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In this paper, a combined air/water source heat pump water heater is presented. At ordinary time, the heater can be used for hot water heating in water-source mode to improve the energy efficiency. While in cold season, it gives priority to air-source mode for water heating to improve operational safety. Experiments were conducted to investigate the thermodynamic performance of the heater in each operation mode, and the experiment results were analyzed. The research indicated that its operation was reliable during the long-time running. This paper offers a promising energy-saving method in future. [ABSTRACT FROM AUTHOR]

• A direct evaporative cooler (DEC) integrates with split air conditioner (SAC). • DECSAC significantly improves C O P by 10.54 %−70.14 %. • Total cost rate (T C R) of DECSAC reduces by 5.07 %−25.36 %. • Water consumption for 1 kWh energy saving varies between 5.5 – 9.8 L. • Simple payback period lies between 1.21 to 2.99 years with maximum I R R being 59 %. As concerns regarding energy consumption and environmental impact continue to grow, the need for efficient and sustainable cooling technologies becomes increasingly significant. Among various alternatives, direct evaporative cooling (DEC) has emerged as a promising solution due to its energy-efficient operation and low environmental footprint. This paper aims to provide a comprehensive thermo-economic assessment of a 5.25 kW capacity split air conditioner (SAC) integrated with direct evaporative cooling, focusing on evaluating its performance, energy consumption, coefficient of performance (C O P) , and economic viability. A numerical model is developed to determine the reduction in the condenser inlet air temperature due to direct evaporative cooling. The ambient temperature (30–45 ⁰C), relative humidity (20–80 %), and evaporator temperature (3–12 ⁰C) are taken as the design variables. Box–Behnken design (BBD) technique of response surface methodology is applied for multi-objective optimization. The C O P , total cost rate (T C R) , and total exergy destruction ( E ˙ D , t ) are set as the objective functions. Cooling capacity, life period, operation time, interest rate, maintenance factor, and electricity cost are taken as constants. The thermoeconomic optimization evolved maximized C O P enhancement of 68.94 %, and reduction in TCR and E D , t by 26.12 % and 57.23 %, respectively. The water consumption to energy saving ratio varies from 5.5 to 9.8 L/kWh for different months of the cooling season. The thermoeconomic performance and sustainability of DECSAC is observed to significantly improve compared to conventional SAC specifically in hot-dry climates. The simple payback of the proposed system ranges between 1.21 to 2.99 years depending upon the operating conditions. [ABSTRACT FROM AUTHOR]

This study focused on investigating the drying behaviors of nectarine slices under varying drying temperatures (Tdrying) through the utilization of energy and exergy analysis methodologies, alongside an exploration of the drying kinetics employing diverse mathematical models. The drying process was carried out using a closed-type heat pump drying (HPD) system. The findings revealed a reduction in drying time with an increase in temperature. Notably, the condenser, compressor, and drying cabinet exhibited their highest exergy efficiencies at a Tdrying of 45 °C, while the evaporator demonstrated its highest exergy efficiency at 35 °C. The highest exergy efficiencies were achieved at a Tdrying of 45 °C and calculated as 65.94%, 77.95% and 80.53% for the condenser, dryer and compressor, respectively. Among the considered models, Aghbashlo et al. demonstrated the most optimal fit for moisture ratio. The Deff values ranged from 5.476 × 10-10 to 1.095 × 10-9 m² /s within the Tdrying range of 35 to 45 °C. As the Tdrying elevated, the Deff also raised. Using an Arrhenius-type equation, the expression for the temperature dependence of Deff was established. The determined activation energy value for moisture diffusion was 56.50 kJ/mol. [ABSTRACT FROM AUTHOR]

Due to the increase in human population, there is an ever-increasing demand for energy in different sectors which leads to environmental problems like climate change, rise in temperature, and global catastrophes. Cooling systems have become a very essential element in recent decades for mankind. The present system focuses on the design and fabrication of a counter-flow humidification setup which uses biomass-based charcoal as the packing material. Air velocity and water flow rate have been varied along with the density of charcoal. Output parameters such as a change in pressure (ΔP), Coefficient of performance (COP), evaporation rate (ER), humidification efficiency (HE), specific cooling capacity (SCC), and energy consumption (EC) are evaluated. Performance parameters obtained for charcoal are compared with that of standard Celdek Packing. Through experiments, it is found that humidification efficiencies for Celdek and charcoal packing are 77.45% and 57.40% respectively. The overall coefficient of performance obtained is 1.41 for charcoal and 3.17 for Celdek packing. Among the three densities which were considered, charcoal packing with a density of 400 kg/m3 exhibited higher performance with respect to COP, HE, ER, and SCC. Similarly, a water flow rate of 0.4 lpm gave a maximum performance and 0.7 lpm gave the least. It is concluded that charcoal can be considered one of the highly efficient biomass-based materials contributing to sustainable energy related to cooling applications. [ABSTRACT FROM AUTHOR]

The performance of the refrigeration system is largely influenced by the heat exchanger, and there are various methods for increasing heat exchange efficiency. In this paper, the effect of changes in the internal shape of an evaporator with different heat transfer areas on the performance under actual refrigerator operating conditions was analyzed. The type of evaporator includes a grooved evaporator and a composite grooved evaporator with a relatively large heat transfer area. The performance evaluation was evaluated by refrigerant optimization, on-off operational test, and steady state energy test. The optimum refrigerant amount for both systems is 76 g. When a composite grooved evaporator was used, monthly energy consumption was relatively saved by 2.7 kWh/month. In addition, the composite grooved evaporator has consumption and 2.2 % higher cooling capacity than the grooved evaporator. In conclusion, COP improved by 1.33 %. [ABSTRACT FROM AUTHOR]

In this paper we aim to make a comparison between three types of heat pumps: air-to-water, water-to-water, ground-to-water. We show that, from a construction point of view, the difference between the three types of heat pumps is the source from which the additional heat is extracted. We point out that the heat pump is the installation that transfers heat from a colder medium to a warmer medium. Most often, pumps extract heat from water, air or ground/geothermal sources and transfer it into the home via underfloor heating, radiators, etc. Any decision to install heat pump equipment must be carefully considered, taking into account all four elements (energy consumption, installation costs, existence of the chosen heat source and its accessibility) that influence the technical and economic efficiency and the proper functioning of the equipment. [ABSTRACT FROM AUTHOR]

