Hybrid Refrigeration System Research Articles

Advances on a SPTC/JTC/ADR system for sub-Kelvin cooling

Sub-kelvin cooling technologies are a critical technology for advanced deep space astrophysical observations. The configuration with adiabatic demagnetization refrigerator (ADR) precooled by Stirling-type pulse-tube cryocooler (SPTC) /Joule-Thomson cryocooler (JTC) is most attractive one for such space applications. In order to meet the demands of future national space science missions, the Technical Institute of Physics and Chemistry (TIPC, CAS) and the Shanghai Institute of Technology and Physics (SITP, CAS) have carried out collaborative research. After separately optimizing SPTC, JTC, ADR, and efficient coupling of the three, a sub-Kelvin SPTC/JTC/ADR hybrid refrigeration system is proposed, built, and tested. The hybrid refrigeration system can achieve a no-load minimum temperature of 661 mK and maintain a temperature of 0.9 K without load for 3.78 h, making it the first space-application-targeted sub-Kelvin refrigerator in China.

Renewable-driven hybrid refrigeration system for enhancing food preservation: Digital twin design and performance assessment

This study presents a new method for sustainable cooling systems using a hybrid refrigeration system powered by hybrid renewable energy sources. The system comprises a modular unit of vertical wind turbines integrated with bio-photovoltaic films to provide sustainable energy. The hybrid refrigeration system combines evaporative and solar thermal-driven adsorption cooling systems. In addition, a finite volume of soil is proposed for thermal energy storage. Experimental data inform the development of a digital twin for an integrated system, soil thermophysical characteristics, wind turbine performance, and technical specifications for other system components. This sustainable cooling package is cost-effective and space-efficient, particularly in remote or off-grid locations. Notably, the evaporative cooler and chilled water coil contribute to a cooling effect of 20.4 kW, and solar power generation reaches 12.38 kW at an intensity of 1053 W/m2. The annual electrical output averages 1.7 kW at a wind speed of 3.5 m/s. Under best conditions, wind power can surge to 7.99 kW at 9.88 m/s. The ratio of power generated by wind to solar energy ranges from 1.1 to 1.3. The system effectively meets a peak thermal energy demand of approximately 74 GJ/month, facilitated by solar collectors, underground thermal storage, and a renewable energy-fed auxiliary heater. This study paves the way for future techno-economic optimisation and advancements in sustainable energy solutions for remote cold storage facilities.

Performance evaluation and comparative study on a novel solar-heat-driven ejection-compression hybrid cooling system with subcooling storage

Refrigeration technology contributes to 10∼15% of global energy consumption, resulting in significant carbon emission. Solar-driven ejection-compression refrigeration system is promising for reducing electricity consumption and carbon emissions. However, existing solar ejection-compression refrigeration systems suffer from drawbacks of low heat utilization efficiency, oversized solar collectors, and thermal leakage due to large temperature differences of storage devices. Addressing these challenges, this study proposes and investigates a new solar-assisted ejector-compressor hybrid refrigeration system with subcooling storage coupled at intermediate temperatures. The system model is established, and the ejector model is experimentally validated. Through system modelling, an energetic and exergetic performance comparative analyses are conducted. The results indicate that the COP of the proposed system is 9.7% higher than that of traditional system combinations, producing the same cooling capacity with the same generating heat. Moreover, considering the stored cooling energy can be fully converted to cooling energy at evaporating temperatures, the COPh of the new system reaches 8.29, 24.5% higher than traditional systems. The cooling storage at 15°C with 0.325 ejector entrainment ratio suggests a reduction of approximately two-thirds in energy storage, lower temperature differences, and reduced thermal leakage, leading to decreased space and economic costs and improved energy performance. Additionally, as the COPh, COPgh, and ηex of MCS mode consistently outperform those of ZCS and HCS modes, the MCS mode is prioritized in system operation. This study underscores that the new system offers superior overall energy efficiency and requires smaller storage devices compared to traditional systems, revealing its promising practical applications.

