scholarly journals Investigation on the Performance of a Solar Hybrid Refrigeration System Using Environmentally Friendly Fluids

2020 ◽  
Vol 38 (4) ◽  
pp. 960-966
Author(s):  
Latra Boumaraf ◽  
Rachedi Khadraoui
Keyword(s):  
Cooling Capacity ◽  
Operating Conditions ◽  
Mechanical Compression ◽  
Refrigeration System ◽  
Perfect Gas ◽  
Entrainment Ratio ◽  
Medium Temperature ◽  
D Model ◽  
Constant Section ◽  
Solar Refrigeration

In order to evaluate the performance of a hybrid compression / ejection refrigeration system using solar energy at low or medium temperature, a simulation model of its behavior based on those of its various components has been developed. It includes in particular for the ejector, a 1-D model of the "constant section mixing" type developed in optimal transition regime. The refrigerants tested are steam for the ejector loop and the R1234yf (replacing the R134a) for the mechanical compression loop. The behavior of the H2O vapor flowing in the ejector is considered that of the perfect gas. The properties of refrigerants are calculated using REFPROP® software, everywhere else. For a cooling capacity of 10 kW and air conditioning operating conditions, the model allows to determine the main parameters of the ejector and its entrainment ratio, the thermal and mechanical COP of the whole refrigeration system as well as the necessary surface of the solar collector. Furthermore, the influence of the temperature of the boiler, the condenser, the intercooler as well as that of the evaporator on the mechanical COP of the hybrid system and the solar collection surface in particular, were examined. The results highlight that the solar refrigeration system with hybrid cycle compression/ejection using the refrigerants H2O/R1234yf allows an increase of the mechanical COP higher than 50% compared to that of the conventional refrigeration system and thus constitutes an acceptable ecologically system that can compete with the latter.

scholarly journals Parametric analysis of a combined ejector-vapor compression refrigeration cycle

2020 ◽  
Vol 15 (3) ◽  
pp. 398-408
Author(s):  
I Ouelhazi ◽  
Y Ezzaalouni ◽  
L Kairouani
Keyword(s):  
Current Model ◽  
Operating Conditions ◽  
Coefficient Of Performance ◽  
Refrigeration Cycle ◽  
Vapor Compression ◽  
Refrigeration System ◽  
Entrainment Ratio ◽  
Constant Area ◽  
Vapor Compression Refrigeration Cycle ◽  
Vapor Compression Refrigeration

Abstract From the last few years, the use of efficient ejector in refrigeration systems has been paid a lot of attention. In this article a description of a refrigeration system that combines a basic vapor compression refrigeration cycle with an ejector cooling cycle is presented. A one-dimensional mathematical model is developed using the flow governing thermodynamic equations based on a constant area ejector flow model. The model includes effects of friction at the constant-area mixing chamber. The current model is based on the NIST-REFPROP database for refrigerant property calculations. The model has basically been used to determine the effect of the ejector geometry and operating conditions on the performance of the whole refrigeration system. The results show that the proposed model predicts ejector performance, entrainment ratio and the coefficient of performance of the system and their sensitivity to evaporating and generating temperature of the cascade refrigeration cycle. The simulated performance has been then compared with the available experimental data from the literature for validation.

Performance Analysis on a Solar-Driven Air-Cooled Ejector Refrigeration System for Air-Conditioning Using Ammonia as Refrigerant

2014 ◽  
Vol 501-504 ◽  
pp. 2282-2287 ◽  
Author(s):  
Yu Hang Liao ◽  
Wei Lu ◽  
Lie Pan
Keyword(s):  
Performance Analysis ◽  
Solar Irradiance ◽  
Air Conditioning ◽  
Cooling Capacity ◽  
Climatic Conditions ◽  
Operating Conditions ◽  
Refrigeration System ◽  
Outdoor Temperature ◽  
Indoor Temperature ◽  
Changing Trend

