Two Phase Pressure Drop and Boiling Heat Transfer in Micro Pin Fin Channel

Abstract

In this paper, boiling experiments were conducted to study two-phase pressure drop and the heat transfer coefficient in a staggered array micro pin fin channel of degassed water at a mass flux range of 9.3 to 46.6 kg/m2s and a heat flux of 0.5 to 0.9 W/cm2. Copper was used for the pin fin array microchannel heat sink, which was 31 mm in width and 82 mm in length. Micro pin fins, of 400 μm in diameter and 700 μm in height, were manufactured using a micro milling machine on the channel block. The distance between two pin fin surfaces is 300 μm. A thin film heater, which supplies a maximum constant heat flux of 1.55 W/cm2, was attached underneath the heat sink. From the experimental results, at a vapor quality of up to 0.04, the boiling heat transfer coefficient decreased as the quality increased. Results show that the heat transfer coefficient is dependent on the mass flux. The data also showed that the pressure drop increased with increasing mass flux. The data obtained in this study were compared to the existing correlations of boiling pressure drop and heat transfer coefficients. Results showed that the correlation with boiling pressure drop of Qu and Siu-Ho[22] yielded a prediction of 21.3% average error Additionally, as a result of comparison with the four existing correlations of boiling heat transfer coefficient, all correlations had a lower prediction for the heat transfer coefficients obtained in this study. Through visualization, it was found that the bubbles generated between the fins began to grow and moved downstream. We observed a stationary vapor pocket in which bubbles did not flow.