Experimental study of new refrigerant mixtures to replace R12 in domestic refrigerators

An experimental study on the replacement of R12 in domestic refrigerators by new hydrocarbon/hydrofluorocarbon refrigerant mixtures has been carried out. Parameters and factors, affecting the performance characteristics of these refrigerants, based on experimental data have been compared to those of R12. The results show that butane/propane/R134a mixtures provide excellent performance parameters, such as coefficient of performance of refrigerator, compression power, volumetric efficiency, condenser duty, compressor discharge pressure and temperature, relative to a 210 g charge of R12. In addition, the results support the possibility of using butane/propane/R134a mixtures as an alternative to R12 in domestic refrigerators, without the necessity of changing the compressor lubricating oil used with R12.     

Investigation of refrigerating system with R12 refrigerant replacements

This paper deals with the influence of R12 working fluid replacements on energy efficiency and global warming expressed by values of Coefficient of Performance (COP) and Total Equivalent Warming Impact (TEWI). Experimental investigations are presented which relate the use of refrigerants R134a, R401A, R409A, R22 and the mixture of R134a with R12 to the values of COP and TEWI of refrigerating system in comparison with R12 application. It is shown that the use of R134a, R401A and R409A refrigerants enables the increase of COP coefficient and significantly reduces the value of TEWI in comparison with R12 application.     

Experimental investigation of R290/R600a mixture as an alternative to R134a in a domestic refrigerator

R134a is the most widely used refrigerant in domestic refrigerators. It must be phased out soon according to Kyoto protocol due to its high global warming potential (GWP) of 1300. In the present work, an experimental investigation has been made with hydrocarbon refrigerant mixture (composed of R290 and R600a in the ratio of 45.2:54.8 by weight) as an alternative to R134a in a 200 l single evaporator domestic refrigerator. Continuous running tests were performed under different ambient temperatures (24, 28, 32, 38 and 43 °C), while cycling running (ON/OFF) tests were carried out only at 32 °C ambient temperature. The results showed that the hydrocarbon mixture has lower values of energy consumption; pull down time and ON time ratio by about 11.1%, 11.6% and 13.2%, respectively, with 3.25–3.6% higher coefficient of performance (COP). The discharge temperature of hydrocarbon mixture was found to be 8.5 to 13.4 K lower than that of R134a. The overall performance has proved that the above hydrocarbon refrigerant mixture could be the best long term alternative to phase out R134a.     

喷射制冷系统工质性能综合比较

在比较制冷工质的优劣时,不仅应考虑系统COP,还应考虑循环泵的耗功及压力容器中的压力水平。根据饱和蒸气压将八种环境友好型制冷工质分为四组(R141b&R123,R600a&R142b,R134a&R152a,R290&R717),分组的依据是每组制冷工质的饱和蒸气压曲线非常相近。比较结果表明,R123和R141b、R142b和R600a的热力性能都非常相近,但R123和R600a对环境的影响更小;R152a相比R134a,具有更低的压力和循环泵功、更小的环境影响,但性能系数却更大。     

Thermodynamic analysis of R422 series refrigerants as alternative refrigerants to HCFC22 in a vapour compression refrigeration system

In the present study, the first and second law analysis of R422 series refrigerants (R422A, R422B, R422C and R422D) is presented as an alternative to HCFC22. A computational model, developed in engineering equation solver software, is employed for comparing the performance of these refrigerants in vapour compression refrigeration cycle. The thermodynamic properties of the R422 series refrigerants are computed using Refprop version 7.0. The parameters computed are volumetric cooling capacity (VCC), compressor discharge temperature, coefficient of performance (COP), exergetic efficiency and efficiency defects in system components. The results indicate that VCC, COP and exergetic efficiency for HCFC22 are higher in comparison with R422A, R422B, R422C and R422D. The efficiency defects in the condenser are largest followed by throttle valve, compressor and evaporator. Thus, the design improvement of condenser is of utmost importance to reduce the overall irreversibility and improve the system performance. Copyright © 2009 John Wiley & Sons, Ltd.     

Thermodynamic performance of R502 alternative refrigerant mixtures for low temperature and transport applications

In this study, two pure hydrocarbon refrigerants, R1270 (propylene) and R290 (propane), and three binary mixtures composed of R1270, R290 and R152a were tested in a refrigerating bench tester with a scroll compressor in an attempt to substitute R502, which is used in most low temperature and transport refrigeration applications. The test bench provided 3–3.5 kW capacity, and water and water/glycol mixture were employed as the secondary heat transfer fluids. All tests were conducted under the same external conditions, resulting in the average saturation temperatures of −28 and 45 °C in the evaporator and condenser, respectively. The test results showed that all refrigerants tested had 9.6–18.7% higher capacity and 17.1–27.3% higher COP than R502. The compressor discharge temperature of R1270 was similar to that of R502, while those of all the other refrigerants were 23.7–27.9 °C lower than that of R502. For all alternative refrigerants, the charge was reduced up to 60% as compared to R502. There, of course, was no problem with mineral oil, since the mixtures were mainly composed of hydrocarbons. Since some of them are mixtures, one can change their compositions a little to suit various needs in many applications without significant deterioration of the performance. Overall, these alternative refrigerants offer better system performance and reliability than R502 and can be used as long term substitutes for R502 due to their excellent environmental properties.     

