Xavier Tardif

Thermal management in electric vehicles is an extremely important topic since it has a direct impact on the mile range. In winter conditions in particular, the abundant heat coming from combustion in the thermal engine is not available and the HVAC system weighs heavily on the battery balance. The challenge is to minimize the vehicle consumption while keeping at the same time an acceptable level of thermal comfort for the driver and the passengers. The glazing can be an effective leverage of improvement of the vehicle cabin thermal performances and glazing solutions exist for summer and winter conditions. The main improvements are provided by the use of double glazed units (DGUs) and thin coatings to functionalize the glass surface; those solutions exist and are available commercially. With numerical calculations we confirm the large positive impact of the DGU on the heating power consumption of a city bus in winter conditions. While a single glazing cannot equal the performances of a DGU, we show that the use of the ComfortSky® low-emissivity coating provides an appreciable improvement. We discuss a methodology to experimentally characterize thermal comfort in transport vehicles. We demonstrate its technical feasibility and its relevance on two coaches in summer conditions. Both were equipped with DGU, but, in the coach where a low-emissivity ComfortSky® coating was used, a lower operative temperature was measured, indicating a better thermal comfort. The results of thermal comfort measurements can be used to further reduce the energy consumption by refining the HVAC settings.

During the forming of thermoplastic parts, the control and optimization of heat transfer are crucial because they impact on the quality of final part. The modeling of heat transfers requires a comprehensive and accurate knowledge of thermo-physical and crystallization properties of the polymer. However the experimental determination of these parameters is time consuming and requires several devices. In this work, we present a new apparatus associated to a methodology able to determine simultaneously the specific volume, the thermal conductivity and parameters of a crystallization kinetic model. This home-built PvT device is designed such as heat transfer is 1D through the radius of a sample with experimental conditions close to processing conditions: high temperature (up to 400°C), high cooling rate (up to 200K/min) and very high pressure (up to 200MPa). This apparatus controls the applied pressure on the sample while measuring its volume variation which corresponds to a direct measurement of the specific volume. Then the thermal conductivity and the crystallization kinetics are estimated without intrusivity by inverse methods based on a heat transfer model with moving boundaries, which takes temperature and crystallinity gradients into account. Our apparatus and methodology are tested on isotactic polypropylene, which is extensively studied in the literature. Measurements (specific volume) and estimated values (thermal conductivity and crystallization kinetics) are close to literature ones.

In this work, we present an apparatus associated to a methodology that is able to determine simultaneously and according to temperature (up to 400°C) the specific volume (up to 200MPa), the thermal conductivity and the temperature function of the crystallization kinetics. The PvT-XT is a home-built device that is able to impose and quantify 1D heat transfer through the radius of a sample. This apparatus controls the applied pressure on the sample while measuring its volume variations. The associated moving boundary model takes into account the temperature and crystallinity gradients. Specific volume is determined from direct measurement whereas inverse methods are used to estimate the thermal conductivity and the crystallization kinetics (with cooling rates up to 200K/min). Specific volume measurements are compared with literature results and exhibit a very good agreement. Thermal conductivity identified in the present paper is also very close to literatures values. Finally identification of kinetic function values is consistent with previous studies.