Performance Of Refrigeration System Research Articles

Effect of prime mover regenerator radius on the performance and characteristic of acoustic field of thermoacoustic refrigerator driven by prime mover

Refrigerated truck is indispensable transportation for food and medicine. However, the truck has been using the harmful substance such as CFC or HCFC. Therefore, an alternative cooler is essential such as thermoacoustic refrigerator. The refrigerator is driven by the thermoacoustic heat engine (prime mover), so the prime mover can convert the thermal or waste heat into the acoustic energy for driving the refrigerator. There are some parameters that can improve the efficiency of the refrigerator system. The aim is to investigate the impact of prime mover regenerator radius on the efficiency and characteristic of acoustic field. It was found that the best performance of the whole refrigeration system was achieved when the radius is 0.68. The engine and cooler efficiency are 84% and 38%, respectively. In addition, the acoustic field characteristic was also analyzed to elucidate the mechanism in the refrigerator system.

Technical evaluation of solar-activated absorption refrigeration systems and operating conditions: a case study in Culiacán-Mexico

This research shows the methodology for technical evaluations of the energy performance of absorption refrigeration systems activated with solar energy. This document determines the optimal installation angle of the solar thermal collectors that activate the chiller. Also, the cooling energy Qe, Coefficient of Performance (COP), and hourly Seasonal Coefficient of Performance (SCOP) are determined for each month of the year and recommendations are made for operation in the city of Culiacán, Mexico. The absorption cooling system achieved a Qe of 400.9 kW, a COP of 0.778, and a SCOP of 0.557.

Influence of compressor speed on the performance of low pressure vapor-injected refrigeration systems

For the problems of high compressor discharge temperature and system performance decay during the operation of cold storage, a parallel flow heat exchanger based low pressure make-up gas refrigeration system experimental bench was designed and built, and the changes of refrigeration system performance were analyzed under different compressor speeds. The results show that when the compressor speed increases from 2500 rpm to 4500 rpm, the compressor discharge temperature increases, the refrigeration capacity increases by 39.53% and the compressor power increases by 38.89%, in addition, as the speed increases, the system COP shows a trend of first increasing and then decreasing, with the best value of 2.71 at 3500 rpm.

Effect of superheat on refrigeration system performance of refrigerated truck

According to the characteristics of variable operating conditions and high exhaust temperature of the refrigeration system of the refrigerator truck, the change of the superheat at the outlet of the evaporator is adjusted by a new electronic expansion valve, and a performance test-bed using the R404A refrigerant is built to study the influence of the superheat at the outlet of the evaporator on the performance of the refrigeration system of the refrigerator truck. The results show that in the process of increasing the superheat at the outlet of the evaporator, the outlet temperature of the evaporator increases and the evaporation temperature decrease, the cooling capacity of the system is reduced by 8.4%, and the COP of the system increases first and then decreases; At this time, the optimal superheat at the evaporator outlet is 6?C, and the system COP reaches the optimal value of 2.856.

Mass flow characteristics prediction of refrigerants through electronic expansion valve based on XGBoost

In an effort to enhance the prediction accuracy of the mass flow characteristics of refrigerants through electronic expansion valves (EEVs), this study develops a mass flow model using the XGBoost machine learning algorithm. Utilizing experimental data from open literature for refrigerants R1233zd(E) and R245fa, the model aims to accurately predict the mass flow coefficient in EEVs, a crucial aspect for improving the performance and efficiency of refrigeration systems. The model's performance is evaluated using the coefficient of determination (R2) on the training and test datasets, revealing a minimal performance gap and no overfitting issue. Remarkably, our model's predictions for R1233zd(E) and R245fa datasets align consistently with experimental data, with 96.4 % and 90.6 % of the predicted data deviating from the experimental ones within ±5 %, respectively. Further, the root-mean-square error (RMSE) and coefficient of variation of the root mean square error (CV-RMSE) values are quite low, with 2.2 % and 2.33 % for R1233zd(E), and 4.23 % and 4.47 % for R245fa, indicating high prediction accuracy. Compared to the original models, the paper approach with the XGBoost algorithm significantly improves prediction accuracy. This advancement provides a promising direction for developing more efficient and reliable control strategies for refrigeration systems in various applications.

