Hydrocarbon Refrigerants Research Articles

Drop-in and retrofit refrigerants as replacement possibilities of R134a in domestic/commercial refrigeration and automobile air conditioner applications

According to the EU F-gas Regulation, the phase-out of the high global warming potential (GWP) refrigerants (with higher than 150 GWP value) had been established. The most currently existing household and commercial refrigerators and automobile air conditioners applications based on single-stage vapour compression systems operate with R134a as working fluid. The present paper aims, to review and evaluate the performance of a set of eco-friendly alternatives refrigerants to replace R134a, without change or with minor modifications in refrigeration equipment. The theoretical and experimental studies performed in this field of research were reviewed for this objective. These alternative refrigerants are some of HFCs, HFOs and HCs and their mixtures, which are expected to be an excellent candidates in many refrigeration applications. There are Many replacement possibilities had been proposed viz. drop-in replacement, retrofit refrigerant, and new systems. The results exhibited that the most suitable refrigerants as R134a drop-in substitutes are R1234yf, R152a, R450A, and R513A. The pure R1234ze and its mixtures are not suitable drop-in replacements of R134a but can be a good alternative to R134a only in new refrigeration systems. In terms of hydrocarbon refrigerants R290, R600, and R600a could replace R134a with some modifications to existing refrigeration systems to overcome the flammability issue. We should be using certain HFC and HC mixtures with the lowest TEWI index.

Performance of multi-walled CNTs suspended with hydrocarbon refrigerant (R600a) and lubricating oil in vapour compression refrigeration system

A single evaporator household refrigerator with a total volume of 70 L is used to evaluate multi-walled carbon nanotubes (CNTs) nanolubricant as a drop-in replacement for pure lubricant. Continuous running on the refrigerator is done with varying concentrations of multi-walled CNTs nanolubricant and different mass charges of R600a. The results show that using R600a with multi-walled CNTs nanolubricant concentration of 0.4 g/L to 0.6 g/L and a charge of 50 g to 60 g more result in a decreased pull downtime and evaporator temperature of -8 and -11 °C, respectively. Using 0.4 g/L multi-walled CNTs nanolubricant and 50 g of R600a, the lowest electric energy usage is attained. Higher refrigeration is attained with this combination. The pull-down time is lower and also the power consumption of the refrigerator is lower than those of pure lubricant in the refrigerator by about 25.9 %, 20.2 %, and 13.7 % for 50 g, 60 g, and 70 g, respectively, while using multi-walled CNTs nanolubricant of 04 g/L to 0.6 g/L. Finally, the proposed multi-walled CNTs nanolubricant appears to be a good choice for replacing pure lubricant in the refrigerator.

Analysis of the performance of air blast freezer by using hydrofluorocarbon and hydrocarbon refrigerants

The air blast freezer has been used as a freezing method in the fish processing units before being frozen for a long time in cold storage. For this reason, the use of hydrocarbon refrigerants that are more environmental friendly has become a demand and a central issue in the future. This paper presents a performance analysis of using R290 and R600a as a drop-in replacement to R404A and R507A. The system performance analysis is based on the evaporation temperature variation using CYCLE_D-HX software with the condensation temperature maintained constant. The important quantities analyzed are mass flow rate, pressure ratio, temperature discharge, heat released, power consumption, coefficient of performance and refrigeration efficiency. The results show that at minimum evaporation temperature, system performance using R290 and R600a is on average ±14% higher compared to R404A and R507A. R290 has characteristics that are closer to R404A and R507A so it is more suitable to replace the two refrigerants compared to R600a. However, this is a performance analysis that can lead to higher performance than normal conditions.

