Refrigerant Mixtures Research Articles

Design and Development of R32a and HFO-1234yf Refrigeration blend in Air conditioning System

Abstract: Refrigeration and air-conditioning systems become an integral part of modern society. Electricity-driven vapour compression systems have been dominating the heating, ventilation, air conditioning and refrigeration (HVAC&R) industry. The working fluids of these systems often contribute to the environmental issues in the forms of direct and indirection emissions. Pure refrigerants are often limited inmeeting criteria such as efficiency, flammability, toxicity, and compatibility. Meanwhile, refrigerant mixtures offer flexibilities to tune these criteria, This paper will review the status worldwide on technical and policy search for next-generation refrigerants with both low Global Warming Potential (LGWP) and low Life Cycle Climate Performance (LCCP) with particular focus on R410A replacement for unitary A/C & H/P. R32 and the HFO blends offer potential solutionsbut all involve tradeoffs among Global Warming Potential (GWP), efficiency, safety, and cost. With the U.S. mandating new higher regional efficiency standard taking effect January 2015, there is even more pressure in finding a LowGWP refrigerant solution that is affordable and can sustain efficiency and reduce charge requirement. This paper focuses more on R32 as the available data for HFO blends is limited. And Mixing of both R32a and HFO-1234yf in Ac To Study the performance two different next generation refrigerants R32 and Hfo-1234yf.To determine most promising refrigerant blend for air conditioning system test observe, anaylize and compare result obtained with conventional refrigerant. To determine impact of R32 and HFO-1234yf refrigerant as a replacement of R410A

Thermodynamic and economic analysis of refrigerant mixture R290/R1234ze used in an ORC-EERC system for low temperature heat sources

In the process of promoting carbon neutrality, heat driven refrigeration technology has been widely concerned due to its ability to make use of low-grade thermal energy and improve energy utilization. A novel combined organic Rankine cycle and ejector expansion refrigeration cycle (ORC-EERC) system is proposed in this study. To lower global warming potential and flammability, refrigerant mixture R290/R1234ze is chosen as the working fluid. The proposed ORC-EERC system with ejector and vapor–liquid separator are compared with those of the traditional organic Rankine cycle and vapor compression refrigeration cycle (ORC-VCC) by thermodynamic and economic analysis. The simulation results show that the ORC-EERC can achieve higher exergy efficiency and produce lower cooling temperature. Under typical conditions, the total coefficient of performance of ORC-EERC increased by 17.32% and its levelized cost of cooling decreased by 10.45% compared with the ORC-VCC. Furthermore, the ORC-EERC can remarkably improve performance at a lower freezing temperature or a higher condensing temperature. The results of the proposed cycle show that the ORC-EERC system has great application potential in freezers.

Boiling heat transfer of binary and ternary mixtures in multiple rectangular microchannels

In this study, the boiling heat transfer of binary and ternary refrigerant mixtures in a horizontal multiport tube with multiple rectangular microchannels was investigated. The influences of the mass velocity, vapor quality, and heat flux on the heat transfer were evaluated for near- and non-azeotropic mixtures of R410A, R32/CF3I, R32/R1123, R32/R1234yf, R1123/R32/R1234yf, and CO2/R32/R1234yf. The obtained results were compared with those of pure refrigerants R1234yf and R32. For R1234yf at low mass velocity, the flow patterns were estimated as intermittent (plug) and slug-annular flows with an extremely thin liquid film. The heat transfer coefficient decreased when the heat flux was increased because dry patch areas formed and expanded on the sides of the noncircular microchannel. The near-azeotropic mixtures with small temperature glides exhibited heat transfer characteristics similar to those of the pure refrigerant. Conversely, the heat transfer coefficients deteriorated slightly under lower mass velocities. The heat transfer coefficients of binary and ternary mixtures with larger temperature glides were significantly different from those of pure refrigerants and near-azeotropic mixtures; they decreased with decreasing mass velocity owing to mass diffusion resistance. The heat transfer coefficients of binary mixtures with large temperature glides decreased monotonically as the mass velocity decreased, and the heat transfer noticeably deteriorated at lower mass velocities. The heat transfer model was developed for rectangular microchannels by considering the heat transfer contributions of thin liquid film evaporation due to surface force, forced convection, and nucleate boiling. Moreover, this model considers the flow pattern of multiple microchannels, heat transfer degradations due to dry patches and mass diffusion resistance, and dryout incipience quality. The results of the present model agree well with the heat transfer coefficients, including those of binary and ternary mixtures, in the pre- and post-dryout regions with a mean percentage error of 3.1%.