A COMPARATIVE ANALYSIS OF HYPOTHESIS IN THE MODELING OF A HYBRID COMPRESSION REFRIGERATION CYCLE

This paper presents a comprehensive thermodynamic analysis of a hybrid refrigeration system that integrates an evacuated tube solar thermal collector into a vapor compression refrigeration cycle. The proposed analysis comprises two distinct approaches: an isovolumetric model and a compressible flow model. The former assumes a constant specific volume within the solar heat exchanger, while the latter applies principles of compressible fluid dynamics. The study compares these models with a reference work, emphasizing similarities and disparities. The investigation systematically varies key parameters, including evaporator and condenser temperatures, inlet and outlet temperatures of the heat exchanger, and heat load. By varying these parameters, the coefficient of performance (COP) and compressor work are evaluated, elucidating the impact of heat addition on the system's performance. Additionally, the influence of different working refrigerant fluids, such as R22 and R410A, is examined under various design point conditions. The results demonstrate the potential energy savings achievable by the hybrid system, with reductions in electrical power compared to the conventional compressor, as solar heat is introduced. While the isovolumetric analysis closely aligns with the reference work, the compressible flow modeling highlights sensitivity to inlet conditions. Although not directly comparable, the latter approach presents promising trends within specific design point ranges. Comparisons of performance curves for different refrigerant fluids further validate the models and assist in potential fluid selection. Overall, the outcomes indicate a promising avenue for energy-efficient refrigeration systems and provide valuable insights for engineering design and optimization.

Study of a Novel Hybrid Refrigeration System, with Natural Refrigerants and Ultra-Low Carbon Emissions, for Air Conditioning

Due to its environmental benefits, CO2 shows great potential in refrigeration systems. However, a basic CO2 transcritical (BCT) refrigeration system used for airconditioning in buildings might generate massive indirect carbon emissions for its low COP. In this study, a novel CO2 transcritical/two-stage absorption (CTTA) hybrid refrigeration system is broadly investigated, and both energy efficiency and life cycle climate performance (LCCP) are specifically engaged. The theoretical model shows that optimal parameters for the generator inlet temperature (TG2), intermediate temperature (Tm), and discharge pressure (Pc), exist to achieve maximum COPtol. Using the LCCP method, the carbon emissions of the CTTA system are compared to six typical refrigeration systems by using refrigerants, including R134a, R1234yf and R1234ze(E) etc. The LCCP value of the CTTA system is 3768 kg CO2e/kW, which is 53.6% less than the BCT system and equivalent to the R134a system. Moreover, its LCCP value could be 3.4% less than the R1234ze(E) system if the COP of the CO2 subsystem is further improved. In summary, the CTTA system achieves ultra-low carbon emissions, which provides a potential alternative to air conditioning systems in buildings that can be considered alongside R1234yf and R1234ze(E) systems.

Performance optimization of thermoelectric and vapor compression hybrid refrigeration system by allocating power

To enhance the refrigeration efficiency of the thermoelectric and vapor compression hybrid refrigeration system and optimize the allocation of power during system operation, a dimensionless parameter, the power allocation ratio coefficient (θ), is proposed. It represents the ratio of the input power of the thermoelectric refrigeration system to the total input power. A mathematical model of the hybrid refrigeration system is established to investigate the impact of θ on the cooling temperature (Tc), cooling capacity (Qc), and coefficient of performance (COP) of the system. An experimental platform is constructed to validate the mathematical model and explore the relationship between the optimal θ and system operating parameters. The findings demonstrate that, under a constant total input power, as the θ increases, the cooling temperature initially decreases and then increases, whereas the Qc and COP first increase and then decrease. There exists an optimal power allocation relationship for the two-stage refrigeration system, which maximizes the refrigeration performance of the hybrid refrigeration system. When the total input power is 100 W, the optimum θ is 0.52, resulting in a cooling temperature of −55.23 °C and a COP of 0.13. As the total input power increases, the optimal θ decreases. The cooling temperature rises, the optimal θ increases. The ambient temperature increases, the optimal θ also increases. An optimized relationship equation is obtained by fitting the calculated results of the operating parameters and the optimal θ, providing a theoretical basis for the control of power allocation in practical operation of the two-stage refrigeration system within the hybrid refrigeration system.

