Experimental research on flow boiling thermal-hydraulic characteristics in novel microchannels

This paper reports experimental research of the microchannel flow boiling system for thermal management in electronic devices. Under different operational conditions, the flow boiling characteristics of HFE7100 in two novel microchannels: microchannel with Tesla valve (MCTV), microchannel with sector bump (MCSB) were studied. The effects of mass flow rate, inlet temperature and heat flux to the flow boiling characteristics regarding the two structures were analyzed and more outstanding structure for flow boiling cooling system was found. The results report that the boiling state in both two novel microchannels are stable, the pressure drop fluctuation is about 0.8% to 3.9%, but the heat transfer coefficient of MCSB is approximately 45 % higher and the pressure drop of MCSB is 25% lower than that of MCTV in average. One reason is the ribs of MCSB has stronger ability to segment bubble and vapor slug which contributes to smaller average volume of bubble/vapor slug and proportion of vapor phase. Another is that the geometry of MCSB is smoother and the local flowing velocity near the rib is larger which is beneficial for bubble nucleation and separation. In addition, the effective heat flux for ONB of MCSB is larger than that of MCTV. It is concluded that MCSB has superior thermal-hydraulic performance in flow boiling process than MCTV. The proper correlation is selected and revised for the prediction of heat transfer coefficient of two microchannels. Generally, the prediction error of the revised correlation is no more than 30%.