Cascade Refrigeration Cycle Research Articles

Enhancing Semiconductor Chiller Performance: Investigating the Performance Characteristics of Ultra-Low-Temperature Chillers Applying a Liquid Receiver

This study investigates the implementation of a cryogenic chiller utilizing a mixed-refrigerant cascade refrigeration cycle (MRCRC). In this setup, R-404A is employed in the high-temperature circuit (HTC), while a mixture of refrigerants is utilized in the low-temperature circuit (LTC). Unlike a conventional MRCRC that operates without a receiver to maintain the composition ratio, this research explores the impact of receiver installation on system performance. Experiments were conducted with and without a receiver to assess performance improvements and device behavior. With a fixed refrigerant charge of 4 kg, the suction and discharge pressures of the LTC compressor remained low and stable after the receiver’s installation. The addition of a receiver significantly reduced the cooling time, with further reductions observed as the refrigerant charge increased. The system achieved evaporative heat capacities of 0.59, 1.76, and 2 kW for refrigerant charges of 4, 7, and 9 kg, respectively. Notably, at the maximum refrigerant charge of 11 kg, the evaporative heat capacity peaked at 3.3 kW. These findings indicate that incorporating a receiver is crucial for enhancing the cooling performance of cryogenic coolers using mixed refrigerants and stabilizing device operation. This contrasts with previous studies that omitted receivers due to concerns over potential alterations in the composition ratio of the mixed refrigerant.

Energy-exergy-economic-environmental (4E) analysis and multi-objective optimization of a cascade refrigeration system

The present work focusses on 4E analysis of a 50 kW cooling capacity cascade refrigeration cycle covering the aspects of energy, exergy, economic and environment analysis. The numerical investigation and the multi-objective optimization is carried out for the system using the refrigerant pair R170-R600a and R41-R600a. The refrigerant pair is selected based on the environmental implications in terms of GWP and ODP. Multi-objective optimization of the objective functions is carried out using a heat transfer search optimization algorithm to evaluate the optimal performance of the system. The effect of evaporator temperature, condenser temperature, LTC condenser temperature and LTC condenser temperature difference on the exergy efficiency and total cost of the system is studied. A set of multiple optimal solutions is presented using the Pareto optimal curve and TOPSIS criteria is employed to select the optimal operating condition. Compared to the refrigerant pair R170-R600a, the system with R41-R600a operates at better exergy efficiency and lower total cost. At the TOPSIS selected optimal condition, exergy efficiency and the total cost of the CRS is 63.5 % and 65,228 $/year for the refrigerant pair R41-R600a and 62.6 % and 67,690 $/year for R170-R600a, respectively. The distribution of variables shows that the effect of the evaporation temperature, condensation temperature and the LTC condenser temperature is profound in obtaining the optimal solution.

Thermodynamic performance analysis and environmental impact assessment of cascade refrigeration cycles using eco-friendly nano-refrigerants

There is a lack of research in the literature on the application of nanoparticles to different cascade cycle configurations with environmental refrigerants in ultra-low temperature refrigeration applications. This study is the first on the use of nano-refrigerants in cascade refrigeration cycles. In this study, the effect of 2 wt.% of CuO to RE170 and R170-pure refrigerant utilization in cascade vapor compression refrigeration cycle (CVCRC), cascade ejector refrigeration cycle (CERC) and cascade ejector intercooler refrigeration cycle (CEIRC) are investigated to achieve higher performance values in ultra-low temperature applications. For CVCRC, CERC and CEIRC, the increases in terms of coefficient of performance (COP) with the use of nano-refrigerant were found to be 12.77 %, 8.20 %, and 6.37 %, respectively, and 18.55 %, 14.05 %, and 6.07 %, for exergy efficiency. Upon scrutinizing the results with nano-refrigerant in relation to the COP, the analysis revealed that the CEIRC cycle exhibited an improvement ranging from 13.43 % to 20.49 % in comparison to CERC. Additionally, with nano-refrigerant, the CEIRC cycle demonstrated an increase ranging from 42.39 % to 75.41 % when compared to CVCRC in COP. It was observed that the utilization of CEIRC led to a 13.03 % decrease in kg CO2 emissions in compared to CERC and a reduction of 32.53 % compared to CVCRC with using nano-refrigerant.