Measurement of vapour pressure, miscibility and thermal conductivity for binary and ternary refrigerant lubricant mixtures in the context of heat pump tumble dryers

Household appliances need to be both efficient and cost-effective. As a result, electrically driven tumble dryers were converted to heat pump driven ones several years ago in order to comply with energy directives, in this case in Germany. In order to increase the efficiency of heat pumps of different performance classes, the use of zeotropic refrigerant mixtures can be useful, since the temperature glide during the phase change of the refrigerant mixture can be adapted to the temperature gradients of the secondary fluids. In order to take advantage of this unique property, a refrigerant mixture selection was carried out by a screening procedure using REFPROP. Within the investigation presented here, two different zeotropic refrigerant blends, propane (R290)/dimethyl ether (DME or RE170) (30 wt.%/70 wt.%) and R152a/carbon dioxide (R744) (90 wt.%/10 wt.%) are focused on as substitutes with low global warming potential (GWP) for R134a in heat pump tumble dryers. The focus is on the interaction between the refrigerant mixtures and the respective lubricant to ensure usability in the heat pump tumble dryer. A specialised polyolefin-based (POE) lubricant was chosen for each refrigerant blend. Because the numerous combinations of possible refrigerant mixtures can lead to unanticipated challenges with oil mixtures, additional experimental investigations are necessary to ensure the compatibility of the lubricant and refrigerant mixture combination in the temperature ranges associated with the investigated application. Therefore, measurements of the vapor pressure, miscibility gaps and thermal conductivity of the refrigerant-lubricant mixture have been carried out and are the focus of this paper.

Multipolar SAFT-VR Mie Equation of State: Predictions of Phase Equilibria in Refrigerant Systems with No Binary Interaction Parameter.

An extension of the SAFT-VR Mie equation of state is proposed to predict the properties of multipolar fluids. The new model, referred to as multipolar M-SAFT-VR Mie, incorporates the general multipolar term developed by Gubbins and co-workers, which accounts for dipole-dipole, quadrupole-quadrupole, and dipole-quadrupole interactions. A modification of the third order terms in the perturbation theory results in an accurate description of the simulation data for multipolar Lennard-Jones fluids. Both the M-SAFT-VR Mie and polar soft-SAFT models are extended to account for polarizability, and a good agreement is obtained with molecular simulation data. The M-SAFT-VR Mie model is applied to refrigerant systems, and it is found that including both dipole and quadrupole moments in molecular models leads to more accurate results than using only a dipole moment. The new model provides excellent predictions of the vapor-liquid equilibria of zeotropic and azeotropic refrigerant mixtures without the need for binary interaction parameters, making it a valuable tool for formulating low-GWP working fluids.

