Performance Of Refrigeration Cycle Research Articles

Experimental optimization of replacing R22 with R417A without any other changes in configuration of residential air‐conditioning systems based on energy and exergy analysis

AbstractIn this paper, the optimal refrigerant mass charge amount of R417A, as a substitute for R22, was experimentally investigated in a split‐type air‐conditioner with no changes in system configuration. Experiments were conducted for both refrigerants over a range of mass charge from 500 to 850 g in a 12,000 Btuh−1 split air‐conditioner as the case study which is a conventional refrigeration system in residential sector of Iran. In order to study the effect of refrigerant mass charge on performance of refrigeration cycle, energy and exergy analysis were performed to determine cooling capacity, energy efficiency ratio (EER) and exergy efficiency. Results showed that the maximum EER for R22 and R417A are 2.48 and 2.41, and the maximum exergy efficiencies obtained for R22 and R417A are around 7.3% and 7%, respectively. Based on both EER and exergy efficiency, the optimum mass charge for R22 and R417A refrigerants are around 640 g and 650 g, respectively. In addition, it was found that under optimal charge conditions, the cooling capacity, EER and exergy efficiency of the system while working with R417A are lower than R22, just by 2.5%, 3%, and 4.5% respectively. Comparison results indicate that R417A can be considered as a suitable substitute for R22, which can almost provide the same performance without need to change the system components.

Performance evaluation of the solar-driven multi-ejector refrigeration cycle without an auxiliary heat source

• Performance of a novel solar-driven multi-ejector refrigeration cycle is evaluated. • The proposed system does not need an auxiliary heat source and cooling system. • System is equipped with an internal heat exchanger, regenerator, and storage tank. • Sensitivity analysis and the system’s parametric optimization are carried out. • 75% lower solar collector area is required by the proposed system. Solar-driven ejector refrigeration (SER) systems have been granted special attention as a green and sustainable replacement for conventional vapor compression cooling systems. However, despite their significant advantages, SER systems suffer from a relatively low coefficient of performance and failure at high ambient temperatures and low solar radiations. Therefore, the need for an auxiliary heat source and cooling system has hindered their adoption in practice. In an attempt to eliminate the need for an auxiliary heat source and cooling system, this contribution puts forward a novel Solar-driven Multi-Ejector Refrigeration (SMER) system with an internal heat exchanger, a regenerator, and a storage tank. A numerical model of the proposed SMER system and a computational fluid dynamics model of the ejector have been developed. The developed model is then used to evaluate the dynamic annual performance of the proposed SMER system through a case study. Shape optimization is also carried out to optimize each ejector based on its specific working conditions. The sensitivity of the system performance to design parameters is also analyzed, and the optimum design parameters are determined. According to the results, the proposed SMER system can provide up to 94% of the required cooling load of the sample building with a 250 m 2 solar collector area. However, the conventional SER system can provide only 71% of the building load. It is also demonstrated that the proposed SMER system requires a 75% lower solar collector area than the conventional SER system to provide 100% of the required cooling load.

Experimental investigations of vapour compression refrigeration system using electrohydrodynamic (E.H.D.) effect

The Vapour compression refrigeration system is most commonly used in a domestic refrigerator, Cold storage, and other cooling devices such as air conditioning. For the improvement in the performance of the vapor compression refrigeration cycle, several improvement methods have been successfully used. Such techniques are classified as Passive, Active, and combined active and passive techniques. In passive techniques, fluid additives or some special geometrical shape such as rough surface, inserts, fins, etc., is required. On the contrary, an active technique requires some external force in the form of electric field, acoustic, or vibrations. In the present research, the electrohydrodynamic (E.H.D.) effect is used to enhance the performance of a vapour compression refrigeration system. In this study, the condenser of the vapour compression refrigeration system is experimentally evaluated for the impact of an electrical body force. By evaluating the result of C.O.P with and without the electrohydrodynamic effect. It is found that the theoretical C.O.P. of vapour compression refrigeration system increases by 10% with the application of the electrohydrodynamic effect.

