声空化强化沸腾换热的试验观察与分析.pdf

w, xuantu.cecm
第45卷第1期
机械工程学报
Vol45 No.1
2009年1月
OURNAL OF MECHANICAL ENGINEERING
DOI;10,3901/JME.2009,01.073
声空化强化沸腾换热的试验观察与分析
孙宝芝姜任秋准秀兰2刘登演
(1.哈尔滨T程大学动力与能源工程学院哈尔滨150001
2.中国科学院工程热物理研究所北京100080
摘要:以乙醇为T作液体,对声空化作用下直径为20mn的水平铜管的沸腾传热进行试验研究。试验中对空化强度及超声
換能棒和试件间的聞离进行測定。试验研究发现,南空化对过冷沸腾有显著强化作用;在核态沸騰区,声空化树沸腾起始区
域的强化率最大,但是随热流密度的增加,强化率逐渐减小;当热流密度相等时,强化率随空化强度的增加而增大。声空化
引起的液体的观湍动及由于声沖流的存在导致的边界层厚度的滅薄,直接或间接地影响加热表面上气泡胚胎的生成、长大
和脱离
关键词:声空化沸腾换热传熱强化
中图分类号:TK124
Experimental Observation and Analysis of Enhancing Boiling
Heat ransfer with Acoustic Cavitation
SUN Baozhi IANG Renqiu HUAI Xiulan. LIU Dengying
(1. College of Power and Energy Engineering, Harbin Engineering University, Harbin 150001
2. Institute of Engineering Thermophysics, Chinese Academy of Sciences, Beijing 100080)
Abstract: A series of experiments are carried out to make clear the effects of acoustic cavitation on boiling heat transfer from a 20
mm diameter circular copper tube taking alcohol as working liquid. The cavitation intensity and the distance between the bottom of
ultrasonic transducer and the test section are measured in experiments. The experimental research shows that sub-cooled boiling can
be enhanced by acoustic cavitation. In the nucleate boiling region, maximum enhancement rate appears in the initiation region of
boiling heat transfer, but the enhancement rate decreases with the increase of heat flu. The enhancement rate increases along with
the increasc of cavitation intensity when heat flux isn, t changed. Macroscopic turbulence of the liquid caused by ultrasonic cavitation
and decrease of the thickness of boundary layer induced by acoustic shock wave can directly or indirectly infuence bubble formation
and growth and departure on the wall
.ey words: Acoustic cavitation Boiling heat transfer Heat transfer enhancement
许多研究者就超声波对对流传热的影响展开
研究。研究结果2表明,超声波对自然对流传热有
显著强化作用。但是,超声波对沸腾换热的影响,
声空化是指向液体中辐射声波时,在一定压力不同学者看法不-一。 ISAKOFFL-研究了声振动对核
下液体中出现的微小气泡随着声压的变化做脉动、态沸腾换热的影啊,硏究发现怖界热流密度有所增
振荡,或伴随有生长、收缩以致破灭的象。液体加,但沸换热曲线无显著偏移。WONG等断定
声空化的过程是集中声场能量并迅速释放的过超声振动对充分发展核态沸腾没有任何影响
程。近10几年来,声空化及其相关效应的理论价 MARKELS等叫曾报道低频超声对临热流密度有
值和大应用潜力,越来越受到国内、外专家的显著影响,而高频超声对过渡沸騰影响较大
关
最近,PARK等观察到超声削弱了R-113的
饱和核态沸腾,却能強化过冷沸腾。IDA等?研究
家重点基础研究发展计(73计划,C200050和家自然科学了超声波对闫然对流、核态沸腾及膜态沸腾换热的
基金(50376063)資助项日。20080107收到初稿,2008!028收到修改高