International Research Journal of Engineering and Technology (IRJET) e-ISSN: 2395-0056 Volume: 11 Issue: 05 | May 2024
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p-ISSN: 2395-0072
Thermodynamic analysis of two-stage transcritical Ethane refrigeration cycle with expander Gaurav Jain1, Ansh Singh2, Aditi Ahlawat2, Amandeep Kushwaha2, Altaf Hussain2, Prateek Yadav2 1Assistant Professor, Dept. of Mechanical Engineering, JSS Academy of Technical Education, Noida, Uttar Pradesh,
India
2Student, Dept. of Mechanical Engineering, JSS Academy of Technical Education, Noida, Uttar Pradesh, India
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Abstract - In this paper, thermodynamic performance
Subscripts 1-6 2s, 4s c e gc im is ex
comparison of the following refrigeration cycles: Two Stage with Expander (TSE) and Two Stage with an Expansion Valve (TSEV) using Ethane has been carried out. The effect of operating parameters such as gas cooler exit and evaporator temperatures on optimum values of gas cooler and intermediate pressure and on the coefficient of performance (COP) has been investigated and comparison is done between both cycles. The TSE cycle had higher COP over the TSEV cycle for all studied conditions. Replacing the expansion valve with an expander resulted in lower gas cooler and intermediate pressure for all studied conditions. The temperature of refrigerant at the exit of high-pressure stage compressor is almost similar for both the cycles. The analysis is performed while simultaneously optimising the gas cooler and intermediate pressures. Temperature of evaporator and gas cooler exit is differed between 0C to -30C and 35 - 50C, respectively. An optimum gas cooler and intermediate pressure can be obtained to maximise the performance of cycle. The TSE cycle yields average 31.73% and highest 38.64% COP improvement over the TSEV cycle. The gas cooler exit temperature and efficiency of compressor majorly determine the performance of the cycle. A performance improving device should minimize the gas cooler outlet temperature and reduce cycle’s operating pressures which would also help ensure safer operation. The results of this analysis are aimed to provide basis for system design and optimization of Ethane based refrigeration system.
1.INTRODUCTION The demand for alternate refrigerants to reduce energy consumption has become a worldwide concern. One way of reducing energy consumption is by enhancing the performance of refrigeration cycle. Refrigeration systems and use of synthetic refrigerants contribute to worldwide global warming. Alternatively, natural refrigerants such as ethane can be used which has very low Global Warming Potential (GWP) and zero Ozone Depletion Potential (ODP). Ethane (C2H6) has similar properties as CO2 [1]. The critical temperature of Ethane is 32.2°C which is very close to critical temperature of carbon dioxide i.e. 31.1°C. Besagni et al. [2] stated that an appropriate working fluid for refrigeration system is one which provides high performance in all working environment. To achieve optimal performance, careful consideration is given to the refrigerant thermo-physical properties. Calm et al. [3] studied vapor compression-based refrigeration systems to be used with next generation of refrigerants. Nasruddin et al. [4] revealed that a temperature of -80°C can be achieved in ethane-based refrigeration cycles. Agrawal et al [5] studied CO2 and N2O based two-stage transcritical cycle with intercooling and revealed staging of compression resulted in performance enhancement. Baek J et al. [6] suggested equipping an expander to produce work to drive the high stage compressor to maximise performance of two-stage cycle with intercooling. Yang et al. [7] concluded a maximum improvement of 33% in COP of expander based single stage transcritical cycle compared to expansion valve-based cycle. Also, Yang et. al [8] concluded that optimum intermediate pressure of the two-stage transcritical refrigeration cycle with expander varied from the geometric mean of gas cooler
Key Words: Two-stage, transcritical, refrigeration, expander, ethane, Nomenclature COP h HP LP P q t, T w
coefficient of performance specific enthalpy (kJ kg-1) high pressure low pressure pressure (MPa) specific heat transfer (kJ kg-1) temperature (C) specific work (kJ kg-1) efficiency
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refrigerant state points isentropic compression state compressor evaporator gas cooler intermediate isentropic expander
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