Comparing and optimizing the potential advantages of a salinity-gradient solar pond for either absorption-based or ejector-based refrigeration cycles combined with thermoelectric generators

This study compares the applicability of two popular refrigeration cycles for air-conditioning, i.e., absorption-based (Model 1) and ejector-based (Model 2), combined with a salinity-gradient solar pond. Indeed, there exists a gap in comparing the performance of solar pond-based refrigeration cycles to which this study intends to respond. In addition, utilizing zeotropic mixtures in an ejector refrigeration cycle integrated with a solar pond and selecting the most suitable zeotropic for such a framework has not been regarded in the literature. Both models are boosted using thermoelectric generators for low-temperature waste heat recovery and electricity generation. Energy, exergy, economic, and environmental investigations with a net present value analysis are implemented, and multi-objective optimization using non-dominated sorting genetic algorithm-II is conducted. As another principal point, this paper performs a case study to illustrate the performance of models regarding an actual climate condition. Results show that using Butane-R143a zeotropic increases the advantages of Model 1; however, Model 2 is the most suitable selection for the solar pond. According to the optimum state, Model 1 possesses exergy efficiency and Levelized cost of products of 17.93% and 0.12 $/kWh, which are 0.84 percentage points and 83% better than Model 2. But Model 2 has a better environmental performance by mitigating 22% further carbon dioxide than Model 1.

Impact of a thermoelectric subcooler heat exchanger on a carbon dioxide transcritical refrigeration facility

To improve the performance of vapour compression refrigeration cycles, the inclusion of a thermoelectric subcooler for low-medium power units has been the focus of recent studies due to its robustness, compactness and simplicity of operation. In thermoelectric systems, it has been demonstrated that the heat exchangers used in the hot and cold side of the thermoelectric modules have a critical impact in the performance of the system. This influence has not yet been studied for thermoelectric subcooling systems in vapour compression cycles. This work, for the first time, evaluates the impact that the heat exchangers of a thermoelectric subcooler, included in a transcritical carbon dioxide refrigeration cycle, have, in the performance of the refrigeration cycle. The influence is quantified in terms of: optimum working conditions, coefficient of performance and cooling capacity. The results show that, through an optimization of the heat exchangers of the thermoelectric subcooler, the performance improvements on the coefficient of performance using this technology are boosted from 11.96 to 14.75 % and the upgrade in the cooling capacity of the system rises from 21.4 to 26.3 %. Moreover, the optimum gas-cooler working pressure of the system is reduced and the optimum voltage supplied to the thermoelectric modules increases.

Effect of Capillary Tube Shapes on The Performance of Vapour Compression Refrigeration Cycle Using Nano-Refrigerant

Abstract: The main aim of this experimental study was to check the coefficient of performance on the Vapour Compression Refrigeration System by changing the shape of the capillary tube and by changing the refrigerants. Investigated the effect of Nano Refrigerant on the Coefficient Of Performance of Vapour Compressor Refrigeration Cycle. Compared the Coefficient Of Performance on the basis of R-22 (Difluoro-Monochloro Methane (CHF2CL) or R-22) and Al2O3 Nano particles mixed R22.The shape of the capillary tubes and the refrigerants is altered to study its effect on the performance of vapour compression refrigeration cycle. The shapes of Capillary tubes used were Serpentine Shape and Cubic Shape.

Thermodynamic analysis of a novel multi-target temperature transcritical CO2 ejector-expansion refrigeration cycle with vapor-injection

