COMPARATIVE ANALYSIS OF CASCADE REFRIGERATION SYSTEMS’ PERFORMANCE and ENVIROMENTAL IMPACTS

Year 2019, Volume: 2 Issue: 2, 97 - 108, 15.11.2019

Ebru Mancuhan Barış Tunç Kübra Yetkin Cem Çelik

Abstract

The aim of our study
is to propose a theoretical model to analyze the energy efficient and
environment friendly cascade system for various refrigerant pairs. In order to
realize, the optimum cascade evaporation temperature (T_OPT,CAS,E)
which maximize the performance, COP values are
determined for different refrigerant pairs of the system. After the optimization,
two different cases have been investigated through a thermodynamic analysis to
discover the best refrigerant pair for the system. Natural refrigerant CO₂
is selected instead of R404A which has high Global Warming Potential (GWP)
value for the low temperature cycle (LTC). On the other hand, synthetic
refrigerants (R134a, R152a) and a natural refrigerant (NH₃) are
chosen for the high temperature cycle (HTC). In order to determine, an energy
efficient and environmentally friendly cascade system, R134a/CO₂,
R152a/CO₂ and NH₃/CO₂ refrigerant pairs are
investigated in Case 1. On the other hand, R134a/R404A,
R152a/R404A and NH₃/R404A refrigerant pairs are investigated in Case
2. In calculations, the evaporation temperature (T_E) is varied from
-20^oC to -40^oC in LTC. The condensation temperature (T_C)
is considered to be between 30^oC and 45^oC in HTC. Mass
flow rate requirements of systems for various refrigeration capacities (Q_Evap)
are calculated for different refrigerant pairs. Moreover, the COP_max
and total equivalent warming impact (TEWI) values of the system’s refrigerant
pairs are evaluated and compared for various operating conditions.

Keywords

Cascade system, Optimization, TEWI, COP

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