Alternatives to HCFC-22 for air conditioners

Some selected fluids have been assessed for their suitability as alternatives to HCFC-22 for air conditioners. Only those refrigerants with zero ozone depletion potential are considered. NIST CYCLE_D has been used for the comparative thermodynamic analysis. Among the refrigerants studied (HFC-134a, HC-290, R-407C, R-410A, and three blends of HFC-32, HFC-134a and HFC-125), HFC-134a offers the highest COP, but its capacity is the lowest and requires much larger compressors. The characteristics of HC-290 are very close to those of HCFC-22, and compressors require very little modification. Therefore, HC-290 is a potential candidate provided the risk concerns are mitigated as had been accomplished for refrigerators. For retrofitting, R-407C is probably the best candidate.     

-150℃四级自复叠制冷系统的实验与分析

搭建了一种四级自复叠制冷系统,采用由R600a、R134a、R23、R14、R50和R740等6种工质组成的非共沸混合制冷剂,经过调试与实验,成功得到了-150℃的柜内温度。讨论了该低温箱体的降温特性、压缩机的运行特性和混合工质的节流特性。研究表明,压缩机的吸、排气压力和温度关乎系统能否安全稳定的运行,每级毛细管的长度关乎系统的降温特性。     

Experimental study of R152a and R32 to replace R134a in a domestic refrigerator

This paper presents an experimental study of R152a and R32, environment-friendly refrigerants with zero ozone depletion potential (ODP) and low global warming potential (GWP), to replace R134a in domestic refrigerator. A refrigerator designed and developed to work with R134a was tested, and its performance using R152a and R32 was evaluated and compared with its performance when R134a was used. The results obtained showed that the design temperature and pull-down time set by International Standard Organisation (ISO) for small refrigerator were achieved earlier using refrigerant R152a and R134a than using R32. The average coefficient of performance (COP) obtained using R152a is 4.7% higher than that of R134a while average COP of R32 is 8.5% lower than that of R134a. The system consumed less energy when R152a was used. The performance of R152a in the domestic refrigerator was constantly better than those of R134a and R32 throughout all the operating conditions, which shows that R152a can be used as replacement for R134a in domestic refrigerator.     

A comparative study of water as a refrigerant with some current refrigerants

Water as a refrigerant (R718) is compared with some current natural (R717 and R290) and synthetic refrigerants (R134a, R12, R22, and R152a) regarding environmental issues including ozone depletion potential (ODP) and global warming potential (GWP), safety (toxicity and flammability), operating cost, refrigeration capacity and coefficient of performance (COP). A computer code simulating a simple vapour compression cycle was developed to calculate COPs, pressure ratios, outlet temperatures of the refrigerants from the compressor, and evaporator temperatures above which water theoretically yields better COPs than the other refrigerants investigated. The main difference of this study from other similar studies is that both evaporator temperature and condenser temperature are changed as changing parameters, but the temperature lift, which is the temperature difference between condenser and evaporator, are held constant and the irreversibility during the compression process is also taken into consideration by taking the isentropic efficiency different from 100%. It is found that for evaporator temperatures above 20°C and small temperature lift (5 K), R718 gives the highest COP assuming exactly the same cycle parameters. For medium temperature lifts (20–25 K), this evaporator temperature is above 35°C, whereas for even greater temperature lifts it decreases again. Furthermore, with increased values of polytropic efficiency, R718 can maintain higher COPs over other refrigerants, at lower evaporator temperatures. Copyright © 2005 John Wiley & Sons, Ltd.     