Experimental study on refrigeration system performance of pure electric refrigerator car based on medium pressure air supply

In view of the low refrigeration efficiency of the refrigeration system of the pure electric logistics car under the high temperature environment, an experimental platform of the refrigeration system based on medium pressure air supply of the pure electric refrigerator car was built with R404A as the refrigerant, the experiment results show that the system refrigerating capacity, COP and EER decrease with the increase of external environment temperature under the same internal environment temperature, the compressor power and exhaust temperature increase with the increase of the external environment temperature. When the external environment temperature is 43 °C, the medium pressure air supply technology is obviously better than the non-air supply technology, the refrigerating capacity increased by 4.1–12.73 %, the compressor power and EER changed little, the COP increased by 1.3–6.38 %, and the exhaust temperature reduced by 3.4 °C-7.11 °C, especially at -3 °C, the system refrigerating capacity decreases by 30.1 %, the compressor power increases by 35.6 %, the COP and EER distribution decreases by 51.24 % and 42.68 %.

Application of response surface methodology and desirability approach to optimize the performance of an ultra-low temperature cascade refrigeration system

In this paper, multi-objective optimization of an ultra-low temperature cascade refrigeration system is presented using response surface methodology and desirability approach. Evaporation temperature, high-temperature circuit and low-temperature circuit condensation temperature, cascade temperature difference, and superheat degrees of the compressor suction are chosen as the variables, whereas COP, total exergy destruction and exergy efficiency are adopted as the responses that simultaneously maximizing COP and exergy efficiency while minimizing the exergy destruction. The quadratic models for three responses are obtained after the analysis of variance. The interactive influences of the variables on the responses are indicated. The results present that the maximum deviations between the predicted and actual values for the COP and exergy efficiency are 0.84% and 0.96%, whereas the deviations for the exergy destruction are within ± 2% accounting for 96% of the samples. Evaporator temperature, condenser temperature, cascade temperature difference, ect. are found to be important parameters which cause great conflicts among the objective functions. A group of optimum values for the input variables are selected and validated. The derivations between predicted modeling and simulation values for the COP, total exergy destruction, and exergy efficiency are −0.604%, 2.886%, and 0.0452%, respectively, indicating that the method is efficient to optimize the performance.

REACHER: the exploration of the use of reactive working fluids for thermodynamic cycles

REACHER: the exploration of the use of reactive working fluids for thermodynamic cycles With the aim to effectively increase the performances of power plants, refrigeration systems and heat pumps, this project proposes the use of equilibrated reactive working fluids instead of inert ones. It applies an original methodology that integrates thermodynamic and kinetic predictive tools to discover and characterise suitable reactive fluids, allowing for the quantification of the effects of reaction features on system performance and optimal architecture.

Experimental comparison of critical performance for variable geometry ejectors with different mixer structures

To further optimize the performance of Solar-driven Ejector Refrigeration system under variable driving conditions, ejectors design using conical-cylindrical mixers are more effective than using cylindrical mixers were elucidated. The effects of the nozzle exit position (NXP), area ratio (Ar), and expansion ratio (E) on the performance of the conical-cylindrical mixer ejector (CCME) and the cylindrical mixer ejector (CME) were investigated. It was revealed that compared with the performance of the CME at the optimal nozzle exit position, the variable geometry CCME exists a NXP range where both the critical entrainment ratio (Ercri) and critical compression ratio (Ccri) are larger. This NXP range can be widened by appropriately reducing the NXP or Ar of the CCME under a specified expansion ratio. Besides, under variable expansion ratios, the expansion ratio range in which both Ercri and Ccri of the CCME are better than those of the CME can be widened by appropriately reducing the NXP or Ar of the CCME. The results demonstrated that the CCME is more suitable for variable expansion ratios than the CME. This implies that using the variable geometry CCME has a higher energy utilization efficiency in a Solar-driven Ejector Refrigeration system than that of using the CME. This work provides a promising guide for achieving higher energy efficiency of an ejector refrigeration system under variable driving conditions.