Q-learning-based metaheuristic algorithm for thermoeconomic optimization of a shell-and-tube evaporator working with refrigerant mixtures

Q-learning-based metaheuristic algorithm for thermoeconomic optimization of a shell-and-tube evaporator working with refrigerant mixtures

Theoretical performance studies on environment friendly refrigerants used in refrigeration units

European Union regulations stipulate that household refrigeration systems must operate with fluid refrigerants that possess low global warming potential (GWPs). In this work, theoretical performance of six binary and one ternary mixture (which consists of R13I1, R290, R161, R32, R1234yf, and R1234ze(E)) was investigated. The performance parameters such as coefficient of performance (COP), refrigeration effect (RE), volumetric cooling capacity (VCC), discharge temperature, pressure ratio, and specific power consumption of all considered refrigerant mixtures is studied with respect to the evaporator temperature range of -18 to 180C and the condenser temperature range of 40 to 550C. The properties corresponding to different operating conditions for the refrigerants considered in this study are estimated using REFPROP 10. The findings demonstrated that, when compared to R134a, all the investigated refrigerants exhibited very low specific power consumption (apart from M9, M10, and M14-M16), and high volumetric cooling capacity (VCC) (apart from M11 and M13) under the operating conditions of evaporator temperature -180C and condenser temperature 400C. M1-M3 and M11-M13 gave similar and within 10% deviation in coefficient of performance, while M3 and M11-M13 refrigerant mixtures offer significantly low discharge temperatures when compared to R134a. Refrigerant mixtures M2 and M11 consistently exhibited a better performance in comparison to R134a in the aspect of majority of the performance parameters considered in this study. Finally, it is understood that M2 and M11 are two possible alternative refrigerants to conventional refrigerants used in small refrigeration units (R134a and R22). Further, it is also identified that these mixtures are non-flammable, possess zero ODP and low GWP values.

Measurement of vapor-liquid equilibrium for the binary system propene (R1270) + trans-1,3,3,3‑tetrafluoropropene (R1234ze(E)) at temperatures from 288.18 K to 318.18 K

The search for alternative refrigerants that are environmentally friendly and highly efficient has become one of the most urgent and important issues facing the refrigeration industry. R1270 has excellent thermodynamic properties, but its high flammability limits its range of applications. R1234ze(E) is an environmentally friendly refrigerant with negligible flammability though it has the drawback of poor heat transfer performance. R1270 can be blended with R1234ze(E) as a new mixture refrigerant. vapor–liquid equilibrium (VLE) is the basic physical property of mixtures. The vapor–liquid equilibrium data have been measured for the binary system R1270/ R1234ze(E) based on the liquid-phase cycling method at four temperatures (288.15 K, 298.15 K, 308.15 K, 318.15 K). All the experimental data were regressed by the Peng-Robinson (PR) equation of state (EoS) with the Huron–Vidal (HV) mixing rule involving the non-random two-liquid (NTRL) activity coefficient model, and the PR EoS relating to the van der Waals (vdWs) mixing rule. The results show that the predicted values by the two models are in good agreement with the experimental data, and the prediction accuracy of the PR + HV + NTRL model was higher than that of the PR + vdWs model. In addition, azeotropic behaviors of the binary mixture have been found in the measured temperature range.

Thermal Conductivity Calculation Model for Refrigerant Mixtures in the Vapor Phase

Thermal conductivity measurements of ten refrigerant mixtures (R-404A, R-406A, R-407C, R-409A, R-410A, R-415A, R-507A, R-227ea/R-134a 61.5/38.5, R-227ea/R-134a 88.8/11.2 and R-227ea/R-134a 45/55) in the gas phase are analyzed. The thermal conductivity was studied with the same experimental setup, which improved the reliability of the results, excluding thereby systematic errors caused by using different methods to measure thermal conductivity. The reported experimental data have 1.5 % to 2.5 % uncertainty at 0.95 confidence level with a coverage factor of k = 2. Equations for calculating thermal conductivity depending on temperature and pressure are given for each mixture. The equations for thermal conductivity on the dew line and in the ideal gas state are obtained. A model for predicting thermal conductivity on a wide range of state parameters is proposed based on obtained experimental data and the theory of thermodynamic similarity. A comparison of the experimental data with the calculation model gives the standard deviation at 0.4 % to 2.1 %, which does not exceed the measurement error.