Evaluation of Correlations of Flow Boiling Heat Transfer of R600a in a Flat-Plate Solar Collector/Evaporator

In the current research work, the behavior of the boiling heat transfer coefficient in a flat-plate solar collector/evaporator, component of a direct-expansion solar-assisted heat pump (DX-SAHP) was studied using a hydrocarbon refrigerant with zero Ozone Depletion Potential (ODP) and low Global Warming Potential (GWP). The main dimensions of the collector/evaporator are 0.8, 3.8, and 1000 mm of the fin thickness, internal diameter, and length, respectively. Five experimental tests were realized at different times of the day for obtaining the results, with mass velocities varying between 197.59 and 267.26 kg·m-2·s-1, and the heat flux having values between 72.83 and 488.27 W·m-2. The operating values in tests, such as refrigerant pressure and temperature, were taken in a built prototype. The numerical analysis was carried out considering different correlations proposed by Chen, Wojtan, and Kattan. The Wojtan mathematical model offered the best projection of the heat transfer effect for the different transition zones of a two-phase flow along the pipeline. The boiling heat transfer coefficients had approximate maximum values of 8.2, 8.5, 7.8, 6.7, and 5.8 kW·m-2·K-1 for the A, B, C, D, and E tests prediction by Wojtan. Moreover, the boiling heat transfer coefficients increased as the mass velocity enhanced and the rise of vapor quality as the mass velocity was fixed. In this study, the effect of solar radiation, vapor quality on the measured heat transfer coefficient was analyzed.

Energy, Exergy, and Environmental (3E) Analysis of Hydrocarbons as Low GWP Alternatives to R134a in Vapor Compression Refrigeration Configurations

The phase-down of hydrofluorocarbons and substitution with low global warming potential values are consequences of the awareness about the environmental impacts of greenhouse gases. This theoretical study evaluated the energy and exergy performances and the environmental impact of three vapor compression system configurations operating with the hydrocarbons R290, R600a, and R1270 as alternatives to R134a. The refrigeration cycle configurations investigated in this study include a single-stage cycle, a cycle equipped with an internal heat exchanger, and a two-stage cycle with vapor injection. According to the results, the alternative hydrocarbon refrigerants could provide comparable system performance to R134a. The analysis results also revealed that using an internal heat exchanger or a flash tank vapor injection could improve the system’s efficiency while decreasing the heating capacity. The most efficient configuration was the two-stage refrigeration cycle with vapor injection, as revealed by the exergy analysis. The environmental impact analysis indicated that the utilization of environmentally-friendly refrigerants and improving the refrigeration system’s efficiency could mitigate equivalent CO2 emissions significantly. The utilization of hydrocarbons reduced the carbon footprint by 50%, while a 1% to 8% reduction could be achieved using the internal heat exchanger and flash tank vapor injection.

Enhancement of household refrigerator energy efficiency by studying the effect of refrigerant charge and capillary tube length

Experiments were carried out initially by considering pure R134a and hydrocarbon refrigerant mixtures such as (R290/R600a) (HCM1 44/56, HCM2 50/50, HCM3 54/46, HCM4 64/36, and HCM5 74/26 wt %). Tests are conducted at the atmospheric temperature of 30°C in a domestic refrigerator system. The performance parameters such as pull-down time, desired effect, power consumption, and running cost of the system are to be analysed at different evaporator temperatures, the mass of refrigerant and varying length of capillary tubes. To evaluate the refrigeration effect, Power consumption and COP of the domestic refrigerator at various freezer temperatures (–9°C, –12°C & –15°C) were selected. Results report that out of all the alternative mixtures the amount of energy input was less consumed in the case of HCM1 at a minimal expansion length of 6.3 mm. In the case of HCM5, the least energy was consumed at a capillary length of 5.24 mm whereas in the case of R134a it was at 3.3 mm.

