Microscale measurement of wall-temperature distribution at a single vapor bubble for evaluation of a nucleate boiling model

Abstract

An experiment is designed for evaluation of an existing nucleate boiling model. An essential aspect of the model is the description of heat and mass transfer in a tiny thin film area where the vapor bubble is attached to the wall. A considerable amount of the total heat transferred from the heater flows through this “micro region.” The high local heat flux in the micro region leads to a local cooling. The associated wall temperature drop underneath this area is calculated with the nucleate boiling model and measured with an optical method using thermochromic liquid crystals (TLC). In the first ground experiment a thin liquid film evaporator was built with a thin electrically heated wall featuring two-dimensional, high-resolution temperature measurement by TLCs. The measured temperature distribution corresponds to the calculated one. The second experimental setup for l-g and reduced gravity conditions is designed to establish a stationary bubble of appropriate size to enable optical observation of the circular temperature drop. A qualitative evaluation of the model seems to be possible with this experiment.