Prediction of Critical Heat Flux of Mixtures Flowing in Channels

Boiling of mixtures in channels is involved in many chemical processes, and refrigerant mixtures are finding a rapidly increasing use in the refrigeration industries. Hence, reliable prediction of CHF (critical heat flux) is needed. There is no published method that has been verified over a wide range of parameters. In this study, available data for CHF in tubes and annuli were compared to general correlations for tubes and annuli, which are well-verified for single-component fluids. This paper presents the results of this comparison. It was found that general correlations for single-component fluids were in satisfactory agreement with data for mixtures. The data included mixtures of refrigerants and chemicals, reduced pressure 0.02 to 0.8597, mass flux 200 to 3798 kgm−2s−1, temperature glide 2.1 to 21.9 K, and critical quality −0.46 to 0.99. The data for annuli were predicted with a MAD (mean absolute deviation) of 13.6%, and the data for tubes had a MAD of 13.9% when compared to the Shah correlations for single-component fluids. Based on the results of the present data analysis and results of research on pool boiling, a range is identified in which pure fluid correlations can be used for mixtures. This will be useful in the design of heat exchangers involving the boiling of mixtures in channels.

Exergy and performance analysis of low GWP and Non-flammable HFO based refrigerant mixtures as alternatives to R134a

R1234yf and R1234ze(E) can be potential retrofits for the conventional refrigerants used in domestic refrigerator provided their flammability is controlled. In this study, the inerting effect of the dilutants R125, R134a, R227ea and R245fa on R1234yf and R1234ze(E) based ternary mixtures is studied theoretically. R152a, R161 and RE170 are used as the secondary refrigerants with R1234yf and R1234ze(E) based ternary mixtures. Minimum inerting concentration (most important parameter that decides the flammability of the mixture) is estimated with thermal balance method (TBM) and modified thermal balance method (MTBM) for the selected mixtures. The calculated MIC values are compared with 86 experimental data points (both binary and ternary) available in the literature. It is calculated that TBM and MTBM predicted the minimum inerting concentration values (for a majority of the mixtures) within ±30% and ±8% respectively when compared with the experimental data. The COP ratios of the non-flammable mixtures (that are proposed with MTBM) are estimated and is found to be maximum at a volumetric cooling capacity ratio close to 0.8. It is also calculated that the exergy efficiency varied between 0.54 to 0.64 for the low GWP mixtures (M1 to M5) proposed in this study.

Outstanding performance of PIM-1 membranes towards the separation of fluorinated refrigerant gases

The recycling of depleted high global warming mixtures of fluorinated gases (F-gases) with close-boiling or azeotropic behavior requires advanced separation processes to obtain effectively the pure components. Herein, several types of PIM-1 membranes were tested for the first time towards the separation of hydrofluorocarbons and hydrofluoroolefins, showing extraordinarily high permeability coefficients for the value-added difluoromethane (R-32), up to 4100 barrer, coupled with high selectivity for the F-gas pairs of interest. Additionally, the solubility of selected F-gases in PIM-1 was measured and fitted to the dual-mode and Guggenheim, Anderson and de Boer sorption models. The separation performance of the standard PIM-1 and a highly branched PIM-1 was examined with the mixture R-410A (containing R-32 and pentafluoroethane R-125) to assess the influence of the membrane topology on the mixed-gas permeation properties over time (physical aging). Considering that the branched PIM-1 membrane was the least impacted by the aging phenomena, it was used to recover high purity R-32 (concentration in the permeate side as high as 98.9 vol % was achieved) from refrigerant gas mixtures R-410A and R–454B (mixture of R-32 and R-1234yf) in continuous long-term experiments. Results showed the great potential of PIM-1 membranes for the separation of R-32 from refrigerant mixtures collected from end-of-life equipment.

