Development of measurement technology for surface heat fluxes and temperatures

A technique for the measurement of surface temperature and surface heat flux was developed. This technique involves two steps: (1) measurement of the inner block temperatures near the surface using special micro temperature sensors; and (2) solving an inverse heat conduction problem (IHCP) to obtain the surface heat flux and surface temperature by using the measured inner block temperature data as input. For the inner block temperature measurement, special T-type temperature sensors with a common positive pole were introduced. A total 10 special micro temperature sensors are placed radially at a pitch of 0.5 mm and at a depth of 3.1 μm beneath the boiling surface. The developed system was used to measure the change in the surface heat flux and surface temperature during a boiling process. Experiments were performed for pool boiling at atmospheric pressure. The results from the experiments showed that the special T-type temperature sensors with a common positive pole can measure the temperature change during a boiling process. By using the measured inner temperatures, one-dimensional IHCP was solved to obtain the change of the surface heat flux and surface temperature with the time. The increase in the surface heat flux with the formation of big bubbles was calculated successfully.

► We developed special T-type temperature sensors which sharing a common positive pole. ► The temperature sensors were placed at a depth of 3.1 μm and at a pitch of 0.5 mm beneath the surface of interest. ► The sensors were used to measure the temperature change under a boiling bubble. ► With using the measured temperature data, we solved the inverse heat conduction problem to derive the surface heat flux and surface temperature during a boiling process.