Refrigerants R22 Research Articles

Experimental and numerical investigation of thermal performances of R290 and R1234yf refrigerants in a cold room

In today’s world, most of the currently used refrigerants in refrigeration systems have an important influence on global warming. This study presents the experimental and numerical consumption of thermal and energy performances comparison of new generation low GWP R290 and R1234yf refrigerants for a cold room. Evaporator temperatures of −9 °C, −6 °C, −3 °C, and condenser temperatures of 25 °C, 30 °C, 35 °C were utilized as the operational parameters. Results revealed that the highest COP values in the system for R290 and R1234yf were 3.99 and 3.41, respectively. An average 11.1% increase in the cooling capacity was determined with R290 compared to the R1234yf refrigerant. In the second part of the study, evaporator surface temperature and air velocity distributions in the cold room for R290 and R1234yf refrigerants occurring until the cold room temperature reached from the ambient temperature to 0 °C were numerically shown using Ansys Fluent 18.1. Numerical analysis using experimental data indicated that the evaporator surface had a lower temperature with R290 refrigerant than R1234yf. Results of the study highlighted the usability of R290 refrigerant instead of R1234yf in refrigeration systems in terms of thermodynamic performance.

Research on the electric vehicle heat pump air conditioning system based on R290 refrigerant

Based on the selection of refrigerant replacement for electric vehicle heat pump air-conditioning system, the ideal refrigerant replacement R290 is chosen as the working medium of the system. The feasibility and superiority of the electric vehicle heat pump air-conditioning system with water loop based on R290 refrigerant are verified by setting up a performance test platform. The experimental results show that the high temperature (55 °C) refrigeration capacity of the system is 5.77% higher than that of CO2 system, the COP of the system is 1.05 higher, and the isentropic efficiency of the system is more than 80% in the low temperature (- 20 °C) heating mode, the system has better and stable heating performance. This paper is beneficial to the further research and application of environment-friendly refrigerants, and further promote the development and research of heat pump air-conditioning system of efficiency electric vehicle.

Determination of defrost efficiency and energy efficiency index value using different defrost methods and refrigerants: An experimental study

In this study, open-type refrigeration cabinets were designed and manufactured using hot gas and electrical resistance defrost methods and R290, R449A and R404A refrigerants. The aim of this study is to determine the temperature increase of the products during the process, CO2 emission amount, defrost efficiency, and energy efficiency index (EEI) value with different defrost methods and refrigerants for commercial refrigeration systems. The increase in package temperatures during the defrosting process was determined as 1.33 °C in the electrical method. The results showed that the hot gas method was 7.15% more efficient in terms of defrosting efficiency. The EEI value was calculated as 78.76 with the use of R290 in the hot gas method and the energy class was determined as F and the hot gas emit 5.9% less CO2 than in the resistance experiments. In the hot gas defrost method, it was seen that 20.3% less energy was consumed compared to the total consumption. It was observed that R290 refrigerant and the hot gas defrost method were the most suitable for commercial systems in terms of defrosting process losses, total energy consumption, and temperature rise of the cooled product during defrosting.

Optimizing Calibration for a Capacitance-Based Void Fraction Sensor with Asymmetric Electrodes under Horizontal Flow in a Smoothed Circular Macro-Tube.

In this study, a technique that uses a capacitance sensor with an asymmetric electrode to measure the void fraction of a refrigerant was developed. It is known that the void fraction and flow pattern affect the measured capacitance. Therefore, the relationship between the void fraction and capacitance is not linear; hence, a calibration method for obtaining accurate measurements is necessary. A calibration method was designed in this study based on repeated capacitance measurements and the bimodal temporal distribution to calibrate the atypical and repetitive flow patterns of slug flow and its transition to the intermittent flow regime. The calibration method also considers the weighted-average relation for the gradual transition of the intermittent to annular flow pattern according to the change from low to high quality. The proposed method was experimentally analyzed under the conditions of R32 refrigerant, a tube inner diameter of 7.1 mm, saturation temperature of 25 °C, mass flux of 100–400 kg m−2 s−1, and vapor quality of 0.025–0.900, and it was validated using a quick-closing valve (QCV) system under identical conditions. A relative error of 2.99% was obtained for the entire system, indicating good agreement between the proposed and QCV-based methods.

