Conventional Vapor Compression Refrigeration System Research Articles

Unsteady-state entropy generation analysis of the counter-flow dew-point evaporative coolers

The surging demand for air conditioning, especially in hot climates, underscores the urgency of strategies aimed at curbing fossil fuel reliance and fostering energy saving strategy. Despite the longstanding utility and advantages of the conventional mechanical vapor compression refrigeration system, sustainability hurdles persist owing to its pronounced electricity demand. While evaporative cooling, harnessing water evaporation, emerges as a more efficient alternative, its efficacy is contingent upon environmental conditions. Addressing this, dew-point evaporative cooling (DPEC) presents an innovative direction, showcasing superior efficiency by directing supply air into a wet channel. This study delves into the thermodynamic losses within a counter-flow configured DPEC system, employing a transient entropy generation model rooted in the second law of thermodynamics to provide a comprehensive analysis of DPEC’s performance. Key findings that emerged from this study reveal that (1) the transient entropy generation is intricately distributed across different layers of the dew point evaporative cooling (DPEC) system, including dry air, wet air, the channel plate, and the water film; (2) Parametric analyses highlight the significant impact of factors on entropy generation, inlet air temperature has a minimal effect on system efficiency, but higher temperatures increase thermal losses. Excessive humidity limits evaporative potential, while low humidity significantly increases entropy generation. The system performs optimally at a working ratio of 0.3 and lower air velocities (within the inlet air velocity range of 0.6 to 2.2 m/s). Channel length has little impact, while the system is more sensitive to channel height, with a height of 2.5–3.5 mm being conducive to better performance. Experimental validation demonstrates the model’s accuracy in predicting system performance. The research contributes to a deeper understanding of DPEC systems, offering insights for achieving optimal operating conditions and enhancing overall efficiency in the pursuit of sustainable development.

Simulation Study on Performance of Solar-Powered Desiccant Wheel and Ground Source Heat Pump Air Conditioning in Qingdao

In China, a large amount of the total energy consumption is made up of building energy, particularly in humid regions. The conventional vapor compression refrigeration systems cannot effectively control the indoor humid and thermal environment. Therefore, this article proposes a solar-powered desiccant wheel and ground-source heat pump (SDW-GSHP) air conditioning system. The energy consumption of the system is mainly from sustainable sources of solar and geothermal energy, showcasing excellent energy efficiency and environmental friendliness. The desiccant wheel (DW) processes latent heat loads, and the GSHP processes the sensible heat load. The regeneration air of the DW is heated by a solar collector. The operational performance of the system was simulated by using TRNSYS during the typical summer week (15 July to 22 July) in Qingdao. The simulation results indicated that indoor temperature was maintained within 25.8–26.2 °C and the relative humidity was maintained in the range of 57–61%. The COP of the SDW-GSHP air conditioning system was 42.1% higher than that of the DW air conditioning system with electric heating regeneration, and electricity saved 43.7%.

Performance analysis and optimization of a solar assisted heat pump-driven vacuum membrane distillation system for liquid desiccant regeneration

Liquid desiccant air-conditioning (LDAC) system is one of the excellent alternatives to conventional vapor compression refrigeration system due to its great energy-saving potential. However, regeneration of diluted liquid desiccant is the main energy-consuming process, and its performance plays a significant role in LDAC system. Recently vacuum membrane distillation (VMD) is becoming an emerging and promising separation process rely on the advantage of high permeate flux and low energy losses. The interest of usage solar energy techniques for feed solution heating in VMD systems is regarded as a sustainable path for membrane distillation process. In this work, a solar-driven VMD system incorporating a vapor-compression heat pump for liquid desiccant regeneration is introduced. An adapted solar/heat pump hybrid heating strategy has been devised to establish a connection between the heat-demanding process and the solar thermal supply. A comprehensive multicriteria assessment of energy, exergy, and environmental evaluation is conducted, and the influences of crucial parameters on both key components and system performance are evaluated to ensure a systematic examination. Results show that both the COP and STEC decrease obviously with the growth of the inlet solution temperature, whereas SEEC is improved abviously from 410.6 kW·h/m3 to 566.1 kW·h/m3 due to the effect of heat pump. The exergy analysis indicates that exergy losses in solar collector and stratified heat storage tank accounted for over 80 % of the total exergy losses. Additionally, single-objective optimization and multi-objective optimization are employed to explore the optimum operating conditions of key componets and whole system. Results show the ideal optimal solution can be obtained with a COP of 19.92 and a SEEC of 142.89 kW·h/m3 when the weights of COP and SEEC are taken as [0.5, 0.5].