Condensation heat transfer of binary and ternary mixtures inside multiport tubes

This study investigated the condensation heat transfer of pure refrigerants and binary and ternary mixtures inside horizontal multiport tubes with multiple square minichannels. The effects of mass flux, vapor quality, heat flux, channel size, and channel shape were evaluated using pure refrigerants R32 and R1234yf; binary mixtures R32/R1234yf, R32/R1123, R32/R13I1, and R410A; and ternary mixtures R1123/R32/R1234yf and CO2/R32/R1234yf. For pure refrigerants, the heat transfer coefficient in the annular and churn flow regimes decreased monotonically with decreasing vapor quality. By contrast, the heat transfer coefficient in the plug flow regime was higher over a wide vapor quality range because of the thin condensate film formed by surface tension. Smaller channels exhibited higher heat transfer coefficients. The square minichannels exhibited higher heat transfer coefficients than the circular minichannels, except in the region with high mass flux and high vapor quality. For binary and ternary mixtures, the heat transfer coefficients significantly decreased with decreasing mass flux and vapor quality and were strongly deteriorated at lower mass fluxes. Compared with the annular and churn flow regimes, in the plug and slug-annular flow regimes, where heat transfer through the thin liquid film was dominant, the effect of mass diffusion resistance in deteriorating heat transfer was the most pronounced. A new heat transfer model for pure refrigerants inside multiport tubes with multiple rectangular minichannels was developed considering the contributions of vapor shear stress and surface tension. The proposed model was verified using a dataset of pure refrigerants, and a mean absolute percentage error (MAPE) of 11.5% was achieved. Furthermore, a new heat transfer model that considers the heat transfer deterioration of non-azeotropic refrigerant mixtures was proposed, which could predict 508 datapoints with an MAPE of 13.3%.

A comprehensive study on the performance of vertical ground-coupled heat pumps

Vertical Ground-Coupled Heat Pump (VGCHP) systems are a green and sustainable alternative to conventional heating, ventilating, and air-conditioning systems. However, their main drawback is the high initial installation cost of the Vertical Ground Heat Exchanger (VGHE), which has hindered their widespread adoption. Improving the performance of VGCHP to reduce their installation and operating costs requires a comprehensive study that scrutinizes the long-term effects of various involving parameters on the performance of the system. This contribution presents a comprehensive study investigating various influential factors, including climate type, refrigerant type, borehole depth, and type of compressor and circulating pump, on the VGCHP system performance. For this aim, a detailed model of the VGCHP is developed that includes detailed heat pump modeling, fast and accurate VGHE analytical modeling, and recommended constraints of the ASHRAE standard. The developed heat pump model is compatible with both pure and refrigerant mixtures. The five-year operation of 180 cases is simulated. Based on five-year simulation results and sensitivity analysis, 90 cases are selected, and their 20-year operation is investigated. The results demonstrated that the heat pump type is the most influential parameter on the Coefficient of Performance (COP), and the climate type is the most influential parameter on the maximum thermal load provided to the building per VGHE unit length. Moreover, optimum design parameters are determined based on short- and long-term simulation results. Furthermore, the response surface method is implemented to develop predictive equations for COP and maximum thermal load as a function of influential factors.

Alternative blends of CO2 for transcritical refrigeration systems. Experimental approach and energy analysis

As a natural refrigerant, Carbon Dioxide (CO2) has been extended in almost all refrigeration fields due to its environmental friendliness, high availability, and high technological development in the main components of the cycle. However, despite the benefits, CO2 is limited to high-capacity applications due to the cost of components and the complex cycle arrangements to overcome the low coefficient of performance (COP) at high ambient temperatures. A simple but effective method to solve this issue involves mixing CO2 with other refrigerants obtaining a new refrigerant mixture with higher critical points, lower working pressures and low global warming potential (GWP). Depending on the mixture percentage, the mixture flammability can be suppressed, and the performance of the refrigeration plant can be increased.Building on this, this work determines theoretically different CO2­based zeotropic blends as an alternative to pure CO2 with the restrictions of non-flammability, GWP below 150 and higher COP than pure CO2. The results suggest two blends of CO2/R1270 and CO2/R32 that have been prepared and energetically tested in a vertical display cooler using pure CO2 as a reference. The results revealed that CO2-blends reduce energy consumption by up to 17.2 % at the ambient temperature of 25 °C and up to 12.2 % at 30 °C. Moreover, the results with CO2-blends were closest to those obtained with pure R1270 and better than R134a under the same operating conditions.