Study on a novel hydrogen liquification process applying mixed-refrigerant for pre-cooling and cryogenics

Reducing the energy consumption of hydrogen liquefaction process is an urgent issue to improve the economy of liquid hydrogen transportation. A novel large-scale hydrogen liquefaction system, with a capacity of 100 TPD, is proposed in this paper. The pre-cooling system is composed of a mixed-refrigerant (MR) refrigeration cycle and a CO2–NH3 cascade refrigeration cycle. Due to the auxiliary pre-cooling effect of the CO2–NH3 cascade cycle, temperature of the pre-cooled hydrogen can be as low as −200.9 °C. A modified MR Joule Brayton cycle with an additional compressor is used as the cryogenic system to cool the hydrogen from −200.9 °C to −252.2 °C. Besides, a four-stage ortho-to-para conversion (OPC) process is utilized. Performance of the novel system is investigated and optimized using the Aspen HYSYS software. According to the results, the lowest specific energy consumption (SEC) of the proposed process is 6.15 kWh/kgLH2 and the exergy efficiency is as high as 67.4%. Based on the energy analysis, the best system coefficient of performance is 0.1751 with a 96.3% of p-H2 in the liquid hydrogen. In addition, compared to the initial conceptual system, the proposed system exhibits significant performance enhancements, a 20% reduction in SEC and a 27.9% increase in exergy efficiency. A sensitivity analysis is conducted to assess the impact of refrigerant composition and hydrogen pressure on the system, resulting in the determination of the optimal proportions of refrigerant components and the optimal inlet pressure. Results of the study can provide theoretical reference for the further development of large-scale hydrogen liquefaction technology.

Energy, exergy, environmental and exergoeconomic (4E) analysis of an ultra-low temperature cascade refrigeration system with environmental-friendly refrigerants

To ensure the efficacy of some special vaccines, the ultra-low temperature storage below −80 °C is strictly required and the classical cascade refrigeration system has a good application prospect in the production, storage, transportation and distribution of COVID-19 vaccines. Previous investigations are mainly focused on the thermodynamic performance of cascade refrigeration cycles (CRSs) to generate low temperature, and the impact of cascade refrigeration cycles on environmental and exergoeconomic aspects is few involved. In this paper, an energy-exergy-environmental-exergoeconomic (4E) analysis model was built to investigate the comprehensive performance of an ultra-low temperature cascade refrigeration system. Eight environmental-friendly refrigerant pairs, including R290-R170, R290-R1150, R717-R170, R717-R1150, R1270-R170, R1234yf-R170 and R1234yf-R1150, were chosen and the associated refrigeration performance was compared. The results show that the optimal refrigerant pair is propane-ethane (R290-R170). Compared with HFC refrigerant pair R404A-R508B CRS, R290-R170 CRS could improve the COP by 5.94%, save 5.68% power consumption, reduce 29.67% carbon dioxide emission and decrease 5% exergy economic cost. This work is significant to select environmental-friendly nature refrigerants, enrich understanding of comprehensive performance of cascade refrigeration system and enhance depth research on ultra-low temperature refrigeration.

Multi-objective optimization of the organic Rankine cycle cascade refrigeration cycle driven by sugar mills waste heat

The research on the recovery of low-grade thermal energy carried away by boiler flue gas is significant for sugar mills. This paper designs a waste heat recovery system based on sugar plant flue gas, integrating absorption refrigeration cycle and the organic Rankine cycle, and the effects of nine working fluids on the system are investigated. The aim is to realize the multi-form conversion of energy. The performance of the system is evaluated in terms of energy, exergy, and economic metrics. Multi-objective optimization is performed with the method of the NSGA-II genetic algorithm. The results show that Butane is the most suitable working fluid for ORC. The exergy efficiency of the system is 32.125% before optimisation, with an increased space cooling capacity of 15820.56 MW per year for the sugar mill. The exergy destruction analysis of the system reveals that the generator accounts for the highest proportion of exergy destruction (50.8%). The entire system shows the LCOE is as low as 0.0406$/kWh under the optimized condition. The optimized system can obtain an estimated annual electricity sales revenue of $136,300, and the sugar mill can save $308,600 in cooling costs. In addition, the payback period can be shortened to 5.79 years.

