Mohammad Bahrami - Graduated Student of MSc in energy engineering, Department of Energy Engineering, Graduate School of the Environment and Energy, Science and Research Branch, Islamic Azad University, Tehran, Iran,
Ali Asghar Hamidi - Professor of Chemical Engineering, Department of Chemical Engineering, Tehran University,
Navid Bagheri - Young Researchers and Elites Club, Department of Energy Engineering, Graduate school of the Environment and Energy, Science and Research Branch, Islamic Azad University, Tehran, Iran,

Currently it is not an easy matter for decision makers in commercial refrigeration to make a definitive choice when it comes to refrigerants and system type. For the last decade, many refrigerant options and system architectures have appeared both on paper and in practice. Performance of a new two-stage trans-critical CO2 refrigeration cycle containing internal heat exchanger, intercooler, ejector, and separator, has been analyzed after modification. In this work, for improvement of the COP, a portion of saturated vapor coming out of separator combined with the supercritical vapor coming out from internal heat exchanger. The performance of the new cycle was compared with the internal heat exchanger two-stage trans-critical cycle that identified base cycle in this paper. Computed results showed that new cycle improved the maximum coefficient of performance, COPmax, by 8.5% compared to the internal heat exchanger two-stage cycle (base cycle). The impacts of operational parameters such as gas cooler and evaporator temperatures and pressure of gas cooler, on cycle performance have been investigated. Obtained results are validated against those available in the literature and there is excellent agreement between them.

Refrigeration cycle, Internal heat exchanger, Two-stage, Trans-critical, COP