Solubility, Diffusivity, and Permeability of HFC-32 and HFC-125 in Amorphous Copolymers of Perfluoro(butenyl vinyl ether) and Perfluoro(2,2-dimethyl-1,3-dioxole)

R-410A, an azeotropic mixture composed of 50 wt % difluoromethane (HFC-32, CH2F2) and 50 wt % pentafluoroethane (HFC-125, CHF2CF3) used in residential and commercial air-conditioning applications, will be phased down due to the high global warming potential (GWP) of HFC-125. The HFC-32 can be reused in low-GWP blends containing hydrofluoroolefins (HFOs); however, incumbent separation technology, fractional distillation, cannot separate azeotropic mixtures. Membrane technology provides the opportunity to achieve a selective separation of azeotropic HFC refrigerant mixtures with lower energy consumption and capital requirements. This study explores the use of amorphous perfluoropolymers for the separation of R-410A. The permeability, solubility, and diffusivity of HFC-32 and HFC-125 were measured in copolymers of perfluoro(butenyl vinyl ether) (PBVE) and perfluoro(2,2-dimethyl-1,3-dioxole) (PDD). Pure gas permeability of HFC-32 and HFC-125 were measured using a static membrane apparatus and the pressure-rise method. Solubility measurements were obtained using a gravimetric microbalance, and diffusivity was calculated using a Fickian model. The results indicate that a high permeability and selectivity of HFC-32/HFC-125 can be obtained with a 50 wt % PBVE and 50 wt % PDD copolymer and that the separation is diffusion-driven over the entire range of compositions tested.

In situ measurement of circulation composition of refrigerant mixture in heat pump system with NIR absorption spectroscopy

Near-infrared absorption spectra of difluoromethane (R32) and 2,3,3,3-tetrafluoropropene (R1234yf) were experimentally measured for superheated gas and subcooled liquid under different temperature and pressure conditions. Molar attenuation coefficients at wavelengths of 1.59, 1.64, 1.70 and 1.78 μm were obtained using 1.5 μm wavelength data as a reference spectrum. Attenuation coefficient of the gas phase R32 refrigerant showed significant variation depending on the operating conditions, where liquid phase showed relatively constant absorption characteristics at different pressures and temperatures. Furthermore, the attenuation coefficients were distinctive between R32 and R1234yf and absorption peaks and intensities were identical. The estimation model of absorption characteristic for refrigerant mixture was then constructed using the liquid phase spectra of the pure refrigerants at each wavelength with validation using the experiment data of upward flow with circulation compositions of R32 : R1234yf = 30 : 70, 50 : 50 and 70 : 30 mass%. The estimated data qualitatively showed good agreement with the measured spectra in point of dependency on composition ratio. However, up to 15% deviation was found in the 1.59 μm spectra where R1234yf has relatively strong absorption. Further investigation, spectra dependency of refrigerant mixture on molecular interactions and of pure refrigerant on broader range of conditions, including pressure near critical point, are considered to be necessary to improve the estimation model.

Flow boiling heat transfer of zeotropic mixture refrigerants R454B and R449A in a smooth horizontal tube

