Domestic Refrigeration System Research Articles

Numerical and experimental study of the transient behavior of a domestic vapor compression refrigeration system – Influence of refrigerant charge and ambient temperature

In this work, two transient mathematical models are presented for simulating a vapor compression refrigeration system of domestic refrigerator using R134a. One, the thermal model, is based on the application of the first law of thermodynamics and the second, capacitive model, adds the evaluation of the refrigerant mass distribution in the system. An experimental procedure to calculate the thermal conductance and capacity of system components (compressor, condenser, capillary tube, evaporator, cabinet) is presented. Experimental data describing the transient behavior of the refrigeration system are also obtained to validate the simulation procedures. The domestic refrigerator studied is a vertical two compartments refrigerator. The simulation results follow the measured experimental trends and are very satisfactory when compared to the transient and time averaged experimental data. The maximum relative error obtained for simulated temperatures was about 5.65%. Parametric analyses were conducted to identify the influence of refrigerant charge and ambient temperature on the refrigeration system performance. The optimum refrigerant charge has distinct values regarding the operational condition of the system. In the pull-down operation the highest COP is attained for 105g and 140g of refrigerant for transient and the steady-state regimes, respectively. In the on-off operation the optimum refrigerant charges are 105g for transient operation (placing goods inside the compartments) and around 70g to 95g for stationary condition (without goods). Excepting for small refrigerant charges ~50g, the higher quantity of refrigerant during the entire system operation is in the evaporator. For low refrigerant charges, 50–70g, it is also shown a refrigerant migration between condenser and evaporator under the effects of thermal loads when compressor is turned on. Ambient temperature augmentation by 18°C decreases refrigerator COP without thermal load in 10% and 16% for pull-down and on/off operations, respectively. The presented experimental results are new and can be used by other researchers for validating their own simulation models. The developed models can considerably improve the design of domestic refrigeration systems by manufacturers.

Design and Performance of Solar PV Integrated Domestic Vapor Absorption Refrigeration System

The arrival of new technologies has increased the energy demand day by day and does not seem to slow down at any time soon. High energy demand is adding risk on energy depletion and cause of various environmental issues. Air conditioner, chiller, and refrigerator occupy a considerable amount of the world’s total energy usage and have also proved to be a massive contributor to various environmental impacts. This technology might sound like a luxury on the surface, but they are in high demand to achieve food security. They can also help lifesaving vaccines to reach even the isolated parts of the world. Even though solar thermal refrigeration is a popular field, this paper solely concentrates on PV integrated refrigeration. In this paper, a renewable integration technology where a solar photovoltaic system is used to supply the electrical energy required to drive an absorption cycle is studied and compared with the commercial AC absorption refrigeration system. The Coefficient of Performance (COP) of the AC and DC system was 0.18 and 0.14. The simple payback of the system is 10.2 years.

Performance of a domestic refrigerator in varying ambient temperatures, concentrations of TiO2 nanolubricants and R600a refrigerant charges

This study investigates the effect of varying test conditions including ambient temperature (19, 22, and 25 °C), mass charges of R600a refrigerant (40, 50, 60, and 70 g), and concentrations of TiO2 nanolubricant (0, 0.2 and 0.4 g/L) on the performance of a slightly modified 100g R134a domestic refrigeration system. The investigated parameters include evaporator air temperature, energy consumption, coefficient of performance, and second law efficiency of the system. The results showed that the performance of the refrigeration system at 0.2 and 0.4 g/L concentrations of TiO2 nanolubricant, improved at optimum ambient temperature and R600a mass charge conditions. At optimum conditions, the evaporator air temperature and energy consumption reduced within the range 5.26 to 26.32 %, and 0.13 to 14.09 % respectively, while the coefficient of performance and second law efficiency increased within the range 0.05 to 16.32 %, and 2.8 to 16 %, respectively. However, at other conditions (non-optimum), the energy consumption and evaporator air temperature were higher and within the range 0.28 to 8.26 %, and 5 to 40 % respectively, while the coefficient of performance and second law efficiency reduced within the range 2.99 to 10.94 %, and 0.55 to 13.43 % respectively. In conclusion, we observed variations in the performance of the refrigerator with varying test conditions.