The performance of a solar-driven air-cooled ejector refrigeration system using ammonia as refrigerant with rated cooling capacity of 10.5kW was analyzed for air-conditioning purpose. The cooling capacity of the proposed system increases with the rising of indoor temperature and enhancement of solar irradiance, while decreases with the rising of outdoor temperature. The COP has similar changing trend with that of the cooling capacity except that it increases rapidly with the enhancement of solar irradiance firstlyand then become stable by and large after solar irradiance exceeding a certain value. The cooling capacity is 6.3~52kW and the COP 0.06~0.11 under the normal operating conditions with indoor temperature over 27, outdoor temperature below 38°C and solar irradiance surpassing 500 W/m2. The proposed system can match the climatic conditions in air-conditioning season of Nanning, a typical city in hot summer and warm winter region.

scholarly journals Evaporator Frosting in Refrigerating Appliances: Fundamentals and Applications

Energies ◽  
2021 ◽  
Vol 14 (18) ◽  
pp. 5991
Author(s):  
Christian J. L. Hermes ◽  
Joel Boeng ◽  
Diogo L. da Silva ◽  
Fernando T. Knabben ◽  
Andrew D. Sommers
Keyword(s):  
First Principles ◽  
Simulation Models ◽  
Cooling Capacity ◽  
Operating Conditions ◽  
Coefficient Of Performance ◽  
Trial And Error ◽  
Refrigeration System ◽  
Duty Cycles ◽  
Transfer Principles ◽  
Frost Layer

Modern refrigerators are equipped with fan-supplied evaporators often tailor-made to mitigate the impacts of frost accretion, not only in terms of frost blocking, which depletes the cooling capacity and therefore the refrigerator coefficient of performance (COP), but also to allow optimal defrosting, thereby avoiding the undesired consequences of condensate retention and additional thermal loads. Evaporator design for frosting conditions can be done either empirically through trial-and-error approaches or using simulation models suitable to predict the distribution of the frost mass along the finned coil. Albeit the former is mandatory for robustness verification prior to product approval, it has been advocated that the latter speeds up the design process and reduces the costs of the engineering undertaking. Therefore, this article is aimed at summarizing the required foundations for the design of efficient evaporators and defrosting systems with minimized performance impacts due to frosting. The thermodynamics, and the heat and mass transfer principles involved in the frost nucleation, growth, and densification phenomena are presented. The thermophysical properties of frost, such as density and thermal conductivity, are discussed, and their relationship with refrigeration operating conditions are established. A first-principles model is presented to predict the growth of the frost layer on the evaporator surface as a function of geometric and operating conditions. The relation between the microscopic properties of frost and their macroscopic effects on the evaporator thermo-hydraulic performance is established and confirmed with experimental evidence. Furthermore, different defrost strategies are compared, and the concept of optimal defrost is formulated. Finally, the results are used to analyze the efficiency of the defrost operation based on the net cooling capacity of the refrigeration system for different duty cycles and evaporator geometries.

Retrofitting of R404a Commercial Refrigeration Systems with R410a and R407f HFCs Refrigerants

2015 ◽  
pp. 260-294 ◽  
Author(s):  
Mauro Gamberi ◽  
Marco Bortolini ◽  
Alessandro Graziani ◽  
Riccardo Manzini
Keyword(s):  
Global Warming ◽  
Low Temperature ◽  
Global Warming Potential ◽  
Experimental Analysis ◽  
Cooling Capacity ◽  
Operating Conditions ◽  
Environmental Benefits ◽  
Medium Temperature ◽  
Air Temperatures ◽  
The Eu

This chapter presents an experimental analysis about the retrofitting of two commercial stationary refrigeration systems marketed by an Italian leading company of the sector. Such systems operate both at medium temperature (MT) and low temperature (LT) and they are originally designed to work with the high global warming potential (GWP) hydrofluorocarbon (HFC) R404a fluid (GWP = 3922). The purpose is to investigate the performances of HFCs R410a (GWP = 2088) and R407f (GWP = 1825) chosen as effective alternatives to HFC R404a, due to their compatibility, non-flammability and market availability. Furthermore, such fluids meet the EU restrictions in force in the next future for high GWP HFCs. The experimental analysis compares the performances, in terms of COP and cooling capacity, of R404a and the two identified alternatives under different operating conditions, i.e. chamber and condenser inlet air temperatures. In case of comparable performances, significant environmental benefits are introduced by the adoption of R407f and R410a in the MT and LT refrigeration systems.