Kajian eksperimental pemakaian Hidrokarbon Musicool 22 sebagai pengganti R 22 untuk mesin pengatur udara AC split terhadap konsumsi listrik

The use of synthetic refrigerant R22 has been banned by the government which can cause damage to the ozone layer causing global warming effects. temperature (ΔT°C) of the evaporator during the test time at the time of the study. The method used in this research is to vary the refrigerant R 22 and Musicool 22 with a pressure variation of 60,70,80 Psi, the size of the room studied is 3x4x2,5 m and Split AC Changhong, LG, and Panasonic with 1 PK power. Research results it can be seen that each brand of Split AC has a different effect of electricity consumption, the lowest and highest electricity consumption at a pressure of 60 and 80 Psi. Musicool 22 refrigerant is more energy efficient than R22. It can be seen that each brand of Split AC has the effect of the temperature difference (ΔT°C) of the evaporator, which differs the highest at a pressure of 60 and 80 Psi. Musicool 22 refrigerant is more suitable for LG and Changhong brands.

Influence of the temperature difference between the heat source and the evaporation temperature in ORC systems working with natural refrigerants

The use of waste heat in many branches of industry is limited due to temperature in the range of 30 to 100oC. One of the methods of using waste heat are devices that implement the Organic Rankine Cycle (ORC). In currently used ORC systems, the heat source temperature is at least 80oC, while the low temperature heat source (usually atmospheric air) has a temperature of 30oC. The work analyzes the influence of the organic fluids properties on the performance of the proposed installation driven by the waste heat and working based on the ORC. The basic operation parameters in nominal conditions were determined for three selected natural refrigerants R290, R600a, R717 and one synthetic R245fa. The condensing temperature 30oC were defined as a nominal value. The research results compare how the generated electric power will change depending on the temperature difference between the temperature of the heat source and the temperature of evaporation. It turns out that for a device with finite dimensions, the maximum power is obtained for a specific evaporation temperature. And this is not the highest temperature that can be achieved. The highest evaporation temperature allows for the highest efficiency of the system, but not the maximum of capacity.

Numerical Study on Liquid-Return Characteristics in the Accumulator of the R290 Rotary Compressor

Liquid often exists in the accumulator of the rotary compressor during the process of startup or defrost of air-conditioning systems. Too much liquid entering the compressor cylinder would result in excessive pressure caused by the liquid compression, which is a great threat to the compressor. The liquid return through the liquid-return hole is the key to ensure the stable operation of the compressor. In this paper, the liquid-return characteristics in the liquid-return holes of the accumulator, including the mass-flow rate, liquid velocity and pressure difference between the liquid-return holes, during the startup process of the R290 rotary compressor are numerically investigated. The numerical simulation using the fluent volume of fluid (VOF) method was experimentally validated with the error of 1.55%. The comparison of liquid-return characteristics using different refrigerants is conducted. Effects of refrigerant solubility in the oil, refrigerant/oil-mixture type, liquid-return-hole diameter and compressor frequency on the liquid-return characteristics and liquid shape trough the liquid-return hole are discussed. The results show that the surface tension and viscosity of the liquid are the main factors affecting the liquid-return speed. The liquid-return rate of the refrigerant R290 is slower than that of other refrigerants R22 and R410A. The liquid-return rate increases with the increase in the compressor frequency. We conclude that for air-conditioning systems using R290 as refrigerant, increasing the number of return holes or the hole diameter is necessary to improve the liquid-return characteristics of the compressor. This research will provide theoretical guidance for the optimization of liquid return of rotary compressors using new refrigerants.

Numerical analysis of a two-phase injection refrigeration cycle using R32

The present paper reports the performance of a popular refrigerant R32 (Difluoromethane, CF2H2) experiencing the two phase injection process. Two phase injection process may lower the discharge temperature of a multistage compressor. In order to investigate the role and impact of two-phase injection on a compressor, a Scroll compressor is selected because scroll compressor has high tolerance for liquid refrigerant. A reputed compressor is chosen where all the operating conditions and specifications are available in public domain. The modelling and analysis of refrigeration system is carried out using a simple MATLAB code. Around 200 iterations were performed for four different condensing and evaporating temperatures. The maximum reduction in discharge temperature is found to be 44°C when compared to R410A used in the same system.