To improve the problem of low temperature at night in winter due to the lack of thermal storage in large-span plastic tunnels, an air thermal energy utilization system (ATEUS) was developed with fan-coil units to heat a large-scale plastic tunnel covered with an external blanket (LPTEB) on winter nights. The ATEUS was composed of nine fan-coil units mounted on top of the LPTEB, a water reservoir, pipes, and a water circulation pump. With the heat exchange between the air and the water flowing through the coils, the thermal energy from the air can be collected in the daytime, or the thermal energy in the water can be released into the LPTEB at night. On sunny days, the collected thermal energy from the air in the daytime (Ec) and released thermal energy at night (Er) were 0.25-0.44 MJ/m² and 0.24-0.38 MJ/m², respectively. Used ATEUS as a heating system, its coefficient of performance (COP), which is the ratio of the heat consumption of LPTEB to the power consumption of ATEUS, ranged from 1.6-2.1. A dynamic model was also developed to simulate the water temperature (Tw). Based on the simulation, Ec and Er on sunny days can be increased by 60%-73% and 38%-62%, respectively, by diminishing the heat loss of the water reservoir and increasing the indoor air temperature in the period of collecting thermal energy. Then, the COP can reach 2.6-3.8, and the developed ATEUS can be applied to heating the LPTEB in a way that conserves energy. [ABSTRACT FROM AUTHOR]

Air source heat pumps have gradually become a widely used heating solution worldwide due to their advantages of high efficiency, energy conservation, and environmental protection. However, air source heat pumps also face some challenges in practical applications, such as unstable heating and performance degradation in low-temperature environments. In order to improve these problems, based on the cascade heat technology, a new type of dual-source synergetic heat pump system is designed using air energy and biomass waste heat dual heat sources. In order to study its performance, a simulation model of the heat pump system was first constructed using distributed-parameter method. In order to verify the effectiveness of the model, an 18-kW heat pump experimental unit was constructed. By comparing the three key parameters of user side outlet water temperature, high-temperature compressor power, and system coefficient of performance (COP), the results show that the maximum error does not exceed 11 %; Secondly, in order to improve the stability and operational efficiency of the system, a three-level control strategy was designed based on considering the coordination of different grade heat sources; Finally, based on the above, the operating characteristics of the heat pump system were investigated through testing under different external input conditions. The research results indicate that by utilizing cascade heating and parallel heat exchange technology, the heat pump system can achieve stable heating even under large fluctuations in external working conditions. At the same time, compared with air source heat pumps, the COP can be improved by 69.7 % in low-temperature environments. The system results not only provide reference for the design and operation of new heat pump systems, but also provide practical and feasible solutions for the problem of decreased heat pump performance in low-temperature environments. • A new type of dual-source synergetic heat pump system is designed. • A 18 kW prototype unit of the heat pump system are constructed and tested. • A three-level control strategy for regulating the heat pump system is proposed. • The proposed heating device can enhance clean energy utilization and COP greatly. [ABSTRACT FROM AUTHOR]

Commercial solutions in the area of data center cooling available on the market are universal solutions that use dedicated control methods and are to able function properly in a wide range of working conditions. The functional limitations resulting in their application were our motivation for developing our own system architecture and a dedicated control algorithm. Historical data from an operating cooling system were analyzed. On that basis, a rule-based controller was developed, the purpose of which is to correctly switch between operating modes. The time constants of the automation actuators and the dynamics of the changes that occur in the cooling process were identified. The control strategy was experimentally validated throughout 2017. The efficacy of the second solution and the effectiveness of the control algorithm throughout the calendar year were demonstrated. Our solution allows individual control of each element of the cooling system. This enabled the extension of the operation time in the free-cooling mode by 2064 h throughout the year, a 69% increase in the COP coefficient of the cooling system and a reduction in electricity consumption by 206.9 MWh due to longer operation in the freecooling mode. [ABSTRACT FROM AUTHOR]

GWP (Global Warming Potential) and ODP (Ozone Depletion Potential) occupy an important place in global warming. This has led to the use of refrigerants with low GWP and ODP in cooling systems. Commonly used in cooling systems, R404A refrigerant has a very high GWP value despite having zero ODP. In this study, the exergetic performance analyses of the refrigerants, which may be alternative to R404A, in a theoretical cooling cycle were given comparatively. As an alternative to R404A refrigerant, R452A, R455A and R454C fluids are examined comparatively. COP and exergy destruction, for each refrigerant were examined separately and results were graphically analyzed. COP values of HFO group refrigerants were found as 2.472, 2.312, 2.632, 2.309 for R404A, R452A, R455A and R454C, respectively. In terms of exergy efficiency of HFO group refrigerants were found as 41.5%, 38.8%, 43.9%, 38.7% for R404A, R452A, R455A and R454C, respectively. As a result, thermodynamic properties, GWP and ODP values, energetic and external perspective; As an alternative to the R404A fluid, the best fluid selected is R455A, then R452A and R454C, respectively. The best choice for these alternative refrigerants in cooling systems is R455A. [ABSTRACT FROM AUTHOR]

Today, demand for soil source heat pump, air source heat pump and water source heat pump types with low energy input and high temperature performance has been increasing considering the region where the system will be built, geological structure, geographical location and seasonal conditions. In this study, a PV-T collector which produces 190W rated power with 72 cell single crystal silicon module cell panel has been used for supporting the ground source heat pump. Energy and exergy analyzes for each element in the PV-T assisted heat pump system has been done with the help of EES (Engineering Equation Solver) program. In PV-T hybrid system, total electrical power is 1422 W and total thermal power is 4397 W. Thermal efficiency of PV-T collector has been calculated as 49.7% and electrical efficiency as 15.2%. The efficiency contribution of the collectors to the PV-T welded heat pump system has been 67.9%. It has been observed that the total electrical power and the total thermal power increases as the intensity of heat goes up. In this study, the COP of the heat pump system has been calculated as 4.41. The highest exergy destruction has been observed in the condenser. [ABSTRACT FROM AUTHOR]

A new type of well-adapted solar assisted heat pump drying system (SAHPDS) was put forward to choose and switch more efficient and energy-saving drying mode according to outdoor environment. The drying characteristics of shiitake mushroom, energy consumption level and running characteristics of system under five drying modes were investigated systematically. The drying modes were independent solar drying system (ISDS), independent closed heat pump drying system (ICHPDS), and SAHPDS of closed, open and semi-open modes. The results concluded drying system performed well in each mode. In ISDS, inlet air temperature of drying chamber can reach above 50 °C, heat collection efficiency of solar air collector (SAC) is 0.562 and SMER is 3.56 kg/kWh. In ICHPDS, the average COP is negatively correlated with air temperature and loading capacity, while positively correlated with air speed. In SAHPDS (assisted only by SAC), the average air temperature is 59.17, 62.38 and 60.83 °C in open, closed and semi-open modes at air speed of 3.5 m/s. With the corresponding modes, the heat collection efficiency of SAC was 0.526, 0.223 and 0.434 respectively. The average COP is 3.08, 2.68 and 3.20, which is significantly more energy-saving than ICHPDS mode in order to obtain same air temperature. In the later drying period, it switched to the closed drying mode of SAHPDS (only assisted by solar collector (SC)). In addition, the energy saving rate can reach 37.96% compared with ICHPDS under the same condition. The study provides a guidance and reference for the operation mode switch of SAHPDS with higher energy saving and efficiency. • A new type of well-adapted SAHPDS was proposed. • A more energy-saving drying mode can choose and switch according to outdoor environment. • Five drying modes of system performed well. • In later drying period, the energy saving rate can reach 37.96%. [ABSTRACT FROM AUTHOR]