Effect of Hydrofluorocarbons and Hydrofluoroolefins in a Household Refrigerator as a Substitute for R134a

2019 ◽  
Vol 969 ◽  
pp. 199-204
Author(s):  
Shaik Mohammad Hasheer ◽  
Kolla Srinivas
Keyword(s):  
Cooling Capacity ◽  
Operating Conditions ◽  
Coefficient Of Performance ◽  
Condensation Temperature ◽  
Outlet Temperature ◽  
Refrigeration System ◽  
Volumetric Cooling ◽  
Work Done ◽  
Theoretical Results ◽  
Hfc 152A

Now a days R134a can be used in domestic refrigerators and in air conditioning of automobiles. As per Kyoto protocol the usage of R134a is restricted due to their higher GWP value. The GWP value of this refrigerant is around 1430. So in this article, thermodynamic analysis of HFC-152a, HFO refrigerants-1234ze(E) and 1234yf was done in a household refrigeration system as direct substitute to HFC-134a.The performance of the household refrigerator was compared in terms of outlet temperature of the compressor, volumetric cooling capacity (VCC), refrigeration effect, work done by the compressor and coefficient of performance (COP). The entire analysis is carried out at various operating conditions of condenser and evaporator temperatures i.e. condensation temperature of 25°C,35°C & 45°C and evaporating temperatures ranging between −20°C to 10°C.From the theoretical results, it can be concluded that R1234yf can be used as a direct substitute to R134a.

scholarly journals Performance characteristics of low global warming potential R134a alternative refrigerants in ejector-expansion refrigeration system

2016 ◽  
Vol 37 (4) ◽  
pp. 55-72
Author(s):  
Shubham Mishra ◽  
Jahar Sarkar
Keyword(s):  
Cooling Capacity ◽  
Area Ratio ◽  
Coefficient Of Performance ◽  
Air Conditioner ◽  
Refrigeration System ◽  
Alternative Refrigerants ◽  
Entrainment Ratio ◽  
Maximum Improvement ◽  
Maximum Coefficient ◽  
Volumetric Cooling

AbstractPerformance assessment of ejector-expansion vapor compression refrigeration system with eco-friendly R134a alternative refrigerants (R152a, R1234yf, R600a, R600, R290, R161, R32, and propylene) is presented for air-conditioning application. Ejector has been modeled by considering experimental data based correlations of component efficiencies to take care of all irreversibilities. Ejector area ratio has been optimized based on maximum coefficient of performance (COP) for typical air-conditioner operating temperatures. Selected refrigerants have been compared based on area ratio, pressure lift ratio, entrainment ratio, COP, COP improvement and volumetric cooling capacity. Effects of normal boiling point and critical point on the performances have been studied as well. Using ejector as an expansion device, maximum improvement in COP is noted in R1234yf (10.1%), which reduces the COP deviation with R134a (4.5% less in basic cycle and 2.5% less in ejector cycle). Hence, R1234yf seems to be best alternative for ejector expansion system due to its mild flammability and comparable volumetric capacity and cooling COP. refrigerant R161 is superior to R134a in terms of both COP and volumetric cooling capacity, although may be restricted for low capacity application due to its flammability.