Performance improvement potential of ejector-based dual-evaporator refrigeration system using photovoltaic modules and nano-refrigerant

This paper presents a novel system for resolving the high energy consumption of conventional vapor compression refrigeration systems. An ejector-based dual-evaporator refrigeration system (EDERS) is developed utilizing photovoltaic (PV) modules and a nano-refrigerant (NR) with 0.5 wt% of Al2O3. This novel arrangement combines four promising environmentally friendly technologies: dual-temperature cycle, ejector, PV panel, and NR. The comprehensive thermodynamic analysis and optimization of the proposed system, energetic and exergetic analysis methods are incorporated to evaluate the performance of nanoparticle (NP)-doped EDERS in this study. The results demonstrate that the use of Al2O3 NP compared with utilizing pure R134a EDERS notably improves performance under typical operating conditions. Specifically, the coefficient of performance (COP), volumetric cooling capacity, and exergy efficiency (ηex) are 7.14 %, 4.33 %, and 8.91 % higher, respectively. Moreover, the compressor power and total exergy destruction are 6.76 % and 9.94 % lower, respectively. Additionally, under the operating conditions considered in this study, the required PV area is reduced by 5.31 %–8.07 %, whereas the COP and ηex values improve by 5.64 %–8.39 % and 5.38 %–10.06 %, respectively. The study also finds that the COP and ηex values of (R600a + Al2O3) surpass those of (R134 + Al2O3), whereas the COP and ηex values of (R1234ze(E) + Al2O3) and (R1234yf + Al2O3) are smaller than those of (R134 + Al2O3). This suggests that the performance benefits of NPs may vary depending on the specific refrigerant used in the system. The results can be employed as a useful guide for the application of NRs to multi-evaporator refrigeration systems before setting up an experimental system.

Performance analysis of dual-evaporator ejector refrigeration system in different configurations: Experimental investigation

This study aimed to assess the effectiveness of an ejector refrigeration cycle, using a laboratory-scale experimental system operating in different configurations. The investigated configurations consisted of a conventional vapour compression refrigeration (CVCR) system and a dual evaporator ejector system (DEES) operated in two modes: DEES with a single thermal expansion valve (DEESA) and DEES with dual thermal expansion valves (DEESB). The findings revealed that the utilization of the ejector enhanced the refrigerant's mass flow rate. Additionally, the DEESA configuration achieved higher cooling capacities compared to the CVCR. Moreover, the DEESA configuration achieved up to 21% higher coefficient of performance (COP) values. On the other hand, when the system was operated in the DEESB configuration, it yielded lower evaporation temperatures and higher superheating degrees in comparison to DEESA. Based on the evaluations, it can be concluded that the ejector operates more efficiently in systems with dual evaporators, thereby making positive contributions to overall system performance.

Optimization and thermo-economic performance of a solar-powered vapor absorption cooling system integrated with sensible thermal energy storage

Higher demand for refrigeration systems adversely affects power grids, causing blackouts, increased electricity expenses, and carbon emissions. However, using renewable energy thermally driven refrigeration absorption systems is a promising alternative. The higher initial cost and dependency on local weather, large space area for installation, and complex design are hurdles for the widespread of these systems compared to the conventional vapor compression refrigeration systems. This study uses response surface methodology to model a real vapor absorption machine (VAM) incorporated with the measured data. This VAM is the refrigeration machine of a solar-powered absorption cooling system (SPACS) integrated with thermal energy storage for milk chilling installed and operated in Jaipur (India). The weather data for 2022 is used in performance and productivity analysis in this study. The results show that most of the summer months, the system can produce desired cooling to take down the 1000 l of milk within 3 h as per standards ISO 5708 – 2 II. Moreover, the solar loop still has sufficient driving heat to charge the 1000 l cold storage tank/another milk tank. During winter days, it takes a significant system response time (SRT) to reach the thermal energy storage (TES) up to 95 °C; after that, VAM operates significantly underperforming due to weak solar insolation; even the system cannot provide cooling to the first milking. The system produces monthly cooling energy of up to 2356 kWh in summer and is reduced to 620 kWh during monsoon and winter. The maximum value of the coefficient of performance (COPVAM) is achieved as 0.55 with an average of 0.41–0.46 during summer months whereas 0.34–0.39 during monsoon and winter days. The system's energy efficiency ratio (EER) ranges from 2.5 to 6.5, with an overall average of 4.55, which is far better than the conventional vapor compression refrigeration systems. The LCOE for the SPACS has been estimated to be 0.177 $/kWh, whereas the simple payback period is 12.4 years, and the discounted payback period is 19.7 years.