Comparative exergy and energy analyses of compression–absorption cascade refrigeration cycles with varied configurations and ejector implementations

This study aims to assess the feasibility and performance, as well as the exergy loss, of utilizing ejectors in absorption–compression cascade configurations for low-temperature refrigeration systems. The coefficient of performance (COP) is used to measure system efficiency, including COP.A (COP of the absorption chiller), COP.C (COP of the compression side) and COP.Ca (COP of the cascade configuration). The results highlight the importance of ejector placement on the absorption side for optimal performance. Configuration D1, with an ejector on the absorption side, demonstrates an 85% improvement in COP.A, approximately 10% in COP.C and nearly 100% in COP.Ca compared to configurations without an ejector. However, in certain cases, using an ejector on the compression side is not feasible from a second-law perspective, particularly for higher compression-side evaporator temperatures. Nonetheless, the study suggests that configuration D0, which includes an ejector on the absorption side coupled with a simple compression cycle, is applicable for these conditions and performs similarly to D1 in other temperature ranges. These findings provide valuable insights for optimizing ejector placement in absorption–compression cascade configurations and advancing the development of more energy-efficient refrigeration systems.

Energy, exergy, and economic analysis of compression-absorption cascade refrigeration cycle using different working fluids

Compression-absorption cascade refrigeration cycle (CACRC) combined with vapor-compression refrigeration and absorption refrigeration cycle attracts great interest due to the less electricity consumption and utilization waste heat. In this work, the performance of the CACRC system was investigated using 16 refrigerants in the vapor compression section and H2O-LiBr in the absorption refrigeration section. Energy, exergy and economic analysis of the CACRC system were carried out and the results were compared. Results show that RE170/H2O-LiBr presents the better coefficient of performance and exergy efficiency amongst all the studied fluids. In addition, the economic optimization, multi-objective optimization, and thermodynamic optimization of the CACRC system based on the RE170/H2O-LiBr working fluid were also carried out.

Performance Evaluation of Cryogenic Liquefaction System Precooled by Combined Vapour Compression-Absorption Refrigeration System

Liquefaction is a high-energy-consuming process. One of the most efficient methods of lowering energy consumption use is to run a precooled cycle with a cascade refrigeration system. When compared with the vapour compression system, the merit of adopting a cascade system is that it consumes very less energy. Another advantage is that non-traditional energy sources such as geothermal and solar might be used to power these cycles. This paper examines a precooled Linde Hampson-liquefaction system using a double-stage cascade vapour compression-absorption refrigeration cycle that consists of an absorption system at the high-temperature stage and a compression system at the low-temperature stage to generate cooling at a small temperatures by using various refrigerants in the absorption and compression sections. The system's performance was evaluated by employing various combinations of natural refrigerants in the absorption section. Liquefaction of Nitrogen is carried out using a precooled Linde Hampson system and precooled liquefaction using a cascade refrigeration cycle. Nitrogen was liquefied using two methods in the current study. A thorough examination of the precooled system was conducted, and it was discovered that by employing a cascade refrigeration cycle, the input required per unit mass of gas liquefied is decreased. The performance metrics of the liquefaction system, such as Figure of Merit (FOM) and Liquid Yield, were discovered for both scenarios, and it is concluded that the usage of a cascade refrigeration system has more efficiency and consumes less energy than a system without an absorption chiller. The use of a precooled Linde Hampson system with cascade cycles improved liquefaction characteristics by 5-7%.

Influence of gas density on void fraction and pressure drop in upward vapor–liquid flow