Thermoeconomic, environmental and uncertainty assessments and optimization of a novel large-scale/low carbon hydrogen liquefaction plant integrated with liquefied natural gas cold energy

Abstract Presently, the liquefaction of hydrogen represents a promising solution to alleviate challenges associated with its storage and transportation. It is crucial to formulate methodological frameworks for scrutinizing hydrogen liquefaction routes to enhance energy efficiency. This paper endeavors to establish, assess feasibility, and refine a novel approach for a high-capacity hydrogen liquefaction facility, leveraging the cold energy from liquefied natural gas (LNG). This new route utilizes four hybrid refrigeration systems, each designed to handle 50 × 103 kg daily. Significant energy savings are achievable through the primary utilization of LNG’s energy in the precooling stage and the generation of electrical power during the vaporization phase. The architecture of this novel route is crafted around the principles of energy conservation, incorporating thermodynamic assessments alongside economic and environmental viability studies. Furthermore, the performance of this innovative hydrogen liquefaction method is thoroughly evaluated across both non-optimized and optimized scenarios. Advanced techniques such as composite curve and uncertainty analyses are employed to provide a detailed examination of heat cascades and cost differentials. The findings indicate that managing LNG’s cold energy is crucial for refining the hydrogen liquefaction route, potentially reducing the specific power requirement of the optimum route by 27.4% compared to its non-optimum counterpart. Moreover, in the optimized scenario, there is a decrease of ~4.72% in unit production expenses, 26.26% in CO2 emissions, and 21.85% in specific power usage for avoided CO2 emissions.

Performance of hybrid vaccine freezer that combined thermoelectric coolers with vapor compression refrigeration: Experimental assessment

AbstractIn the medical field, refrigeration systems are used to store and transport vaccines, blood, and other medical supplies that require specific temperature ranges to remain effective. As technology continues to advance, the demand for more efficient and sustainable refrigeration systems is also increasing. The freezer compartment is typically designed to maintain a temperature of −18°C to −23°C for storing frozen items. Consequently, this work aims to develop a hybrid refrigeration system that combines a thermoelectric cooler system (TEC) and a vapor compression refrigeration cycle (VCC) system to achieve lower temperatures than conventional refrigerators. Also, the performance of the proposed hybrid refrigeration system is experimentally assessed with various operating conditions, including varying the voltage delivered to the system. The experimental results exhibited that the temperature inside the freezer room reached −33°C, while the cold side temperature is −47°C. Also, the maximum coefficient of performance of the VCC system, TEC, and hybrid system is 2.07, 1.06, and 0.37, respectively, at a DC voltage applied of 6 V. Moreover, the results revealed that the hybrid system combining a TEC and a VCC system can be a valuable technology for specific applications with low temperatures and limited capacity requirements.

Experimental analysis of the temperature distribution inside vaccine freezer compartment based on hybrid refrigeration system

