CAJ | 학술논문

对水力直径分别为0.72 mm的矩形扁材多孔管和0.86 mm的圆形扁材多孔管中单相流体换热特性以及流动压降进行了实验研究。流体Re 小于500时，随着热通量的增大，Nu减小；随着Re的增大，热通量对Nu的影响减小，Nu趋于一致。实验结果显示，这些变化是由于入口段效应和共轭效应相互制约的结果。圆形扁材多孔管的Nu高于矩形扁材多孔管的Nu。对于乙醇溶液，低热阻时，入口温度越高，压降随热阻的增大降低的斜率越小，随着热阻值的增大，压降降低速率减小趋于平缓。对水、酒精和丙酮进行了单相对流换热的研究。通过比较发现，3种流体的换热特性并不相同，而且差别很大。在同一热通量和入口温度条件下，相同Re，乙醇的Nu最大，丙酮次之，水的Nu最小。同时测试了不同乙醇浓度水溶液的换热特性，发现随着乙醇浓度的增大，溶液的Nu由基本保持不变到随着Re的增大而增大，并且乙醇浓度越大相邻浓度间的Nu差别越大，出现以上现象的理论原因还有待进一步的研究。
대수력직경분별위0.72 mm적구형편재다공관화0.86 mm적원형편재다공관중단상류체환열특성이급류동압강진행료실험연구。류체Re 소우500시，수착열통량적증대，Nu감소；수착Re적증대，열통량대Nu적영향감소，Nu추우일치。실험결과현시，저사변화시유우입구단효응화공액효응상호제약적결과。원형편재다공관적Nu고우구형편재다공관적Nu。대우을순용액，저열조시，입구온도월고，압강수열조적증대강저적사솔월소，수착열조치적증대，압강강저속솔감소추우평완。대수、주정화병동진행료단상대류환열적연구。통과비교발현，3충류체적환열특성병불상동，이차차별흔대。재동일열통량화입구온도조건하，상동Re，을순적Nu최대，병동차지，수적Nu최소。동시측시료불동을순농도수용액적환열특성，발현수착을순농도적증대，용액적Nu유기본보지불변도수착Re적증대이증대，병차을순농도월대상린농도간적Nu차별월대，출현이상현상적이론원인환유대진일보적연구。
An experiment was performed to study the heat transfer characteristics of liquid flow through two multi-port extruded (MPE) micro-tubes with water, ethanol, acetone and ethanol/water mixtures. The cross-section geometries of two tubes were rectangular (approximate square) and circular, and with hydraulic diameters of 0.72 and 0.86 mm respectively. The results showed that at Reynolds number (Re) below 500, Nusselt number (Nu) decreased with increasing heat flux butNu approached a minimum for increasing heat flux atRe> 500. Experimental results showed that such change was caused by the effect of entrance function and conjugate heat transfer. The experimentalNu of the circular multi-tube was higher than that of rectangular multi-tube. For ethanol, pressure drop decreased dramatically with increasing thermal resistance beginning at a low thermal resistance. Additionally, the higher the inlet temperature, the smaller the slope of pressure drop decrease against thermal resistanc. Further investigations of water, ethanol and acetone were conducted.Nuof ethanol were highest and thoseof water were the lowest among three solutions with the same heat flux and inlet temperature. Experiments of rectangular multi-tube, with different mixing ratios of ethanol/water showed that the trend ofNu againstRe remained unchanged at low ethanol concentration. Furthermore, the higher the ethanol concentration, the faster the growth rate ofNu againstReand the greater theNu difference between adjacent concentrations. Theoretical reasons for this remains to be further studied.