Basic Study on reduction of measurement time for evaluating thermophysical properties of insulation heat dissipation sheet based on quasi-steady state measurement

This paper describes an improved measurement method for fast evaluation of thermophysical properties of an insulation sheet. The sheet is used to insulate inverter and water cooling jacket in an electric or hybrid electric vehicles. A large number of iterations of steady state measurement is required to perform parameter study for various composition of the sheet. However, steady state measurement generally needs very long time even only once. From the above reasons, it is necessary to reduce measurement time while keeping accuracy. Here, quasisteady state method is one of the methods of reducing measurement time by performing a prediction while keeping accuracy. Transient temperature response and steady temperature can be obtained by prediction faster than steady state method. Accuracy of prediction and measurement time will be changed by controlling application range. In this report, the availability of quasi-steady state method was investigated by comparing prediction results with steady state results of 3D thermal analysis and experiment. Especially, thermal conductivity was evaluated as a criterion. Then, the predicted thermal conductivity was derived from the predicted steady temperature. Through the investigation, in terms of accuracy, the quasi-steady state method was available when surrounding condition was perfectly insulated. On the other hand, in terms of the reduction of measurement time, a thinner thickness of metal block required a shorter measurement time because of the decrease in the heat capacity.