Recently, the demand for refrigeration globally has been increasing in the fields of vaccine storage, medical services, food preservation, and cooling for electronic components. This has resulted in the generation of more electrical power and thus releasing more CO2 around the world which has led to many climatic changes, such as global warming. The vapour compression refrigeration cycle (VCC) is the most common as it has a high coefficient of performance (COP), although it only operates down to temperatures of around −20 °C. The thermoelectric cooler (TEC) modules offer a featured method for cooling technology, which is not mainly considered by energy efficiency but offers distinctive merits in specific applications. Although the TEC system is not conventionally known for incomparable energy efficiency, it offers a range of exceptional attributes that make it a desirable option for certain scenarios. Therefore, this work aims to assess the performance of the innovative hybrid vaccine freezer system depending on how well the VCC system and the TEC work together. Also, the temperature distribution within the freezer compartment has been investigated under various operating conditions. The newly developed hybrid vaccine refrigerator system consists of four pieces of TEC-12706 modules that function well at low temperatures. The results indicate that the best coefficient of performance (COP) of 1.05 is achieved with a total power consumption of 172.8 W when the TEC is operating at 5.5 V and the fan is running at 12 V. The cooling capacities of the freezer and cooler compartments are 9.2 W and 165 W, respectively. Furthermore, the best distribution and lowest temperatures were obtained, with temperatures in the lateral area of −40 °C compared with −37 °C in the central area.

Comparison of an absorption-compression hybrid refrigeration system and the conventional absorption refrigeration system: Exergy analysis

This paper presents an exergy analysis considering different operating conditions of an alternative configuration of an ammonia-water hybrid absorption refrigeration system, where part of condensation heat is recovered and supplied to generator (RCHG-ARS). In order to identify and quantify the irreversibilities in each component of the cycle and its variations, the exergy efficiency and the relative exergy loss of the system were evaluated. Moreover, the results obtained were compared with those obtained by the conventional ARS cycle. Furthermore, the effect of the internal heat exchanger effectiveness on the exergy efficiency and relative exergy loss was analyzed. The results indicate that the generation temperature and the exergy efficiency of the RCHG-ARS cycle decrease in 24 °C and 30%, respectively, it in comparison to ARS cycle at the conventional generation pressure (11.67 bar). However, to decrease the generator pressure at 5.94 bar, the evaporation temperature for the RCHG-ARS decreases in 19.3 °C and the exergy efficiency can be 0.20% higher than the obtained with the ARS cycle. It is also revealed that the exergy efficiency for the RCHG-ARS cycle become more significant at lower condensing and evaporating temperatures as well as lower generator pressures and higher internal heat exchanger effectiveness respect to ARS cycle. Moreover, the minimum values of relative exergy losses are obtained at higher generator temperatures or lower evaporating and condensing temperatures in the RCHG-ARS cycle. Finally, it can be concluded that the main components that increase the relative exergy destruction in the RCHG-ARS cycle are the generator, absorber and the compressors.

Performance Simulation of Hybrid Refrigeration System Using Eutectic Salt PCM For Eco Reefer Container

Today, fresh, chilled, or frozen products usually use reefer containers. The main problem with using reefer containers is the large energy consumption of 3.6kW/TEUS and the continuous supply of electric power. One solution available is using Phase Change Material (PCM) in the hybrid refrigeration system combined with a vapor compression system. Using PCM, the temperature of the reefer container can be maintained for several hours of cooling with the compressor off. This research aims to simulate the performance of a hybrid refrigeration system using PCM and the distribution of cooling air temperature in a laboratory-scale eco-reefer container. A simulation was performed using numerical software and CFD software. From the simulation analysis, the power value of the compressor at -20 °C is 0.3794 kW for the conventional system, 0.463 kW for the 22% NaCl PCM hybrid system, and 0.411 kW for the 20% Propylene Glycol PCM hybrid one. The COP value is 2,560 for the conventional system, 2,572 for the 22% NaCl PCM hybrid system, and 2,569 for the 20% Propylene Glycol PCM hybrid one. The CFD simulation results that PCM NaCl and Propylene Glycol can maintain the reefer container room temperature and product load.

