the source of air conditioning systems and higher or lower interior surface area; (vi) the riders are difficult to change position inside an automobile; (vii) the air conditioning does not work when nobody inside a car or when the engine shut off; leading to extreme environmental conditions. ...
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The main purpose of any vehicular climatic control in terms of heating and air conditioning (AC) systems is to achieve maximum thermal human comfort with energy efficient. Therefore, it is important to analyse the temperature distribution and air-flow field in the cabin compartment to achieve the highest and rapid human comfort. This paper adopted a Berkeley human comfort model to show the behaviour of a vehicular human sensation and comfort at different airflow velocity levels. A temporal history, local sensation (LS), and comfort (LC) were analysed for different body segments with the addition of the overall sensation (OS) and the overall comfort (OC) inside the passenger compartment under summer period weather conditions. This study revealed that: because of the air velocity plays crucial impacts on both convectionand evaporation mechanisms which directly effects on the heat losses from the body and thermal human comfort, the controlling of air movement with the temperature helps the environmental cabin to achieve the comfort zone faster than the sole control of the temperature only. When activated the air conditioning systems, the vehicular environmental parameters will change dramatically and a rapid transient occurred especially in the first few minutes.
... Today, the expanding interest and growing market for refrigeration and cooling have prompted the consumption of primary energy to operate it, negative environmental issues, and cause for the increment of electricity peak load. As the quantity of customary vapor compression cooling machines develops (in excess of 100 million units sold in 2014) [1]. The refrigeration and air conditioning systems consume around 30% of total worldwide energy consumption [2]. ...
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... It is also an HFC and will be phased down 100% by 2034 [21]. R123 is used in chillers due to its high thermodynamic efficiency [22] and reduced possibility of leakages, but it is HCFC compound with a B1 classification, and it has been a cause of tumors in livers and pancreases due to long term inhalation and hence, it is expected to be phased out by 2025 [23]. Due to the large GWP values of the previous generation of refrigerants, the USA's Environmental Protection Agency (EPA) has decided to systematically phase out HFCs to 50% by 2024, 80% by 2029, and 100% by 2034 [24]. ...
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Global warming is one of most severe environmental concerns that our planet is facing today. One of its causes is previous generation refrigerants that, upon release, remain in atmosphere for longer periods and contribute towards global warming. Potentially this can be solved by replacing the previous generation high global warming potential (GWP) refrigerants with environment friendly refrigerants. Potentially, this scenario requires the analysis of new refrigerants for comparison of thermodynamic properties of previously used refrigerants. In the present research, numerical study was conducted to analyze thermodynamic performance of specifically low GWP hydroflouroolyfens (HFO) refrigerants for actual vapor compression refrigeration cycle (VCRC) with constant degree of 3 K superheat. Output parameters included refrigeration effect, compressor work input, coefficient of performance (COP) and volumetric refrigeration capacity (VRC) which were calculated by varying the condenser pressure from 6 to 12 bars and vapor pressure from 0.7 to 1.9 bars. Results showed that R1234ze(Z) clearly possessed desired thermodynamic performance. Drop in refrigeration effect for R1234ze(Z) was merely 14.6% less than that of R134a at 12 bar condenser pressure; minimum drop among candidate refrigerants. Drop in COP was minimum for R1234ze(Z) which was 5.1% less than that of R134a at 9 bar condenser pressures and 4.7% less than that of R134a at 1.9 bar evaporator pressure whereas COP values of other refrigerants dropped more drastically at higher condenser pressures. R1234ze(Z) possessed favorable thermodynamic characteristics which has GWP of 7 and can serve as alternative refrigerant for refrigeration systems for sustainable environment.
... The air conditioning system is extremely important in healthcare buildings to provide a comfortable environment to patients, physicians, staffs and visitors with acceptable indoor air quality, more energy efficient and cost reduction [1]. Proper air conditioning of medical care facilities is helpful to prevent and treat diseases. ...
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Hospitals and other healthcare facilities are complex environments that require a special consideration to HVAC design as in requirement a large amounts of ventilation, which leads to high amount of energy consumption. This manuscript presents a description of chilled water/ HVAC systems for health care facilities. A case study of a Farah hospital located in Amman/ Jordan was implemented to perform cooling load using radiant time series (RTS). This paper manipulates the effect of changing relative humidity with dry bulb temperature on the cooling load, power consumption and chiller selection using three types of building namely: commercial building, hospital building and green hospital building to choose the best indoor design conditions with minimum power consumption. To reduce the energy cost for chiller, a solar photovoltaic was proposed to overcome the portion of the air conditioning power requirement and reduce the demand on the electrical grid. A proposed solar photovoltaic technology unit was analyzed and modeled using a hybrid optimization model for renewable energies (HOMER) software. The results revealed that: (i) the applying green building criterion will lead to significant reduction in cooling load and power consumption up to 25%; (ii) A higher relative humidity and in design inside temperature, a lower cooling load and power consumption required, (iv) PV systems sizing depend on load data, solar radiation, battery data, inverter data and investment cost of the system, and finally (v) there is a potential to adopt solar PV as strategic and alternative option to reduce the cooling cost.
... About 65% of electrical energy consumption in Saudi Arabia goes to the building sector mainly for air conditioning purposes. Statistical analysis indicated that 70% of this total building energy demand was for refrigeration and air-conditioning [14,15]. In general, one-third to one half of the annual total electricity consumption is required for cooling and refrigeration processes in the domestic cities, with more than of eighty percent of electricity generated from fossil fuels, resulting in more emissions and increased global warming [16]. ...
... Owing to the multiple individual indoor units (IUs), VRF systems could serve several rooms simultaneously using variable capacity compressor and electronic expansion valves [14]. Since its introduction in the 1980's in Japan [15], VRF systems have been used widely in small-to middle-sized office buildings especially in Asian countries due to the advantages such as individual control for occupants, good part-load performance, and easy maintenance [16][17][18]. ...
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Conference Paper
Full-text available
Hospitals and other healthcare facilities are complex environments that require a special consideration to HVAC design as in requirement a large amounts of ventilation, which leads to high amount of energy consumption. This manuscript presents a description of chilled water/ HVAC systems for health care facilities. A case study of a Farah hospital located in Amman/ Jordan was implemented to perform cooling load using radiant time series (RTS). This paper manipulates the effect of changing relative humidity with dry bulb temperature on the cooling load, power consumption and chiller selection using three types of building namely: commercial building, hospital building and green hospital building to choose the best indoor design conditions with minimum power consumption. To reduce the energy cost for chiller, a solar photovoltaic was proposed to overcome the portion of the air conditioning power requirement and reduce the demand on the electrical grid. A proposed solar photovoltaic technology unit was analyzed and modeled using a hybrid optimization model for renewable energies (HOMER) software. The results revealed that: (i) the applying green building criterion will lead to significant reduction in cooling load and power consumption up to 25%; (ii) A higher relative humidity and in design inside temperature, a lower cooling load and power consumption required, (iv) PV systems sizing depend on load data, solar radiation, battery data, inverter data and investment cost of the system, and finally (v) there is a potential to adopt solar PV as strategic and alternative option to reduce the cooling cost.
... They also mentioned that the EEV has a better performance than that of conventional expansion devices, and it could provide the best flow and quality control. Furthermore, Alahmer et al. [19] studied the multi-split variable refrigerant flow systems in a simulation manner. The Indoor unit contains an EEV, which controls the refrigerant flow rate according to the cooling or heating load of different indoor units. ...