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2012 年 07 月 20 日
Seminar - Micro Two-phase Heat Transfer by Prof. Wei Li

Date:   20 July 2012 (Friday)

Time:   11:00 am – 12:00 pm

Venue:  EF305, The Hong Kong Polytechnic University

Abstract:
A tricky aspect of micro/mini-scale two-phase heat transfer studies is how to identify the macro-to-micro/mini-scale threshold. That means, how small a channel can be called a micro/mini-channel such that its behavior starts to deviate from the predictions of conventional macro-channels. We developed a general criterion to classify a channel as micro-channel or macro-channel. Experimental results of saturated-flow boiling heat transfer in micro/mini-channels for both multi- and single-channel configurations were obtained from the literature. The collected database contains 4,228 data points, covering a wide range of working fluids, operational conditions, and different micro-channel dimensions. Seven existing correlations were evaluated against the database to verify their respective accuracies. A combined non-dimensional number Bo*Rel0.5 = 200 was introduced as the new conventional-to-micro/mini-channel criterion. This criterion is further confirmed by experimental data of CHF, pressure drop.  Wave surface of boundary layer, a new concept is advanced. It is the interface between the main flow and the boundary layer. It is generated by a tiny density difference which results from velocity difference between the main flow and the boundary layer in the flow. When fluid moves, wave elements will be generated on the surface of the boundary layer. The size of a wave element is so small that it is impossible to conduct experiments to observe it directly. The size of a wave element is so small that it is impossible to conduct experiments to observe it directly. A series of “enlarged size” experiments to show the oscillatory behaviors of wave elements were conducted. A mathematical analysis based on the relationship of continuity was developed. Both the spatial and the temporal oscillatory behavior are presented in the experimental results as predicted by the theoretical analysis. The author’s ongoing projects cover a wide research area in Heat Transfer as reflected in the following papers. For the past two years, He published a dozen journal papers as the corresponding author.

Biosketch:
李蔚,博士、教授、博士生导师,西安交通大学本科毕业,分配到珠海格力电器从事换热器研发。1993年去美国宾州州立大学(The Pennsylvania State University)自费留学,作为国际著名学者Ralph•Webb教授(1985年美国传热学最高奖ASME Heat Transfer Memorial Award获得者)的硕士和博士研究生6年,1998年获得博士学位。毕业后在美国从事微尺度强化传热、液体可逆催化析氢微纳通道反应器、传热与制冷技术等研究。2004年获马里兰大学 (University of Maryland)传热论坛颁发的卓越贡献奖(Distinguished Contribution)。2006年辞职,作为“杰出引进人才”归国加入浙江大学能源学系。现任中国工程热物理学会--传热分会理事、铁道车辆热工--教育部重点实验室--学术委员会委员;美国机械工程师学会(ASME)委员、SCI源刊《Journal of Enhanced Heat Transfer》的中国区编委--Editor for China。回国六年以来,兢兢业业。在相关领域取得多项成果:建立了流体边界层界面微纳尺度波动的新概念及理论数学模型;发现了区分常规管道与微管道的新临界准则数,在此基础上,归纳出了新的微通道两相流压降、传热系数和临界热流量的普适关联式;发现了微通道催化两相流的倒置环向流现象和解决办法;建立了四维热质传递特性理论-振弦理论分析方法;率先研制成功微通道全铝平行流冷凝器和蒸发器空调系统并推动实现产业化;开展激光烧蚀与蒸发波热力壅塞前沿实验/理论研究。主持国家863项目、国家自然科学基金项目、国家回国留学人员启动基金、浙江省自然科学基金项目、企业资助的技术研发项目等多项。参加国家973计划子课题2项。国内外核心期刊上发表论文近100篇;6 篇被正面收录到美国研究生教科书。中国专利11项,其中发明专利4项。2007年和2009年全国传热年会两次作大会主题报告。国际会议特邀报告3 次,多次参与举办国际学术会议或分会。指导12名研究生,包括4名博士研究生。研究生发表SCI论文以及获专项奖金人数和档次,在能源系年年名列前茅。2011年,1名硕士生去MIT读博士;3名博士生:一名获教育部博士生引领计划奖(全系3名),一名获教育部博士生新人奖(全校25名)。一名获中国科学院吴仲华研究生传热学奖(全国2名)。