Review on application and research of trans-critical CO2 refrigeration system in food freezing and cold storage

As people pay more and more attention to environmental problems, the GWP and ODP of traditional halogenated hydrocarbon refrigerants are generally higher, and the natural refrigerants with low GWP are more mentioned. As a natural refrigerant, CO2 is excellent in safety and environmental protection. CO2 as a refrigerant also plays a role in various industries, especially in the food industry. In the actual use of CO2 trans-critical refrigeration system in food refrigeration, it is found that there are some defects in CO2 system. Therefore, in order to solve the problem of low efficiency in trans-critical CO2 cycle, this paper analyses the research of some technologies in trans-critical CO2 refrigeration system that can improve system performance, COP and refrigeration capacity, and summarizes the problems in recent years progress in energy efficiency. In this paper, the working principle, technical characteristics and the improvement of system performance of various improved technologies are discussed in detail, and the previous research is summarized.

Cooling System Performance Comparison of Refrigerant R-134a and MC-134 on Ice Slush Machine

Ice Slush Machine uses a direct cooling vapor compression system. The primary refrigerant used in such a system mostly is hydrofluorocarbons (HFCs), such as R134a. R134a is a retrofit for refrigerant R-12 which is included in the chlorofluorocarbon (CFC) type of refrigerant. CFC-type refrigerants have a dangerous impact on the environment. Hydrocarbon refrigerant MC-134 is an alternative for R-134a because it has a low potential value for environmental damage. The secondary refrigerant used was propylene glycol and the product used was 3.5 liters of Coca-Cola. From the test results when the system using R134a had an average COP actua l and an average COP carnot of 2.6 and 4.55, respectively, and the energy consumption was 1.571 kWh with an average efficiency of 57%, while in a system with MC-hydrocarbon refrigerant 134 obtained an average COP actual and an average COP carnot of 2.8 and 4.5, respectively and the energy consumption of 1.325 kWh with an average efficiency of 62%. Therefore, MC-134a had COP actual greater than R-134 and electrical energy consumption of MC-134 was less than R-134a.

Fantastic barocalorics and where to find them

Barocaloric materials have the potential to offer greener and more efficient alternatives to conventional refrigerants that exploit vapor compression for cooling and heating applications. The barocaloric effect, a temperature change in response to hydrostatic pressure, is widespread in materials; however, only in the last few years have giant and colossal barocaloric effects approaching those of commercial hydrocarbon refrigerants been discovered. These barocaloric effects are associated with large changes in the degrees of freedom within the material and can take various forms. Here, we discuss this variety and categorize barocaloric materials based on the degree of freedom that underpins the barocaloric effects. We use this framework to identify material families to explore for potential barocalorics.

Performance Evaluation of a Split Unit Air-Conditioner Retrofitted with Hydrocarbon Refrigerant (HC22)

The performance evaluation of a small capacity split unit air-conditioner when retrofitted with hydrocarbon refrigerant (HC22) was presented in this paper. Unlike traditional hydrofluorocarbon refrigerant (HCFC22) which possess ozone depletion potential (ODP) and high global warming potential (GWP), the HC22 refrigerant has zero ODP and a GWP value less than 3. Experimental work was carried out in a controlled environment which mimics an office room, with surrounding temperature varied from 25°C, 30°C and 35°C to simulate the typical cooling loads in Malaysia. The performance of HC22 refrigerant was compared with that of HCFC22 at these temperatures. The results show that the coefficient of performance (COP) of HC22 is higher, ranging from 3.5% to about 11% in comparison to HC22. The observation during experiments also shows that a typical HCFC22 can be retrofitted without any issue. The COP values obtained were 6.03, 6.35 and 6.15 for HC22 and 5.71, 5.66 and 5.63 for HCFC22 respectively. It can be concluded from this study that HC22 can be retrofitted directly to a HCFC system but other issues such as refrigerant flammability and safety issues shall be taken into account.