Refrigerant mass distribution in an invertible air-to-water heat pump: effect of the airflow velocity

This paper presents the results of refrigerant mass distribution measurements carried out in an invertible air-to-water heat pump. The unit works with refrigerant R32 and produces a nominal cooling capacity equal to 60 kW. Experimental tests have been performed during both cooling and heating operations using the quick-closing valves technique to isolate the charge within the components of the system. A mathematical model, developed to predict the refrigerant charge in the heat exchangers of the heat pump and its performance, is described and validated. The model includes a physical description of the heat transfer mechanisms in the condenser and in the evaporator. The model employs void fraction correlations to calculate the refrigerant mass in the two-phase regions of the heat exchangers. In the finned coil heat exchanger, the model can account for the effects of the airflow maldistribution, which has been also experimentally measured. When the not uniform air velocity is considered, the refrigerant charge in the heat exchangers is modelled within ±10%. The results of the model showed that the airflow maldistribution can increase the total refrigerant charge in chiller mode by 12.7% and decrease the performance of the system by 11%, compared to the case of uniform air velocity.

Flammability and performance studies of eco-friendly ternary refrigerant mixtures used in vapour compression systems.

The present article analyses the refrigerant safety parameters flammability, global warming potential (GWP) and coefficient of performance (COP) for twenty-seven combinations that contain two flammable and one non-flammable (dilutant) component. The flammability of the flammable refrigerants R290, R600, R600a, R152a and R161 were investigated with different dilutants such as R245fa, R13I1 and R134a. To determine the minimum inerting concentration (which decides the flammable zone), two methods were used: thermal balance method (TBM) and the modified thermal balanced method (MTBM). The MICs estimated with both the methods are compared against the 50 experimental datapoints available in the literature (for different ternary mixtures). It was found that for all the ternary mixtures, majority of the MIC values estimated with MTBM are within ± 8% while with TBM are within ± 30%. Fifty-five ternary mixture compositions were identified (from the proposed twenty-seven mixture combinations) using the MICs predicted by MTBM. The COPs of the identified mixtures M1-M6, M8-M12, M14-M24, M26-M30, M34-M39 and M53-M54 are estimated to be less than 10% of the COP of R134a (at the same operating conditions). It is also estimated that the corresponding GWP value of the mixtures (M1 to M6, M8 to M12, M14 to M24, M26 to M30, M34 to M39, M53 and M54) are reduced by 91 to 99% when compared to R134a (GWP = 1300).

Energy impact evaluation of different low-GWP alternatives to replace R134a in a beverage cooler. Experimental analysis and optimization for the pure refrigerants R152a, R1234yf, R290, R1270, R600a and R744

Due to the entry into force in 2014 of the European F-Gas Regulation n° 517/2014 and the subsequent Kigali amendment, the phase-out of the medium and high-GWP refrigerants has speeded up in all refrigeration fields. The effect on the plug-in or stand-alone systems has meant that other environmentally friendly refrigerants must replace the R134a with low or ultra-low GWP maintaining the same operating conditions and reducing the energy consumption. Extended examples of these fluids are the hydrocarbons R600a and R290 and the inorganic fluid R744 (CO2). However, there are other alternatives to the HFCs R152a and R1234yf or the hydrocarbon R1270 that have hardly been analysed and can make a positive contribution to this sector. Accordingly, this work aims to evaluate the behaviour of a commercial beverage cooler experimentally when it is optimised with six alternatives to the HFC R134a: R152a, R1234yf, R290, R1270, R600a and R744. Results demonstrated that fluids R290, R1270, R152a, R744 and R600a reduce the energy of R134a in 27.5%, 26.3%, 13.7%, 3.9% and 1.2%, respectively, while the use of R1234yf increases the energy usage to 4.1%.

Assessing the Energy Consumption and Driving Range of the QUIET Project Demonstrator Vehicle

This article summarises the experimental testing campaign performed at the Joint Research Centre (JRC) on the demonstrator battery electric vehicle (BEV) of the European Union Horizon 2020 research project QUIET. The project, launched in October 2017, aimed at developing an improved and energy-efficient electric vehicle with increased driving range under real-world driving conditions, focusing on three areas: improved energy management, lightweight materials with enhanced thermal insulation properties, and improved safety and comfort. A heating, venting, and air conditioning (HVAC) system based on the refrigerant R290 (propane), a phase change material (PCM) thermal storage system, infrared heating panels in the near field of the passengers, lightweight materials for seat internal structures, and composite vehicle doors with a novel atomically precise manufacturing (APM) aluminium foam are all the breakthrough technologies installed on the QUIET demonstrator vehicle. All these innovative technologies allow the energetic request for cooling and heating the cabin of the demonstrator vehicle under different driving conditions and the weight of the vehicle components (e.g., doors, windshields, seats, heating, and air conditioning) to be reduced by about 28%, leading to an approximately 26% driving range increase under both hot (40 °C) and cold (−10 °C) weather conditions.