The influence of gas density on the void fraction, flow map, and pressure drop was examined for an upward vapor–liquid flow. The knowledge of the flow map is necessary to ensure a safe operational condition in a nuclear zone at high pressure. Moreover, the pressure gradient and its volumetric flow rate are related to the profitability of petroleum wells. Considering these scenarios, a modified cascade refrigeration cycle was constructed to generate and measure single-phase streams with different liquid and vapor density ratios. These single-phase liquid and vapor streams were mixed and injected into an upward vertical test section with an inner diameter of 26.64 mm and length of 5.8 m. The pressure ranged from 1.7 to 2.3 MPa, liquid–vapor density ratio ranged from 10.2 to 15.2, and total mass flux ranged from 733.1 to 882.9 kg.s−1.m−2. The void fraction, pressure gradient, and frictional pressure component were measured using quick-closing valves, temperature probes, and absolute and differential pressure sensors. The experimental data and transition line behavior of the flow map at high pressures in an upward two-phase flow as well as the proposed correction factors for the pressure gradient and its frictional component reflect the novelty of this study. Most existing studies have focused only on the influence of the gas density on the horizontal flow. A key observation of our study is that the liquid–vapor density ratio significantly changes the churn and annular transition lines. According to a vertical flow map found in the literature, the disappearance of the churn region can be foreseen and an annular transition occurs at lower gas velocities. The liquid–vapor density ratio does not influence the void fraction or slip velocity ratio; both increase with the superficial vapor velocity. Correction factors for the pressure gradient and its frictional component were proposed. The mean deviation for the pressure gradient was reduced from 27 % to 16 % after application of the correction factor. Half of the experimental points presented absolute relative errors lower than 30 % for the frictional pressure gradient. A cross-validation between the experimental data reported by other authors and the proposed correction factors was conducted to assess their response. In this cross-validation, 126 additional experimental points were used for the pressure gradient whereas 1270 points were used for its frictional component. Overall, the mean deviation of the pressure gradient was reduced from 92.7 % to 31.9 % after the application of the correction factor. Similarly, the mean deviation of the frictional gradient was reduced from 70.7 % to 31.3 % after the application of the correction factor. There was no evident influence of the liquid–vapor density ratio on the total pressure gradient and drift relationships for Froude numbers spanning from 2.6 to 7.4.

Thermodynamic and Environmental Analysis of Novel Cascade Refrigeration Cycles with Ejector and Intercooler for Ultralow Temperatures Using Eco‐Friendly Refrigerants

The present study introduces a novel cascade ejector intercooler refrigeration cycle (CEIRC) and a novel cascade ejector booster refrigeration cycle (CEBRC), which are designed to improve ultralow temperature (ULT) refrigeration system performance based on various refrigerants in terms of energy, exergy, and environment. Through the analysis conducted with eco‐friendly refrigerants for CEIRC, the refrigerant pair exhibits the highest performance that is found to consist of RE170 for high‐temperature cycles and R170 for low‐temperature cycles. These refrigerants have very low global warming potential and are eco‐friendly. The coefficient of performance (COP) reveals improvements of 3.20–9.51%, 10.55–19.12%, and 31.96–65.97% over the CEBRC, cascade ejector refrigeration cycle (CERC), and cascade vapor compression refrigeration cycle (CVCRC), respectively, resulting in corresponding exergy efficiency improvements of 3.18–9.49%, 10.48–19.12%, and 31.87–65.98%. The total compressor power and exergy destruction are also compared, indicating that the CEIRC exhibits the best performance among the four. CEIRC achieves a COP increase of 11.6% compared with the cascade refrigeration cycle, which is considered the cycle with the highest performance operating at ultralow temperatures in the literature, which is CERC. The kg CO2 effect of the CEIRC is 11.35% lower than that of the CERC.

Ultra-Low-Temperature Refrigeration Systems: A Review and Performance Comparison of Refrigerants and Configurations

During the last decade, many industrial and medical applications have shown a requirement for low-temperature-cooling usage (from −40 to −80 °C), which cannot be efficiently obtained via the conventional refrigeration systems usually employed for medium-temperature applications (from 0 to −40 °C). A proper ultra-low-temperature (ULT) refrigeration system design is essential to achieve the desired output. The performance can be maximised via the suitable selection of the configuration and refrigerant for a specific temperature range. This work contributes a detailed overview of the different systems and refrigerants used in ultra-low-temperature applications. Different systems, such as single-stage vapour compression, multi-stage, cascade, auto-cascade, and air refrigeration cycles, are presented and discussed. An energy analysis is then carried out for these systems identifying the optimal system design and refrigerant selection to achieve the highest performance. This paper aims to provide the reader with a comprehensive background through an exhaustive review of refrigeration systems suitable for ultra-low-temperature applications. The effectiveness of these systems is proven numerically, mainly based on the temperature level and purpose of the application.