Experimental study of bubble behaviors during boiling of a hydrocarbon refrigerant

The present work emphasizes the experimental observation of bubble behaviors in pool boiling of a pure (hydrocarbon, HC) refrigerant on coated surfaces. A refrigerant R-600a was used as one of HC refrigerants in this study. The coated surface was prepared by using a thermal spraying method where copper powder was coated over the copper substrate surface having an inside diameter of 16.6 mm and 201 mm length. The bubble behaviors during the saturated boiling of refrigerant were captured by a high-speed camera and characterized as number of nucleation sites, diameter of departing bubbles, and departure frequency. The boiling augment depends on the surface characterization, which affects the bubble dynamics during boiling processes. The number of nucleation sites and diameter of departing bubbles vary as an increase of applied heat flux. The departure frequency of bubble reduces as heat flux increases. The present outcomes compared with the experimental data of refrigerant R-134a to demonstrate the reason behind the current results. Data of this study were correlated in the form of non-dimensional terms and differentiated with the available predicted correlations.

Comparative analysis of an environmentally friendly refrigerant with DI water when used in a thermosiphon heat pipe

The focus on building better and efficient cooling techniques for electronic gadgets are gaining importance day-by-day. Among the various techniques being studied passive cooling techniques using heat pipes are gaining momentum; the challenge being finding a suitable working fluid which would enhance the performance of these devices. With the present scenario demanding eco-friendly alternatives, the researchers have tried using R600a, a hydrocarbon refrigerant with zero Ozone Depletion Potential. The optimum fill ratio of 50% was determined experimentally at an orientation of 90° from horizontal. Experiments were carried out to find the performance parameters of the thermosiphon heat pipe at the said fill ratio by varying the input heat from 20 W to 140 W with an increment of 20 W each. Next, the working fluid was replaced by de-ionized water and experiments were repeated. The results suggest that the resistance of the heat pipe thermosiphon reduced by 27% when R600a was used. Also, heat transfer coefficients at the evaporator and condenser section increased by a significant margin of 19% and 30% respectively when R600a was used in comparison to DI water.

A simulation of R32 refrigerant mixing with R1270 to reduce GWP R410A on wall mounted air conditioning

Refrigerant R410A is a cooling barrier that is still widely used for air conditioning. This R410A contains the Fluoro element which can increase the value of GWP. In this research simulation, we used an AC unit using R410A with the aim of reducing GWP (Global Warming Potential) by mixing synthetic refrigerant with hydrocarbons. R410A still has content GWP: Mixing using R32 / R1270 refrigerant is predicted to reduce the GWP value because R1270 is one of the hydrocarbon refrigerants that has a GWP value of only: 3. By using Refprop software it can be simulated a mixture composition starting from 50/50, 40/60, 30/70, 20/80 and 10/90. From the results of the mixture simulation conducted, obtained a mixture approaching the characteristics of R410A, namely in the mixture: 20/80 with COP: 5.17 while R410A: 4.12. Compression ratio: R410A: 2.0 and for mixed refrigerants 20/80: 1.9. The refrigerant effect of mixed refrigerants is 20/80: 254,51, R410A: 162,77. Using this refrigerant mixture can reduce the GWP value and improve the performance of the AC cooling system. This refrigerant has considerable potential to replace the R410A.

Experimental modeling of refrigerants at high ambient temperature

High ambient temperature is well known to have an adverse impact on air conditioners; it lowers their cooling capacity along with their coefficient of performance. Moreover, air conditioning plays a significant role in damaging the environment as it contributes to both global warming and ozone depletion. In the past few decades, the Montreal agreement was introduced to protect the ozone layer from substances that contribute to its depletion. Developing countries are now facing the challenges of phasing out HCFCs such as R22 in the air conditioning sector. The aim of this study is to find an alternative refrigerant that can replace R22 after its phase out. The new refrigerant must have low environmental impacts and should be able to withstand operation in high ambient temperature countries. In this study, the hydrocarbon refrigerant R290 and the hydrofluorocarbon R410A were selected as alternatives. Furthermore, experimental testing was carried out on the baseline refrigerant R22 and R410A using a 7kW ducted split unit at three outdoor conditions: 35oC, 48oC, and 52oC. From the experimental results, a model based on R22 and R410A was developed using Engineering Equation Solver (EES). The model was successful in verifying the experimental results within a 15% error range and was tested again with external data from (Eltalouny & Nielsen, 2016) [10]. After confirming its validity, the model was simulated to predict the performance of the alternative refrigerant R290 under the same experimental conditions and input data. To test the model’s validity on R290, results from Eltalouny & Nielsen (2016) were used. The model succeeded in predicting the COP and power consumption. The refrigerants demonstrated deterioration in their performance at elevated temperatures compared to their performance at a typical operating regime. With proper safety measures, and enhancement to the compressor efficiency, R290 can be considered as a promising alternative.