Investigative comparison of R134a, R290, R600a and R152a refrigerants in conventional vapor compression refrigeration system

This work represents the performance comparison of conventional vapour compression refrigeration system (VCRS) using various refrigerants such as R134a, R152a, R600a and R290. The theoretical model has been utilized for computing work input to the compressor, refrigerating effect and coefficient of performance (COP) for R134a, R290, R600a and R152a refrigerants. This investigation has been done for the evaporator temperature range of -30 °C to 10 °C and the condenser temperature range of 40 °C to 45 °C. In this performance analysis it is seen that R290 shows favourable properties and can serve as best refrigerant among all in the group. R290 shows almost equal COP to R600a in large operating temperature range and it has very high refrigerating capacity comparatively to R134a together with its low global warming potential and ozone depletion potential. R152a and R600a also show some satisfying properties.

Performance of Solar Hybrid Cooling Operated by Solar Compound Parabolic Collectors under Weather Conditions in Riyadh, Kingdom of Saudi Arabia

The scientific aim of this work is to encourage energy conservation. This article offers a fresh perspective on renewable energy in the air conditioning sector, the country’s economic growth, and environment-friendly techniques to overcome global warming challenges. In this research, a solar vapor absorption refrigeration (SVAR) system was combined with a conventional vapor compression refrigeration (VCR) system to analyze their combined performance, employing a compound parabolic collector (CPC). The goal was to assess the performance of a solar hybrid cooling system using this non-tracking solar collector. CPC was validated for heat output with 2.9% uncertainty by utilizing an engineering equation solver (EES). Other system components were also validated with EES and then extended to a larger-capacity solar hybrid cooling system. The results of this research indicate that CPC is effective in providing the required heat to SVAR throughout the year without any tracking, and the integration of SVAR in series with the VCR condenser produces 83% higher COP than the system that integrates VCR with the condenser of the SVAR system for Riyadh. The configuration results in high values of exergy COP and an efficiency of 88% and 84%, respectively, increases the cooling capacity of the VCR by 68%, and decreases the carbon emission by 166.4%.

Sustainability framework of intelligent social houses with a synergy of double-façade architecture and active air conditioning systems

Social houses are built around the world to fulfill the basic needs of the growing population, especially middle-income families. Owing to the low budget available for such houses around the globe, necessary energy codes are often compromised. This research, through a methodological sustainability framework, presents the case study of Mexico with the objective to address this worldwide issue. More than 100,000 social houses were built in Mexico just in the year 2021 without strictly following any definitive building energy codes. Eventually, this is a ticking bomb, if left unaddressed, that can bring serious energy and environmental consequences connected with various social issues. Thus, as a research gap, the conventional 4E (energy, exergy, economic, and environmental) analysis cannot fully address such a complex energy-environmental-economic-social nexus. This work proposes an integrated sustainability framework of the practicability of the bioclimatic architecture of such a social house including energy, economic, environmental, and social assessment (novel addition to the analysis). The novel methodology is implemented on a novel technological advancement where double-façade architecture (i.e., solar chimney) is installed through a synergy and intelligent operation with an active air conditioning system including a desiccant enhanced air cooler and novel dew-point evaporative cooler. The article makes use of conventional physics-based modeling of thermal machines combined with an artificial neural network digital twin-based data-driven non-sorting genetic optimization of solar chimneys for various climatic conditions of Mexico. The optimal points are evaluated using annual climatic data to maintain the thermal comfort conditions and the results have suggested an increase of ∼48% through intelligent integration of double-façade architecture with the Maisotsenko cycle air cooler. Life-cycle economic assessment has suggested the Levelized cost of air conditioning be between 0.0096 and 0.0390 USD/kWh and can save up to ∼273 MXN per month with a real payback period of ∼8 years. Environment assessment has reported mitigation of up to ∼5668.59 kgCO2/year as compared to conventional vapor compression refrigeration systems. The social assessment is conducted on a pilot scale to directly ask the people of Mexico about their perception of the installation of the solar chimney while giving the fact that the initial price of the social houses can increase between 2.5 and 4%. It is reported that ∼62% of the sample is willing to install it even with a high price tag with a motive to initiate the climate change mitigation phenomena. The importance of the work has concluded that the government needs to take drastic and tough decisions to further regulate the energy efficiency in the social houses and limit the constructors to offer sustainable building construction.

