scholarly journals Exergetic and Economic Evaluation of a Transcritical Heat-Driven Compression Refrigeration System with CO2 as the Working Fluid under Hot Climatic Conditions

Entropy ◽  
2019 ◽  
Vol 21 (12) ◽  
pp. 1164 ◽  
Author(s):  
Jing Luo ◽  
Tatiana Morosuk ◽  
George Tsatsaronis ◽  
Bourhan Tashtoush
Keyword(s):  
Ambient Temperature ◽  
Climatic Conditions ◽  
Working Fluid ◽  
Refrigeration System ◽  
Exergetic Efficiency ◽  
Evaporation Temperature ◽  
Aspen Hysys ◽  
Operation Conditions ◽  
Heating Capacity ◽  
Refrigeration Machine

The purpose of this research is to evaluate a transcritical heat-driven compression refrigeration machine with CO2 as the working fluid from thermodynamic and economic viewpoints. Particular attention was paid to air-conditioning applications under hot climatic conditions. The system was simulated by Aspen HYSYS® (AspenTech, Bedford, MA, USA) and optimized by automation based on a genetic algorithm for achieving the highest exergetic efficiency. In the case of producing only refrigeration, the scenario with the ambient temperature of 35 °C and the evaporation temperature of 5 °C showed the best performance with 4.7% exergetic efficiency, while the exergetic efficiency can be improved to 22% by operating the system at the ambient temperature of 45 °C and the evaporation temperature of 5 °C if the available heating capacity within the gas cooler is utilized (cogeneration operation conditions). Besides, an economic analysis based on the total revenue requirement method was given in detail.

scholarly journals Energetic and exergetic analyses of carbon dioxide transcritical refrigeration systems for hot climates

2015 ◽  
Vol 19 (3) ◽  
pp. 905-914 ◽  
Author(s):  
Farivar Fazelpour
Keyword(s):  
Carbon Dioxide ◽  
Heat Pumps ◽  
Climatic Conditions ◽  
Exergy Efficiency ◽  
Refrigeration System ◽  
Long Period ◽  
Operation Conditions ◽  
Scientific Papers ◽  
System Operating

In the last two decades many scientific papers and reports have been published in the field of the application of the carbon dioxide as a refrigerant for refrigeration systems and heat pumps. Special attention has been paid to the transcritical cycle. However, almost no papers discussed such cycles for hot climates, i.e., when the temperature of the environment is higher than 40?? during a long period of time. This paper deals with the energetic and exergetic evaluation of a CO2 refrigeration system operating in a transcritical cycle under hot climatic conditions. The performance and exergy efficiency of the CO2 refrigeration system depend on the operation conditions. The effect of varying these conditions is also investigated as well as the limitations associated with these conditions.

Operation Conditions Analysis on Solar Energy Compression-Injection Secondary Refrigeration System

2012 ◽  
Vol 178-181 ◽  
pp. 139-143
Author(s):  
Fei Fei Zhang ◽  
Qi Tian ◽  
Li Yuan Yin
Keyword(s):  
Solar Energy ◽  
Injection System ◽  
Condensation Temperature ◽  
Economic Factors ◽  
Refrigeration System ◽  
Cooling Temperature ◽  
Evaporation Temperature ◽  
Operation Conditions ◽  
Heat Collector ◽  
Intermediate Cooling

The COP of compression-injection secondary refrigeration system is increased by 20%-50% than traditional compression-injection system. This paper analyzes the operation conditions on generation temperature, intermediate cooling temperature, condensation temperature and evaporation temperature in the compression-injection secondary refrigerating system powered by solar energy. Comprehensively considering technical and economic factors, the results show that generation temperature should be increased and condensation temperature should be decreased. In addition, the area of solar heat collector and the COP of the system should be considered when we chose the intermediate cooling temperature.

Application of exergy method to an irreversible inter-cooled refrigeration cycle

2005 ◽  
Vol 219 (8) ◽  
pp. 661-667 ◽  
Author(s):  
C-K Chen ◽  
Y-F Su
Keyword(s):  
Heat Transfer ◽  
Working Fluid ◽  
Refrigeration Cycle ◽  
Refrigeration System ◽  
Exergetic Efficiency ◽  
Finite Rate ◽  
Efficiency Criterion ◽  
Internal Dissipation ◽  
Exergy Method ◽  
Internal Irreversibility

The exergy method, based on the maximum exergetic efficiency criterion, has been applied to an irreversible inter-cooled refrigeration cycle. The exergetic efficiency defined as the ratio of the rate of exergy output to the rate of exergy input is taken as the objective function to be maximized. Multi-irreversibilities include finite-rate heat transfer, internal dissipation of the working fluid, and heat leaks between heat reservoirs. The maximum exergetic efficiency can be determined analytically by introducing the internal irreversibility parameter, which represents the degree of internal irreversibility. The corresponding performances of the irreversible refrigeration system are obtained simultaneously. The results show that the exergy method can be used as an effective criterion in designing an irreversible inter-cooled refrigeration system.