Analysis and Research of Compound Refrigeration based on Logic Control Battery

In order to ensure the safety and stability of the power battery, the design of refrigeration system is very important. Firstly, a battery model based on logic control and lumped heat parameters was established to determine the real-time and accurate state of battery heat generation, heat transfer, radiation heat dissipation and battery temperature. The feasibility of the simulation model is verified by the experimental results. Secondly, the refrigeration system of battery air cooling and liquid cooling is established, and a new composite cooling system is proposed and built. By changing the wind speed and flow rate, the variation of the cooling effect of air cooling and liquid cooling with the medium flow rate was analyzed. The results show that, in a certain range, the larger the flow rate, the more obvious the cooling effect of the cooling method, and the flow rate is positively correlated with the cooling effect. In order to compare the cooling effect of the new composite cooling system, the temperature rise curves, temperature difference curves and energy consumption of different cooling methods were analyzed under the discharge rates of 4C and 8C.he results show that when the system tends to be stable, the total energy consumption of liquid cooling and mixed cooling is almost the same, and the energy consumption of air cooling is the largest. According to the analysis of the maximum equilibrium temperature difference inside the battery unit when the temperature is stable, the temperature difference of the composite cooling method is the smallest, about 1℃. Moreover, by analyzing the fluctuation range of battery pack temperature when it is stable, the fluctuation of composite refrigeration is the smallest, only 2℃. In conclusion, the hybrid refrigeration system based on logic control has good cooling performance.

Experimental studies on absorption-compression hybrid refrigeration system using 1,1,1,2-tetrafluoroethane/tetraethylene glycol dimethyl ether as working pair

The feasibility of combining novel halogenated hydrocarbon-based working pairs with low-pressure compression-assisted absorption refrigeration system (LCARS) was proved for the first time from the experimental perspective. An experimental prototype of the absorption-compression hybrid refrigeration system with a 1 kW cooling capacity was designed and tested to explore actual performances of selected R134a-DMETEG and performance improvements from compression in LCARS. At an evaporation temperature of approximately 5 °C, as the hot water inlet temperature and the solution flow rate change from 75 to 95 °C and 1.2–2.7 L/min, respectively, the coefficient of performance (COP) in the single-stage absorption refrigeration system (SSARS) varies from 0.211 to 0.412. At an increased evaporation temperature of approximately 10 °C, as the hot water inlet temperature and flow rate increase from 70 to 80 °C and 1.18–2.89 L/min, respectively, the COP in the SSARS varies from 0.238 to 0.552, while the COP in LCARS is improved and varies from 0.470 to 0.617. The LCARS increases the COP by a maximum of 91.04 % and can utilize a lower-grade heat source more efficiently due to its higher optimal COP at reduced hot water inlet temperatures. This study provided one feasible technical approach of combined use of R134a-DMETEG and LCARS to make up for the application limitations of traditional working pairs, contributing to application promotions of absorption systems, especially for the occasions with high requirement on safety and lightweight.

설비공학 분야별 최근 연구 동향: 2021년 설비공학논문집 발표논문에 대한 종합적 고찰

This article reviews the papers published in the Korean Journal of Air-Conditioning and Refrigeration Engineering in 2021. The purpose of this article is to understand the status of current research issues in the areas of heating, cooling, ventilation, sanitation, and indoor environments of buildings and plant facilities. Summary of this paper is follows.<BR> (1) The topics of the paper in the field of building mechanical system were the energy consumption, indoor environment analysis, building energy saving, ventilation system, renewable energy system and law of mechanical facilities.<BR> (2) The topics of the research in the field of indoor environment were the IAQ, ventilation, air cleaning, cooling/heating load, renewable energy, zero-energy building, building energy performance etc.<BR> (3) The research topics in the field of refrigeration in 2021 include robust temperature control of variable speed refrigeration system, R32 liquid-injection showcase vapor compression system, hybrid dessicant dehumidifying system, compressor torque calculation by differential pressure measurement, FAPO zeolite adsorbent, compression-adsorption hybrid refrigeration system and so on.<BR> (4) The topics of the papers published in the field of heat were heat transfer, a heat exchanger and a battery, etc. <BR> (5) The topics of the papers published in the field of heat transfer were the air flow rate inside drum of clothes dryer, the dynamic behavior and thermal performance of a solar water heater, a higher energy density storage system using sensible heat or phase change of water, factors affecting performance characteristics of falling film evaporation using R-1233zd(E) refrigerant and the underground seawater intake system in a power plant.

