两相湍流热对流中传热增强的实验研究  

An Experimental Study on Heat Transport Enhancement in Two⁃Phase Turbulent Thermal Convection

作　　者：王伟 王牧 韦萍 WANG Wei;WANG Mu;WEI Ping(School of Aerospace Engineering and Applied Mechanics,Tongji University,Shanghai 200092,China;Shanghai Key Lab of Vehicle Aerodynamics and Vehicle Thermal Management Systems,Shanghai 201804,China)

机构地区：[1]同济大学航空航天与力学学院,上海200092 [2]上海市地面交通工具空气动力与热环境模拟重点实验室,上海201804

出　　处：《力学季刊》2023年第3期525-536,共12页Chinese Quarterly of Mechanics

基　　金：国家自然科学基金(12272271);中央高校基本科研业务费专项基金。

摘　　要：Rayleigh-Bénard(RB)湍流热对流是一个经典的流体力学模型,传统的RB热对流系统采用单一流体作为工作介质.然而在实际工业生产和大自然中,对流的工作介质往往是多成分多相(譬如气相与液相共存).本文进行了气液两相热对流系统的实验,研究了相变引起的全局体积变化以及热对流系统的传热规律.实验采用径高比Γ≡D/H=0.5的圆柱形对流槽,工作介质为去离子水与氟化液(HFE7000),其中氟化液在装置中的体积分数占比为Φ=0.86%.实验中,上下板的温差保持为30℃,控制参数范围是2.54×10^(9)<Ra<5.63×10^(9),底板温度35℃<T_(b)<48℃.我们发现,氟化液HFE7000在大气压下的沸点为Tcr<40℃,然而氟化液的体积在底板温度T_(b)<42.5℃之后就不再发生变化.全局传热分为3个区间,在区间Ⅰ内,即T_(b)<42.5℃,系统的传热效率Nu变化较小.在区间Ⅱ内,42.5℃<T_(b)<45℃,当氟化液达到最大汽化体积之后,Nu大幅提高,随着底板温度的增加,最大传热提高了43%.在区间Ⅲ内,T_(b)>45℃,Nu保持不变.我们发现这与气泡的整体运动距离相关.Rayleigh-Bénard(RB)convection is an ideal model to study the turbulence involving heat transport.In the traditional RB convection,generally,only one kind of fluid in a single phase was used.However,in nature and industrial process,turbulent flow involves with multiple components of fluid and multiple phases.In the present work,we conduct experiments on gas-liquid two-phase thermal convection system,and investigate the global volume change due to phase change and the heat transport in twophase turbulent thermal convection.Two kinds of fluids,de-ioned water and Fluoride-Carbonate HFE7000 were used.The fluid HFE7000 took up 0.86%volume of the cylindrical cell,whose aspect ratio wasΓ≡D/H=0.5.We found that the fluid HFE7000 has a boiling point Tcr=40℃at 1 atmosphere pressure.The volume of fluids reaches a constant value for T_(b)>42.5℃.The relationship between global heat transport Nusselt(Nu)number and T_(b)can be divided into 3 regimes.In regimeⅠof T_(b)<42.5℃,the global Nu varies little with T_(b).In regimeⅡof 42.5℃<T_(b)<45℃,Nu increases with T_(b),with the enhancement of Nu up to 43%.In regimeⅢof T_(b)>45℃,Nu reaches a constant value.In two-phase RB,Nu is related to the average traveling distance of bubbles.

关 键 词：热对流 相变 传热 气泡流 

分 类 号：X125[环境科学与工程—环境科学] X126