Study On The Characteristics Of Heat Transfer And Pressure Drop In Mini-channel By Electric And Ultrasound Field

The mini-channel has the advantages of small volume,high heat transfer efficiency and low working medium demand,and has broad application prospects in solving the heat dissipation problems of small size and large heat flux.In order to obtain the heat transfer equipment with better heat transfer performance in the mini-channel,two active heat transfer enhancement technologies,electric field and ultrasound field,were introduced into the minichannel to study the heat transfer and pressure drop characteristics of R141 b flow boiling in the mini-channel under the synergy of a single physical field and a mixed physical field.The main research contents are as follows:(1)The boiling heat transfer characteristics of R141 b flow in the mini-channel under the action of electric and acoustic fields alone were experimentally studied.It is found that the heat transfer coefficient increases with the voltage under the action of electric field,and the heat transfer coefficient increases by 57% when the voltage is 800 V.The heat transfer coefficient under the action of ultrasound field is related to the arrangement mode of ultrasound field.The enhanced heat transfer effect of the arranged ultrasonic waves at the outlet,the imported ultrasonic waves and the import and export ultrasonic waves is enhanced in turn.The heat transfer coefficient of the simultaneously applied ultrasonic waves at the import and export is increased by 75%.(2)The boiling heat transfer characteristics of R141 b flow in the mini-channel under the synergistic effect of electric field and ultrasound field were experimentally studied.The frequency coordination of voltage and ultrasound field,the power coordination of voltage and ultrasound field,and the import and export coordination of voltage and ultrasound field are discussed.It is found that the enhancement effect of heat transfer under the synergistic effect of electric field and ultrasound field is significantly enhanced,and the enhancement factor of the synergistic effect of electric field and ultrasound field can reach 2.24 at most.(3)COMSOL software was used to simulate the distribution of electric field and ultrasound field around bubbles in the channel.Combined with high speed camera,found that under the electric field and ultrasound field synergy,channel and increased the number of air bubbles,the ultrasound field generated by microbubbles gradually grow into small bubbles after oppressed jitter on the heat transfer surface,limited to the movement of bubbles have similar,bubble behavior changes prompted intrinsic meniscus zone to the thin liquid film zone,greatly enhanced boiling heat transfer ability of mini-channel.(4)Experimental study on the flow boiling pressure drop characteristics of separate electric field,separate ultrasound field,and the synergy between electric field and ultrasound field.The results show that the total pressure drop under the synergistic effect of the electric field and the ultrasound field increases by 15.8%,and the two-phase friction pressure drop per unit length will increase with the increase of the electric field strength and the ultrasound field strength.The two-phase pressure drop under the synergistic effect is greater than the two-phase pressure of a single physical field.In addition,the action of the electric field and the sound field makes the bubble movement in the channel more complicated and intense,which exacerbates the instability in the channel.