Reducing building energy consumption and increasing the use of renewable energy are essential to energy conservation. Photovoltaic thermoelectric heat pumps have been considered as a sustainable measure to supply detached houses with hot water, especially those that even do not have access to the power grid. This paper investigates a stand-alone photovoltaic/thermal integrated thermoelectric water heating system (PV/T-TEWH). A dynamic model of PV/T-TEWH is developed and validated. The performance of the system in Lhasa, Beijing, Changsha and Guangzhou is simulated and analyzed respectively, and the economics of the system are compared. Results show that PV/T-TEWH can rely on the electric energy it generates without additional power supply when the current is less than or equal to 1.4 A in Lhasa and 1.0 A in Beijing, Changsha and Guangzhou. The annual total heat gain of the PV/T-TEWH system increases as the operating current increases, but the COP of the system falls with the rise of operating current. When the system is operating at the currents of 0.6 A, 1.0 A, 1.4 A, and 1.8 A, the payback period shortens with the increase of current. Lhasa has the shortest payback period among four cities and it is only 2.2 years when the working current is 1.8 A. The PV/T-TEWH system provides a new method for building hot water supply, especially for detached houses in remote areas. • This paper proposes and investigates a photovoltaic/thermal integrated thermoelectric water heating system (PV/T-TEWH). • A dynamic model suitable for simulating the PV/T-TEWH system is developed and validated. • The annual performance of the system in Lhasa, Beijing, Changsha and Guangzhou is simulated and analyzed. • The economics of the system in different cities are compared. [ABSTRACT FROM AUTHOR]

Ground-source heat pump (GSHP) systems contribute significantly to the reduction in energy consumption and CO 2 emissions. The vast territory, abundant geothermal sources, and different climatic zones of Southwestern and Northwestern China provide significant opportunities for the application of GSHP technologies. In this study, a statistical study was performed to assess the general performances and identify the existing problems of GSHP systems located in the abovementioned areas. Twenty-eight GSHP projects, including groundwater heat pumps, soil-source heat pumps, and surface water heat pumps were selected. Water temperature, energy consumption, coefficient of performance (COP), energy efficiency ratio (EER), and thermodynamic perfectibility were analysed. The energy efficiency of GSHP systems were assessed according to the national standard. In addition, barriers and problems in GSHP applications are discussed herein. It is concluded that the average cooling COPs of SSHP, GWHP and SWHP units are 4.9, 4.7, and 4.2, respectively, with SSHP unit being the highest. The average heating COPs of SSHP, GWHP and SWHP units are 4.3, 4.2, and 4.2, respectively with SSHP unit being the highest. The SSHP has the best performance in both seasons amongst three GSHP types. Furthermore, though 89% of the systems can meet the requirements of national standard, more than 50% of them work at the lowest allowable energy efficiency value. This paper attempts to provide essential clues for the adoption feasibility and technical guidelines of GSHPs in the target areas. • 28 GSHP projects including GWHP, SSHP and SWHP were selected in this study. • The field performance and thermodynamic perfectibility of the GSHPs were analysed. • The energy efficiencies of GSHPs were assessed according to the national standard. [ABSTRACT FROM AUTHOR]

Predicting the heating and cooling (HC) energy performance of a building is essential in the understanding and energy-efficient control of HC systems. The aims of this study were to develop and propose advanced and accurate energy prediction models using deep learning techniques. Also, to assess the importance and the significance of the relevant variables used in the models. The models were developed based on measured data collected in an educational building and were classified into different prediction time groups at 3-min, 15-min, 30-min, and 1-h time intervals. The inputs used in the models for the HC system and the EHP were selected through a variable selection process based on domain knowledge and correlation analysis. The results also indicate that the operational factors of the HC system had greater influence on the energy consumption than the indoor and outdoor temperatures. The performances of developed models indicate that a deep learning approach can be effectively applied to predict and understand the electric energy consumption of a HC system. Furthermore, the variable selection process and the important variables identified through it can be applied to energy prediction of HC systems in other buildings. • Deep learning approaches with variable selection process was proposed and validated. • The proposed approach accurately predicted building energy consumption and COP. • The variable selection method was useful in developing energy prediction models. • The important variables for the prediction model were identified. [ABSTRACT FROM AUTHOR]

In the present study an experimental investigation is carried out to predict the performance of ground source heat pump systems with using different soil type under Karabuk prevailing conditions. A series of experiments were conducted on designed and produced experimental test rig. This study examines the effect of five different soil types on the performance and energy consumption of a heat pump. The experimental analysis showed that the evaporator capacity provided by sand was 46% and 42% higher than the capacity provided by red soil at the air-flow rates of 0.087 kg/s and 0.015 kg/s, respectively. In terms of the condenser capacity, sand provided 46% and 30% higher capacity than red soil at the air-flow rates of 0.087 kg/s and 0.015 kg/s, respectively. On the other hand, red soil consumed 8% and 6% less energy than sand at the air-flow rates of 0.087 kg/s and 0.015 kg/s. The capacities provided by other soil types and their energy consumption ranged between these values. In terms of the COP values, red soil provided 6% higher performance than sand and humus soil at the air-flow rates of 0.087 kg/s and 0.015 kg/s. The performance values obtained with other soil types ranged between these values. [ABSTRACT FROM AUTHOR]

• The basics of single-stage continuous absorption systems are explained. • The different studied working pairs in the literature are presented. • A performance comparison for the different systems is performed. • The advantages and disadvantages of each working pair are discussed. The global energy demand is increasing at alarming rates. Until 2040, most of this energy will still be coming from fossil fuels, which generate pollution and global warming, thereby increasing the need for cooling (higher energy demand) and creating a vicious circle. Absorption systems represent a possibility for contributing to the reduction of fossil fuels consumption and CO 2 emissions. These systems can run on renewable energies and heat waste; however, to date they possess high initial investment costs. The present review offers an up-to-date global overview of the small-capacity (≤ 50 kW) single-stage continuous absorption systems operating on binary working fluids for cooling from the theoretical, experimental, and commercial points of view, with a special focus on the comparison of cycle performance between the different families of refrigerants and working pairs. The main objective is to provide information for a good understanding of the evolution of these systems over the past 40 years as well as the main advantages and disadvantages of using different working pairs. [ABSTRACT FROM AUTHOR]