Energy impact of the Internal Heat Exchanger in a horizontal freezing cabinet. Experimental evaluation with the R404A low-GWP alternatives R454C, R455A, R468A, R290 and R1270

• It has been tested the IHX effect in the energy performance of a freezing cabinet. • Test has been carried out with R404A and its current low and ultra‐low GWP alternatives: R468A, R454C, R455A, R290 and R1270. • It has been measured Energy saving with all refrigerants and operating conditions tested. • Greater energy saving as greater the heat sink temperature is. • No significant increment in compressor discharge temperature. This work analyses the influence of the Internal Heat Exchan ger (IHX) on the energy performance of a vapor compression cycle associated with a freezing cabinet using different R404A low-GWP alternatives. Among them, the refrigerants R454C (GPW 100 =146), R455A (GPW 100 =146), R468A (GPW 100 =146), R290 (GPW 100 =5) and R1270 (GPW 100 =1.8) have been tested in a horizontal freezing cabinet maintaining a product target temperature of -20°C at the heat rejection temperatures of 20, 30 and 40°C. The results from tests show that the use of the IHX reduces energy consumption in all scenarios without significantly increasing the compressor's discharge temperature. For a test period of 16 h, the refrigerants that offer better reductions are R404A and R1270, followed by R455A, R290, R454C and R468A. The maximum energy saving is rated to 9.2% at the heat rejection temperature of 40°C, demonstrating that the enhancement of the IHX is better as higher the heat rejection conditions are.

Pre-Cooling Concrete System in Massive Concrete Production: Energy Analysis and Refrigerant Replacement

Several techniques for cooling mass concrete structures were developed in order to increase structural integrity and reduce the influence of cement hydration, which sometimes causes cracking in concrete structures, negatively affecting their durability. This research focuses on cooling system design, initial investment, and the influence of different refrigerants on cooling system performance aims in producing higher quality massive concrete. Cooling aggregates in massive concrete structures such as desert dams can be performed by employing cooled air from an air conditioning duct system or chilled water. The experimental study illustrates the relationship between the coefficient of performance COP, the evaporator temperature, cooling capacity, and refrigerant mass flow rate as a function of the evaporator temperature, cooling capacity, and refrigerant mass flow rate. The findings of the experiments were utilized to verify a numerical model developed utilizing engineering equation solver (EES) software. The performance of the vapor compression of the cooling systems was compared using alternative refrigerants, including R22, R32, and R410a at different operating conditions. This study revealed that R22 refrigerant has a higher coefficient of performance than R32 and R410A, while R32 has the highest cooling capacity among other refrigerants.

The Effect of Retrofitted Refrigerant and Environmental Temperature on the Performance of Air Conditioner: An Experimental Study

There are several factors that influence the efforts to increase the performance of an air conditioner (AC), one of which is the selection of working fluid, environmental condition, and device components. Refrigerant is the most vital substance which determines the efficiency of the cooling machine. In addition, ambient air temperature and humidity are other important factors that affect the performance of the cooling machine. Therefore, it is extremely crucial to calculate the environmental condition, which is the air temperature, so that the cooling machine can work optimally. Currently, the refrigeration system uses R-22 refrigerant. However, the use of R-22 has a high ODP (ozone depletion potential) value, thus having a risk of damaging the ozone layer. As a safer alternative, the use of hydrocarbon refrigerants, such as R134a and R290, can solve this problem as they do not have any ODP. This study was conducted by retrofitting the synthetic refrigerant in Air Conditioner (AC) 1 HP with various types of hydrocarbon refrigerant. The outside air temperatures used were 30°C, 50°C, 60°C, and 70°C, while the airflow velocity across the condenser also varied, namely 4.8 m/s, 5.8 m. /s, 6 m/s, and 6.6 m/s. From the results of this study, it is known that retrofitting synthetic refrigerants into hydrocarbon refrigerants can increase the coefficient of performance (COP) of the air conditioner. The uses of R134a and R290 hydrocarbon refrigerants increase the COP by 19% and 24.5%, respectively. In addition, lower ambient temperature will reduce the required electrical power. R290 Refrigerant has the best COP value compared to R22 and R134a.

