Enhanced Heat Transfer Of Flow Boiling In Narrow Gap Based On Different Mode Interacting Boiling

Boiling heat transfer,owing to its good heat transfer performance,has been widely used in nuclear energy,chemical industry,biomedical,aerospace,microelectronic machinery and other fields closely related to heat transfer technology.For example,with the rapid development of electronic chip in recent years,the amount of heat exchange required by electronic devices is also rising linearly,making the heat flux reach MW/m² magnitude.This heat flux value has exceeded the critical heat flux of pool boiling and conventional flow boiling with water as the working fluid.Therefore,increasing the critical heat flux of boiling heat transfer is the key to improving the performance of cooling technology and is an urgent need in industrial applications.This study focuses on the experimental study of flow boiling characteristics in a micro-channel,which has broad application prospects in the cooling of micro-small heating elements such as electronic chips and explores new technologies for improving critical heat flux.In this study,the effect of nonuniform heat transfer plate on flow boiling was investigated.Two types of materials with different thermal properties（copper and polytetrafluoroethylene）were alternately arranged inside the heat transfer plate near the surface to realize the temperature distribution on the heat transfer surface and different-mode-interacting boiling（the coexistence of nucleate boiling and film boiling）.The feasibility of the nonuniform heat transfer plate was also verified in this paper.It was found that temperature fluctuation and different boiling modes will be formed on the heat transfer surface,which will promote the boiling heat transfer.To investigate the effect of the different-modes-interaction boiling on the flow boiling characteristics in micro-channel,a micro-channel flow boiling experimental system was designed.The size of micro-channel section was 1.84 mm×70 mm,the channel length was 280 mm,the surface size of the heat transfer plate was 10 mm×10 mm,and the working fluid was deionized water.Furthermore,the effect of the inlet velocities v=0.1,0.2,0.4 m/s,subcooling（?）T_sub=2,10,20,30 K and Polytetrafluoroethylene（PTFE）arrangement directions on different-modes-interacting boiling in micro-channel were studied.As a result,it is shown that the different-mode-interacting boiling on the nonuniform plate can effectively enhance the CHF of flow boiling compared with the uniform copper plate.In addition,for the PTFE parallel-arranged heat transfer plate,the inlet velocity and subcooling have a significant effect on the critical heat flux and similar trends were found.Decreasing the inlet velocity rate and the subcooling will increase the ratio of critical heat flux enhancement.Finally,the effect of PTFE arrangement direction on flow boiling was analyzed.It is found that the ratio of critical heat flux enhancement of the parallel arrangement is better than that of vertical arrangement.For all of the experimental conditions in this study,the highest ratio of critical heat flux enhancement is approximately 53.1% for inlet velocity v=0.1 m/s and subcooling（?）T_sub=2 K.