In the present paper, a multi-target temperature ejector-expansion subcooler vapor-injection refrigeration cycle is proposed in order to improve the performance of natural fluid CO2 refrigeration cycles. A thermodynamics model to simulate a two-phase ejector cycle integrating a vapor-injection is first established from the energetic and exergetic perspectives. The behavior of the new cycle is then analyzed, and the adjustment direction of the cooling capacity and the evaporating temperature is pointed out. Furthermore, the new cycle is also compared with the subcooler vapor-injection refrigeration cycle and the ejector-expansion refrigeration cycle. The obtained results show that the behavior of the evaporators is affected by the bypass mass ratio and the entrainment ratio, and the two parameter determines the direction of adjusting the cooling capacity distribution and the evaporating temperature. The COP of the new cycle is about 17.9–29.4% and 2.8–7.8% higher than that of subcooler vapor-injection refrigeration cycle and ejector-expansion refrigeration cycle; the exergy efficiency of new cycle is about 14–28.2% and 3.7–11.3% higher than that of subcooler vapor-injection refrigeration cycle and ejector-expansion refrigeration cycle; and it is also found that the performance of the new cycle is improved more significantly under low cooling temperature and high ambient temperature conditions.

Performance Analysis of Ejector Expansion Refrigeration System on The Basis of Area Ratio

Vapour compression refrigeration system is the conventional way existing for the refrigeration these days. Although to overcome the loses in conventional method there are several ways to improve the performance of vapour compression refrigeration cycle. This paper provides an alternative method of increasing the performance by varying the area ratio of the ejector. As Ejector is the most simple and economical replacement of throttling valve. A Simulation model is developed and parametric study of ejector is done. It was found that there will be increase in performance as area ratio is changed. This cycle is named as Ejector expansion Refrigeration System.

Design and analysis of a novel solar compression-ejector cooling system with eco-friendly refrigerants using hybrid photovoltaic thermal (PVT) collector

• A novel solar cooling system is designed and analyzed. • The solar cooling efficiency increased by 33.1 %. • The COP of the refrigeration cycle is improved by 8.23 %. • R290 has the best performance in the system. World faces cold crunch and solar energy exploitation plays a vital role in facing this problem. This study aims at improving the performance of combined solar ejector vapor compression refrigeration cycles ( EVRC ) with two evaporators using a photovoltaic thermal ( PVT ) collector. The PVT collector supplies the system's required power, such as compressor and water circulator pump. The outgoing water is further used to cool the condenser and subcool the condenser outlet refrigerant to improve the system efficiency. This work also investigates the utilization of the environmentally friendly refrigerants of R1234yf, R600a, and R290 to reduce the global warming issue by replacing the typical R134a refrigerant. The results showed that the optimal water flow rate for the highest system efficiency and the lowest exergy destruction is 0.05 kg/s. With the passage of water (with optimal flow rate), the collector's electrical efficiency, total solar cooling efficiency, and refrigeration cycle performance coefficient ( COP ) can be increased by 11%, 33.1%, and 8.23%, respectively, compared to the non-cooling state. The R290 refrigerant also performs best in terms of maximum efficiency and lowest system exergy destruction, among other refrigerants, with COP and solar cooling efficiency of 3 and 0.52, respectively, which is 4.8% and 4.6% higher in comparison with the R134a.

Effect of Adsorbent on the Performance of Double Effect Adsorption Refrigeration Cycle with Adsorption Heat Recovery

This study investigates the performance of double effect adsorption refrigeration cycle that utilizes the adsorption heat of a high-temperature adsorbent heat exchanger for desorption of a low-temperature one. Because there is a freedom to select an adsorbent for each adsorbent heat exchanger, the combination of adsorbents such as silica gel, FAM-Z01, FAM-Z02 and FAM-Z05 were examined. The temperature of an external heat source was assumed to be 90°C. Dynamic cycle simulation was employed to estimate the performance in terms of coefficient of performance (COP) and specific cooling power (SCP). The results show that the combination of the adsorbents FAM-Z01 and FAM-Z02 for the low-temperature heat exchanger and high-temperature one, respectively, is the most effective to achieve high COP as well as high SCP. The results also indicate that the COP=1.0 is attainable when the mass allocation of the adsorbents and the cycle time are selected appropriately. From the viewpoint of maximizing the cooling power, COP=0.9 is suggested for the best design, where the mass of high-temperature side is equal to the mass of low-temperature side.

