Investigate partial cabin air re-circulation strategy to improve HVAC system's heating performance using 1D simulation 2020-01-0159
In cold weather conditions, cabin heating performance is critical for retaining the thermal comfort. Heat is absorbed from the engine by circulating coolant through the engine water jacket and same will be rejected by the heater core. A variable speed blower is used to transfer heat from the heater core to the passenger compartment through floor ducts. The time taken to achieve comfortable cabin temperature determines the performance and capacity of heating ventilating and air conditioning (HVAC) system. In current automotive field, the engine options are provided to customers to meet their needs on the same vehicle platforms. Hence few engine variants cannot warm the cabin up to customer satisfaction. To improve the existing warm up performance of system, Positive thermal coefficient heater (PTC), electric coolant PTC heater, auxiliary pump etc. can be used which increases the overall cost of the vehicle.
During warm-up, HVAC system operates in 100% fresh mode. In this study, Partial cabin re-circulation is investigated to understand the effect on the cabin warm-up. In order to demonstrate this phenomenon, a one dimensional (1D) modelling approach is used for simulation and predicted the performance of different percentage of partial cabin air re-circulation. Baseline correlation simulation is done with vehicle test data to reproduce the same test conditions in 1D software (KULI®). Model output parameters such as floor duct outlet air temperature, Cabin warm-up temperature are correlated at 0% partial re-circulation in other words 100% fresh mode. By increasing the partial re-circulation by 10% at each simulation run up to a maximum of 30%, increase in the floor duct outlet air temperatures is observed. An improvement of 8% in the floor duct outlet temperature is witnessed through 1D model. This strategy can be applied to upcoming vehicle to improve the cabin warm-up performance.