Validation of experimental measurement using infrared thermometry for the subcooled flow boiling experiment

The subcooled flow boiling experiment in a vertical (rectangular) channel has been recently performed in Texas A&M University (TAMU). In this experiment, a midwave infrared (IR) camera is used to measure the local temperature variations at the heated wall. The wall consists of the soda-lime glass substrate coated with a thin ITO layer so that we can achieve a nearly constant heat flux by means of electrical Joule heating. Since the current facility has the multi-layer design of test section with different optical properties, the surface temperature at the ITO-side which is exposed to the flow cannot be captured directly from the IR camera. Therefore, the theoretical process to infer the correct wall temperature need to be established and validated based on the better understanding of the materials' optical properties. In this paper, the experimental procedures for validating the IR-based measurement technique for the subcooled flow boiling experiment at TAMU are presented and the results are discussed. During this process, the optical properties of the materials can be identified and it is demonstrated that the ITO surface temperature can be estimated successfully through the suitable calibration process.