Energy and Exergy Analysis of Cascade Refrigeration System Using MC22 and MC134 on HTC, R404A and R502 on LTC

Low temperature storage with a single refrigeration system only stable up to 228 K temperature. The purpose of this study is to develop a low temperature cool storage with cascade refrigeration system, with hydrocarbon refrigerants in terms of energy and exergy analysis. Experimental research in laboratories using refrigerant hydrocarbon MC22 and MC134 on the hight temperature circuit, and R404A and R502 using on low temperature circuit. Condenser heat exchanger using a type of exchanger plate. Resulting from this research, obtained that result the MC22/R404A, MC22/R502 and MC134/R404A refrigerant pair can reach a temperature of 220 K. The MC22/R404A refrigerant pair has god performance, COP, total loss exergy, and exergy efficiency is better than MC22/R502, and MC134/R04A refrigerant pairs.

Simulation of Mixing Synthetic with hydrocarbons Refrigerant to Reduce the Value of Global Warming Potential with Refprop Software

The problem of global warming or called GWP (Global Warming Potential) that occurs in the earth’s atmosphere, one of which comes from synthetic refrigerants used in household air-conditioning refrigeration machines. R410A is a refrigerant that still contains GWP: 1942. Hydrocarbon refrigerant is a refrigerant that does not contain ODP (Ozone Depleting Potential) and a very small GWP. By using ref prop software, the mixing process can be simulated to obtain refrigerants that have characteristics similar to R410A. Mixing using R32 / R290 ingredients varied with percentage compositions ranging from 50/50, 40/60, 30/70, 20/80, and 10/90. From the simulation results, a mixture approaching R410A with 10/90 composition with COP: 3.85 for R410A and 5.76 for 10/90 mixture was obtained. Compression ratio: R410A: 2.8 and for mixed refrigerants 10/90: 1.8. The refrigerant effect of mixed refrigerants is 10/90: 264,13, R410A: 161,68. By using this refrigerant mixture can reduce the GWP and improve the performance of the Air Conditioning cooling system so that it has a reduced GWP value that can be obtained significantly and has a large enough potential to replace the R410A.

Refrigerant Charge Optimization of Air Conditioning System with Hydrocarbon Refrigerant

Determination of the amount of refrigerant in a vapor compression refrigeration system requires several approaches depending on the design and installation of the piping on each refrigeration component. For chiller systems or other packaged systems that are already loaded with refrigerant and do not require piping installation in the refrigeration system, the amount of refrigerant that is loaded into the unit is based on testing at the factory. Optimization of the amount can be done when the test is carried out in the laboratory setting and the chiller is operated with the target capacity and the performance. However, for chillers that have been installed on-site and are not in the design condition, the amount of refrigerant that must be input varies greatly to obtain optimum conditions. In this research, we will calculate the amount of hydrocarbon refrigerant R290 that must be done to achieve the most optimum or efficient conditions, in the 56 TR capacity chiller system that is installed at the Makara Art Center, Universitas Indonesia. The use of refrigerants, especially the hydrocarbon type R290, is expected to have the least amount of refrigerant possible, so it is important to determine the lowest charging with the best efficiency. The chiller system is also installed with the addition of the LSHX component which in previous studies showed the possibility of decreasing the contents of R290The refrigerant charge reduction from its optimum amount decreases the system’s efficiency. The reduction of refrigerant charge of 3.3% results in COP decrease up to 3.9%. It is then imperative that proper charging as well as minimizing leaks is important to keep the chiller works at its maximum efficiency.