Thermodynamic design and experimental study of a condensation recovery system for VOCs

During the storage and transportation process of crude oil on tankers, the light hydrocarbon components in liquid form have the tendency to evaporate and vaporize easily, resulting in wasted resources and environmental pollution. The current petroleum volatile organic compounds (VOCs) recovery system such as absorption and membrane separation applied to crude oil tankers is unable to fulfil the requirements of existing VOCs emission standards. In contrast, the condensation method of VOCs recovery technology has the benefit of a straightforward process principle, and the recovered liquid hydrocarbons can be utilized directly. It is thus vital to develop a condensation recovery system for petroleum VOCs that is compatible with crude oil tankers. To attain the condensation and recovery of the non-azeotropic gases, such as CH4, C2H6, C3H8, and N2 in the feed gas, this paper proposes a low-temperature VOCs condensation recovery system with graded cooling and liquefaction separation for crude oil tankers. The proposed system initially utilizes a R404A/R23 double-stage cascade refrigeration cycle to cool the VOCs below −75 ℃ to liquefy most heavy hydrocarbons. Then, a low-temperature nitrogen expansion cooling cycle is utilized to cool the VOCs to approximately −160 °C to recover the remaining light hydrocarbons. The condensation process is simulated by Aspen HYSYS to study the variable operating conditions. The recovery of total hydrocarbons in the outlet tail gas in the simulation results is analyzed and found to be up to 95.50 %. Under identical refrigeration capacity circumstances, decreasing the inlet pressure, increasing the inlet flow rate, and increasing the methane mole fraction in VOCs component, all lead to declining trends of total hydrocarbon recovery and methane recovery rate. Specifically, the effects of four different hydrocarbon component ratios on total hydrocarbon recovery and total cooling load are investigated at a constant nitrogen content and refrigeration capacity. Furthermore, the optimal design and analysis process for the flow path section of the turbine expander under the cryogenic conditions is discussed. The results demonstrate that the outlet temperature through the turbine expander is at least −172.1 °C, and the cooling capacity can be up to 4.5 kW with a margin of 80 %. Finally, through the comprehensive VOCs condensation recovery experiments, the proposed system successfully achieves the liquefied separation and recovery of CH4, C2H6, and other hydrocarbons. The recovery rate of the total hydrocarbons in the outlet tail gas reaches 96.21 %, conforming to the VOCs emission standards and regulations. The findings of this study provide a viable technical resolution in the field of petroleum VOCs recovery from crude oil tankers.

A fast method for the calculation of refrigerant thermodynamic properties in a refrigeration cycle

Modeling and simulating dynamic and complex energy systems that are composed of a large number of components where every component model is described by mathematical equations can take high computational time. The calculation of the refrigerant thermodynamic properties has a big impact on the computational speed of the model. In an attempt to speed up simulations, two implementation methods for the calculation of refrigerants’ thermodynamic properties were investigated, the Coolprop thermodynamic equations of state and the Implicit fitting method. A complex dynamic cascade refrigeration cycle was developed and simulated using the two fluids implementation methods. The advantages and disadvantages of each method were discussed. The results show that using the implicit fitting method instead of Coolprop for the simulations of complex dynamic systems in Dymola will accelerate the simulation by about 30 times. In addition, the implicit method is accurate and offers more flexibility for modeling complex realistic energy systems.

Cost Optimization of Heat Exchanger Inventory in Cascade Refrigeration Cycles

Cost Optimization of Heat Exchanger Inventory in Cascade Refrigeration Cycles

Evaluation and optimization of a novel cascade refrigeration system driven by waste heat

Direct discharge of waste heat from internal combustion engines (ICEs) is unfavorable for the efficient and clean fuel utilization. Here, a novel combined absorption-compression cascade refrigeration cycle is proposed to efficiently capture low-grade waste heat and supply cooling capacity for food freezing in vessels or refrigerated trucks. The intention of this work lies in: i) Comprehensively evaluating the performances of the proposed system; ii) Gaining the optimal operating conditions of the system. Aimed that, analysis models of energy, exergy, economy, and environment are set up to evaluate the sweeping performances. Further, multi-objective optimization is introduced to obtain the optimal operating parameters including evaporation and condensation temperature of the low-temperature stage, generation temperature and condensation temperature of the high-temperature stage, and cascade temperature differences. By applying multi-objective optimization, the coefficient of performance and exergy efficiency of the system are elevated from 1.283 to 1.547, and 0.222 to 0.246, respectively, the discharge amount of carbon dioxide are reduced from 71.40 to 59.57 tons year−1, and annual total cost are decreased from 16,028 to 15,055 $ year−1 compared to initial operating conditions.