Thermodynamic Analysis of Air-Cycle Refrigeration Systems with Expansion Work Recovery for Compartment Air Conditioning

As a requirement for sustainable development, air-cycle refrigeration has received wide attention as a candidate for environmentally friendly air conditioning technology. In this study, the thermodynamic performance of air refrigeration cycles is investigated in compartment air conditioning. The effects of compressor efficiency, expander efficiency, ambient humidity, all-fresh-air supply and ambient pressure on the cycle performance are presented. The effects of compressor arrangement in the high-pressure cycle and the low-pressure cycle are compared. An open-loop high-pressure cycle has a larger COP than that of an open-loop low-pressure cycle but requires larger heat exchange. The performance of air refrigeration cycles with full fresh air is studied, and the influence of fresh air is discussed. Schemes for condensed water recirculation with wet compression are proposed, which can improve the COPs of open-loop low-pressure cycles by 44.7%, 48.8% and 48.4%. In the air conditioning of plateau trains, open-loop high-pressure cycles have slightly lower COPs, but they can supply air with elevated pressure and oxygen concentration.

Enhancing the performance of a CO2 combined refrigeration and power (CRP) cycle driven by engine exhaust gas by using heat exchangers in optimized locations

Carbon Dioxide (CO2) has proven its efficiency as a working medium for power and cooling productions in vehicles and refrigerated trucks driven by engine exhaust gases. The main drawbacks of this system are the high/low critical pressure/temperature of the CO2 which leads to high compressor power and low efficiency. In the present paper two modifications by insertion of two heat exchangers in bottom and top CO2 compound cycles driven by engine exhaust gas are proposed to overcome on these drawbacks. Energy and exergy analysis are used to evaluate and compare their performances with the basic system. The results show that (i) the feasibility of using the proposed systems was justified and has proven potentials of energy and fuel consumption saving compared to traditional engine + stand-alone refrigerator, (ii) proposed modifications on the basic system (System I) by incorporated heat exchangers (System II and System III) has proven its potential for higher energy efficiency and refrigeration capacity and can recover about 18.33%, 20.38% and 19.22% of the energy of the exhaust gases for driven the compound CO2 cycle, (iii) parametric, comparison and optimization studies, showed that the proposed system (system II) has the highest refrigeration capacity, energy efficiency and fuel consumption cost saving with optimal values of 20.4%, 0.1819 kg/kWh, 7.1%, respectively.

Research Summary and Literature Review on Modelling and Simulation of Heat Pumps for Simultaneous Heating and Cooling for Buildings

A heat pump for simultaneous heating and cooling (HPS) is a refrigeration machine by which the productions of heating and cooling energies are simultaneously valorized. This introductory article presents the uses of heat pump productions under the form of an analysis of thermal demands of different types of buildings and a literature review of real installations and experimental systems, which are the basis of the construction of numerical models. The applications of HPSs are diverse: space heating and cooling, domestic hot water (DHW), hot water for desalination process, etc. Means and methods for improving the performance of refrigeration cycles and the management of heat and cold productions are developed, including modeling and simulation. New refrigeration circuit architectures were designed. A focus is paid on refrigerants. Prototypes combining heating-cooling, heating-cooling-DHW and cooling-desalination have been developed, built and tested to validate the models. Even though a strong simultaneity of thermal demands is essential, the results show that HPSs are generally very efficient systems.

Experimental Investigation of Performance of Conventional Vapor Compression Refrigeration Cycle Using Geothermal Cooling in Extreme Hot Weather Conditions