Performance investigation of hybrid adsorption-compression refrigeration system accompanied with phase change materials − Intermittent characteristics

In the current study, intermittent characteristics of hybrid adsorption-compression refrigeration systems are evaluated, notably for cold storerooms. This hybrid system utilizes ultra low-grade heat (65 °C) and works with natural refrigerants. Herein, the dual-bed adsorption system operates with a working pair of silica gel/water (R718), while isobutane (R600a) is adopted for the compression system. Phase change material (PCM) is additionally incorporated to prolong the compressor off durations and improve the stabilization of the air temperature inside the cold storeroom. Mathematical modeling of the proposed systems is established using MATLAB/SIMULINK framework and validated with relevant literature. An examination of the temporal behavior of the hybrid system’s leading indicators such as temperature profiles, cooling capacity, COP, electric power, and electricity demand based on the intermittent characteristics has been conducted and compared against the baseline system. The results demonstrate that the energy saving of the hybrid system during the intermittent operation mode (37%) outperforms the continuous operation mode (31.63%). Also, the hybrid system at the steady-state stage attains COP of ∼4 compared to ∼2.3 for the baseline system. However, incorporating PCM into the hybrid system abates the air temperature fluctuation inside the cold storeroom, diminishes the cyclic operations, and reduces the on-time ratio by 24.1% compared to the baseline system (34.8%) while slightly reducing the system COP. The utilization of hybrid refrigeration systems accompanied by PCM has significant profit over conventional compression systems in the market.

Numerical investigation and optimization of a proposed heat-driven compression/absorption hybrid refrigeration system combined with a power cycle

On the basis of the energy distribution characteristic of flue gas, a heat-driven compression/absorption hybrid refrigeration (CAHR) system combined with a power cycle is proposed and designed. In the proposed system, a power cycle with NH3/H2O as working fluid is driven by the heat of flue gas to produce mechanical work for the hybrid system. On the basis of the models of the turbine and compressor, the mathematical model of the proposed CAHR system is built up by considering the conservations of mass and energy of working fluids. Then, the validation and energy conservation of the mathematical model are conducted. The total heat conductance of each component is calculated under basic condition. The influences of NH3/H2O mass fraction, turbine outlet pressure, generation temperature, and compression ratio on the operating parameters of the CAHR system are simulated and analyzed in detail. Taking COP as the optimization objective, the above four parameters are optimized. The thermal performances of CAHR system are compared with those of the heat-driven double-effect absorption refrigeration. Comparison results show that the thermal performances of the proposed CAHR system are better than those of the heat-driven double-effect absorption system.

New environment friendly working pairs of dimethyl ether and ionic liquids for absorption refrigeration with high COP

To overcome the limitations of absorption refrigeration system brought by commercial working pairs of NH3/H2O and H2O/LiBr for the utilization of low-grade heat, a new class of working pairs consisting of dimethyl ether (DME) and ionic liquids (ILs) are developed. The solubilities of DME in three ILs [BMIM][BF4], [BMIM][PF6] and [BMIM][Tf2N] were firstly measured and correlated. Then, COPs of the single-effect absorption refrigeration system (ARS) and absorption-compression hybrid refrigeration system (ACRS) using DME/IL were calculated under different conditions. The maximum COP of ARS using the three DME/IL working pairs can be up to 32.0% larger than that using NH3/H2O, while the maximum COP of ACRS using the three DME/IL working pairs can be up to 38.3% larger than that using NH3/H2O under studied conditions. The three DME/IL working pairs also show much better cooling performance than HFC/IL and HFO/IL working pairs which are R152a/[HMIM][Tf2N] and R1234ze(E)/[HMIM][Tf2N]. In ACRS, DME/ILs can drop the optimal generation temperature in ARS by more than 10 K. DME/ILs are very promising alternative absorption refrigeration working pairs due to the high COP, wide applicability and environmental friendliness.