A performance comparison of vapour-compression refrigeration system using various alternative refrigerants

A theoretical performance study on a traditional vapour-compression refrigeration system with refrigerant mixtures based on HFC134a, HFC152a, HFC32, HC290, HC1270, HC600, and HC600a was done for various ratios and their results are compared with CFC12, CFC22, and HFC134a as possible alternative replacements. In spite of the HC refrigerants' highly flammable characteristics, they are used in many applications, with attention being paid to the safety of the leakage from the system, as other refrigerants in recent years are not related with any effect on the depletion of the ozone layer and increase in global warming. Theoretical results showed that all of the alternative refrigerants investigated in the analysis have a slightly lower performance coefficient (COP) than CFC12, CFC22, and HFC134a for the condensation temperature of 50 °C and evaporating temperatures ranging between − 30 °C and 10 °C. Refrigerant blends of HC290/HC600a (40/60 by wt.%) instead of CFC12 and HC290/HC1270 (20/80 by wt.%) instead of CFC22 are found to be replacement refrigerants among other alternatives in this paper as a result of the analysis. The effects of the main parameters of performance analysis such as refrigerant type, degree of subcooling, and superheating on the refrigerating effect, coefficient of performance and volumetric refrigeration capacity are also investigated for various evaporating temperatures.     

Transcritical CO2 refrigerator and sub‐critical R134a refrigerator: A comparison of the experimental results

This paper describes experiments comparing a commercial available R134a refrigeration plant subjected to a cold store and a prototype R744 (carbon dioxide) system working as a classical ‘split‐systems’ to cool air in residential applications in a transcritical cycle. Both plants are able to develope a refrigeration power equal to 3000 W. The R744 system utilizes aluminium heat exchangers, a semi‐hermetic compressor, a back‐pressure valve and a thermostatic expansion valve. The R134a refrigeration plant operates using a semi‐hermetic reciprocating compressor, an air condenser followed by a liquid receiver, a manifold with two expansion valves, a thermostatic one and a manual one mounted in parallel, and an air cooling evaporator inside the cold store. System performances are compared for two evaporation temperatures varying the temperature of the external air running over the gas‐cooler and over the condenser. The refrigeration load in the cold store is simulated by means of some electrical resistances, whereas the air evaporator of the R744 plant is placed in a very large ambient. The results of the comparison are discussed in terms of temperature of the refrigerants at the compressor discharge line, of refrigerants mass flow rate and of coefficient of performance (COP). The performances measured in terms of COPs show a decrease with respect to the R134a plant working at the same external and internal conditions. Further improvements regarding the components of the cycle are necessary to use in a large‐scale ‘split‐systems’ working with the carbon dioxide. Copyright © 2009 John Wiley & Sons, Ltd.     

Performance of alternative refrigerant R430A on domestic water purifiers

In this study, performance of R430A is examined numerically and experimentally in an effort to replace HFC134a used in refrigeration system of domestic water purifiers. Even though HFC134a is used predominantly in such a system these days, it needs to be phased out in near future in most of the developed countries due to its high global warming potential. To solve this problem, cycle simulation and experiments are carried out with a new refrigerant mixture of 76%R152a/24%R600a using actual water purifiers. This mixture is numbered and listed as R430A by ASHRAE recently. Test results show that the system performance is greatly influenced by the amount of charge due to the small internal volume of the refrigeration system in water purifiers. With the optimum amount of charge of 21–22 g, about 50% of HFC134a, the energy consumption of R430A is 13.4% lower than that of HFC134a. The compressor dome and discharge temperatures and condenser center temperature of R430A are very similar to those of HFC134a for the optimum charge. Overall, R430A, a new long term environmentally safe refrigerant, is a good alternative for HFC134a in domestic water purifiers requiring no major change in the system.     

The performance of a triple pressure level absorption cycle (TPLAC) with working fluids based on the absorbent DMEU and the refrigerants R22, R32, R124, R125, R134a and R152a

This paper compares the performance of a single-stage triple pressure level (TPL) absorption cycle with different refrigerant–absorbent pairs. Four HFC refrigerants namely: R32, R125, R134a and R152a which are alternative to HCFC, such as R22 and R124, in combination with the absorbent dimethylethylenurea (DMEU) were considered. The highest coefficient of performance (COP) and the lowest circulation ratio (f), were found as a function of the generator temperature for a given evaporating and cooling water temperatures. The sensitivity of the COP and f for evaporator and cooling water temperatures changes at the maximum COP for the best three working fluids were also examined. It was obtained that the preferable pair is R124–DMEU and among working fluids based on HFC the preferable pair is the R125–DMEU.     