Thermodynamic investigation of a centrifugal reverse Brayton cycle for refrigeration in air conditioning filed

The reverse Brayton cycle (RBC) is known to exhibit a lower coefficient of performance (COP) when compared to conventional vapor-compression refrigeration systems. To tackle this issue, this study proposes a centrifugal reverse Brayton cycle (CRBC) that features a rotating heat exchanger, which utilizes the conversion mechanism between equal potential energy and pressure energy to enhance system performance. The findings indicate that the COP of the CRBC is roughly inversely proportional to the working fluid density, making CO2 a more suitable option for CRBC systems than conventional working fluids. We propose three different cycles for the CRBC system: the diamond cycle, trapezoid cycle, and rectangle cycle. From both technical and operational perspectives, the trapezoid cycle appears to be the preferred choice for CRBC. When the isentropic efficiency of the CRBC system exceeds 95%, its coefficient of performance (COP) ranges from 5.31 to 5.7, whereas the COP of transcritical carbon dioxide refrigeration cycle (tCO2), air RBC, and CO2 RBC are around 4.3, 1.9, and 0.79, respectively. This suggests that the performance of the CRBC system surpasses that of RBC by a significant margin, while achieving comparable performance to conventional vapor compression refrigeration systems. Moreover, the dimensionless power reflecting the installation capacity requirements for CRBC, tCO2, air RBC and CO2 RBC are around 0.2, 0.35, 5.3 and 1.9, respectively. This indicates that the compressor/expander capacity demand for system CRBC approaches the thermodynamic minimum.

Study on the ejector-expansion refrigeration system for low-temperature freezer application: Experimental and exergetic assessments

In this study, the authors propose applying the ejector-expansion refrigeration system (ERS) to develop a -50 °C low-temperature freezer. The main performance of the ERS based prototype freezers were investigated by experimental and exegetic methods. The influences of nozzle throat diameter and compressor displacement on ejector performance were discussed in detail. The higher efficiency and transiting exergy efficiency of ejector could be obtained with a larger nozzle throat diameter and compressor displacement. When the nozzle throat diameter rises from 0.4 to 0.7, ejector efficiency and transiting exergy efficiency increase from 16.1% to 20.1% and 26.1% to 30.2%, respectively. Moreover, these results demonstrated that the ERS-based freezer could operate stably with appropriate nozzle throat diameter and compressor displacement. Compared with the conventional single-stage vapor compression refrigeration system (CVRS), the compression ratio of ERS was reduced by 15.8%. In addition, the system performance decreased with the increase of capillary tube length. When capillary tube length varied from 40 mm∼ 80 mm, the COP of the freezer decreased from 0.59 to 0.52, and the overall exergy efficiency of freezer decreased from 22.1% to 17.1%. This research confirms that the ERS could provide a novel way for developing a -50 °C low-temperature freezer.