Theoretical assessment of new low global warming potential refrigerant mixtures as eco-friendly alternatives in domestic refrigeration systems

Refrigerants of low global warming potentials (GWPs) of ≤ 150 are required by regulations as working fluids in domestic refrigeration systems. Therefore, this study theoretically investigated the performance of five new refrigerant mixtures (R440A, R441A, R444A, R445A and R451A) with zero ODP and GWPs of less than 150. The results showed that all the investigated refrigerants exhibited very low pressure ratios and discharge temperatures in comparison with R134a with average discharge temperatures of R451A and R440A lower by 8 and 7% respectively, than that of R134a. R451A and R440A have similar vapour specific volume and pressure-temperature characteristics with those of R134a which confirmed that they could be used as replacement for R134a. R440A and R451A have advantages of better COPs and volumetric cooling capacity (VCC) in comparison with R134a. Their average COPs are higher by 14 and 5% respectively, than that of R134a. The specific power consumptions (SPCs) of R441A and R445A are significantly higher by average of 57 and 44% respectively; while those of R440A and R451A are lower by average of 8 and 4% respectively, in comparison with R134a. In general, in terms of all the performance parameters considered, R441A and R445A consistently performed poorly, while R440A and R451A achieved better performance than R134a in all aspects. Beside the flammability of these two refrigerants, in which their use require following the established rules and regulations for the safety precautions, they can serve as long term eco-friendly substitute refrigerants for R134a in domestic refrigerators.

Performance Evaluation of Domestic Refrigerator with Waste Heat Recovery System

The objective of the article is to study the performance of domestic refrigerator with waste heat recovery system. The usage of domestic refrigeration systems are increasing every day due to the requirement. During the operation of domestic refrigeration system, heat is rejected through the condensing coil to the atmosphere and leads to thermal pollution. Hence this heat can be recovered by suitable waste heat recovery system and employed for useful domestic applications. Hot chamber box has been fabricated and assembled with the domestic refrigerator. Experimental analysis has been carried out under air cooled condenser and hot chamber condenser with different loading conditions like no load, 1 litre, 3 litres, 5 litres, and 10 litres of water in the evaporator unit. COP is calculated for all the loading conditions and compared with air cooled condenser and hot chamber condenser. COP of all the loading conditions is maintained almost in the same range value. COP value is obtained in the range of 5 to 5.5 for the air cooled and hot chamber condensation modes. Hence the performance of domestic refrigerator is not changed due to the running of hot chamber box. Due to installation of hot chamber box waste heat is recovered from the condenser coil. The maximum heat recovery is arrived in the range of 31.15 to 33.66 kJ/kg.

Recent Developments in the Search for Alternative Low-Global-Warming-Potential Refrigerants: A Review

Conventionally, the CFC-type refrigerants were used until Montreal Protocol which stated that CFC refrigerants cause ozone depletion and should be replaced with alternative refrigerants. The alternative refrigerants are safe for ozone but they have comparatively high flammability, toxicity and global warming potential. Thus they need careful handling. In Kyoto Protocol, it was stated that the currently used refrigerants with high global warming potential need to be replaced with yet other alternative refrigerants with low global warming potential. This paper comprehensively reviews those recent studies that focused on the possible replacement of currently in-use refrigerant with a comparatively more environmental-friendly alternative refrigerant. Initially, the progression of refrigerants through different generations has been described and discussed. A list of currently in-use refrigerants has been presented. Then, the scientific developments for the replacement of listed refrigerants are thoroughly reviewed and critically analyzed. From the comprehensive review, it was found that R1234yf has the most potential to be a suitable low-flammable replacement for R134a for domestic refrigeration and automotive air-conditioning systems. Also, R32 has the most potential to be a suitable alternative of R410A.

Dataset and ANN model prediction of performance of graphene nanolubricant with R600a in domestic refrigerator system.