Domestic refrigerators have become an indispensable part of the modern life. Since they are connected to the electric mains and operate throughout the day and year, they consume a lot of energy. Several experimental studies show that the addition of phase change material in the refrigerators at various locations improves the energy efficiency of the refrigerators. In this work, an experimental study was conducted to explore and reveal the improvement in energy efficiency of a small-scale refrigeration system when PCM was applied between the evaporator coil and the insulation. It was observed that the addition of PCM for a thickness of 0.03 m could reduce the heat ingress inside the evaporator by 15-19%. Moreover, the compressor ON cycle time and the temperature fluctuation inside the freezer cabinet were also relatively lesser. The per day energy consumption was reduced by 15.7-17.3% and the improvement in COP was found to be 17.4% with the addition of PCM. The refrigeration system was able to retain its desired temperature level for a period of 5 h even after the power supply was switched OFF. This idea of incorporating PCM between coil and insulation could be extended to household refrigerators so as to reduce the energy consumption. This would come handy in case of power outages which are very common in places having low grid reliability. [ABSTRACT FROM AUTHOR]

Domestic refrigerator is one of the major energy-consuming appliances, and the enhancement of its energy efficiency plays a vital role in implementing the energy conservation policies and green building concepts in residential sector. The major strategies used to improve the performance of domestic refrigerators are the replacement of existing components, use of alternative refrigerants and the reduction in condensing pressure. Therefore, in this work, the conventional air-cooled condenser has been replaced with water-cooled condensers such as shell-and-coil and brazed-plate heat exchangers to maintain a low compression ratio and condensing pressure. The performance of a domestic refrigeration system retrofitted with water-cooled condensers has been studied using experimental methods. The result showed that the system with water-cooled condensers reduces the pull-down time and the per day energy consumption by 70% and 3.5%, respectively. Moreover, the proposed system can improve the COP and exergy efficiency by 6.4% and 4.9%, respectively. Compared to shell-and-coil heat exchanger, the system with brazed-plate heat exchanger can reduce irreversibility and TEWI by 3.9% and 3.7%, respectively. In this study, the system with brazed-plate heat exchanger showed better performance than the shell-and-coil heat exchanger for all operating conditions. [ABSTRACT FROM AUTHOR]

Today, the use of heat pump systems and their application in drying is increasing day by day. For this reason, the type of heat pump, the choice of heat pump and the type of refrigerant to be used in the heat pump are very important. In study, air source (HAD), ground source (GSHPD), chemical source (CSHPD) and hybrid source heat pump dryer are included. Solar assisted air source heat pump dryers (SAHPD), such as improved quality control, lower energy consumption, high coefficient performance and high thermal efficiency have been provide many advantages than the other heat pump dryers. [ABSTRACT FROM AUTHOR]

In this study, an existing laboratory heat pump is converted to a refrigeration unit in order to evaluate efficiency, power consumption, pressure and temperature variations and optimal charge amount of the system in new mode using refrigerant R-407C. Refrigerant charge amount has a key role in the terms of performance, operating cost (regarding to the charge reduction and energy consumption) and environmental concerns in all heat pump and refrigeration systems, which work on the same principles. Heat pump charge amount is the subject of many research, but less studies have been done in the case of refrigerators and freezers where the system works in the transient condition, on the contrary to the heat pump units. Although this study has been devoted to a detailed attempt to examine the possibility of converting the heat pump into the refrigerator, energy aspects of the whole system and the compressor have been analyzed under different working conditions. In the installed setup, the COP value of the system is tested with charge amount between 1 kg and 7 kg, but obtained results show that, this value is so lower than that of heat pump unit due to restricted energy source in cooling chamber. [ABSTRACT FROM AUTHOR]

Recently, Egypt is facing an energy problem due to the increase in consumption and population. There are two ways to face this issue; first, the world should be more interested in renewable energy resources and the second is the efficient use of energy. Refrigeration and air conditioning systems have a high rate of electrical power consumption. For that, the objective of the present work is to enhance the performance of the vapor compression cycle as well as to reduce the energy consumption resultantly. To achieve these goals, the performance of a vapor compression cycle with nanomaterials additives to the primary loop of refrigeration (refrigerant loop) is investigated experimentally. Mineral oil and polyol ester oil with Al2O3 nanomaterials additives are used to enhance the performance in the vapor compression cycle with R-143a refrigerant. The stability of nanofluids was first tested by using sedimentation test. The results showed that the optimum concentration for nanolubricant is 0.1% mass percentage. Results revealed that the refrigerant heat transfer coefficient increased by 22% maximum when nanofluids were used. Moreover, exergy efficiency increases by 20% when mineral oil and Al2O3 nanoparticles were used. The experimental results indicate that R-134a and mineral oil with Al2O3 nanoparticles enhance the vapor compression cycle performance by 22.5% theoretically and 10% actually with 10% less energy consumption. These results were obtained with 0.1% mass fraction of nanolubricant oil. Moreover, experimental results indicate that the polyester oil with Al2O3 nanoparticles mixture has better performance than mineral oil with Al2O3 nanoparticles mixture by 7.5% in theoretical COP and 19.5% in actual COP. [ABSTRACT FROM AUTHOR]

Temperature difference between the evaporator and the product during a freezing process is one of the sources of irreversibility. Application of three-steps evaporator temperature during the freezing course is expected to lower the irreversibility and improve energy efficiency of the system. The purpose of this research is to analyze the energy and exergy efficiency of a refrigeration system with three-steps temperature for freezing process. The experiment was conducted using laboratory scale freezer equipped with three expansion valves to provide the required temperature level at each step. Thermodynamic properties of the refrigerant during the process were obtained by using Engineering Equation Solver (EES). The results show that freezing with three temperature steps gave total COP of 2.66, higher than COP of the fixed temperature process, which was 2.40. Exergy analysis shows that average irreversibility of the compressor with stepping temperature operation was higher than that of fixed temperature operation, which was mainly affected by the higher irreversibility during the first step of the stepping temperature operation. It is concluded that compressor work needs to be adjusted to the real work requirement by using an equipment such as inverter in order to take advantage of the stepping temperature operation in terms of more efficient use of power by the compressor. [ABSTRACT FROM AUTHOR]