Ejector Profile Modelling for Heat-Driven Ejector Refrigeration System Without Involving Shock

2015 ◽  
Author(s):  
Binoe E. Abuan ◽  
Menandro S. Berana
Keyword(s):  
Waste Heat ◽  
Fluid Dynamic ◽  
Cooling Capacity ◽  
Coefficient Of Performance ◽  
Vapor Compression ◽  
Refrigeration System ◽  
Entrainment Ratio ◽  
Evaporator Temperature ◽  
Major Disadvantage ◽  
And Performance

Heat-driven ejector refrigeration system is one of the fastest emerging technologies in cooling applications for years. This is due to the fact that it can harness cooling capacity from waste heat sources at above 80 °C. Low coefficient of performance (compared to commercial vapor compression systems) is the major disadvantage of the said system, and thus it became a topic of research studies in the field of cooling. The work required by the compressor in a vapor compression cycle (VCC) can be eliminated by using waste heat from any available heat source. Although a relatively lower COP was obtained, the savings using the ejector refrigeration system can cover all the disadvantages and proved that this system can be actually helpful if implemented in the real working systems with waste heat. In this study, a mathematical model for determining ejector parameters and performance was developed and applied to a system where shock was tried to be avoided. The model was coded into a computer program to allow easier computation of the ejector geometric and thermo-fluid dynamic parameters with varying input data such as the refrigerant to be used, evaporator and condensing temperatures, entrainment ratio, and velocity of the fluid flows. An ejector refrigeration system using ammonia, propane, R22, R134a, R1234yf, and R245fa as refrigerants was simulated using the said model. A boiler or generator temperature of 90 °C, a condenser temperature of 40 °C, and a refrigerating capacity of 35kW were maintained for all the refrigerants; however, the evaporator temperature was varied within the range of −10 °C to 10 °C, depending on the behavior of the system. A combination of a short straight section and then a converging-diverging profile was used for the combined mixing section and diffuser to smoothly decelerate the fully mixed supersonic flow exiting the short mixing section and thereby avoid shock waves in the section. The resulting parameters including the ejector dimensions, pressure and Mach number were determined along the length of the ejector. For all the simulation runs, the fluids respond as expected and the expansion energy was utilized from the high pressure side of the ejector as shown in the trend of pressure along the length of the ejector. Ejector size varies a little for different refrigerants; the calculated range of length is from 0.14 m to 0.36 m — this range shows the compactness of the resulting ejectors. The results show that a VCC refrigeration system can be replaced by a heat-driven ejector refrigeration system with the ejector that was designed from the simulations. Since the two systems are designed to have the same refrigerating capacity and working temperatures, it can be projected that savings can be made by using the ejector system. The compactness of the ejector produced in the simulations show a good potential for this kind of refrigerating system to be manufactured and mass produced.

Design and Evaluation of MEMS-Based Stirling Cycle Micro-Refrigeration System

2011 ◽  
Author(s):  
Dongzhi Guo ◽  
Jingsheng Gao ◽  
Alan J. H. McGaughey ◽  
Matthew Moran ◽  
Suresh Santhanam ◽  
...  
Keyword(s):  
Volume Ratio ◽  
Cooling Capacity ◽  
Operating Conditions ◽  
Heat Extraction ◽  
Dead Volume ◽  
Working Fluid ◽  
Phase Lag ◽  
Refrigeration System ◽  
Cold Side ◽  
Stirling Cycle

A Stirling cycle micro-refrigeration system composed of arrays of silicon MEMS cooling elements has been designed and evaluated thermodynamically. The cooling elements are each 5 mm-long, 2.25 mm-wide, have a thickness of 300 μm, and are fabricated in a stacked array on a silicon wafer. A 0.5 mm-long regenerator is placed between the compression (hot side) and expansion (cold side) diaphragms. The diaphragms are 2.25 mm circles driven electrostatically. Helium is the working fluid, pressurized at 2 bar and sealed in the system. Under operating conditions, the hot and cold diaphragms oscillate sinusoidally 90° out of phase such that heat is extracted to the expansion space and released from the compression space. The bulk silicon substrate on which the device is grown is etched with “zipping” shaped chambers under the diaphragms. The silicon enables efficient heat transfer between the gas and heat source/sink as well as reduces the dead volume of the system, thus enhancing the cooling capacity. In addition, the “zipping” shaped substrates reduce the voltage required to actuate the diaphragms. An array of vertical silicon pillars in the regenerator serves as a thermal capacitor transferring heat to and from the working gas during a cycle. In operation, the push-pull motion of the diaphragm makes a 300 μm stroke and actuates at a frequency of 2 kHz. Parametric study of the design shows the effects of phase lag, swept volume ratio between the hot space and cold space, and dead volume ratio on cooling capacity. At TH = 313.15 K and TC = 288.15 K and assuming a perfect regenerator, the thermodynamic optimization analysis gives a heat extraction rate of 0.22 W per element and cooling capacity of 30 W/cm2 for the stacked system. Evaluation of the stacked system shows that the COP will reach 6.3 if the expansion work from the cold side is recovered electrostatically and used to drive the hot side diaphragm.