This work evaluated the steady state performance of R600a in the base lubricant and graphene nanolubricant. The measuring instruments required and their uncertainties were provided, step by step method and procedures for preparation of graphene nanolubricant concentration and substituting it with the base lubricant in domestic refrigerator system are described. The system temperatures data was captured at the inlet and outlet of the system components. Also, the pressures data was recorded at the compressor inlet and outlet. The data was recorded for 3 h at 30 min interval at an ambient temperature of 27 °C. The experimental dataset, Artificial Neural Network (ANN) training and testing dataset are provided. The artificial intelligence approach of ANN model to predict the performance of graphene nanolubricant in domestic refrigerator is explained. Also, the ANN model prediction statistical performance metrics such as Root Mean Square Error (RMSE) and Mean Absolute Deviation (MAD), Mean Absolute Percentage Error (MAPE) and coefficient of determination (R2) are also provided. The data is useful to researchers in the field of refrigeration and energy efficiency materials, for replacing nanolubricant with the base lubricant in refrigerator systems. The data can be reuse for simulation and modelling vapour compression energy system.

Adaptive neuro-fuzzy inference system (ANFIS) approach for the irreversibility analysis of a domestic refrigerator system using LPG/TiO 2 nanolubricant

This work presents an adaptive neuro-fuzzy inference system (ANFIS) artificial intelligence methodology of predicting the 2nd law efficiency and total irreversibility of a refrigeration system running on LPG/TiO2–nano-refrigerants. For this purpose, substractive clustering and grid partition approaches were utilized to train the ANFIS models required in estimating the 2nd law efficiency and total irreversibility using some experimental data. Furthermore, predictions of ANFIS models with subtractive clustering approach was found to be more accurate than ANFIS models predictions with grid partition approach. The predictions of ANFIS models with subtractive clustering approach were also compared with experimental results that were not included in the model training and predictions of already existing ANN models of authors previous publication. The comparison of variance, root mean square error (RMSE), mean absolute percentage error (MAPE) were 0.996–0.999, 0.0296–0.1726 W and 0.108–0.176 % marginal variability values. These results indicate that the ANFIS model with subtractive clustering approach having cluster radii 0.7 and 0.5 can predict the 2nd law efficiency and total irreversibility respectively, with higher accuracy than authors’ previous publication ANN models.

A Comparative Study of Multiple Regression and Artificial Neural Network models for a domestic refrigeration system with a hydrocarbon refrigerant mixtures

Abstract Present paper discus with the development models such as Multiple Regression Analysis (MRA) and Artificial Neural Networks (ANN) for a domestic refrigeration system to predict the performance of a system using Hydrocarbon Refrigerant Mixtures (HCRM). The experiments conducted with the changing evaporator temperature (Te), different hydrocarbon refrigerant mass (mr), and variation in capillary tube length (Lc). The ANN model working with the feed backward back-propagation and Levenberg-Marquardt training algorithm is used to develop the model. This model is used to predict the performance considerations such as power consumption, refrigeration effect and COP. Similarly to develop an MRA and it has been checked for adequacy and significance. Finally, the ANN model is an excellent agreement to a multiple regression model with the coefficient of determinations (R2) of 0.989. The minimum correlation coefficient obtained with the ANN method is higher than the maximum correlation coefficient obtained from the MRA. Also, the value of the error of the ANN method is much less than the MRA method indicating the higher confidence coefficient of the ANN. These values indicate that the developed ANN model is more reliable and accurate than the multiple regression analysis. Based on the above study reveals that the ANN approach is a better technique than MRA for performance and prediction of domestic refrigeration system with high accuracy

Thermodynamic Analysis of Low GWP Refrigerant Mixtures in a Refrigerator as Replacement to R-134A

Abstract Chlorofluorocarbons and hydro chlorofluorocarbons (HCFCs) are replaced by hydroflourocarbons (HFCs) which is not harmful to the ozone layer. However, few of HFCs have a relatively high global warming potential (GWP) and are subject to further examination due to growing concerns about global climate change. The goal now is to find the next generation of environmentally sustainable work fluids with an insignificant direct environmental impact in terms of ozone depletion and global warming potential. This document introduces the mixture of low-GWP refrigerants like R440A, R430A, R1234ze (E)/152a (50:50 by mass), R290/600a (40/60), R290/600(60/40), R290/600(50/50), ARM 42,ARM 42a and AC5 are used to replace R-134a in a domestic refrigeration system without doing any modifications to the system. The performance of the refrigerator was observed in terms of volumetric cooling capacity, blower discharge temperature, and coefficient of performance, refrigeration effect and energy consumption of a blower.