R245fa阻燃特性理论与试验研究

分析了R245fa的阻燃,试验研究了R245fa在电打火(点火能约为100 J)和普通打火机点火两种条件下对R290、R152a、DME、R600a的阻燃特性,提出了新的评判阻燃组分阻燃特性强弱的指标(阻燃系数K),并对R245fa作用于各可燃工质的阻燃效果进行分类．试验结果表明,点火能大小、点火源形式对可燃工质燃爆极限影响很大；R245fa对碳氢类可燃工质阻燃效果差；对HFC类的阻燃效果相对较好；R245fa的阻燃效果比R134a的差．     

Energy and exergy analysis of vapor compression refrigeration system using pure hydrocarbon refrigerants

This study presents a comparison of energetic and exergetic performance of a vapor compression refrigeration system using pure hydrocarbon (HC) refrigerants. In this study, four different pure HCs propane (R290), butane (R600), isobutane (R600a) and isopentane (R1270) are used in theoretical analysis. R22 and R134a are also used in the analysis. For the analysis, EES package program was used for solving thermodynamic equations of the refrigerants. Results have been presented graphically. According to results, differences of coefficient of cooling performance values of these refrigerants are quite small. Energetic and exergetic efficiency values obtained with R1270 and R600 are higher than R600a and R290. Copyright © 2009 John Wiley & Sons, Ltd.     

喷射器性能及太阳能喷射制冷系统工质的优化

考虑实际流体热力学性质、混合效率和激波等因素,建立了喷射器热力学模型,计算结果与文献中实验数据吻合很好。文中计算了采用环境友好工质R134a、R152a、R717、R290、R600a时喷射系数及喷射制冷系统性能系数。结果表明,对于确定几何参数的喷射器,喷射系数和喷射制冷系统性能系数主要取决于膨胀比与压缩比,两者分别随膨胀比的增加而增大,压缩比的增加而减小。太阳能驱动喷射制冷系统时(发生温度在80℃左右),采用R134a可以使喷射系数和喷射制冷系统能效比最大,明显优于其他工质。     

A zero ODP replacement for R12 in a centrifugal compressor: an experimental study using R134a

It is well believed that the hydrofluorocarbons (HFCs) and their mixtures are the most promising candidates to substitute the conventional refrigerants, chlorofluorocarbons (CFCs) and HCFCs which contain chlorine atoms in the molecule. This substitution is necessary for the harmful action of CFCs and of HCFCs toward atmospheric ozone layer damage because the disruption of ozone has been attributed to chlorine. For this reason they must be replaced by more environment‐friendly refrigerants, as the new family, designated as HFCs, that are chlorine free. Centrifugal compressors differ from positive displacement compressors in two major respects: high vapour volume flow for a given physical size and lower pressure ratio. They are particularly suited to applications where differences between evaporator and condenser temperatures are low. The preferred properties for fluids used in centrifugal compressors differ in certain important aspects from those preferred for fluids used in positive displacement units. In particular centrifugal compressors typically utilize fluids such as CFC114, CFC113, CFC12 and CFC11 for which many potential candidate replacements exist; however, for CFC12, HFC134a is the most suitable replacement. A comparison of the refrigerants HFC134a and CFC12 has been carried out and the results from the tests, using data from a refrigerating plant operating with a centrifugal compressor are reported. The chilled water cooling plant, with a refrigerating capacity of 6500 kW is made up of a centrifugal two‐stage compressor, a condenser linked to a cooling tower, an economizer and a flooded evaporator. Experimental results show that a lower coefficient of performance is found when R134a is used as substitute for R12; the difference between the COP values decreases rising the compression ratio. Copyright © 2002 John Wiley & Sons, Ltd.     

Performance analysis of single-stage refrigeration system with internal heat exchanger using neural network and neuro-fuzzy

In this study, artificial neural networks (ANNs) and adaptive neuro-fuzzy (ANFIS) have been used for performance analysis of single-stage vapour compression refrigeration system with internal heat exchanger using refrigerants R134a, R404a, R407c which do not damage to ozone layer. It is well known that the evaporator temperature, condenser temperature, subcooling temperature, superheating temperature and cooling capacity affect the coefficient of performance (COP) of single-stage vapour compression refrigeration system with internal heat exchanger. In this study, COP is estimated depending on the above temperatures and cooling capacity values. The results of ANN are compared with ANFIS in which the same data sets are used. ANN model is slightly better than ANFIS for R134a whereas ANFIS model is slightly better than ANN for R404a and R407c. In addition, new formulations obtained from ANN for three refrigerants are presented for the calculation of the COP. The R² values obtained when unknown data were used to the networks were 1, 0.999998 and 0.999998 for the R134a, R404a and R407c respectively which is very satisfactory.     

A comparison of the operating performance of alternative refrigerants

This paper provides a comparison of the operating performance of three alternative refrigerants for use in a vapour compression refrigeration cycle. The refrigeration capacity and COP of R401A, R290 and R134A were compared with those of R12 when used in a propriety vapour compression refrigeration unit initially designed to operate with R12. The results indicate that the performance of R134a is very similar to that of R12 justifying the claim that it is a drop in replacement for R12 but of the refrigerants tested it gave the poorest performance. When viewed in terms of green house impact however R290 showed the best performance.