Experimental and Theoretical Study on the Cooling Performance of a CO2 Mobile Air Conditioning System

Dandong Wang,Binbin Yu,Junye Shi,Jiangping Chen

doi:10.3390/en11081927

Abstract

CO2 (GWP = 1) is considered as a promising natural alternative refrigerant to HFC-134a in mobile air conditioning (MAC) applications. The objective of this study is to investigate the cooling performance characteristics of a CO2 MAC system. A prototype CO2 MAC system, consisting of a CO2 electrical compressor, CO2 parallel flow microchannel heat exchangers, and an electrical expansion valve, was developed and tested. Factor analysis experiments were conducted to reveal the effect of outdoor temperature on the cooling performance of this CO2 MAC system. Compared with a conventional R134a MAC system, the prototype CO2 MAC system achieved comparable cooling capacity, but had COP reductions of 26% and 10% at 27 °C and 45 °C outdoor conditions, respectively. In addition, based on refrigerant properties, theoretical cycle analysis was done to reveal the impact of evaporator, gas cooler and compressor, on the system cooling performance. It is concluded that the increase of overall compressor efficiency or the decrease of gas cooler approaching temperature could greatly improve the COP of this CO2 MAC system.

Highlights

As a countermeasure against global warming, the international treaty of the Kigali Amendment to the Montreal Protocol for HFC reduction will be binding on all 197 countries starting 2019, and national regulations in the EU, Japan and the USA are phasing out the use of HFC-134a (GWP = 1430) in mobile air conditioning (MAC) systems [1]
The power consumption for cabin heating in electrical vehicles significantly affects the driving range, resulting in a range reduction of up to 50% for considered cases in cold climate conditions [7]. For these applications remarkable developments have been achieved in recent years with thermoacoustic refrigerators [8], and the use of CO2 as a refrigerant becomes more attractive in mobile heat pump system applications to improve heating efficiency and extend the driving range of electrical vehicles [9,10,11], and to reduce the noise pollution typical of vehicles [12]
The CO2 MAC system is composed of an electrical compressor, a gas cooler, an evaporator, an expansion valve (EXV), an internal heat exchanger (IHX), and an accumulator

Summary

Introduction

The power consumption for cabin heating in electrical vehicles significantly affects the driving range, resulting in a range reduction of up to 50% for considered cases in cold climate conditions [7]. For these applications remarkable developments have been achieved in recent years with thermoacoustic refrigerators [8], and the use of CO2 as a refrigerant becomes more attractive in mobile heat pump system applications to improve heating efficiency and extend the driving range of electrical vehicles [9,10,11], and to reduce the noise pollution typical of vehicles [12]

Objectives

Methods

Results

Conclusion