Browse Publications Technical Papers 2019-01-0912
2019-04-02

Heat Transfer Characteristics of Gas Cooler in a CO 2 Automobile Heat Pump System 2019-01-0912

An automobile heat pump system with conventional refrigerant (HFC-134a or HFO-1234yf) suffers significantly diminishment of heating capacity and system efficiency as the ambient temperature decreases. Natural refrigerant CO2 (GWP = 1) is considered as a promising alternative to HFC-134a in automobile air conditioning (MAC) applications with environmentally friendly advantage. In addition, CO2 automobile heat pump system is a promising heat pump technology for EVs with great heating advantages in a cold climate. This study aims to investigate the supercritical heat transfer characteristics of a compact micro-channel gas cooler applied in an automobile CO2 heat pump system. A simulation model of automobile gas cooler was developed by using segment-by-segment method, and validated by experimental results from Series Gas cooler (SGC) and One Gas cooler (OGC) CO2 heat pump systems. The error of heating capacity between calculated results and experimental results was less than 7%. Using this model, the air and refrigerant temperature distribution as well as the heat transfer coefficient along the refrigerant flow path under the condition of -20 °C air inlet temperature and 9 MPa refrigerant inlet pressure were predicted and analyzed. When the refrigerant thermodynamic state is in the pseudo-critical region, the refrigerant specific heat capacity and heat transfer coefficient will suddenly increase to a high level. Results show that after passing through four slabs of gas cooler, the air temperature can be increased from -20 °C to an average outlet temperature of 39.2 °C. Furthermore, the impact of the number of gas cooler slabs on the heat rejection performance of gas cooler was studied. Results show that with the increase of slab number, the heat rejection performance of gas cooler first increased rapidly, then increased slowly, and finally approached to the heat transfer limit. The lowest heat transfer temperature difference occurs at the last segment of the gas cooler.

SAE MOBILUS

Subscribers can view annotate, and download all of SAE's content. Learn More »

Access SAE MOBILUS »

Members save up to 18% off list price.
Login to see discount.
Special Offer: Download multiple Technical Papers each year? TechSelect is a cost-effective subscription option to select and download 12-100 full-text Technical Papers per year. Find more information here.
We also recommend:
TECHNICAL PAPER

Reduced Pressure Carbon Dioxide Cycle for Vehicle Climate Control: Progress Since 1999

2000-01-0577

View Details

TECHNICAL PAPER

R134A Suction Line Heat Exchanger in Different Configurations of Automotive Air-Conditioning Systems

2001-01-1694

View Details

TECHNICAL PAPER

Properties of Working Fluids for Reduced Pressure Carbon Dioxide Systems

1999-01-1189

View Details

X