Performance investigation of vapor compression refrigeration system using R134a and R600a refrigerants and Al2O3 nanoparticle based suspension

The improvement in performance parameters of refrigeration system using nanofluid has been investigated intensively for many years. The compatibility, stability and feasibility of nanofluid in refrigeration system have been quite challenging. The present experimental work involves the performance of Al2O3 nanoparticle based nanofluid in a vapor compression refrigeration system. The average diameter of 35 nm of Al2O3 nanoparticle with near-spherical morphology used for the experimentation. The lubricant oil of compressors has taken as the base fluid for the synthesis of Al2O3 nanofluid. The nanofluid has synthesized in the experiment of mass fractions of 0.02 wt%, 0.04 wt%, 0.07 wt%, and 0.1 wt% of Al2O3 nanoparticles. Two different types of refrigerant which are synthetic refrigerant (R134a) and hydrocarbon refrigerant (R600a) have used separately for the investigation. The polyester oil (POE) for R134a refrigerant and mineral oil for R600a refrigerant is incorporated in the experimental test rig. The coefficient of performance (C.O.P.), power consumption, compressor discharge pressure, evaporator pressure, and pull-down time were considered as performance parameters for the investigation of the vapor compression refrigeration test rig. The experimental results showed that by using 0.1 wt% of R600a-MO-Al2O3 mixture improves the C.O.P. by 37.2%, reduction in power consumption by 28.7%, increment in compressor discharge pressure by 8.9%, lowered evaporator pressure by 24.7%, and lowered the pull-down time by 17.6% compared to the conventional refrigeration system.

Thermodynamic performance of ammonia in liquefied natural gas precooling cycle

The selection of proper refrigerants for natural gas liquefaction processes play a key role in cycle?s efficiency. Mixed refrigerants have been proven to improve cycle?s exergy efficiency over single pure refrigerant. However, the future of some of these refrigerants with higher global warming potential index are unknown due to the continuous restriction being enforced by the energy and environmental agencies over the past few decades. This study examines the benefits and drawbacks of mixing ammonia, a refrigerant with zero global warming potential index and a high occupational safety characteristic, with lighter hydrocarbon refrigerants such as methane and ethane as a mixed refrigerant in a natural gas liquefaction?s precooling cycle. Results showed, presence of ammonia in mixed refrigerant not only saved in capital cost due to the smaller footprint of plant and smaller cold box, it also lowers the plants precooling operation expense by reducing the required compression power needed for the precooling cycle up to 16.2%. The results of exergy analyses showed that by reducing the molar concentration of more pollutant refrigerant methane and replacing it with ammonia enhanced the cycle?s efficiency by 4.3% and lowered the heat exchanger total exergy loss up to 47.9 kW.

Environment friendly refrigerant options for automobile air conditioners: a review

In this paper, the environment friendly refrigerant options suitable for automobile air conditioners are reviewed. Initially, the thermophysical, thermodynamic and chemical characteristics of the environment friendly refrigerant options are presented. Then, the reviews of research investigations reported on environment friendly refrigerant options (such as hydrofluorocarbons, hydrofluoroolefins, hydrocarbons, carbon dioxide, composite mixed refrigerants and nanorefrigerants) are presented. The limitations and further research needs with environment friendly refrigerant options are identified and listed. The paper concludes that the hydrocarbon refrigerants will dominate the automobile air conditioning sector due to their good thermodynamic, thermophysical and environmental properties. Secondary loop configurations are recommended for the use of hydrocarbon refrigerants to reduce the flammable risk. The carbon dioxide is identified as a good option for electrical vehicles operating at low ambient conditions. The hydrofluoroolefins have short atmospheric life and get decomposed in the atmosphere and form tri-fluoro-acetic acid, which is harmful to the aquatic environment. Hence, hydro-fluoro-olefins are identified as an interim option. The outcome of this review is more helpful to the manufacturers and researchers working in the field of automobile air conditioners.