Improving the Efficiency of a Conventional Vapor-Compression Refrigeration System used for Geothermal and Evaporative Cooling Techniques: Case Study in Iraq

A conventional vapor compression refrigeration cycle is among the most effective technology in refrigeration systems. In the present experimental study, thermal performance and the effect of the condenser temperature have been analyzed. With the decrease in the condenser temperature, the overall performance of the refrigeration cycle is increased. However, the cooling power and efficiency of conventional vapor pressure air conditioning units can experience a significant reduction when operating in extreme weather (hot and dry). This drop is mainly affected by the increase in the temperature (and pressure) of the condenser with an increase in the ambient air temperature. Unfortunately, Iraq experiences the most extreme summer seasons especially in the months of June and July when the temperature reaches or exceeds 50° C. So, ground cooling has been used in areas with a hot environment for split system air conditioners. Evaporative cooling was also performed to lower the coolant temperature of the AC unit used inside the condenser area. Experimental results showed that when using a geothermal heat exchanger, the temperature of the condenser is reduced from 116 to 110 ° C and the coefficient of performance (COP) is improved by 41%. In addition to this when the system uses evaporative cooling the temperature of the condenser is reduced from 110 ° C to 88° C. Moreover, a 65% improvement was made in the COP of the conventional vapor compression refrigeration cycle. Furthermore, with a decrease in the evaporator temperature from 6 to 3.5 °C there was an increase in refrigeration capacity by an average of 52%.

Performance assessment of novel solar still regenerated liquid desiccant-based evaporative air-conditioning system for an office in India

A liquid desiccant-based evaporative air-conditioning system (LDeACS) is one of the excellent alternatives to conventional vapour compression refrigeration system. The liquid desiccant (LD) requires less thermal energy at low temperatures for regeneration, therefore, the use of renewable (solar) energy is a promising source for the regeneration of LD. The prime motive of the research is to assess the applicability of novel solar still (SS) regenerated LDeACS for an office located at tropical savanna humid climate using numerical simulation. The novel solar still provides the combined function of a regenerator and LD heater. The simulation was carried out to evaluate the performance of sub-components of proposed LDeACS by varying the various input operating conditions (inlet mass flow rate of LD; inlet temperature of LD; temperature of absorber plate of SS) of SS. For the simulation, the mathematical model of sub-components of the proposed LDeACS is interlinked using commercial equation solver software. Simulated results indicated that the proposed LDeACS is capable to provide the required human comfort conditions. The parametric analysis of the system revealed that variations in performance parameters of sub-components of LDeACS are more sensitive to the inlet mass flow rate of LD at SS. An increment in the inlet temperature of LD at SS indicates an adverse effect on the performance indices of LDeACS. An increase in absorber plate temperature of SS enhances performance of SS, contrary to expectations, it degrades the performance of the dehumidifier.

Comparative investigation on performance of single-stage and double-stage desiccant dehumidification boxes under hot-humid climatic conditions

Desiccant fixed bed is a prospective alternative for conventional vapor compression refrigeration system. In this paper, a novel structure of fixed bed, desiccant dehumidification box, was constructed and experimented at a sub-tropical city, Guangzhou. Dehumidification performance of the new structure was evaluated by several indicators. Mathematical models were established concerning moisture adsorption rate and moisture ratio. The adsorption heat generated was analyzed by testing sensible heat gain of the process air and heat storage of the desiccant. The result shows that the double-stage desiccant dehumidification box could perform better generally. The maximum dehumidification capacity could reach 3.9 g•kg−1 and 1.6 g•kg−1 on average in condition 4. Maximum dehumidification efficiency (27.8%) was obtained in the same condition when applying the double-stage box. The desiccant saturated at about 6 h in experiments, of which variation in the double-stage box was more stable and lasting, though moisture adsorption rate presents only a little difference in comparison boxes. Exponential models fit the practical curves within 10% relative error. Maximum average temperature rise of the desiccant and process air was 4.3 °C and 3.8 °C respectively in the double-stage box, which was 0.4 °C and 0.9 °C higher than the single-stage box. Around 97% of the adsorption heat was directed to heat storage of the desiccant and only left 3% directed to sensible heat gain of the process air.