Performance Evaluation of Hydrocarbon based Nanorefrigerants Subjected to Periodic Door Openings

Domestic refrigerators are required to be energy efficient and environmentally safe. In this work, a slightly modified domestic refrigeration system was infused with various concentrations (0, 0.2, 0.4 and 0.6 g/L) of TiO2 nanolubricants and R600a refrigerant with a mass charge of 40g. The average energetic characteristics of the test rig at different door openings intervals (0.5, 1, 2, 3 and 5 minutes) were evaluated. The energetic characteristics studied were coefficient of performance (COP), refrigeration capacity, power consumption and cabinet temperature recovery time. The results obtained showed that the use of nanolubricants significantly affect the energetic performance characteristics of the system. Overall, the utilization of 0.6g/L concentration of TiO2 nanolubricant gave the best performance. The COP of the system improved by 22.39 %, while the power consumption decreased by 23.5 % when compared with pure R600a refrigerant.

Experimentation and Performance Analysis of Natural Draft Wire on Tube Condenser

This project is sponsored by the company Whirlpool of India Limited, situated at Ranjangaon MIDC, Pune. A simple design methodology of Wire on Tube heat exchanger used in domestic refrigeration systems focuses on both energy saving and cost reduction in this study. A wire on tube condenser is two-phase natural convection heat exchanger which rejects heat absorbed by the refrigerant in the evaporator and heat addition by compressor to atmospheric temperature changing its phase. The main objective of this research paper is to study impact of condenser tube length and number of wires, its pitches on performance of domestic refrigerator and desire to find optimum design of wire on tube heat exchanger compatible with on/off compressor in 185 liter 3 star single door model. Mathematical model are used to analyze performance of entire refrigeration system. Experiments were conducted under controlled climatic chamber and varying ambient temperature as per BEE standard and procedures. It was found that experimental results have 5% to 8% deviation range with results obtained from mathematical model. Optimum design of wire on tube heat exchanger selected has main focus on both energy saving and cost reduction.

Performance enhancement using appropriate mass charge of R600a in a developed domestic refrigerator

This paper presents performance analysis of a domestic refrigeration system using R600a as refrigerant. Investigation was conducted experimentally to select an appropriate refrigerant mass charge for the system and to compute the cooling system performance characteristics under ambient temperature of 29°C. The choice of the hydrocarbon refrigerant (R600a) became so imperative due to notable influence of chlorofluorocarbons (CFCs), hydrochlorofluorocarbons (HCFCs) and hydrofluorocarbons (HFCs) on global warming and ozone depletion. UNFCCC and Montreal Protocol regulation have banned the use of halogenated refrigerants in cooling and heating systems. The paper reveals that the power consumed by the system using mass charge of 15 g refrigerant was reduced by 9.3 and 10.9% compared with the 10 and 25 g refrigerant mass charges respectively. In addition, the results show that the coefficient of performance (COP) of the refrigeration system while working with 15 g is 24.7 and 20.2% higher than when the system worked with 10 and 25 g refrigerants mass charge respectively. More so, the system attained an evaporator air temperature of -12 °C in 2 hours, which makes 15 g charge refrigerant appropriate for the running of the developed system that has a volume capacity of 68 liters.

A study on heat storage sizing and flow control for a domestic scale solar-powered organic Rankine cycle-vapour compression refrigeration system

This paper presents the off-design modelling of a domestic scale solar organic Rankine cycle (ORC) and vapour compression cycle (VCC) in a coupled operation in different operating modes by using evacuated flat plate (EFP) collectors. Thermodynamic and parametric studies of such coupled system in literature usually assume that the isentropic efficiencies of expander and compressor and the heat exchanger pinch temperature differences are constant. Moreover, studies for directly coupling the ORC-VCC system with solar collectors are somewhat rare. Transient performance of the solar ORC-VCC considering the off-design behaviour of the system components needs to be investigated. A simulation for a period of 24 hrs is conducted by considering the electricity and cooling demand of a 60 m2 office building during a typical day in July for Istanbul. The effect of heat storage capacity on meeting the demand is investigated for a given area of EFP collectors. Moreover, the water flow rate to the boiler is controlled periodically to provide the demanded electricity and cooling. The required EFP collector area and heat storage unit volume have been determined to be 80 m2 and 9.4 m3, respectively. For these design parameters, 25.6 kWh cooling and 18.76 kWh electricity can be generated during a typical day in July. Finally, a simulation is given for such design on a sunny winter day in February, 5.5 kWh electricity and 104 kWh heat can be produced.