Highlights • A full-scale GSHP experiments is conducted for two ventilation parameters. • Gaussian process regression employed to deal with coupled effect of parameters over power change. • The minimum power is derived along with corresponding setpoint when reaching best thermal performance. • An efficient control is identified achieving 0.35 kW(19.77%) energy saving with virtually no PMV deterioration. Abstract This study focuses on the concurrent changes of the PMV-power demand triggered by the two common control variables of the ground-source heat pump (GSHP) system, namely the ventilation rate and supply water temperature from the compressor, to explore their potentials to achieve energy saving while maintaining indoor thermal comfort level. Using the two variables as the intermediate parameters, a set of full-scale experiments was conducted to obtain the resultant changes of indoor environmental conditions and power demand across design space. Statistical models for heat supply and coefficient of performance (COP) of the GSHP system were constructed from the Gaussian process regression (GPR) to derive the PMV and power change separately. Afterwards, the response surface of PMV-power demand were calculated with different configurations of the two control variables. It is identified that the system COP significantly changed from 1.7 to 6.6 due to parameters variations. Such a change in the COP results in non-linearity for the PMV-power demand curves where lowest power demand can be determined with improvements in the PMV level by properly tuning both ventilation parameters. The projection of the PMV-power demand response surface creates the frontier of the power demand for a given PMV level indicate a potential strategy for the GSHP system. For instance, we identified that under the thermally-neutral condition criteria the GSHP system is operated at a power demand of 1.77 kW. However, by changing the ventilation rate and supply water temperature, 20% energy consumption reduction can be achieved with a nearly-same thermal comfort (−0.07 PMV). Finally, the potential efficient control for the GSHP system with the help of the PMV-power demand curves tool is revealed and discussed. [ABSTRACT FROM AUTHOR]

Highlights • The energy performance of liquid chiller is compared using R1234yf and R134a. • The Buckingham π-theorem was applied to modeling drop-in. • The predicted and experimental data are correlated in order to study the accuracy of the model. • R1234yf shows that COP reduces about 2%–11.3% taking R134a as baseline. • Indirect emissions are similar for R1234yf and R134a using several energy sources. Abstract This paper presents a model for a variable-speed liquid chiller integrating a compressor model based on Buckingham π-theorem to accurately predict the system performance when R134a is replaced with R1234yf, using a wide range of data obtained from an experimental setup. Relevant variables such as temperature, pressure, mass and volumetric flow rates, compressor power consumption and rotation speed were measured at several positions along the refrigeration and secondary circuits and were used to validate the developed model. Model results show that cooling capacity and power consumption predicted values are in good agreement with experimental data, within ±5%, being slightly higher for the deviation obtained for R134a than for R1234yf. Moreover, model results indicate that R1234yf has a reduction of coefficient of performance (COP) compared with R134a (between 2 and 11.3%), and that R1234yf COP reduction is diminished at intermediate volumetric flow rate and higher inlet temperature for the evaporator secondary fluid, respectively. On the other hand, an environmental analysis based on TEWI (total equivalent warming impact) method showed that direct emissions are almost negligible for R1234yf. However, there are no environmental benefits in terms of indirect greenhouse gas emissions using R1234yf without system modifications (as for instance the addition of internal heat exchanger or R1234yf new design components), which are required to reduce the liquid chiller climate change contribution using it as low GWP alternative in comparison with the typically used R134a refrigerant. [ABSTRACT FROM AUTHOR]

The electrical performance of photovoltaic (PV) panel is affected by PV cell temperature. The lower PV working temperature leads to higher electrical efficiency and more power outputs. In this paper, heat pipes are used to absorb heat from PV panel for cooling, meanwhile, the absorbed heat is made full use for producing hot water with the combination of heat pump. A heat pipe PV/thermal (PV/T) heat pump system is proposed in this paper. The performance of the system is tested and the electrical performance between PV/T panel and traditional PV panel is compared under the heating mode and heat charging mode. The results show that the daily average values of electrical efficiency, thermal efficiency, COPth and COPPV/T are 12.2%, 33.9%, 2.78 and 3.40 in heating mode respectively, while the values are 12.9%, 25.3%, 1.96 and 2.52 in heat charging mode. The performance of heating mode is better than that of heat charging mode. The electrical efficiency of PV/T panel is improved relatively by 25.7% and 14.2% compared with traditional PV panel under the heating mode and heat charging mode, respectively. [ABSTRACT FROM AUTHOR]

A heat pump dryer can save more energy than other dryers since its drying efficiency is 2-3 times higher than that of other types of dryers. However, the lower bound of evaporating temperature for an R134a heat pump cycle ranges from 5 to 10 °C, when the outdoor air temperature closely approaches the evaporating temperature, it experiences reduced efficiency and ultimately becomes inoperable. To address this issue, a cascade heat pump dryer equipped with a solar collector was considered in order to examine the operability and efficiency of the heat pump cycle, depending on changes in the outdoor air temperature in wintertime. The changes in cascade cycles, depending on the temperature in a drying chamber, were also observed. The results showed that the average coefficient of performance (COP) of the cascade heat pump dryer was approximately 2.6 under the temperature range of -10 to 20 °C. An electrical heater whose COP is less than one should be used in that temperature range. It was also found that COP of the dryer increased by approximately 35% when using a solar collector under a low outdoor air temperature environment. [ABSTRACT FROM AUTHOR]

The performance of zero ozone depletion potential refrigerants is investigated when retrofitted in R22 based air conditioning system. The options evaluated are R407C, R417A, R422D, R427A, and R438A. In order to arrive at most suitable alternative(s) to R22, energy and exergy performance of candidate refrigerants is carried out and compared against that of R22. The COP and exergy efficiencies showed that none of selected refrigerant is as efficient as R22 however their values suggests that each may be considered as potential substitute for retrofitting. Having comparable COP to others but low cooling capacity of R417A makes it less attractive. With comparatively reduced COP, lowest exergy efficiency and highest mass-flow rate, makes R422D the least desirable option. The R407C, R427A, and R438A emerged as most attractive substitutes. The lower discharge temperatures of substitutes will enhance the compressor life. Further, for substitutes there may be a possible change out of expansion valve. [ABSTRACT FROM AUTHOR]

