具有尾流抽吸的高速微射流沸腾传热强化研究

Enhanced Boiling Heat Transfer of High-Speed Water Microjet with Back Suction

摘要

射流沸腾现象具有高热流密度传热潜力,因此成为冷却技术开发方面的研究热点之一．然而,射流有可能导致沸腾气泡在传热面表面滞留,当前利用重力作用等被动方式清除尾流效果并不理想,制约了沸腾传热能力的进一步提升．为了避免上述问题,本文利用尾流抽吸方式有效排除沸腾气泡,防止其在传热面附近滞留,最终提升沸腾临界热流密度(CHF)．通过建立具有尾流抽吸功能的微射流沸腾实验系统,以水为工质在不同工况下针对微射流沸腾传热特性开展研究,详细分析尾流抽吸强度、射流速度、射流/抽吸距离等参数对微射流沸腾传热的影响．实验结果表明：增加尾流抽吸后微射流沸腾具有明显的传热强化效果．在本文的研究参数范围内,CHF均随着射流速度的增加而增大,射流速度对沸腾传热特性有显著影响；同时,调整射流/抽吸距离会对CHF产生影响．CHF在射流/抽吸距离d_i＝d_o＝1.1 mm条件下比d_i＝d_o＝0.5 mm获得提升．实验中获得的最佳数据如下：在尾流抽吸强度0.65 L/min、射流/抽吸距离1.1 mm条件下,射流速度为3.33 m/s时获得8.60 MW/m²的最高临界热流密度；射流速度2.33 m/s时获得了325 kW/(m²·K)的最佳传热系数．

Abstract

The phenomenon of jet boiling has the potential for high heat flux heat transfer,making it one of the research hotspots in the development of cooling technology. However,the jet may cause boiling bubbles to remain on the heat transfer surface,and the current passive methods(such as gravity)to insufficiently remove these bubbles which restricts further improvement of boiling heat transfer. In order to avoiding the above problems,this paper proposed the use of back suction to effectively eliminate boiling bubbles,prevent them from lingering near the heat transfer surface,and ultimately improve the boiling critical heat flux(CHF). This study developed a microjet boiling experimental system incorporating back suction,with water serving as the working fluid. Heat transfer characteristics were extensively analyzed under various conditions,exploring factors such as back suction strength,jet velocity,and jet/suction distance. The experimental results show that adding back suction has a substantial effect of heat transfer enhancement on microjet boiling. Within the experimental conditions of this paper,CHF increases with the increase in jet velocity,which has a substantial impact on boiling heat transfer characteristics. Meanwhile,adjusting the jet/suction distance affectes CHF. For instance,an increase in CHF is observed when the jet/junction distance is set to 1.1 mm compared with 0.5 mm. Under optimal conditions—suction flow strength of 0.65 L/min,jet/suction distance of 1.1 mm,and jet velocity of 3.33 m/s—maximum CHF of 8.60 MW/m² is obtained；a best heat transfer coefficient of 325 kW/(m²·K)is obtained at a jet velocity of 2.33 m/s.

关键词

尾流抽吸 / 射流沸腾 / 沸腾传热 / 临界热流密度 / 强化传热

Key words

back suction / jet boiling / boiling heat transfer / critical heat flux(CHF) / enhanced heat transfer

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基金资助

国家重点研发计划资助项目(2021YFE0192800)