Mitigating environmental burden of the refrigerated transportation sector: Carbon footprint comparisons of commonly used refrigeration systems and alternative cold storage systems

Concerns about potential climate change stemming from refrigerated systems have increased because of the environmental burden of nonrenewable energy use and refrigerants' high global warming impacts. Currently, cold storage systems based on phase-change material (PCM) technology have emerged as an alternative solution to the commonly used vapor-compression refrigeration system (VCRS). This study compares the carbon footprint of a conventional VCRS with an alternative PCM-based cold storage system (PCCSS). As such, we first develop a comprehensive life cycle assessment approach, focused on climate change, to examine the carbon footprint of the two refrigeration systems. To validate this model, we conducted the comparison by addressing key factors—such as various ambient temperatures, refrigeration temperatures, national energy mix and different refrigerants—that influence the two systems' potential climate change impacts. Upon analysis of the key parameters, the results revealed that the PCSSS has a smaller carbon footprint. The PCCSS showed a reduction ranging from 22% to 56% when compared with the conventional VCRS. Our results show that the use-stage is the carbon footprint hot spot in both investigated cases, accounting for 84%–91% of the VCRS's total carbon footprint and around 68% for the PCCSS's. The PCCSS's potential carbon footprint reduction mainly depends on electric grids, which could achieve up to 56% reduction with a lower emission factor than the VCRS, which uses fossil fuels. Moreover, compared to the VCRS, the PCCSS presented a greater potential to reduce the carbon footprint in warmer climates. Additionally, reducing refrigerated temperatures from 0 °C to −18 °C increases the life-cycle carbon footprint of the VCRS by an average of 47% and that of the PCCSS by an average of 58%. Compared with R404A, the carbon footprint for the VCRS was reduced by 1.5–1.8% when using refrigerant R410A (over a 10-year lifespan), while the use of R744 in the same time frame, resulted in a reduction of 3.2%–3.9%. It can be concluded that the PCCSS has an advantage in reducing its carbon footprint during the use stage, but its carbon footprint increases with higher resource input for the production and recycling stage than conventional VCRS. In the future, engine efficiency, clean electricity grids, and refrigerants' global warming potential must be further prioritized for low-carbon refrigeration systems.

THERMODYNAMIC AND HEAT TRANSFER ANALYSIS OF COOLING TECHNOLOGIES: A COMPARATIVE STUDY

Refrigeration systems applications are broadly used in food and drug conservation and in air conditioning systems. Commercial buildings may demand as much as 80% of total electrical power just for powering the air-conditioning system based on conventional vapor compression refrigeration systems (VCRS), which contributes to reach peak demands on the electrical distribution network that could cause an unstable condition. Implementing absorption refrigeration systems (ARS) to produce cooling effects driven by thermal energy could decrease that power demand. Thermodynamic models of these systems can be found in the literature with a variety of working fluids and also integrated with other cycles such as power generation plants. However, a few previous analyses have a direct comparison between ARS and VCRS at the same operational conditions. Thus, the current study aims to simulate and compare two different refrigeration technologies: single stage ammonia-water absorption refrigeration system and vapor compression refrigeration system working with refrigerants R-134a and R-717. Thermodynamic simulation was carried out by evaluating heat transfer rates in the main devices, coefficients of performance, and specific areas of evaporator and condenser. As evaporator temperature decreases from 10°C to -20°C, ARS requires 16.9 kW or 67.5% more heat in generator and COP decreased from 0.601 to 0.359. Utilizing the same comparison parameter, VCRS needed 3.26-3.54 kW or 154-160% more compressor power, depending on refrigerant used, and COP decreased from 6.77 to 2.60 with R-134a and 7.07 to 2.79 using R-717 at the same condensation temperature (40°C). Compared to ARS, condenser specific area required for VCRS is smaller, evaporator is twofold smaller when using R-134a, and is equal when using R-717. Those results can justify the usage of ARS in facilities with high amount of waste heat, mainly on applications working with lower evaporator temperatures.

Environment Friendly Indirect-direct Type Evaporative Cooling Technology: A Review

This paper reports a review based study into the two stage indirect- direct evaporative cooling technology, which is referred as two-stage evaporative cooling (TSEC) system. The direct-type (evaporative) cooling system is widely using natural cooling technology for storage of agricultural produce particularly fruits and vegetables because of its simplicity, eco-friendly and low-cost. But EC system is environment based and got the limitation that cooling of air can be done up to wet bulb temperature. To overcome this and owing to the continuous progress in cooling technology innovations are done by combining other indirect methods with direct type evaporative cooling system. Such system is known as two stage evaporative cooling, includes indirect and direct type cooling system. The indirect cooling has potential to be an alternative to conventional mechanical vapour compression refrigeration system to take up the air conditioning duty. Indirect cooling system is mostly heat exchanger(s) whereas direct cooling is wet pad type system. Combination of these two systems has obtained significantly enhanced cooling performance, with near to 90% and high energy efficiency ratio up to 80. The experimental and research work done on the indirect and direct cooling technology on the basis of their design, structural, type of indirect cooler, materials of construction, pad materials, effectiveness and energy saving have been reviewed and presented. This review paper explains the working principles of two-stage evaporative cooling systems and its performance assessed. This system is energy efficient, environment friendly and having potential for cooling and storage of fruits and vegetables in countries where hot and dry weather prevails for most of the part.