Experimental and numerical study on performance of hybrid refrigeration system that combines vapor compression and thermoelectric systems

As high-quality food preservation has become an important aspect of daily life, a need has developed for domestic household refrigerators with a wide refrigeration temperature range. The temperature range of domestic household refrigerators is generally above −20 °C. In this study, a hybrid refrigeration system that combined vapor compression refrigeration (VCR) and a thermoelectric refrigerator (TER) is investigated for the freezer compartment of a domestic refrigerator with a volume of 0.018 m3. Although an additional 99.5 W of electrical power is consumed, a lower temperature of −38.1 °C is experimentally achieved in the deep freezer compartment of a compact VCR–TER system, with no noise or mechanical parts. In contrast, a temperature of only −8.8 °C is obtained in a typical VCR system. A three-dimensional numerical model is applied to study the performance of the finned heat sink of the TER using FLUENT. The effects of the fin height and fin pitch on the thermal resistance and pressure drop are investigated. The results show that the thermal resistance decreases with an increase in the fin height and increases with an increase in the fin pitch. An optimized finned heat sink with a fin height of 50 mm is obtained, which has a thermal resistance of 0.05 °C/W. It has a higher cooling capacity of 53.6 W than the heat sink with the original fin height of 30 mm. The VCR–TER system has potential application to low-temperature domestic refrigeration systems with a small size and small cooling capacity.

Techno-economic evaluation of a solar PV integrated refrigeration system for a cold storage facility

This paper presents a conceptual study of a solar PV integrated refrigeration system for a cold storage facility based on the conventional vapor compression system for banana fruit. In the first stage, the conventional system has been thoroughly analyzed. Mathematical modelling has shown that the condenser is oversized, while the evaporator was undersized. Furthermore, the air-conditioning compressor was also found to be oversized by approximately 12 kW after an evaluation at no-load and full-load conditions. In the second stage, the optimized system with reduced consumption was integrated to a solar PV field. The solar field sizing, and performance optimization of the proposed PV hybrid refrigeration system was accomplished in PV*SOL tool. The simulations demonstrated that with a 170 m2 solar field, an optimized PV hybrid refrigeration system can achieve 58.1% solar fraction at a performance ratio of 59.2%, under given climatic conditions. With net metering, the hybrid system shows a high economic feasibility with the payback period of 5.2 years. The comprehensive methodology and all-inclusive results are valuable to generate explicit recommendations for repowering along with renewable integration of cold storage facilities operating in the region.

Vapor-liquid equilibrium measurements and assessments of Low-GWP absorption working pairs (R32+DMETEG, R152a+DMETEG, and R161+DMETEG) for absorption refrigeration systems

This research aims to develop novel binary working pairs using low-GWP refrigerants (R32, R152a, or R161) and one chemical absorbent (DMETEG) for absorption refrigeration systems. The solubility data were determined from 293.15 to 343.15 K using a static method and were correlated with the five-parameter non-random two-liquid (NRTL) activity coefficient model with an average relative absolute error of <2.4%. All three binary mixtures exhibited negative deviations from Raoult’s law. DMETEG was further assessed with other organic solvents that were previously measured to verify its highest affinity with HFCs. Based on the obtained VLE data, the thermodynamic performances in both the single-stage absorption refrigeration system (ARS) and the absorption-compression hybrid refrigeration system (ACHRS) were assessed. R161 yielded the highest cooling COP of 0.519–0.555 when the generation temperature was above 135 °C, followed by the R152a at 0.231–0.518 when below 135 °C. Different from the trends of COP variations, R152a had the highest ECOP of 0.091–0.158 when the generation temperature was below 135 °C while R161 showed the highest ECOP of 0.116–0.137 over 135 °C. ACHRS can effectively enhance the cooling performances of ARS via compression and its compression ratios got optimized. Overall, the R161 + DMETEG showed the best potential as the working pair.