Impact of Fe powder sintering and soldering in production of porous heating surface on flow boiling heat transfer in minichannels

¹ Kielce University of Technology, Faculty of Mechatronics and Mechanical Engineering, Al. 1000-lecia P.P. 7, 25-314 Kielce, Poland
² contractor of the project from the Polish National Science Centre (No. DEC-2013/09/B/ST8/02825)

^⁎ Corresponding author: tmpmj@tu.kielce.pl

Abstract

This paper focuses on identification of the impact of porous heated surface on flow boiling heat transfer in a rectangular minichannel. The heated element for Fluorinert FC-72 was a thin plate made of Haynes-230. Infrared thermography was used to determine changes in the temperature on its outer smooth side. The porous surface in contact with the fluid in the minichannel was produced in two processes: sintering or soldering of Fe powder to the plate. The results were presented as relationships between the heat transfer coefficient and the distance from the minichannel inlet and as boiling curves. Results obtained for using a smooth heated plate at the saturated boiling region were also presented to compare. In the subcooled boiling region, at a higher heat flux, the heat transfer coefficient was slightly higher for the surface prepared via soldering. In the saturated boiling region, the local heat transfer coefficients obtained for the smooth plate surface were slightly higher than those achieved from the sintered plate surface. The porous structures formed have low thermal conductivity. This may induce noticeable thermal resistance at the diffusion bridges of the sintered structures, in particular within the saturated boiling region.