The utilization of waste heat instead of fuel combustion is effective in reducing primary energy consumption to mitigate global warming problems. As waste heat sources are not necessarily located close to areas of heat demand, one of the difficulties is that waste heat must be transferred from the heat source side to the heat demand side, which may require the transportation of heat over long distances. From this point of view, we proposed and examined a new idea of heat transportation using ammonia-water as the working fluid in the system named the Solution Transportation Absorption chiller (STA). Our previous studies of the STA were mainly based on the experimental investigation with the STA facility where the cooling power was 25 RT (90 kW). Thus, the Coefficient of Performance (COP) of STA was found to have almost the same value of 0.65 with conventional absorption chillers without depending on the transportation distances. The simulation using AspenHYSYS also examined the same experimental condition. The experimental data showed good agreement with the simulation calculation. In this study, we examined the large-scale cooling power of the STA on the simulation. The intention of this study was to analyze sensitivity with large cooling capacities, the examined cooling powers were from 90 kW (25 RT) to 3517 kW (1000 RT). All cooling power achieved around COP 0.64 including pump power consumption. In addition, we performed a dynamic simulation. The results showed that pipeline size did not affect the cooling capacities and mass flow rates. Furthermore, the stability time of the cooling capacities and mass flow rates were almost the same regardless of the pipeline size and cooling capacity. In other words, the STA may achieve the same COP despite having various complex conditions compared with the conventional absorption chiller. [ABSTRACT FROM AUTHOR]

Refrigerated seawater (RSW) cooling using CO 2 based refrigeration is a relatively new technology that shows promising performance in cold climates. For being a refrigerant CO 2 has a low global warming potential (GWP) and is therefore recognized as an environmentally friendly alternative if the unit is competitive on energy efficiency. However, RSW systems with CO 2 have a significant reduction in energy efficiency if operated in warm seawater due to its low critical temperature. This study investigates the impact ambient temperature and precooling processes have on performance. The results show that for a fixed process design, lower ambient temperature in the Barents Sea results in an average COP of 5.0 compared with 3.0–3.5 in the Mediterranean Sea, or alternatively, that a ship can operate with RSW tanks that are approximately three times bigger if ambient seawater temperature is 10   °C compared to 20   °C. The study also finds that for a fixed ambient temperature case, the RSW tank can be 3.6–1.8 times larger if one third of the tank volume is precooled. [ABSTRACT FROM AUTHOR]

The solid desiccant heat pump (SDHP) system is a novel thermodynamic appliance, intended to improve the energy efficiency of the conventional air conditioning. In the SDHP, desiccant coated heat exchangers are adopted as the evaporator and the condenser instead of the conventional sensible heat exchangers. This article aims to investigate the performance of the SDHP under typical weather conditions. Experiments are conducted to evaluate the system in terms of the supply air condition, the electricity consumption and the coefficient of performance (COP). The experimental results show that the system can obtain high COP and improved supply air quality. With the outdoor air of 36.3 °C, 23 g/kg, it can provide cold and dry supply air of 26 ° C, 8.9 g/kg and the corresponding COP reaches to 7.0. In winter, the system can realize heating and humidification simultaneously. With the outdoor air of 9.4 °C, 4.4 g/kg, the supply air from the system is 26.6 ° C, 14.1 g/kg and the COP reaches up to 6.3. [ABSTRACT FROM AUTHOR]

In present study, an attempt has been made to review the applications of artificial neural network (ANN) for predicting the performance of solid desiccant cooling systems. Different types of neural networks are applied to model the solid desiccant cooling systems. With use of experimental data, an ANN model was developed which is based on different algorithms. Available experimental data were divided into two categories for training and testing of the ANN model. Later on, trained ANN model was tested for predicting the performance of system based on various input and output parameters such as air stream flow rates, temperatures and humidity ratios, pressure drop, dehumidifier effectiveness, cooling capacity, regeneration temperature, power input, coefficient of performance etc. So, present review proposes the use of ANN based model to simulate the relationship between inlet and outlet parameters of the system. The ANN predictions for these parameters usually agreed with the experimental values with higher correlation co-efficient. The previous studies show that ANNs can be used with a higher precision in guessing the performance of solid desiccant cooling systems. This review is useful for making opportunities to further research of ANNs and its feasibility which is becoming common in the coming days. [ABSTRACT FROM AUTHOR]

Through the experiment, the coefficient of performance (COP) of air source heat pump with changing water temperature in the tank was studied, when the ambient temperature remains almost unchanged. Then the COPs of the air source heat pump at different supply and return water temperatures were calculated out based on the tested model.The results showed that COP equals 3.1, when the supply/return? water temperature was 21℃, and it would decrease by 0.04 with every 1℃ temperature dropping; when the water temperature reached 55℃, COP stood at only 0.74, and the water temperature rose 1℃, COP reduced 0.12. For the supply and return water of 50℃ / 40℃ compared to that of 50℃ / 45℃, COP increased by 10.3%; similarly, for 45℃ / 40℃ compared to 50℃ / 40℃, COP increased by 12.9%. The system COP decreased with increasing supply and return water temperatures, and the rate of reduction was affected by the heat loss of the piping system. [ABSTRACT FROM AUTHOR]

To improve the energy efficiency and environment friendliness of space heating in rural areas of North China, air source heat pump was appointed to be suggested substitution for existing small coal boilers. The utilization of air source heat pump for space heating in North China still face challenges and problems such as heating capacity, frosting, and low COP. High efficient refrigerant should be developed to further optimize the air source heat pump for space heating. Aimed to find the refrigerant which has higher COP in dynamic heating process, different pure HFC refrigerants including R32, R134a, R143a, and R152a were analyzed and compared. The results show that R152a has higher COP than other refrigerant candidates, and R152a could be a reasonable choice of pure HFC refrigerant for space heating air source heat pump in rural residential buildings of North China. [ABSTRACT FROM AUTHOR]

We herein evaluate the use of a chemical heat pump (CHP) for upgrading waste heat produced during the hydration of CaCl 2 . The reactor module employed was an aluminum plate-tube heat exchanger bearing corrugated fins, a porous Ni plate, and the CaCl 2 sample in the form of a packed bed. The volumetric heat output and input characteristics of the reactor module were evaluated experimentally, the coefficient of performance (COP) was calculated for the heat upgrading cycle, and the hourly heat output for the system was determined. We found that the obtained waste heat could be upgraded from 100 to 155 °C, and the maximum volumetric heat output and input obtained were 380 and −280 kW·m −3 , respectively. It was therefore apparent that a high performance reactor module could be obtained by reducing the heat and mass transfer resistances in the packed bed. In addition, using this reactor model, a coefficient of performance (COP) value of 0.48 was achieved for the heat upgrading cycle. Furthermore, upon switching the step time of the heat release and storage steps, an hourly heat output of 72 kW h·m −3 was achieved with a reaction fraction of 0.8. Our results therefore demonstrate that the use of our CHP system for upgrading waste heat would be expected to improve the energy efficiencies of industrial processes. [ABSTRACT FROM AUTHOR]

