Experimental Research on the Flow Boiling Heat Transfer Characteristic of Dilute Emulsion in Micro-Channel

The flow boiling heat transfer and pressure drop characteristics in a micro-channel heat sink were studied through experimental tests at three hydraulic diameters, on two different fluids (pure deionized water and 1% FC-72/water emulsion), at three mass flow rates and a range of effective wall heat flux. The normalized flow and heat transfer performance factors of the microchannel heat sink with different fluids were obtained under various conditions. The flow patterns on the heated wall of the micro-channel under typical flow boiling conditions were visualized. The results show that the introduction of FC-72/watcr emulsion dispersive phase into the micro-channel makes the bubbles more easily escape from the wall due to the disturbance of dispersive phase boiling, which makes nuclear boiling occur in advance and enhances heat transfer on the heated wall. However, the heat transfer enhancement on the targeted wall decreased as wall temperature increases. For micro-channels with 217,um and 433,um in heights, compared with the cases of pure deionized water, the heat transfer coefficient increased by 63. 8% and 103. 5% respectively if 1% FC-72/water emulsion was adopted. But the pressure drop in the micro-channel increased slightly. As the wall temperature increased, the pressure drop in the micro-channel decreased at first and then increased, while the normalized flow-heat transfer factor increased at first and then decreased. If the continuous phase of FC-72/watcr emulsion achieves the nuclear boiling, the normalized flow and heat transfer performance factor would reach the maximum value. In this study, the measured maximum values of the normalized flow-heat transfer factor equal to 1. 41 and 1. 91 for the 217 jum and 433,um micro-channel, respectively. © 2023 Xi'an Jiaotong University. All rights reserved.