新型三维内微肋管水平管内凝结分层流局部换热系数研究

本文研制了一种新型相交换热强化管即三维内微肋管。通过实验得到了三维内微肋管水平管内凝结流型区的类别、分层流区判据以及强化凝结换热的性能．通过分析和逐步回归得到了计算分层流区三维内微肋管水平管内凝结局部换热系数的准则关系式。该式与实验数据在±30％范围内吻合。

三维内微肋管内凝结流型分区及分层波状流换热关联式

Studies of two-phase flow patterns and their transitions during condensation have gained increasing interest because heat transfer characteristics are strongly dependent on flow patterns.Therefore,it is very important to know flow pattern inside a condenser at certain flow conditions and hence to develop heat transfer correlations consistent with the prevailing heat transfer mechanism in each flow pattern. The condensation heat transfer for R134a in two kinds of in-tube three-dimensional (3-D) microfin tubes with different geometries is investigated experimentally.In the range of experimental conditions,six distinguishable flow patterns (annular flow,semi-annular flow,stratified flow,wavy flow,slug flow and plug flow) are recorded by a video camera.The obtained results show that the flow regime transition criterion between annular flow and stratified-wavy flow decreases from Fr equal to 7 to Fr equal to 2 in the Soliman flow regime map.In stratified-wavy flow regime,the average heat transfer coefficients h of the two kinds of in-tube 3-D microfin tubes increase as mass flux increases and the number of microfins in 3-D microfin tube is not the controlling factor of condensation heat transfer performance.The regressed condensation heat transfer correlation from the experimental data of stratified-wavy flow regime is obtained.The disparity of the experimental data is within the limits of ±22%.Combined with the criteria of flow pattern transitions,the correlations can be used for the design of condenser of 3-D microfin tubes.

新型水平三维内微肋管的凝结换热性能

研制了一种新型三维内微肋管。在工质蒸汽进口压力为147、186、226和265kPa下,在凝结液质量流率为33～153kg/(m^2·s)范围内,通过对3种不同微肋尺寸的三维内微肋管的实验,得到了R11在水平管内的凝结换热性能。

R134a在水平三维微肋管内的沸腾换热

实验研究了Ｒ１３４ａ 在水平三维微肋管内的沸腾换热。实验段有效长度３ ．０ ｍ ，内径１２ｍｍ ，工质质量流率１００ ～２７７ ｋｇ／（ｍ２·ｓ） ，热负荷１０ ～２０ ｋＷ／ｍ２ ，饱和压力０．５４ ～０ ．６５ ＭＰａ．实验考察了质量流率，质量干度和饱和压力对换热系数的影响。这种三维内微肋管的换热特性同时与Ｗａｔｔｅｌｅｔ 关系式的预测值进行了比较，得到的换热强化因子在１ ．５ ～２ ．１ 之间。

水蒸汽在水平三维微肋管内的凝结换热及阻力特性

本文以水蒸汽为工质对水平三维微肋管内凝结换热及阻力特性进行了实验研究．与光管和二维管相比，在相同条件下，实验中效果最好的T3管全长平均凝结换热系数分别提高了113％～410％和20％～65％，同时，与二维管相比流动阻力增加较小，最大值不超过6．3％．比较另两种管型（T1，T2管）也证明三维管以较小的流阻增加为代价换取了明显的强化效果．

乙醇三维内微肋热管的传热性能

采用实验研究的方法对三维内微肋热管的强化传热特性进行研究 ,首次报道了以乙醇为工质的三维内微肋热管的传热性能。在实验范围内 ,与光管相比 ,竖直放置时 ,沸腾换热系数可以提高98%～ 190 % ,凝结换热系数可以提高 76 %～ 178%。三维内微肋结构能够同时明显地强化热管的沸腾换热与凝结换热 ,可以有效地减小热管的内热阻。

三维内微肋水热管强化传热实验

首次报道了三维内微肋两相闭式热虹吸管的传热性能.在实验范围内,与光管相比,竖直放置时,平均沸腾换热系数可以提高50%~238%,平均凝结换热系数可以提高100%~222%;小倾角下,平均沸腾换热系数可以提高51%~171%,平均凝结换热系数可以提高42%~170%.三维内微肋结构能够大大强化热管的沸腾换热与凝结换热,有效地减小热管的内热阻.