Design and optimisation of novel cascade mixed refrigerant cycles for LNG production – Part I: Benchmark cascade cycles

Complex cascade refrigeration cycles are typically used for production of liquefied natural gas (LNG). These include the propane precooled mixed refrigerant (C3MR) cycle, the dual mixed refrigerant (DMR) cycle, and the Phillips Cascade cycle. These are highly energy-intensive processes, resulting in many studies focusing on improving their energy efficiency by reducing their shaft power demand. However, their relative performance remains unclear. Modelling assumptions and natural gas feed differ across the published literature. This work models and evaluates these three commercial cascade cycles on a common basis of modelling assumptions, natural gas feed and process complexity (e.g. number of compression stages). However, the performance of the cycles cannot be compared meaningfully without first optimising the designs. The optimisation strategy proposed combines a genetic algorithm, which includes regeneration of the population to improve diversity, with a nonlinear optimisation. A case study demonstrates the effectiveness of this strategy. This work provides a meaningful comparison of the relative efficiencies of these commercial cascade cycles, to provide a basis for benchmarking novel cascade cycle options in a study to follow.

Design and optimisation of novel cascade mixed refrigerant cycles for LNG production – Part II: Novel cascade configurations

Large scale production of liquefied natural gas (LNG) typically employs energy-intensive cascade refrigeration cycles. Three well-established cascade cycles in the LNG industry are the Propane Pre-cooled Mixed Refrigerant (C3MR), Dual Mixed Refrigerant (DMR) and Phillips Cascade cycles. Previous work has focused on improving the energy efficiency of these cascade cycles with various methods (e.g. exergy analysis), as this can bring significant economic benefits. However, potential benefits associated with changes in the configuration of a cascade cycle are usually neglected. This work develops three cascade cycle options, based on structural modifications, to be competitive with the commercial processes. The novel configurations are the CryoMan Cascade cycle, the Bypass Cascade cycle and the Double CryoMan Cascade cycle. The performance of these novel cascade cycles is evaluated with a case study previously used to assess the commercial processes. The optimisation strategy consists of a genetic algorithm with regeneration of the population followed by a nonlinear optimisation. The results obtained demonstrate that the structural changes enable the novel cascade cycles to achieve energy savings of up to 15.6% compared to the C3MR cycle, and up to 5.9% compared to the DMR cycle. Moreover, these energy savings come at the expense of only minor added process complexity, as the number of compression stages and multi-stream heat exchangers are kept the same as in the commercial processes.

Study on solar absorption-compression cascade refrigeration cycle based on temperature and humidity independent

A new solar lithium bromide absorption - compression refrigeration cycle system was proposed for temperature and humidity independent control. MATLAB programming language is used to perform the thermal calculation of the new system, and the cycle characteristics of the typical day of the new system are analyzed. The influence of solar radiation intensity is analyzed. The results show that the new system can realize the cascade preparation and utilization of cooling capacity, and the optimal evaporation temperature makes the new system have higher performance.

Experimental evaluation of low-GWP refrigerants R513A, R1234yf and R436A as alternatives for R134a in a cascade refrigeration cycle with R744

This work presents an experimental analysis of the energy and environmental performance of low-GWP refrigerants R513A, R1234yf and R436A as alternatives for R134a in a cascade refrigeration system that operates with R744 in low-temperature cycle. An apparatus was built using a well-insulated room, where tests were carried out in a steady state condition. In addition to the typical components of a cascade cycle, an intermediate heat exchanger was used to thermally communicate the low and high temperature cycles, thus providing additional superheating and subcooling, respectively. The cooling capacity of the system ranged from 2.2 to 3.8 kW, the evaporation temperature varied from -34 to -24.5 °C and the air temperature inside the cold room ranged from -23.1 to -9.4 °C. The results revealed that the alternative refrigerants are potential substitutes for R134a in cascade refrigeration systems, showing an average increase in the CRC coefficient of performance of 3.1% for R436A, while R1234yf and R513A exhibited a reduction of 3.7% and 4.4%, respectively. The environmental impact analysis considered the scenarios of Chicago (USA) and Curitiba (Brazil), the latter being a southern Brazilian city with a wet climate throughout the year, a warm and mostly cloudy summer, and a short and cold winter. Total TEWI values, compared to those obtained with the originally designed R134a system, showed reductions in CO2 equivalent emission of 46%, 42.1% and 22.5% for refrigerants R436A, R1234yf and R513A, respectively, for the Curitiba scenario, while the values for Chicago were increments of 0.3%, 2.4% and 5.8%, respectively.