Thermodynamic, economic and environmental assessment of a novel organic Rankine cycle-vapor compression refrigeration system using zeotropic mixture

The improvement of system configuration is an effective method to improve performance of the organic Rankine cycle-vapor compression refrigeration (ORC-VCR) system. A novel system with a recuperator on the ORC side and a flash tank on the VCR side is proposed. Firstly, the theoretical model of thermodynamic, economic and environmental performance is constructed. Then, the novel system is compared with the basic ORC-VCR system. Next, the effects of operating parameters on performance of the proposed system are investigated. Finally, a comparison of system performance in different positions of phase transition temperature is carried out. The results show that the coefficient of performance(COP), exergy efficiency, dynamic payback period(DPP), net present value(NPV) and annual emission reduction(AER) of the novel system are 0.38, 5.94 %, 8.89 years, 1.52 × 106 $ and 5.77 × 106 kg, respectively. Compared with the basic ORC-VCR system, the improvement in thermodynamic performance of the novel system is relatively preferable to the deterioration in economic performance. Moreover, the effect of mixture composition on system performance is distinct in different positions of phase transition temperature. It is shown that using zeotropic mixture is not appropriate in all cases. This paper can provide theoretical guidance to further improve performance of the ORC-VCR system.

Performance Analysis of an R744 Supermarket Refrigeration System Integrated with an Organic Rankine Cycle

The energy and economic performance of a transcritical R744 booster supermarket refrigeration system with and without parallel compression and integrated with an organic Rankine cycle (ORC) was investigated. The results obtained were compared with those of a transcritical R744 booster supermarket refrigeration system with and without parallel compression and those of a conventional R404A direct expansion (DX) system. Nine different locations, namely Copenhagen (Denmark), Paris (France), Athens (Greece), New Delhi (India), Phoenix and Miami (US), Madrid (Spain), Bangkok (Thailand) and Riyadh (Saudi Arabia), were considered. It was discovered that the ORC is effective only at ambient temperatures higher than 27 °C when operating without parallel compression and 28 °C when operating with parallel compression. By using the heat recovered from the gas cooler to fuel the ORC, the latter was found to be capable of covering between 4% and 24% of the electricity demand of the R744 system in warm and hot climates (without parallel compression). The simple payback period of the additional investment associated with the ORC was found to be between 1.4 and 2.5 years in warm climate locations, while the same was found to be less than about 0.5 years in locations experiencing hot climatic conditions.

Enhancement of Condenser Performance in Vapor Absorption Refrigeration Systems Operating in Arid Climatic Zones—Selection of Best Option

Generators and condensers are the two vital equipment items that determine the output of vapor absorption refrigeration systems. Arid weather conditions produce a significant reduction in the performance of the vapor absorption refrigeration cycle due to low condenser heat dissipation despite high generator temperatures. Although numerous studies on condenser cooling methods in vapor compression systems have been reported in the literature, solar-operated vapor absorption systems have not been studied. Limitations in generator temperatures of solar-operated vapor absorption systems necessitate a focused study in this area. This study makes the selection of the best choice for condenser cooling from among four different condenser cooling methods which have an impact on the performance of the vapor absorption refrigeration system for effective cooling using solar energy. A solar vapor absorption refrigeration system working with low-grade heat using a compound parabolic collector is considered in this study. Analysis of a vapor absorption refrigeration system for cooling in arid weather conditions is carried out using different condenser cooling methods with Engineering Equation Solver. Initially, the model used in the study is compared with a similar study reported in the literature. Techniques considered are air, water, evaporative, and hybrid cooling techniques. The performance of the vapor absorption cooling system was analyzed using experimental values of a solar compound parabolic collector obtained from real-time measurements for simulating the model. Results show that water cooling can provide suitable condenser cooling and improve the coefficient of performance of the solar vapor absorption refrigeration system using the solar collector. The water-cooled condenser has 1.9%, 3.3%, and 2.1% higher COP when compared to air-cooled condensers for spring, summer, and autumn seasons respectively, whereas the water-cooled condenser cooling recorded 6%, 14%, and 8% higher COP relative to the evaporative cooling method. Cost comparison showed maximum cost for water-cooled condensers and minimum cost for hybrid-cooled condensers. The effect of each cooling method on the environment is discussed.

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.

