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为究明带锯齿的翅片管强化冷凝传热的机理,试制了锯齿翅片管及径向辐射状槽翅片管,以氟利昂F-11为冷凝介质,对上述两种异形翅片管及光滑管进行水平冷凝传热实验.得知这两种异形翅片管的给热系数α,在相同的热流率q下,为光滑管的8～11倍,在相同的冷凝温差△T下,为5～8倍.是普通低螺纹翅片管的1.5～2倍.因而是很有推广价值的传热管.实验结果表明,锯齿翅片管能有效地强化冷凝传热,在于其锯齿扰乱了凝液在沟槽间的流动状况,使凝液从层流向湍流转化.因而α和△T关系不是成简单的线性关系.在低温差下(△T<2℃),凝液呈层流,α值较低.随着△T增大,凝液量增加,并逐渐向湍流转化,因而α值逐渐增大,直至到某一温差下有峰值点(湍流转化点).然后,由于凝液浸没的翅片面积增大,且翅片效率随热流率q增加而降低,故给热系数也随之降低.由于带径向辐射状槽的翅片管的翅片两侧加工有辐射状槽,故能更有效地扰乱凝液的流动,湍流更激烈,因而锯齿翅片管有更高的α值,并显示出更早的湍流转化点.研究了各几何参数对α的影响.翅片距p的影响最大,对氟利昂工质而言,更佳p值为0.6～0.7mm,并研究了p与湍流转化点的关系.翅片增高,α随之增大,但增大比率较小,且耗费材料增加,故适宜的翅片高度h为1.2～1.4mm.
In order to demonstrate the mechanism of the serrated finned tube with enhanced condensation heat transfer, a serrated finned tube and a radial radial finned fin tube were trial-produced. Using freon F-11 as the condensing medium, the above two kinds of deformed finned tubes and smooth The experimental results show that the heat transfer coefficient α of the two kinds of deformed finned tubes is 8 to 11 times that of the smooth tube at the same heat flow rate q, 5 to 8 times, which is 1.5 to 2 times of ordinary low-thread finned tube, thus it is a valuable heat transfer tube.The experimental results show that serrated finned tube can effectively enhance condensation heat transfer, Therefore, the relationship between α and △ T is not a simple linear relationship, and the condensate is laminar at low temperature difference (△ T <2 ℃) α value is lower.As △ T increases, the amount of condensate increases, and gradually transformed into turbulence, so the value of α gradually increases until a temperature difference to a peak point (turbulent transition point.) Then, due to the condensate Immersed fin area increases, and the efficiency of the fin with the heat flow rate q decreases, so the heat coefficient also will be reduced due to radial radial groove with the fins Radial grooves are machined on both sides of the tube fin so the flow of condensate is more effectively disturbed and the turbulent flow is more intense and consequently the serrated finned tube has a higher alpha value and exhibits an earlier turbulent transition point. The influence of each geometric parameter on α was greatest, and the fins had the greatest effect on p, and the better p value was 0.6 ~ 0.7mm for Freon, and the relationship between p and turbulent transition point was also studied. With the increase, but the smaller the rate of increase, and the consumption of materials increased, so the appropriate height of the fin h 1.2 ~ 1.4mm.