Experimental and analytical study of transient convection at film flow-wall interface using infrared thermography

The convection heat transfer of transient flow usually involves transient temperature and transient heat flux at the flow-wall interface. For experimental studies on this type of convection heat transfer problems, it is difficult to take measurement at the flow-wall interface, particularly for liquid flow. A substrate with small thickness can be used. One surface is exposed to the flow, while, on the free surface, there is a thin-skin heat source providing a constant and uniform heat flux, and the temperature at the free surface is measured using infrared thermography. Then the heat transfer coefficient of the transient flow can be obtained based on the temperature measured on the free surface. Two experimental tests of water droplets impacting a water film flow are conducted using this method. We solve a 1-D transient conduction problem, and the derived solution is used to calculate the heat transfer coefficient for the two experiments. Additionally, the lumped capacitance method (LCM) and the present analytical method are compared for calculating convection heat transfer.