Comparative molecular dynamics simulations of homogeneous condensation of refrigerants

Performance improvement and environmental impact are very important issues in the selection of suitable refrigerant for domestic refrigeration systems. The homogeneous condensation of two hydrocarbon (HC) refrigerants, namely, R600 (butane) and R600a (isobutane) and two hydrofluorocarbon (HFC) refrigerants i.e. R134a (1,1,1,2-tetrafluoroethane) and R143a (1,1,1-trifluoroethane) was investigated by molecular dynamics simulations. The thermophysical properties of the four refrigerants, such as the density, internal potential energy, and cell volume of the molecular systems during the condensation process are compared. The influences of the various refrigerants on the potential energy and the cluster formation are described. The results show that vapor molecules undergo a rapid phase transition to a subcooled liquid within a specific time period. In the simulations, clusters of the substances are formed initially, which then aggregate to produce the condensate liquid droplets over time. The densities of all the refrigerants at the liquid phase after condensation agree with REFPROP data. A comparative analysis of the refrigerants was performed based on the saturation ratio to investigate the time of complete condensation in the homogeneous condensation process.

Experimental performance of a safe charge of LPG refrigerant enhanced with varying concentrations of TiO2 nano-lubricant in a domestic refrigerator

This paper presents an experimental investigation of energy consumption and heat transfer performance characteristics of a safe mass–charge of liquefied petroleum gas refrigerant, enhanced with varying concentrations of TiO2 nano-lubricants (i.e. 0.2 gL−1, 0.4 gL−1 and 0.6 gL−1) in a domestic refrigerator. Performance parameters investigated at steady state included: instantaneous and mean power consumption, cooling capacity, coefficient of performance (COP), discharge thermal conductivity and discharge temperature. Analysis was based on temperature and pressure readings obtained from appropriate gauges attached to the test rig. Refrigerant properties were obtained from Ref-Prop NIST 9.0 software. Findings showed that reductions in mean power consumption were observed to be 14, 9 and 8% at 0.2 gL−1, 0.4 gL−1 and 0.6 gL−1 nano-lubricants respectively; the highest mean power consumption was obtained using pure compressor mineral oil while the lowest was with 0.2 gL−1 TiO2 nano-lubricant. The estimated mean cooling capacities for the various compressor lubricants were found to be higher with 0.4 gL−1 and 0.6 gL−1 nano-lubricants than pure compressor lubricant, and lower with 0.2 gL−1 nano-lubricant when compared with pure mineral oil lubricant. All the TiO2-based nano-lubricants were of higher instantaneous and mean COP values than the pure lubricant. All nano-lubricant mixtures were also found to give lower discharge temperatures than the pure lubricant. In conclusion, selected TiO2-based nano-lubricants improved the efficiency of the domestic refrigeration system considerably.

Investigation on the energy and exergy efficiencies of a domestic refrigerator retrofitted with water-cooled condensers of shell-and-coil and brazed-plate heat exchangers

Domestic refrigerator is one of the major energy-consuming appliances, and the enhancement of its energy efficiency plays a vital role in implementing the energy conservation policies and green building concepts in residential sector. The major strategies used to improve the performance of domestic refrigerators are the replacement of existing components, use of alternative refrigerants and the reduction in condensing pressure. Therefore, in this work, the conventional air-cooled condenser has been replaced with water-cooled condensers such as shell-and-coil and brazed-plate heat exchangers to maintain a low compression ratio and condensing pressure. The performance of a domestic refrigeration system retrofitted with water-cooled condensers has been studied using experimental methods. The result showed that the system with water-cooled condensers reduces the pull-down time and the per day energy consumption by 70% and 3.5%, respectively. Moreover, the proposed system can improve the COP and exergy efficiency by 6.4% and 4.9%, respectively. Compared to shell-and-coil heat exchanger, the system with brazed-plate heat exchanger can reduce irreversibility and TEWI by 3.9% and 3.7%, respectively. In this study, the system with brazed-plate heat exchanger showed better performance than the shell-and-coil heat exchanger for all operating conditions.

