Cabin Heat-up Thermal Assessment for Human Comfort in Passenger Car

The HVAC (Heating, Ventilation and Air conditioning) system is designed to fulfil the thermal comfort requirement inside vehicle cabin. Thermal comfort is significantly subjective which predominantly dependent on occupant’s physiological condition. Vehicle AC performance is evaluated by air flow and local temperature thus, thermal comfort assessment is carried out by mapping of velocity and temperature at various places inside cabin. There is need to have Simulation methodology for heating cabin during cold climate to assess ventilation system effectiveness. Thermal comfort modelling involves human manikin, complex cabin material along with environmental condition in expensive transient simulation. Present study employed with LBM (Lattice-Boltzmann Method) based PowerFLOW solver coupled with finite element based PowerTHERM solver to simulate the cold soaking and heating up of cabin. Thermal comfort is subjective to human physiological modelling thus in-built Berkeley human comfort library is used in simulation. Human thermal modelling includes metabolic rate of heat production with effects of clothing’s in external ambient condition. Once human thermal modelling in controlled environment is stabilized, LBM based solver is used to predict the convective heat transfer phenomenon, thereafter conduction and radiation effects are solved using coupling approach in PowerTHERM. Physical tests are conducted in controlled environment of climate chamber. Simulation results obtained are correlated with experimental data. Occupant’s thermal comfort is evaluated using the Predictive Mean Vote (PMV) and thermal comfort sensation scale. This process is further used to study the effect of change in material properties of in-cabin surface, flow delivery, air temperature and heater capacity. This method is useful to predict thermal comfort for various passenger vehicles at low ambient comfort requirements, heater size, and air delivery system effectiveness. This process found even more effective where heater energy and thermal comfort trade-off is essential and sensitivity of two heaters on thermal comfort is discussed in this paper.