Thermodynamic analysis on a magnetic refrigeration system

Magnetic refrigeration utilizes the magnetocaloric effect of a magnetic material, whose temperature changes according to the change of magnetic field strength. It is regarded as an eco-friendly refrigeration technology in that it uses magnetic materials as refrigerants instead of CFC, HCFC, and HFC refrigerants used in vapor compression refrigeration. It is also regarded as an energy-efficient refrigeration technology in that it does not use noisy and power-consuming compressors. This paper presents thermodynamic analysis on a magnetic refrigeration system using experimental results obtained from a magnetic refrigeration apparatus. The magnetic refrigeration apparatus was built using two sets of concentric Halbach cylinders consisting of permanent magnet segments. Specifically the coefficient of performance (COP) of the magnetic refrigeration system was calculated using the energy removed from the working fluid across an AMR bed and the work input to run electric motors.

Performance of hydrocarbon refrigerants in a refrigerator with liquid line magnet and CNT nano-lubricant

The issues of flammability associated with A3-class hydrocarbon-based refrigerants are controllable by limiting their mass charges. However, these reductions in their mass charge below certain limits deteriorate their performance efficiency. In this experimental study, we analyzed the effects of a liquid line magnetic field (Mag), multi-wall carbon nanotube (CNT) nano-lubricant, and the combination of both (Mag-Nano) on the performance of a very low mass charge (i.e., 30 g) of R600a and LPG refrigerants, as a replacement to the 100 g R134a refrigerant in a domestic refrigeration system. The refrigerants were tested with and without CNT nano-lubricant (pure), two pairs of 3000 Gs liquid line mounted O ring N50 permanent magnets (Mag), 0.2 g/L concentration of CNT nano-lubricant (Nano), and in combination with a liquid line magnetic field and CNT nano-lubricant (Mag-Nano). The performance evaluation of the refrigerants includes the determination of coefficient of performance (COP), evaporator air temperature, volumetric refrigeration capacity, instantaneous power consumption, cumulative energy consumption, and energy cost. A reduction in the COP of R600a and LPG was observed to be about 11–42% and 14–26%, respectively, when compared to R134a. The R134a refrigerant had the lowest evaporator air temperature of −24.5 °C and the highest instantaneous power consumption of 74.6 W. The R600a-Mag-Nano refrigerant is the most efficient option, having the lowest instantaneous power consumption, energy cost, and cumulative energy consumption. The adoption of hydrocarbon refrigerants is more cost-effective than using the R134a refrigerant, resulting in a cost saving of about 8–26%. In conclusion, the proposed methods adopted to enhance the performance of refrigeration system, are very safe and effective.

Conical-cylindrical mixer ejector design model for predicting optimal nozzle exit position

Precisely predicting the optimal nozzle exit position (ONXP) of a vapor ejector is highly desirable for optimizing the performance of an ejector refrigeration system. Based on the theory of the shear mixing-layer and the adiabatic frictional flow equations in a conical-cylindrical mixer, a new design model to predict the ONXP for a conical-cylindrical mixer ejector (CCME) is proposed and verified. Furthermore, the evolution laws of the dimensionless optimal nozzle exit position (DONXP) and critical entrainment ratio (Ercri) for different design conditions (i.e., the expansion ratio E and critical compression ratio Ccri) are investigated. Based on a comparison of the experimental values and the predicted data, the relative deviations of the DONXP, Ercri, and Ccri are within ±14.81%, ±16.99%, and ±10.76%, respectively. The critical entrainment ratio decreases as the critical compression ratio increases but increases as the expansion ratio increases, and both with an increasingly slower rate of change. The variations in the DONXP with the varying critical compression ratio and expansion ratio are similar to that in Ercri. Results further indicate that a well-constructed CCME allows the critical entrainment ratio to attain the design values by adjusting its nozzle exit position to the ONXP when the expansion ratio is changed.

Performance Evaluation of LiBr-H2O and LiCl-H2O Working Pairs in Compression-Assisted Double-Effect Absorption Refrigeration Systems for Utilization of Low-Temperature Heat Sources

To improve the performance of conventional double-effect absorption refrigeration systems (DEARS), new series parallel (SP) and reverse parallel (RP) configurations using LiCl-H2O and LiBr-H2O as working fluids, combined with two vapor compressors (VC), are proposed and thermodynamically evaluated. The effects of the distribution ratio (D) and compression ratio (CR) on the system performance are discussed. The results reveal that both configurations can extend the operation ranges of DEARS effectively at a higher distribution ratio, and the performance for low-grade heat source utilization is improved substantially by the use of VC. The compressor positioned between the evaporator and absorber is superior to that between the high-pressure generator and low-pressure generator because of the better performance improvement and larger operating ranges. In all the examined cases, LiCl-H2O systems perform better than LiBr-H2O systems in terms of the coefficient of performance (COP) and exergetic efficiency. At the higher CR of approximately 2, the compression-assisted DEARS can be driven by heat sources below 100 °C with high levels of COPs above 1.16 for the LiBr-H2O working pair and 1.29 for the LiCl-H2O working pair. The system can operate at the optimum condition by adjusting the CR values according to the characteristics of the heat sources.

