Natarajan, S., S, S., Amaral, R., and Rahman, S., "1D Modeling of AC Refrigerant Loop and Vehicle Cabin to Simulate Soak and Cool Down," SAE Technical Paper 2013-01-1502, 2013, doi:10.4271/2013-01-1502.
Simulation has become an integral part in the design and development of an automotive air-conditioning (AC) system. Simulation is widely used for both system level and component level analyses and are carried out with one-dimensional (1D) and Computational Fluid Dynamics (CFD) tools. This paper describes a 1D approach to model refrigerant loop and vehicle cabin to simulate the soak and cool down analysis. Soak and cool down is one of the important tests that is carried out to test the performance of a heating, ventilation and air-conditioning (HVAC) system of a vehicle. Ability to simulate this cool down cycle is thus very useful. 1D modeling is done for the two-phase flow through the refrigerant loop and air flow across the heat exchangers and cabin with the commercial software AMESim. The model is able to predict refrigerant pressure and temperature inside the loop at different points in the cycle. Air side predictions include evaporator air out temperature and the average cabin temperature. In a 1D model, vehicle cabin is represented as a single moist-air volume and heat load entering the cabin through different opaque and semi-transparent surfaces by conduction, convection and radiation is modeled and the simulations predict the average air temperature value inside the cabin. The simulation results agree well with the test results. This analysis helps us to predict the HVAC performance and optimize the components during the early design stages. By employing this methodology, it is possible to reduce the product development time and cost.