Pressure Exchanger for Energy Recovery in a Trans-Critical CO 2 Refrigeration System

Ahmed Elatar, Brian Fricke, Vishaldeep Sharma and Kashif Nawaz
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Ahmed Elatar: Oak Ridge National Laboratory, Oak Ridge, TN 37830, USA
Brian Fricke: Oak Ridge National Laboratory, Oak Ridge, TN 37830, USA
Vishaldeep Sharma: Oak Ridge National Laboratory, Oak Ridge, TN 37830, USA
Kashif Nawaz: Oak Ridge National Laboratory, Oak Ridge, TN 37830, USA

Energies, 2021, vol. 14, issue 6, 1-15

Abstract: Trans-critical CO 2 vapor compression (VC) refrigeration cycles require a high compression ratio, which is associated with high expansion losses. To recover these expansion losses, a pressure exchange process between the low- and high-pressure sides of the VC cycle is proposed and examined in this study. The proposed pressure exchange system is an open type constant volume process where the high- and low-pressure flows mix inside the system. This prototype is inspired by the pressure exchangers used in reverse-osmosis (RO) desalination systems. In this system, a 2D model was generated and modeled using the computational fluid dynamics (CFD) technique. The numerical model ignored any losses due to leakage or hydraulic friction and the process is considered adiabatic. For the modeling, it was assumed that the inlet conditions for the two pressure exchanger flows are similar to the flow conditions at the evaporator and gas cooler outlets in a VC cycle. Two parameters are examined to test the validity of the system and understand their effect on the performance, including the inlet flow rate represented by the inlet velocity and the process time represented by the speed of rotation. A total of nine cases were simulated and analyzed in this study.

Keywords: pressure exchanger; trans-critical CO 2 refrigeration cycle; energy recovery (search for similar items in EconPapers)
JEL-codes: Q Q0 Q4 Q40 Q41 Q42 Q43 Q47 Q48 Q49 (search for similar items in EconPapers)
Date: 2021
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