A compact elastocaloric refrigerator

Elastocaloric cooling is regarded as one of the most promising cutting-edge alternatives to conventional vapor compression refrigeration systems. This technology is based on the temperature change of materials when being subjected to uniaxial stress, which has been observed in polymers, alloys, and ceramics. However, the existing elastocaloric prototypes have a bottleneck problem of an excessive mass ratio between the actuator and the solid-state refrigerant. To overcome this challenge, this study proposes an elastocaloric refrigerator using a single actuator with an inclined angle to produce a vertical tensile force to nickel-titanium (NiTi) shape-memory wires and a lateral motion to translate the NiTi wires between the hot and cold sides. The refrigerator can achieve a 90% improvement in the mass ratio between the solid-state refrigerant and actuator compared to the currently best-reported elastocaloric cooling prototype. The NiTi wires exhibit an adiabatic temperature change of 6.6 K during unloading at the strain of 4.8%. The proposed refrigerator can achieve a 9.2-K temperature span when the heat source and sink are insulated from ambient and has a cooling power up to 3.1 W under zero-temperature-span condition. By using thinner NiTi wires or NiTi plates, the developed elastocaloric refrigerator could be a starting point to promote applications of this technology in the future.

Multi-objective optimization of vapor absorption refrigeration system for the minimization of annual operating cost and exergy destruction

A low-grade energy source-driven thermal compressor-based vapor absorption refrigeration system is considered a better alternative for an electrically operated mechanical compressor-based conventional vapor compression refrigeration system. In this article, multi-objective optimization of a single-stage LiBr–H2O vapor absorption refrigeration system (VARS) and a modified VARS are explored by minimizing the total annual operating cost and exergy destruction of the system. Exergy destruction during the operation is inversely proportional to the total annual cost of the system. Multi-objective optimization can be implemented to optimize these conflicting objectives for both systems. The nonlinear multi-objective model based on the concept of exergy and economic performance are minimized using multi-objective genetic algorithm (MOGA), multi-objective particle swarm optimization (MOPSO), and multi-objective sanitized teaching learning-based optimization (MOs-TLBO) for both VARS and MVARS. The current study also compares the decision variables obtained for minimizing the total annual cost and exergy destruction in basic and modified VARS thermo-economic models. The comparative analysis suggests that MOGA, MOPSO, and MOs-TLBO can be successfully employed to achieve these objectives. MOGA determines minimum annual cost, whereas minimum exergy destruction is reported by MOPSO. On the other hand, when compared to the other two algorithms (MOGA and MOPSO), MOs-TLBO reports a minimum total annual cost of plant operation for the reported minimum exergy destruction by effectively tuning the operating temperature of the system components for both basic and modified VARS. The current study reports Pareto points, which offer an optimal annual cost and exergy destruction based on the requirements using multi-objective algorithms.

Increasing the waste heat absorption performance in the refrigeration system using electromagnetic effect

This paper enables a simulation model for analyzing and predicting magnetic field patterns and their magnetic flux density on the pipe. Different types of arrangements of magnets like series, parallel, and Halbach arrays are utilized and their magnetic flux density and magnetic field intensity are compared on the respective pipes. Electromagnetic field simulation software calculates different magnetic fields and circuit parameters. Using this software, accurate results can be obtained such as the perfect arrangement of magnets and so on. For this experimentation, Neodymium-35 type magnets are used which have appropriate and stable magnetic strength as compared to other magnets. Diffusion absorption refrigeration systems can also be used alternatively in domestic refrigeration, thus replacing conventional vapor compression refrigeration systems. Thus, results obtained by using different magnetic arrangements will be highly beneficial to choose the proper magnetic arrangement in diffusion absorption refrigeration system for various cooling applications.