MULTI-OBJECTIVE OPTIMIZATION OF A R744/R134A CASCADE REFRIGERATION SYSTEM: EXERGETIC, ECONOMIC, ENVIRONMENTAL, AND SENSITIVE ANALYSIS (3ES)

Mohammad Mehdi Keshtkar

doi:10.18186/thermal.581750

Abstract

This work presents the optimization of a two stage-cascade refrigeration system (TS-CRS), based on exergetic, economic, environmental, and sensitive analysis (3ES). R134a and R744 are considered as the refrigerants of high and low temperature circuits, respectively. Two single-optimization strategies including exergetic and economic optimizations and a multi-objective optimization are applied on the problem. In the first step, a comprehensive performance evaluation of different effective parameters, based on the genetic algorithm, used to indicate the optimum operative conditions in single objective strategies. In the next step, a multi-objective optimization is performed with considering a decision-making strategy based on the Pareto frontier using TOPSIS method. The higher exergetic efficiency and lower cost found in the exergetic and economic single-optimization, respectively. The multi-objective optimization results demonstrate that, the total system cost and the exergetic efficiency increase 28.6% and 99.5%, respectively, compared to the base design, and 46.6% higher energy can be saved in the compressors.

Highlights

The cascade refrigeration system (CRS) is a freezing system that uses two kinds of refrigerants having different boiling points, which circulate through their own independent refrigeration cycle and are thermally coupled with each other through a cascade condenser [1]
The higher cost of air-cooled condenser was achieved for lower values of TE since the logarithmic temperature variation between the condensation and ambient temperatures decreased
The findings showed that by enhancing Tsub,L or Tsub,H, the exergetic efficiency and the total annual cost of the CRS increased

Summary

Introduction

The cascade refrigeration system (CRS) is a freezing system that uses two kinds of refrigerants having different boiling points, which circulate through their own independent refrigeration cycle and are thermally coupled with each other through a cascade condenser [1]. This system is employed to obtain temperatures of -40 to -80°C or ultra-low temperatures [2]. Mafi et al [9] performed an exergy analysis for multistage CRS and found that the minimum work depends only on the properties of incoming and outgoing process streams cooled or heated with refrigeration system and the ambient temperature

Methods

Results

Conclusion