scholarly journals ANN Modeling to Analyze the R404A Replacement with the Low GWP Alternative R449A in an Indirect Supermarket Refrigeration System

2021 ◽  
Vol 11 (23) ◽  
pp. 11333
Author(s):  
Morteza Ghanbarpour ◽  
Adrián Mota-Babiloni ◽  
Pavel Makhnatch ◽  
Bassam E. Badran ◽  
Jörgen Rogstam ◽  
...  
Keyword(s):  
Measurement Data ◽  
Field Measurements ◽  
Energy Performance ◽  
Cooling Capacity ◽  
Operating Conditions ◽  
Refrigeration System ◽  
Ann Model ◽  
Ann Modeling ◽  
Temperature Levels ◽  
Variable Operating Conditions

Artificial neural networks (ANNs) have been considered for assessing the potential of low GWP refrigerants in experimental setups. In this study, the capability of using R449A as a lower GWP replacement of R404A in different temperature levels of a supermarket refrigeration system is investigated through an ANN model trained using field measurements as input. The supermarket refrigeration was composed of two indirect expansion circuits operated at low and medium temperatures and external subcooling. The results predicted that R449A provides, on average, a higher 10% and 5% COP than R404A at low and medium temperatures, respectively. Moreover, the cooling capacity was almost similar with both refrigerants in both circuits. This study also revealed that the ANN model could be employed to accurately predict the energy performance of a commercial refrigeration system and provide a reasonable judgment about the capability of the alternative refrigerant to be retrofitted in the system. This is very important, especially when the measurement data comes from field measurements, in which values are obtained under variable operating conditions. Finally, the ANN results were used to compare the carbon footprint for both refrigerants. It was confirmed that this refrigerant replacement could reduce the emissions of supermarket refrigeration systems.

FUZZY-PID CONTROLLER APPLIED TO A REFRIGERATION SYSTEM

2012 ◽  
Vol 20 (02) ◽  
pp. 1250006 ◽  
Author(s):  
JONES ERNI SCHMITZ ◽  
FLAVIO VASCONCELOS DA SILVA ◽  
ANA MARIA FRATTINI FILETI ◽  
LINCOLN CAMARGO NEVES FILHO ◽  
VIVALDO SILVEIRA JÚNIOR
Keyword(s):  
Expert Knowledge ◽  
Cooling Capacity ◽  
Operating Conditions ◽  
Pid Controllers ◽  
Fuzzy Pid ◽  
Refrigeration System ◽  
Experimental Development ◽  
Fuzzy Controllers ◽  
Fuzzy Pid Controller ◽  
Complex Methods

A refrigeration system exhibits a dynamic behavior on which the variables are interdependent and subjected to oscillation, hence, implicating necessity of changes on operating conditions and undesirable energy expenses. These characteristics ratify the importance of adequate dimensioning and equipment selection to find pre-defined operating conditions such as, the maximum cooling capacity and the evaporating and condensing temperatures. The application of fuzzy control in industrial processes is growing fast in the last decades, mainly in processes whose first principle models require complex methods to be simulated. In these cases, the fuzzy controllers’ capacity of acting correctly based only on expert knowledge and on the capacity of inter-relating all the variables of the process are attractive features. This work presents the experimental development and evaluation of fuzzy-PID controllers for the maintenance of the evaporating temperature in a chiller. The system was submitted to load and set-point disturbances accomplishing an analysis based upon error parameters and transient response. The results showed that fuzzy controllers were adapted satisfactorily.

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