Browse Publications Technical Papers 2014-01-0647

Transient Modeling and Validation of an Automotive Secondary Loop Air-Conditioning System 2014-01-0647

As a potential replacement to traditional automotive R134a direct expansion (DX) systems, a secondary-loop system allows for the usage of flammable but low-GWP refrigerants such as propane (R290). However, as the secondary-loop system has an additional layer of thermal resistance, the cycle's transient behavior and cabin thermal comfort during pull-down and various driving cycles may be different from traditional DX systems. This paper presents a Modelica-based model to simulate both steady-state and transient operation of automotive secondary-loop systems. The model includes a lumped cabin component and a secondary-loop automotive air-conditioning system component. The air-conditioning system component consists of a condenser, a compressor, an expansion device, a coolant plate type heat exchanger, a coolant to air heat exchanger and a coolant pump. The developed model was validated against both steady-state and transient experimental data for an R290 secondary-loop system. The steady-state comparison demonstrates a 7.5% deviation of air-side COP compared to the experimental data. The (transient) pull-down performance comparison shows maximum of 2.4% and 1.8% deviations of accumulated compressor power and accumulated capacity compared to the experimental data, respectively. The cabin temperature profile predicted by the model during the pull-down condition is within 1K of experimental data. Finally the validated model was used to study the effects of coolant charge amount and glycol concentration on the cabin thermal comfort. It was concluded that the charge variation of up to 2 liters will not significantly affect the thermal comfort, while a less than 30% glycol concentration is preferred.


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


Members save up to 16% 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:

Comparison of the Accuracy and Speed of Transient Mobile A/C System Simulation Models


View Details


Automotive Evaporator and Condenser Modeling


View Details


Development and Validation of Coolant Temperature and Cooling Air Flow CFD Simulations at Volvo Cars


View Details