Development of fast response heat transfer measurement technique with thin film thermocouples
Abstract A transition boiling on a high temperature solid beyond the Leidenfrost temperature is characterized by a strong unstable heat transfer. This unstable one brings a rapid temperature change beneath the surface in the solid and causes a repetition in time as well as a space of wet and dry on the surface. Therefore, the development of a fast temperature measurement technique is indispensable to understand this transition phenomenon. The developed temperature sensor has a junction of the end face of chromel fine wire of ph0.32 mm diameter, whose position is 3 mm away from the surface of nickel disk of 5 mm thickness and can follow a rapid temperature change within 100 kHz. The heat transfer can be calculated from the measured temperature by using an inverse problem analysis for one dimensional unsteady heat conduction. Besides, the calculated heat flux is also confirmed to be sufficient to capture the characteristics of unsteady boiling heat transfer in the experiment that a sessile ethanol droplet impacts onto the hot surface.