Vapor compression refrigeration systems consume high-grade energy and contribute to global warming and ozone layer depletion due to the environmentally unfriendly refrigerants. The use of hydrocarbons offer good drop-in replacements for the existing halogenated refrigerants in terms of environmental impacts and energy consumption. In this study, a review of the previous studies carried out with hydrocarbons as alternative refrigerants in refrigeration, air conditioning and heat pump, and automobile air conditioning systems is presented. An attempt has been made to cover the current status, possibilities, and problems related to the use of hydrocarbons as alternative refrigerants. Hydrocarbon characteristics, allowable refrigerant charge, flammable properties, and safety considerations are also presented. In addition, the study contains also a useful amount of information about the refrigerant properties, environmental impacts, and replacement strategy of conventional refrigerants. Results showed that in spite of highly flammable characteristics, hydrocarbons can offer proper alternatives to the halogenated refrigerants from the standpoint of environment impact, energy efficiency, COP, refrigerant mass, and compressor discharge temperatures. Roadmap on the future work needs in this field is presented. Finally, a summary of previous studies and strategies on pure HC, HC mixtures, and HC/HFC blends used for different applications has been presented and discussed in detail. [ABSTRACT FROM AUTHOR]

Domestic refrigeration system is one of the major energy-consuming devices. Improving its energy and exergy efficiencies plays a vital role in the energy conservation strategies on domestic energy sector. One of the methods to improve the performance is the replacement of existing components and operation of the system in low condensing pressure. Therefore, in this work, the conventional air-cooled condenser has been replaced with water-cooled brazed plate heat exchanger. Besides the COP, exergy efficiency and irreversibility in all the basic components of a 190-L domestic refrigerator have been studied. The experimental results show that the COP and exergy efficiency of the proposed system are 52-68 and 46-55 %, respectively. This is higher than that of the conventional system. Moreover, the irreversibility of the proposed system is 34 % less than that of the conventional system, and the exergy efficiency of HC mixture is 4-7 % higher than R134a under similar operating conditions. [ABSTRACT FROM AUTHOR]

Aiming to reduce the throttling loss in the vapor compression refrigeration cycle, a bi-evaporator compression/ejection refrigeration cycle (BCERC) using an ejector as the expansion device was experimentally investigated with R134a refrigerant. The effects of the compressor frequency and the operating conditions on the coefficient of performance (COP) and the amount of exergy destruction of each component were studied. The results were compared with that of the conventional vapor compression refrigeration cycle under the same external operating conditions and cooling capacities. Results showed that the refrigeration cycle with an ejector as the expansion device exhibited lower irreversibility for each component and total system in comparison with the conventional vapor compression refrigeration cycle. The COP and the exergy efficiency of the BCERC were higher than that of the conventional system. The COP and exergy efficiency improvements became more significant as the condenser water temperature increased, the evaporator water temperature decreased and the compressor frequency increased. In the BCERC with a constant frequency compressor, the COP and the exergy efficiency could be improved by 16.94–30.59%, 7.57–28.29%, respectively. The COP and the exergy efficiency of the BCERC with a variable frequency compressor could increase by around 32.64% and 23.32%, respectively. [ABSTRACT FROM AUTHOR]

This study presents a comparative analysis of thermodynamic performance of cascade refrigeration systems (CRSs) for refrigerant couples R41/R404A and R23/R404A to discover whether R41 is a suitable substitute for R23. The discharge temperature, input power of the compressor, coefficient of performance (COP), exergy loss (X) and exergy efficiency (η) are chosen as the objective functions. The operating parameters considered in this paper include condensing temperature, evaporating temperature, superheating temperature and subcooling temperature in both high-temperature cycle (HTC) and low-temperature cycle (LTC). The results indicate that an optimum condenser temperature exists for LTC (T 4opt ) at which COP acquires maximum value. Under the same operation condition, the input power of R41/R404A CRS is lower than that of R23/R404A CRS, and COP opt is higher than that of R23/R404A CRS. The maximum exergy efficiency of R41/R404A and R23/R404A CRSs are 44.38% and 42.98% respectively. The theoretical analysis indicates that R41/R404A is a more potential refrigerant couple than R23/R404A in CRS. [ABSTRACT FROM AUTHOR]

This paper presents experimental investigations carried out to study the effect of magnetic field on energy savings in vapour compression system. Application of magnetic field to fluid flow breaks the molecule resulting in a decrease in the viscosity of the fluid. This drop in the viscosity reduces the pumping power required by the compressor as well as enhances the heat transfer rates in the condenser and evaporator due to increased mass flow rates. The net impact is improvement in the COP of the system. Considering the number of refrigerator and air conditioning systems sold globally every year any improvement in the COP could considerably save the energy bills as well as the energy requirement. The main benefit of this investigation is improvement in the system performance improvement in Evaporator capacity or drops in compressor power or increased COP at no cost i.e. no additional input energy. Only cost involved is the initial cost of magnets to be procured for applying suitable magnetic field. The present work was focused on first establishing the effect of magnetic field on the performance of the vapour compression system and then investigating the impact of magnetic-field strength on COP. The magnetic field strength was varied by increasing the number of magnet pairs applied to the liquid line (from condenser outlet to entry of expansion valve). The COP was initially measured without application of magnetic field, and then magnetic field applied to liquid refrigerant was increased by increasing the number of the magnetic pair from 1 to 5. The strength of each magnetic pair was 3000 gauss. The result obtained showed improvement in COP of the system under investigation. The COP of the system increased up to13.13% for R134a and 21.87% for R600a refrigerant. [ABSTRACT FROM AUTHOR]

Because the coefficient of performance ( COP ) is primarily concerned with the core refrigeration system, using it for optimisation purposes may lead to higher than necessary energy consumption. This hypothesis was studied with a simple equation relating this coefficient to the coefficient of system performance ( COSP ), and with a software model based on an R404A refrigeration system installed in a supermarket in north east England. In both approaches the condenser fan power usage was excluded from the COP but included in the COSP . The results showed that, especially for part load conditions, optimising the core refrigeration system for minimum power consumption led to an appreciably higher overall energy consumption with the implication that the condenser fan and compressor controls should be developed together. When using this holistic approach it was found that energy savings of 4.5% could have been achieved based on six months' data from the installed system. [ABSTRACT FROM AUTHOR]