Numerical simulation of a multistage magnetic refrigeration system in the temperature range of liquid hydrogen

Magnetic refrigeration is an important new refrigeration technology in the temperature range of liquid hydrogen. A multistage magnetic refrigeration system between 20 K and 80 K has been proposed, which includes three-stage active magnetic regenerators (AMRs). Based on the multistage system, a two-dimensional transient AMR model is established to research the cycle performance mechanism by considering the compressibility of helium, which has not been done before. Firstly, to simplify the simulation difficulty, the AMR model with ideal magnetocaloric materials (the constant isothermal entropy change of 5.4 J/(kg·K) at 1 T) are investigated in the temperature range between 60 K and 80 K. Some parameters including particle diameter, fluid flow fraction, and filling mass of magnetocaloric materials have been compared and analyzed. Based on the above simulation results, the AMR model with real magnetocaloric materials has been done. In the three-layer AMR, the maximum cooling power of 71.04 W at the cooling temperature of 60 K has been obtained, which is 80.17% larger than that of the one-layer AMR. Then, the cooling performance of the multistage magnetic refrigeration system has been studied. In the system, six magnetocaloric materials are filled in three-stage AMRs based on the filling method of adiabatic temperature change. With the optimal mass flow rates of each stage AMR, the maximum cooling power of 40.09 W has been obtained in the multistage system, and the corresponding thermodynamic second efficiency has been 28.14%.

Performance analysis of vapor compression refrigeration system using varying concentrations of copper oxide (CuO)/mineral oil (MO) based nanosuspension

The nanofluid is being utilized for more than a decade to improve the theocentric properties of various thermal systems. In the presented work, the copper oxide (CuO) nanoparticle suspension is utilized to improve the performance of the vapor compression refrigeration system. Mineral oil is utilized as the base fluid for the synthesis of CuO-based nanosuspension. The nanosuspension is synthesized with a concentration of 0.02 wt%, 0.04 wt% and 0.06 wt%. For the refrigeration system, R600a refrigerant is used. The experimental analysis is carried out in two phases. In the first phase of the experimental analysis, the CuO-based nanosuspension is synthesized and the thermophysical properties such as thermal conductivity, specific heat, and density are evaluated. In the second phase, the synthesized nanosuspension has been incorporated into the refrigeration system. The performance parameters such as COP, power consumption, and pull-down time are investigated using R600a/MO/CuO-based nanosuspension. From the first phase of the experimentation, it is concluded the CuO nanoparticle significantly enhances the thermophysical properties of the pure mineral. A significant gain in thermal conductivity and density is noted along with a reduction in the specific heat of the pure mineral oil. Similarly, from the second phase of the experimentation, it observed that the higher average gain in the COP by 30.2%, reduction of power consumption by 12.53%, and reduction in pull down time is noted by using 0.06 wt% of CuO-MO-based nanosuspension.

A novel method to measure the energy efficiency and performance of an auto-cascade refrigeration cycle

Auto-cascade refrigeration systems are the most used cycles to maintain spaces at ultra-low temperature conditions (-80 to −60 °C). The interest in these systems has risen due to the need to maintain and distribute COVID-19 vaccines. However, there is a lack of experimental validation of the theoretical models that are used to analyse and optimize them. In this work, a novel method to calculate the thermodynamic performance, circulating compositions, and energy efficiency of an auto-cascade refrigeration system is presented. The method is based on the measurements of an experimental auto-cascade plant at temperatures from −83.0 to −59.9 °C. The results of the study showed that the proposed calculation method was able to accurately predict the thermodynamic performance, circulating compositions and energy efficiency of an auto-cascade system. The uncertainty of the predictions was found to be below 1% for circulating compositions and 5.2% for the cooling capacity and COP.