Exergy Analysis of a Solar-Driven Dual Parallel-Connected Ejector Refrigeration System

2016 ◽  
Vol 839 ◽  
pp. 100-106
Author(s):  
Yahya Gaafar Abdella Mohammed ◽  
Tawat Suriwong ◽  
Sakda Somkun ◽  
Timeyo Mkamanga Maroyi
Keyword(s):  
Solar Collector ◽  
Exergy Analysis ◽  
Operating Conditions ◽  
Coefficient Of Performance ◽  
Saturated Steam ◽  
Working Fluid ◽  
Electric Heater ◽  
Exergy Destruction ◽  
Refrigeration System ◽  
Exergetic Efficiency

Nowadays, developing solar cooling technologies, especially ejector refrigeration system, has become preferable to scientific researchers. Exergy analysis is a technique in which the basis of evaluation of thermodynamic losses follows the second law rather than the first law of thermodynamics. An experimental exergy analysis of a solar-driven dual parallel-connected ejector (DPE) refrigeration system was conducted using water as working fluid. Saturated steam with 2 bar and 120oC was provided by heat–pipe evacuated tube solar collector with an assistant of an electric heater. The saturated stream was used as a motive flow for the ejectors. The exergy destruction and exergetic efficiency of the main components of the DPE refrigeration system were determined and compared with those when using a single ejector (SE) under same operating conditions. It was found that the most irreversibilities of both systems occurred at the solar collector, electric boiler and ejectors, respectively. Also, the total irreversibility (Exergy destruction) of the system when using DPE was lower than using a SE. In additions, the exergetic efficiency of the ejector, evaporator, and overall system when using DPE were increased by 21%, 10%, and 27%, respectively. The system thermal ratio (STR) and coefficient of performance (COP) of the system using DPE compared with SE were increased by 20% and 23%, respectively.

scholarly journals THEORETIC-EXPERIMENTAL EVALUATION OF A CASCADE REFRIGERATION SYSTEM FOR LOW TEMPERATURE APPLICATIONS USING THE PAIR R22/R404A

2012 ◽  
Vol 11 (1-2) ◽  
pp. 07
Author(s):  
J. J. Fiori ◽  
C. U. S. Lima ◽  
V. Silveira Jr
Keyword(s):  
Low Temperature ◽  
Coefficient Of Performance ◽  
Working Fluid ◽  
Refrigeration System ◽  
Evaporation Temperature ◽  
Optimal Value ◽  
Cascade Refrigeration System ◽  
The Difference ◽  
Cascade Refrigeration ◽  
Good Agreement

This paper presents a thermodynamic analysis of a cascade refrigeration system using the refrigerant R22 as the working fluid in the high temperature circuit (HT) and the refrigerant R404a as the working fluid in the low temperature circuit (LT). The present analysis aimed to obtain the condensing temperature of the LT that provides an optimal value for the coefficient of performance (COP) of the cycle. Parameters involved in the analysis included the evaporation temperature, the condensing temperature and the difference between the condensing temperature of the LT (TC_LT) and evaporation temperature of the HT (TE_HT) – ΔTCAS. Simulations were performed using the software EES (Engineering Equation Solver). In addition to the analysis, experimental data obtained from a prototype was compared with the simulated results which showed good agreement. The COP varies with the increase in the intermediate temperature; however this variation does not exceed 1%.

Exergetic efficiency optimization of a refrigeration system with multi-irreversibilities

2006 ◽  
Vol 220 (8) ◽  
pp. 1179-1187 ◽  
Author(s):  
Y-F Su ◽  
C-K Chen
Keyword(s):  
Heat Exchangers ◽  
Thermal Conductance ◽  
Coefficient Of Performance ◽  
Working Fluid ◽  
Refrigeration System ◽  
Exergetic Efficiency ◽  
Cold Side ◽  
Finite Rate ◽  
Efficiency Optimization ◽  
Internal Dissipation

Exergetic efficiency optimization has been carried out for a refrigeration system with multi-irreversibilities, including finite-rate heat transfer, internal dissipation of the working fluid and heat leak between the heat reservoirs. The exergetic efficiency is defined as the ratio of the rate of exergy output to the rate of exergy input in the refrigeration system and is considered as an objective function to be maximized. By combining the exergy concept and finite-time thermodynamic theory, the maximum exergetic efficiency is determined analytically. The optimum values of the cycle cooling rate and the coefficient of performance of the system are obtained simultaneously. The influences of various parameters on the maximum exergetic efficiency are investigated by numerical calculation. The allocation problem of a fixed total thermal conductance between the hot-side and the cold-side heat exchangers is also studied. The results show that the method of exergetic efficiency optimization is practical and effective for the evaluation of an irreversible refrigeration system.

First and Second Law Analysis of a Flat Plate Collector Working With Nanofluids

2018 ◽  
Author(s):  
M. T. Nitsas ◽  
I. P. Koronaki ◽  
L. Prentza
Keyword(s):  
Flat Plate ◽  
Second Law Of Thermodynamics ◽  
Climatic Conditions ◽  
Working Fluid ◽  
Second Law ◽  
Inlet Temperature ◽  
Water Tank ◽  
Systems Quality ◽  
Typical Day ◽  
Flat Plate Collector

The utilization of solar energy in thermal energy systems was and always be one of the most effective alternative to conventional energy resources. Energy efficiency is widely used as one of the most important parameters in order to evaluate and compare thermal systems including solar collectors. Nevertheless, the first law of thermodynamics is not solely capable of describing the quantitative and qualitative performance of such systems and thus exergy efficiency is used so as to introduce the systems’ quality. In this work, the performance of a flat plate solar collector using water based nanofluids of different nanoparticle types as a working fluid is analyzed theoretically under the climatic conditions in Greece based on the First and Second Law of Thermodynamics. A mathematical model is built and the model equations are solved iteratively in a MATLAB code. The energy and exergy efficiencies as well as the collector losses coefficient for various parameters such as the inlet temperature, the particles concentration and type are determined. Moreover, a dynamic model is built so as to determine the performance of a flat plate collector working with nanofluids and the useful energy that can be stored in a water tank. The exergy destruction and exergy leakage are determined for a typical day in summer during which high temperatures and solar intensity values are common for the Greek climate.

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