Optimization of a CO 2–C 3H 8 cascade system for refrigeration and heating (original) (raw)
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Sadhana, 2015
Use of organic refrigerants such as Hydrochlorofluorocarbons and Chlorofluorocarbons have been criticized for their adverse impact on the Earth's protective ozone layer and for their significant global warming potential (GWP). CO 2 has been receiving great concern as an alternative refrigerant. Cascade refrigeration systems employing CO 2 are used for low temperature applications. Being a low critical temperature fluid CO 2 transcritical cascade systems offer low COP for a given application. Parallel compression economization is one of the promising cycle modifications to improve the COP of transcritical CO 2 cascaded systems. In this paper, transcritical CO 2 /propylene cascade system with parallel compression economization in the HT cycle has been analysed for cooling/heating applications. An enhancement in COP of 9% has been predicted. Thermodynamic analysis on R744-R1270 cascade refrigeration system has been performed to determine the optimal value of the various design parameters of the system. The design parameters included are: gas cooler outlet temperature and intermediate temperature in the high temperature circuit and evaporator temperature and temperature difference in the cascade condenser in the low temperature circuit.
International Journal of Green Energy, 2019
In this study, a comparative thermodynamic performance analysis of cascade system (CCS) for cooling and heating applications is presented and compared for different refrigerant couples. The CCS consists of the low-temperature cycle (LTC) and high-temperature cycle (HTC). The CO 2 was used as working fluid in LTC, whereas the HFE 7000, R134a, R152a, R32, R1234yf, and R365mfc refrigerants were used in HTC. The heating and cooling coefficients of performance (COP ht , COP cl) and exergy efficiency of CCS are investigated parametrically according to various factors such as the evaporator, condenser, and reference temperatures. After thermodynamic analyses are completed, the COP cl of CCS is obtained as 1.802, 1.806, 1.826, 1.769, 1.777, and 1.835 for CO 2-HFE7000, CO 2-R134a, CO 2-R152a, CO 2-R32, CO 2-R1234yf, and CO 2-365mfc refrigerant couples, respectively. Furthermore, the heat exchanger has the highest exergy destruction rate, whereas the expansion valves have the lowest of exergy destruction rate.
Performance Study of Cascade Refrigeration System Using Alternative Refrigerants
World Academy of Science, Engineering and Technology, International Journal of Mechanical, Aerospace, Industrial, Mechatronic and Manufacturing Engineering, 2014
Cascade refrigeration systems employ series of single stage vapor compression units which are thermally coupled with evaporator/condenser cascades. Different refrigerants are used in each of the circuit depending on the optimum characteristics shown by the refrigerant for a particular application. In the present research study, a steady state thermodynamic model is developed which simulates the working of an actual cascade system. The model provides COP and all other system parameters e.g. total compressor work, temperature, pressure, enthalpy and entropy at different state points. The working fluid in low temperature circuit (LTC) is CO2 (R744) while Ammonia (R717), Propane (R290), Propylene (R1270), R404A and R12 are the refrigerants in high temperature circuit (HTC). The performance curves of Ammonia, Propane, Propylene, and R404A are compared with R12 to find its nearest substitute. Results show that Ammonia is the best substitute of R12. Keywords—Cascade system, Refrigerants, T...
In present study the comparison of thermodynamic analysis of cascade refrigeration system has been done with refrigerant pairs such as CO2-HFE7000, CO2-R134a, CO2-R152a, CO2-R32, CO2-R1234yf, CO2-NH3, CO2-Propane and CO2-Propylene. In these systems, performance of two stage cascade compression system using above different refrigerant couples, have been studied and the effect of condenser temperature & evaporator temperature, has been done. Thermodynamic analysis is carried out by developing computational model in Engineering Equation solver (EES).
