Experimental Investigation of a Thermal Preconditioning of a Car cabin

This paper presents an experimental investigation of two passive thermal preconditioning technologies, pre-ventilation and solar shields, and a combination of both. A Design of Experiment (DOE) was defined in order to evaluate the influence of several parameters (air mass flow and air diffusion mode, size of the air extractors, location and type of solar shield) on the passengers' thermal comfort on entry into the car cabin and after a short A/C running time (10 min). Results show that solar shields are more efficient than pre-ventilation, which means that radiative heat transfers are more effective than the convective heat transfers, even with high air flows. The type of solar shields together with their location on the windows is also influential. After preconditioning, 10 minutes of air conditioning might reduce the air temperature at face level of the front passengers, compared to a non preconditioned car cabin. But for most of the configurations tested, the evolution of air temperature is the same, especially with the pre-ventilation technology. This demonstrates that the high amount of cooling power (around 5kW) needed to cool the car cabin is due to the heat load stored in the car cabin surfaces.