This paper presents a study on the characterization of the performance of a water-to-water heat pump of 40.5 kW fixed heating capacity under different cycling conditions scenarios. Semi-virtual laboratory experiments were conducted to analyse the influence of inertia from 1.23 to 24.7 L/kW on the efficiency of the heat pump operating at partial load. Different parameterizations in standards were compared to assess their ability to predict the energy efficiency degradation caused by cycling. Performance deterioration at part load was found to be highly dependent on inertia conditions, with non-negligible start-up parasitic effects detected for the heat pump under study, particularly for decreasing inertia. Results suggest that current standards for characterising the performance of systems at partial load, such as the European EN14825, should be reviewed to account for the influence of inertia on equipment performance and for the potential occurrence of start-up efficiency losses for water-to-water heat pumps. An expression is derived in this study for the start-up losses degradation coefficient C d and a single parameterization accounting for different sources of efficiency losses is proposed, together with a simple method to determine degradation coefficients from reduced experimentation. [ABSTRACT FROM AUTHOR]

Nanofluid as a heat transfer fluid has been gaining popularity ever since its inception. Consequently, the researchers and experimentalists from the refrigeration industry could not keep themselves away from the ever growing horizon of nanofluid applications. The research on the refrigerant based nanofluids or a nanorefrigerant is slowly but surely increasing. The boiling heat transfer coefficient data for nanofluids and nanorefrigerants have been inconsistent but, in general, researchers have observed a rise in the boiling heat transfer coefficient that encourages them to pursue their research further in this field. Numerous studies regarding nanorefrigerants have shown that the addition of nanoparticles lead to a better system performance and energy efficiency. This review paper is an attempt to summarise all the aspects of nanorefrigerants such as its preparation, thermophysical properties, pressure drop in nanorefrigerants, boiling heat transfer and performance of nanorefrigerants in various domestic refrigerators. [ABSTRACT FROM AUTHOR]

Air-source heat pumps (ASHP) have been widely used for residential heating due to its energy-saving and high efficiency characteristics. However, the performance of an ASHP reduces as the ambient temperature decreases. In order to investigate the effect of ambient temperature on ASHP performance, an ASHP with an internal heat exchanger (IHX) using R404A as refrigerant was developed and studied at low ambient temperatures. The theoretical simulation was first performed to evaluate the performance of the ASHP with IHX and compared with three different cycles. The simulation results were validated by data available from literature and experimental data in this study. The results showed that the R404A ASHP system with IHX had a good potential for residential heating. Further investigation was performed to compare the performance of the R404A ASHP with and without IHX. The comparison results showed that the performance of the ASHP with IHX was far better than that of the ASHP without IHX. As the ambient temperature decreased from 0 °C and −26 °C, the improvement of the heating capacity of the R404A ASHP with IHX increased from 5.91% to 15.92% while the COP improvement increased from 10% to 20%. This indicated that the IHX technology became more and more effective as the ambient temperature dropped lower and lower. [ABSTRACT FROM AUTHOR]

In view of Kyoto protocol, there is a pressing need to reduce the energy consumption and environmental impacts of domestic appliances. In the total energy consumption of household appliances, domestic refrigerator plays a vital role. Alternate refrigerants and improvement in the performance of the components can contribute to tackle the above issue in a domestic refrigeration system. In this paper, the performance of a domestic refrigeration system with brazed plate heat exchanger as condenser, and working with refrigerants such as R290/R600a and R134a was studied using experimental method. The result showed that the system with water-cooled brazed plate heat exchanger reduces the per day energy consumption of a system from 21% to 27% and increases the COP from 52% to 68%, when compared to conventional system. The compressor discharge temperature and dome temperature are also dampened. For R134a and R290/R600a, the TEWI of the system with water-cooled brazed plate heat exchanger is lower than that of the system with air-cooled condenser by 26.8% and 21%, respectively. Among the refrigerants, R290/R600a showed higher performance than R134a. [ABSTRACT FROM AUTHOR]

The use of efficient refrigerator/freezers helps considerably to reduce the amount of the emitted greenhouse gas. A two-circuit refrigerator-freezer cycle (RF) reveals a higher energy saving potential than a conventional cycle with a single loop of serial evaporators, owing to pressure drop in each evaporator during refrigeration operation and low compression ratio. Therefore, several industrial applications and fish storage systems have been utilized by using multipurpose refrigeration cycle. That is why a theoretical performance analysis based on the exergetic performance coefficient, coefficient of performance (COP), exergy efficiency and exergy destruction ratio criteria, has been carried out for a multipurpose refrigeration system by using different refrigerants in serial and parallel operation conditions. The exergetic performance coefficient criterion is defined as the ratio of exergy output to the total exergy destruction rate (or loss rate of availability). According to the results of the study, the refrigerant R32 shows the best performance in terms of exergetic performance coefficient, COP, exergy efficiency, and exergy destruction ratio from among the other refrigerants (R1234yf, R1234ze, R404A, R407C, R410A, R143A and R502). The effects of the condenser, freezer-evaporator and refrigerator-evaporator temperatures on the exergetic performance coefficient, COP, exergy efficiency and exergy destruction ratios have been fully analyzed for the refrigerant R32. [ABSTRACT FROM AUTHOR]

A test facility for the experimental investigation of the R744 vapour compression rack equipped with a multi-ejector expansion work recovery module was designed and manufactured. A comparison of the R744 multi-ejector refrigeration system with the R744 parallel compression system at the same test facility was carried out based on the energy performance characteristics of refrigeration capacity, power consumption, COP, and exergy efficiency. Apart from the system performance comparison, the influence of the pressure level in the flash tank on the system performance for the two alternatives was analysed. The experimental results indicate COP and exergy efficiency improvements of the multi-ejector refrigeration system up to 7% and 13.7%, respectively. The highest values of COP and exergy efficiency were obtained by a multi-ejector refrigeration system with the tank pressure lift close to the maximum value possible to operate the multi-ejector expansion module. The values of the effective compressor efficiencies were significantly different, depending on the operation module (cooling load and heat rejection conditions). [ABSTRACT FROM AUTHOR]

The R22 refrigerant widely used in refrigerating and air conditioning devices is invariably released to the atmosphere due to reasons such as breakdown and/or translocation. As the sales of new devices operating with R22 are decreasing gradually, refrigerants of such available devices should be changed with the ones that are not depleting the ozone layer. In this paper, the amount of consumed energy, cooling capacity and COP values of R417A, R422A, R422D and R424A, which can be used as alternatives to R22, were determined experimentally for a split type air conditioning device at the ambient temperatures of 35, 38 and 41 °C. Basically, COP values of all HFC refrigerants were found to be smaller than that of R22. It was noted that the most suitable refrigerating fluid was R424A, which can be used instead of R22, since the COP of R424A was smaller than that of R22 by 2.5% only at an ambient temperature of 41 °C. [ABSTRACT FROM AUTHOR]