窄缝环形流道内流动传热特性的实验研究

对竖直及水平窄缝环形流道内单相水受迫对流换热进行了实验研究。详细介绍了实验装置和方法。实验结果表明:窄缝环形流道内流动换热的Nu数与普通圆管内公式计算值不同,不能采用传统的圆管内的对流换热模型来计算。窄缝环形流道进行对流换热时,从层流向紊流过渡较普通圆管明显提前。分析了测壁温与分离系数法之间的差别,应用修正的Dittus Boelter公式所计算的窄缝环形流道内的Nu数与实验数据吻合较好。图6参9

Experimental Study on Heat Transfer Characteristics of Flow in a Narrow Annular Duct

An experimental study on forced convection heat transfer of single-phase water in vertical and horizontal narrow annuli was performed. The testing facility and the testing method used are described in detail. Test results show that the heat transferred in a narrow annulus in not the same as that calculated by conventional formulae earmarked for internal flow in round tubes, which therefore shouldn't be used in this case. The transition from laminar to turbulent flow happens markedly earlier than in conventional round tubes. After analyzed the difference between the tube wall temperature measuring method and that of separation coefficients, a modified Dittus-Boelter formula is used to calculate the heat transfer in narrow annular ducts which gives values agreeing quite well with test results. Figs 6 and refs 9.