The well-known traditional vapor compression refrigeration cycle is considered to be the most effective technique used in the field of refrigeration and air-conditioning systems. It’s used almost in every facility including industrials, homes and food storages. There are some environmental hazards concerning the use of vapor-compression cycles such as global warming and ozone layer depletion mainly due to refrigerant's leakages. However, it's still considered as a leading technology for its capability of producing high cooling and heating powers with great coefficient of performance. The present work represents an experimental investigation of the effect of the condenser's temperature on the thermal performance of a conventional vapor compression refrigeration cycle. The geothermal cooling technique was introduced and utilized for cooling the temperature of the condenser that operates in harsh climate conditions. The experiment was performed using two additional heat exchangers for enabling heat exchange with geothermal temperature. The first heat exchanger (primary HX1) was connected directly to the condenser while the other one (secondary HX2) was installed inside the geothermal hole intended for heat exchange with the geothermal temperature. These exchangers (HX1 and HX2) were thermally connected via two PVC tubes with straight water circulating inside them (using a DC water pump). The experimental results proved the success of the current utilized method in improving the thermal performance of the system. Cooling the condenser via geothermal cooling has led to a considerable reduction in the temperature of the refrigerant and improved the overall performance of the cycle. The experimental apparatus showed an increase in both cooling capacity and COP by 25% and 21.5%, respectively. In addition, a considerable enhancement in the temperature of the evaporator was accomplished to reach a minimum temperature of 14.5ºC.

Improving the Engine Efficiency Using a New Combined Refrigeration Cycle for Low-Temperature Heat Source (Waste Heat Recovery)

Passenger and commercial internal combustion engines have relatively large dissipated thermal energy sources that can be used for initiating thermodynamic refrigeration cycles at low temperatures while improving engine efficiency. Researchers have focused on combined power-refrigeration cycles in past studies. This paper presents the operation and performance of a new combined refrigeration system driven by waste heat recovery within the internal combustion engines. For this purpose, the effects of several parameters on the performance of the cycle are examined. Results show that an increase in the engine water temperature, exhaust gas temperature, part-load ratio (PLR), generator temperature, as well as adsorption evaporator temperature had a positive effect on the performance of the cycle. However, the rise in condenser temperature of the adsorption cooling system leads to bad performance. Also, the results indicate that the application of the adsorption refrigeration cycle in the combined cooling cycle, along with the increase in the refrigeration cycle performance by up to 65%, also improves the efficiency of the internal combustion engine.

Comparison of experimental performance of absorption refrigeration cycle using NH3/LiNO3+H2O working fluids with different water component proportions

Regarding the working fluids of absorption refrigeration systems, compared with the binary ammonia/water or ammonia/salt solution, the ternary ammonia/lithium nitrate+water solution has some advantages including small viscosities, good heat-transfer efficiency and low crystallization risk. In this paper, four kinds of NH3/LiNO3+H2O solutions with different water component proportions are selected as working fluids, which is No.1(9.6%) < No.2(18.6%) < No.3(27.6%) < No.4(36.9%), and the experimental performance evaluation was conducted on a prototype of absorption refrigeration system driven by exhaust heat. First, experimental tests were carried out with varying operating conditions to evaluate their influences on performance parameters; the detailed experimental parameters operating with No.2 and No.4 working fluids are presented, and the reasons of the experimental results are explained. Then, the experimental results of four ternary working fluids and binary working fluid were compared and analyzed to evaluate the influences of water mass fraction. Compared with NH3/LiNO3, the cooling capacities of No.1, No.2, No.3, No.4 increased by 10.6%, 17.8%, 24.8%, 26.4%, respectively; the logarithmic mean temperature difference of the solution heat exchanger decreased by 1.2 K, 2.0 K, 2.6 K, 3.9 K, respectively. The comparison results indicate that, for the working fluid with larger water mass fraction, it has better heat and mass transfer characteristics, the system can produce larger cooling capacities and has lower required driven temperatures of heat sources, but the overall coefficients of performance hardly changed with the water mass fraction. The experiments and comparison results provide significant references in practical applications for the selection of working fluids of the absorption refrigeration systems.