Theoretical and experimental investigation of a heat pipe heat exchanger for energy recovery of exhaust air

AbstractHeat pipes and two‐phase thermosyphon systems are passive heat transfer systems that employ a two‐phase cycle of a working fluid within a completely sealed system. Consequently, heat exchangers based on heat pipes have low thermal resistance and high effective thermal conductivity, which can reach up to the order of (105 W/(m K)). In energy recovery systems where the two streams should be unmixed, such as air‐conditioning systems of biological laboratories and operating rooms in hospitals, heat pipe heat exchangers (HPHEs) are recommended. In this study, an experimental and theoretical study was carried out on the thermal performance of an air‐to‐air HPHE filled with two refrigerants as working fluids, R22 and R407c. The heat pipe heat exchanger used was composed of two rows of copper heat pipes in a staggered manner, with 11 pipes per row. Tests were conducted at different airflow rates of 0.14, 0.18, and 0.22 m3/h, evaporator inlet‐air temperatures of 40, 44, and 50°C, filling ratios of 45%, 70%, and 100%, and ratios of heat capacity rate of the evaporator to condenser sections (Ce/Cc) of 1 and 1.5. For HPHE's steady‐state operation, a mathematical model for heat‐transfer performance was set and solved using MATLAB. Results illustrated that the heat transfer rate was in direct proportion with the evaporator inlet‐air temperature and flow rate. The highest HPHE's effectiveness was obtained at a 100% filling ratio and (Ce/Cc) of 1.5. The predicted and experimental values of condenser outlet‐air temperature were in good agreement, with a maximum difference of 3%. HPHE's effectiveness was found to increase with the increase in evaporator inlet‐air temperature and number of transfer units (NTU) and with the decrease in airflow rate, up to 33% and 20% for refrigerants R22 and R407c, respectively. Refrigerant R22 was the superior of the two refrigerants investigated.

TiO2 nanolubricant: An approach for performance improvement in a domestic air conditioner

TiO2 nanolubricant has been used in this experimental work to study the performance of domestic air conditioner. Air conditioner capacity was 1 ton and the original system has R22 refrigerant. Three alternate refrigerant blends-Blend 1 (B1) composed of R32 and R22 (75:25 wt%), Blend 2 (B2) composed of R32 and R600a (75:25 wt%) and R32 refrigerant have been used in this experimental work to compare the thermo-physical performance with R22.0.01% and 0.02% volume concentration TiO2 nanolubricant have been used. All the temperatures and pressures of different section have been recorded using K-type thermocouple and pressure gauge respectively. Results showed that the selected blends with nanolubricant have higher COP compared to R22. Numerically, COP has been increased by about 25%–60% for B1 and B2 with nanolubricant and 20%–30% for R32 with nanolubricant compared to R22. R32 has shown maximum response by increasing about 60% of refrigerating effect compared to R22 while B1 and B2 have 45% more refrigerating effect. For compression work R32 with nanolubricant has similar compression work compared to R22 while B1 and B2 have 33% less compressor work required. Energy consumption has also been reduced for the blends with nanolubricant. B1 and B2 consumed 30% and 28% less power compared to R22 with nanolubricant. B1 and B2 with nanolubricant reduced the exergy loss by 40–70% while R32 reduced the exergy loss by 31% compared to R22. Overall, either B1 or B2 can also be used as an alternative of R22 with TiO2 nanolubricant.