PERFORMANCE EVALUATION OF TWO STAGE CASCADE REFRIGERATION SYSTEM USING NATURAL REFRIGERANTS
IAEME PUBLICATION, 2020
This paper deals with the performance evaluation of two stage cascade refrigeration system with three different natural refrigerants R290(propane), R600a(isobutane) and R1270(propene) in high temperature cycle cascaded independently with R1150(ethene) in low temperature cycle. Analysis of two stage cascade system is carried out with different parameters like mass ratio of refrigerants, total work, coefficient of performance of system and volumetric flow rate of refrigerant(HTC) at i) fixed evaporator temperature, fixed cascade condenser temperature and varying condenser temperature ii) fixed condenser temperature, fixed cascade condenser temperature and varying evaporator temperature and iii) fixed evaporator, fixed condenser temperature and varying cascade condenser temperature.
Performance Analysis of Cascade Refrigeration System with alternate Refrigerants
World Academy of Research in Science and Engineering, 2020
The cascade system containing Vapour compression refrigeration system (VCRS) and thermoelectric refrigeration system has been analyzed at different conditions of load and also with different refrigerants to come up with refrigerants that have low Global warming potential. The study was to identify the performance of this cascade system with alternate refrigerants such as R134a and Hydrocarbon mixtures (R290 and R600a) in a proportion of 50% R290 and 50%R600a. Readings for different loading conditions have been taken for identifying its capabilities. The results indicate that the Coefficient of performance was good in Hydrocarbon mixtures than that of R134a at loading conditions ant it could be a suitable replacement for the cascade refrigeration system.
Performance parameters optimization of cascade refrigeration system using ecofriendly refrigerants
__________________________________________________________________________________ Abstract The present paper presents optimum thermodynamic performance of three cascade vapour compression refrigeration systems. The numerical thermal model have been developed for two stages cascade refrigeration systems and thermodynamic performances in terms of and first law efficiency, second law efficiency system exergy destruction ratio , first law efficiency of lower temperature and high temperature circuit have been computed. The effect of low temperature evaporator on the system first and second law performances and system exergy destruction ratio it was found that as low temperature evaporator temperature is decreasing , the first law and second law efficiencies are increasing and exergy destruction ratio is decreasing .The optimum performance parameters obtained from thermal model have been presented.
Performance comparison of cascade and two-stage refrigeration cycles using natural refrigerants
This paper aims to compare performances of cascade refrigeration systems with two-stage refrigeration systems using exergy method. The considered systems use natural refrigerants, namely carbon dioxide (R-744), ammonia (R-717) and propane (R-290). R-744 is used in the low stage and R-717 or R-290 in the high stage, while the two-stage system uses only R-717 or R-290. Comparison results show that for a given refrigeration capacity, evaporator and condenser temperature and cascade-condenser temperature, the compressor of R744 in the cascade cycle is more compact than those of R-290 and R-717 in the two-stage cycles. While cascade system provides lower exergy efficiency for both the two blends of refrigerants R-744/R-290 and R-744/R-717.
International Journal of Refrigeration-revue Internationale Du Froid, 2007
Analysis of an endoreversible two-stage cascade cycle has been implemented and optimum intermediate temperature for maximum exergy and refrigeration effect have been obtained analytically. Further, the heat reservoir temperatures has been optimised independently. A comprehensive numerical model of a transcritical CO 2 eC 3 H 8 cascade system was developed with intent to verify the theoretical results. It is seen that the simulation results agree well for optimal T L but deviate modestly from the theoretical optimum of T H . It has also been observed that system performance improves as T H increases and unlike theoretical predictions, no optimal T H is present within feasible working temperatures.
Global warming is a very pertinent issue these days because the effects of extreme climate change are becoming quite apparent. Therefore, the first problem to address is the formation of strict regulations regarding emissions into the air. The main emissions to tackle are CFC and HCFC refrigerants. Conventional cascade refrigeration systems until now have been dependent on refrigerants and it is time to find a substitute that is environmentally friendly. This study builds a prototype cascade refrigeration machine using the environmentally friendly hydrocarbon refrigerants (propane, ethane and CO 2 ). Resulting from this research, the characteristics of the pressure and temperature of each component and the COP value at low temperature circuit of load variations using an electric heater at 90 W, 120 W and 150 W result in a COP value of 0.35, 0.48 and 0.60 respectively.