Experimental estimation of local heat flux on boiling surface in a mini-channel

Abstract

The present study suggests two methods for experimental estimation of heat flux distribution of the boiling surface along a mini-channel. In this process, the working fluid is water and the Nano-fluid, water‑copper, and the mini-channel being made of copper. In the first method, the heat flux of the boiling surface is estimated using the steady-state measured temperatures by thermocouples on the channel's wall and Fourier's Law and in the second method by using time history of the measured temperatures on the channel wall and inverse heat transfer method, conjugated gradient method. Results show that both methods estimate the heat flux almost similarly, which confirms that the hypothesis of considering the heat flux of the boiling surface and heater's heat flux as equal is not correct. By means of the estimated heat flux, the convective heat transfer coefficient and the vapor quality along the channel are calculated. Results of the present work are close to Mishiman and San's Equation. Results show the wall's temperature, heat flux of the boiling surface, the convective heat transfer coefficient, and vapor quality are depended on the mass flux as well as boiling flow's structure and nature. Heat flux of the boiling surface and the heat transfer coefficient along the channel declines due to the changes in the movement of the fluid and the bubbles.