ASSESSMENT OF THE PERFORMANCE A VAPOUR COMPORESSION. REFRIGERATION CYCLE WORKING WITH AMMONIA

his paper is a part of the efforts done in order to analyse the performance of vapour compression refrigeration cycles. These technologies are used with a high rate in marine refrigeration and are responsible for important amounts of energy consumptions. The obtained results are indicating the fact that the performance of the cycle is decreased when increasing the condensation temperature and keeping constant the evaporation temperature. Gains in the performance are obtained when degrees of superheating and sub cooling are increased, resulting that the cycle with superheating and sub cooling is superior to the one without these two processes. Ammonia or (R717) is a refrigerant often used on board the ships due to its very good thermodynamic properties. Moreover, the concern regarding the environment and the fact that ammonia is a natural refrigerant, offers to this refrigerant the chance to be adopted in the future plants, on board of new ships. The performance of an ammonia based cycle is discussed in terms of coefficient of performance (COP) and exergy efficiency, the theory of the first and second laws of thermodynamics being fundamental.

Analysis of vapor compression refrigeration cycle using advanced exergetic approach with Taguchi and ANOVA optimization and refrigerant selection with enviroeconomic concerns by TOPSIS analysis

In this study, TOPSIS analysis was applied to decide the optimum refrigerants with cost, safety, environmental and enviroeconomic concerns along with thermophysical properties. A vapor compression refrigeration cycle performance was investigated with the statistical and thermodynamic approaches. COP, exergy efficiency, total, avoidable, and unavoidable exergy destruction rates were calculated for various experimental designs. According to the relative proximity to the ideal solution, the best refrigerants for the system were determined as R513a, R134a, and R448a, respectively. The optimum parameters for the greatest COP and exergetic performance were calculated as A2B3C1D3E3F1. In the optimum case, the best COP and exergy efficiency of 2.65 and 10% and the lowest total exergy destruction of 0.34 kW were achieved for R134a. These are larger than all other 27 experimental patterns. The parameters having an impact on the COP, exergy efficiency, and total exergy destruction rate were found as TEVA > TCON > Refrigerant > ηCOM,H > ηCOM,L > Pin (B > C > A > E > D > F). The evaporator temperature is the most effective parameter on the performance with about 42.8% for the performance. It is followed by that of condenser and refrigerant to be 32.5% and 13.8%. The most effective parameters for the avoidable exergy destruction rate were high- and low-pressure compressors efficiencies, evaporator temperature, and condenser temperature, respectively.

Numerical modeling of droplets injection in the secondary flow of the wet steam ejector in the refrigeration cycle

Steam ejector plays a key role in the refrigeration system. The water has been used as a working fluid because water is more economical and non-toxic. The operating fluid often enters the evaporator as a water liquid and droplets evaporate by absorbing heat. Cooling load changing causes the vapor in the outlet of the evaporator to be accompanied by droplets. Therefore, there are droplets at the inlet of secondary nozzle and flow should be simulated as a wet steam flow with injection droplets at the secondary flow. In this paper, the effects of droplets injection at secondary flow have been investigated on the performance of the refrigeration cycle. For this purpose, the Eulerian-Eulerian method has been used and the results have been validated with experimental data. Six cases are considered with different wetness and number of droplets in the secondary flow. The results of case 6 show COP, T¯outlet, and ER decrease about 22.93%, 15.66%, and 22.93%, respectively. In addition, the steam accompanies by droplets at the outlet of ejector. Therefore, it is essential for designers and operators to model and consider the effects of the droplets on the wall erosion to optimize the wet steam ejector and refrigeration cycle performance.

Exergy and exergoeconomic analyses of an ORC-assisted vapour compression refrigeration cycle

In this study, the thermodynamic performance of a vapour compression refrigeration cycle (VCRC) in which an organic Rankine cycle (ORC) has integrated and that generates electricity by utilising a geothermal source is investigated. The system's energy and exergy performance has evaluated by using various refrigerants used in the ORC system, depending on the evaporator (ORC) temperature (70°C-120°C), and an exergoeconomic analysis has performed to determine optimum operating conditions. As a function of the refrigerant and evaporator temperature, the coefficient of performance (COPsys) of the integrated system has varied between 0.55 and 1.01, whereas the exergy efficiency has varied between 14.20% and 20.16%. The unit exergy cost of the cooled air has been determined as 27.22 USD/GJ under the optimum operating conditions.