Performance of a hydrocarbon driven domestic refrigerator based on varying concentration of SiO2 nano-lubricant

This experimental work studies the performance of varying concentrations of SiO2 nanoparticle in mineral oil lubricant using LPG refrigerant, as a retrofit to R134a in a domestic refrigeration system. The test rig is fitted with thermocouple K, pressure gauges and a watt-meter to monitor the suction, discharge, the condensing temperatures, pressures and power consumption in accordance with ISO 8187 recommendations. Performance parameters investigated included: pull down time, compressor power consumption and input, coefficient of performance and thermal conductivity and viscosity. Findings showed that all the selected charges of LPG refrigerant infused with varying concentrations of nano-lubricants, achieved equal values of -3 °C (ISO 8187), or lower values of evaporator air temperatures at lower refrigerant charges, than the baseline R134a refrigerant. All the selected nano-lubricants based refrigerants resulted in improved Coefficient of Performance (COP) than R134a refrigerant, with COP values ranging from 2.05 with 50 g charge of LPG using 0.4 g/L nano-lubricant to 2.65 with 60 g of LPG using 0.2 g/L SiO2 based lubricant. Lower power input was recorded by the compressor for all the selected charges of SiO2-lubricant based LPG than R134a refrigerants, having 28.81 W (with 60 g charge of LPG using 0.2 g/L) and 39.21 W (with 100 g charge of R134a refrigerant using pure compressor oil lubricant). In addition, at low concentration of nanoparticle in the lubricants based LPG refrigerant, reduction in power consumption of the compressor was observed, whereas higher concentration of nanoparticle in the lubricant, resulted in a rise in power consumption. Furthermore, thermal conductivity values were found to be low at the suction and discharge ends of the compressor for R134a using pure mineral oil lubricant, whereas the values were high for retrofit working fluid (pure LPG refrigerant, and LPG with varying concentrations of nano-lubricants), at the suction and discharge ends of the compressor.

Experimental Study on the Performance Analysis of a Domestic Refrigeration System with Nano Additives and Proven Alternative Refrigerant

Experimental Study on the Performance Analysis of a Domestic Refrigeration System with Nano Additives and Proven Alternative Refrigerant

Energetic and exergetic analysis of a domestic refrigerator system with LPG as a replacement for R134a refrigerant, using POE lubricant and mineral oil based TiO2-, SiO2- and Al2O3-lubricants

This paper experimentally investigated energetic and exergetic performance analysis of a domestic refrigerator using R134a and LPG refrigerants with different lubricants (polyol-ester (POE), mineral oil (MO), and TiO2, SiO2, Al2O3 nanoparticles dispersed in mineral oil).The energetic and exergetic performance analysis of the domestic refrigerator were investigated with test parameters including compressor power consumption, cooling capacity, coefficient of performance (COP), discharge temperature, irreversibility in the components, total irreversibility and second law efficiency. Findings showed that the lowest compressor power consumption and total irreversibility were observed in refrigerator with 40 g charge of LPG/TiO2-MO lubricant (0.2 g/L of TiO2); these values of compressor power consumption and total irreversibility were 15.87% and 31.69%, respectively, lower than for R134a/POE lubricant. In addition, the domestic refrigerator using LPG refrigerant at 40 g charge with TiO2-MO (0.2 g/L TiO2) lubricant, had the highest COP and second law efficiency among the selected nano-lubricants. These values of COP and second law efficiency were 56.32% and 47.06%, respectively, higher than that of R134a/POE. Futhermore, compressor discharge temperature of the domestic refrigerator with 40 g charge of LPG/TiO2-MO lubricant (0.2 g/L of TiO2) was found to be lower than that of R134a/POE. Hence, extended compressor life may be expected with the adoption of TiO2-Mineral oil lubricant. It can be concluded that based on energetic and exergetic performance analysis, the domestic refrigerator using the 40 g charge of LPG/TiO2-MO (0.2 g/L TiO2) performed better than R134a/POE.