EXPERIMENTAL INVESTIGATION OF FLOW BOILING OF ACETONE IN PARALLEL RECTANGULAR MINI-CHANNELS

摘要

Miniaturization of cooling systems has demanded better designing tools for compact heat exchangers. Forced two-phase flow through small channels is an effective way to better performance in a limited space. However, the characteristics of flow boiling in small channels differ from those in regular size channels. The characteristics of flow boiling in compact heat exchangers with parallel rectangular mini-channels of cross sections 0.50 × 0.50 mm, 0.75 × 0.75 mm, 1.00 × 1.00 mm, and 1.50 × 1.50 mm were experimentally investigated. Various parameters and their influence over the two-phase heat transfer coefficient and two-phase factional pressure drop were studied.rnThe two-phase heat transfer coefficient was found independent of quality, except at low qualities. It was also found to be independent of mass flux, and mostly dependent of heat flux. These indicate a dominance of a mechanism similar to nucleate boiling. The correlation by Lee and Mudawar [1] predicted the two-phase heat transfer coefficient with good agreement for the quality range of 0.05 to 0.50. Correlations developed for regular size channels generally overpredicted the data.rnThe two-phase frictional pressure drop was found to increase with mass flux and exit quality. The separated flow model by Lockhart and Martinelli [2] predicted the two-phase frictional pressure drop with good agreement. Other variations of the separated flow model also predicted the data well for particular cases, but all homogeneous models under predicted the data.