The paper reports an experimental investigation of local saturated flow boiling heat transfer of two environmentally-friendly zeotropic mixture refrigerants – R454B and R449A – in a horizontal 8.7 mm ID smooth tube, under high pressure and high heat-flux conditions. The test section is divided into five subsections to obtain quasi-local heat transfer and the refrigerants are heated by hot water in counter-current flow. For R454B, mass flux varied from 201 kg m−2 s−1 to 269 kg m−2 s−1 and the inlet pressure varied from 1.691 MPa to 3.282 MPa. For R449A, mass flux varied from 178 kg m−2 s−1 to 328 kg m−2 s−1 and the inlet pressure varied from 1.449 MPa to 3.244 MPa. The temperature glide and composition shift during flow boiling due to volatility difference between components were investigated. R454B and R449A displayed a temperature glide respectively from 1.12 K to 1.33 K and from 3.04 K to 4.61 K at the inlet of the test section in the present tests. During the process of saturated boiling, for R454B, mass fraction of the less volatile component, R1234yf, in liquid phase was over 7% more than that in vapor phase; For R449A, mass fractions of the less volatile components, R134a and R1234yf, in liquid phase were around 6% and 4% more than those in vapor phase. Thermal resistance and mass transfer resistance were discussed. Before the occurrence of partial dry-out, heat-transfer coefficients of R454B were mainly located between 6.5 kW m−2K−1 and 10 kW m−2K−1 while most of data of R449A lay in the range of 3.5 – 8 kW m−2K−1. The results of heat-transfer coefficient indicate that R454B exhibited greater heat transfer than R449A under close operating conditions. For both refrigerants, the heat transfer performance was locally enhanced in the region of near-zero vapor quality and gradually declines before intermediate vapor quality. After intermediate vapor quality, it tended to rise with vapor quality until a dramatic fall due to partial dry-out.

Theoretical performance comparison for a regenerator-enhanced three-stage auto-cascade refrigeration system using different zeotropic mixed refrigerants

Auto-cascade refrigeration (ACR) systems are widely used at low temperatures. The selection and ratio optimization of zeotropic refrigerants in ACR systems have an important impact on system performance and environmental protection. This study proposes a three-stage regenerator-enhanced auto-cascade refrigeration (RACR) system. Under certain working conditions, the theoretical performances of the three-stage R134a/R23/R14 ACR and RACR systems were compared, and the influence of the refrigerant mixture ratio on the RACR system performance was explored. The system performances of replacing R134a and R23 with different hydrocarbons were compared under different working conditions. The results demonstrated that RACR performed better than ACR alone. A reasonable adjustment to the mixed refrigerant ratio improved the energy efficiency of the RACR system. Water-cooling conditions for the RACR system were suggested, under which the coefficient of performance, thermodynamic perfectness, and exergy efficiency of R600/R170/R14 were 13.8 %, 12.4 %, and 8.4 % higher than those of R600/R23/R14, respectively. The environmental policy, safety requirements, and energy efficiency were considered to obtain −100 °C, R600/R170/R14 with mass fractions of 0.24/0.12/0.64 was the best choice in a water-cooled RACR system.

Water and Ethanol as Refrigerant Mixture Enabling Adsorption Cooling below 0 °C

Adsorption chillers can avoid two types of greenhouse gas emissions from conventional cooling technologies: energy‐related emissions by utilizing waste heat and refrigerant leakage‐related emissions by employing the natural refrigerant water. However, water restricts the minimal cooling temperature to its freezing point. To overcome this limitation, herein, a boiling antifreeze in adsorption chillers is proposed. For this purpose, a databank of over 12 000 molecules for suitable antifreezes is screened and ethanol is derived as the best candidate. Employing ethanol as antifreeze, the experimental feasibility in a lab‐scale adsorption chiller is demonstrated: ethanol can prevent freezing at a cooling temperature of –5 °C and, thus, extend the operating range of the adsorption chiller. Thereby, the favorable properties of water can be partially retained. Furthermore, water–ethanol mixtures to pure water at a cooling temperature of 10 °C are compared: maximal coefficient of performance (COP) and specific cooling power (SCP) decrease by 45% and 42%, respectively, when 14 mol% ethanol is used instead of pure water. Herein, the influence of ethanol on the adsorbed mass and heat transfer during evaporation are crucial. In summary, boiling antifreezes can extend the operating range of water‐based adsorption chillers below 0 °C.