Термодинамічна енергоефективність парокомпресійного теплового насоса на грунтових водах

The thermodynamic energy efficiency of a steam compression heat pump (PKTN) using natural sources of environmental heat, in particular groundwater, is considered in the article. The scheme of PKTN "water-water" for the heat supply system, temperature levels in the general system of PKTN "water-water" are presented and the example of work of the PKTN "water-water" cycle in the p-h diagram for propane (R290) is given. The results of a thermodynamic study of the energy efficiency of the use of PKTN when using groundwater as a source of low-potential thermal energy are presented. The article considers the use of pure hydrocarbons as working substances for PKTN, as well as a method for assessing energy efficiency by exergy analysis of thermodynamic energy conversion processes occurring in PKTN, the working fluid of which is the refrigerant R290. The energy efficiency of PКTN was estimated by the conversion coefficient of TH COP, it is calculated to be 4.5. The thermodynamic efficiency of PKTN in heat supply systems was considered using exergy efficiency depending on the average thermodynamic temperatures of heat carriers in the condenser and evaporator, which characterizes the perfection of energy conversion and is 44%. A thermodynamic study of the effectiveness of PKTN "water-water" for the space heating system using groundwater as a source of low-potential thermal energy. Evaluation of energy efficiency of thermodynamic processes of energy conversion occurring in PKTN "water-water" whose working fluid is a refrigerant R290 (propane) is performed by the method of exergetic analysis. It is shown that the exergetic efficiency of PKTN "water-water" depending on the average thermodynamic temperatures of evaporation and condensation is 44%.

ПЛІВКОВА КОНДЕНСАЦІЯ У СЕРЕДИНІ ГОРИЗОНТАЛЬНИХ ТРУБ ТА МІНІКАНАЛІВ

The article provides a brief description of the semi-empirical model of Ananiev, Boyko and Kruzhilin for calculating heat transfer during the condensation of working substances inside smooth horizontal pipes in a turbulent flow regime. Comparisons of heat transfer calculations based on a semi-empirical model with the results of experimental studies during the condensation of refrigerants, hydrocarbons and specialized substances inside pipes from well-known works by different authors are presented, which indicate good agreement between the results of studies and calculations based on the model, taking into account their boundary values. The presented calculations of heat transfer during condensation inside smooth horizontal pipes and minichannels are performed according to the semiempirical formula of Ananiev, Boyko and Kruzhilin, taking into account the influence of steam velocity on heat transfer processes. The calculation results demonstrate good agreement with the experimental data of various authors on the condensation of refrigerants R22, R134a, R125, R32 , R410A, specialized substances R245fa, Novec649, HFE-7000 and natural hydrocarbons R290, R600a, R1270, and DME for turbulent flow areas. For engineering practice, the presented semi-empirical model for calculating heat transfer during condensation of water vapor, refrigerants R22, R134a, R32, R410A, specialized substance HFE-7000, natural hydrocarbons R290, R600a, R1270 for smooth horizontal pipes (din > 3 mm) can be recommended. In this case, it is necessary to take into account the limits of application of the boundary values of the model. Calculation of heat transfer coefficients by semi-empirical correlation shows that it improves the description of the experimental data of many authors of works on the condensation of refrigerants R152a, R290, R134a, and R32 inside round minichannels (3 mm ≥ din > 200 μm) under turbulent and transient flow regimes. Further studies should include the performance of calculations on theoretical and empirical models for calculating heat transfer during condensation inside minichannels in order to create a general method for calculating heat transfer, taking into account the influence of regime flow parameters.

Selection of refrigerants for refrigeration systems of fruit and vegetable stores

Due to the implementation of the Kigali Amendment to the Montreal Protocol, the paper explores the prospects for replacing HFC refrigerants R404a and R507 in refrigeration machines for fruit and vegetable storages. For the optimal choice of environmentally friendly synthetic and natural refrigerants, calculating the coefficient of performance for single-stage refrigeration machines with direct supply of refrigerant to air coolers was carried out. The calculations were made for the conditions of a sharply continental climate at an atmospheric air temperature of +20°C. It was found, that in the near future such refrigerants as R407a, R407c, and R407f can be used as a replacement for R404a and R507 refrigerants in the new energy efficient systems with reciprocating and scroll compressors in developing countries. In the long term, refrigerants such as R290 (propane), R450a, R455a, and R513a can be used after 2036. The use of refrigerants R450a, R455a, R513a will lead to an increase in capital costs for the creation of refrigeration machines due to the need to increase the volumetric performance of compressors. In addition, R450a and R513a refrigerants have a relatively high global warming potential GWP > 150, which may lead to restrictions on their use in large refrigeration systems. As refrigerants R290 and R455a are flammable, their safe use requires a reduction in their charge weight. Therefore, R290 and R455a can be used either in refrigeration systems for individual cold chambers, or in systems with an intermediate heat transfer liquid.