沸腾-凝结面间距对沸腾凝结共存相变传热规律的影响

An Experimental Study of the Influences of Boiling-Condensation Surface Spacing on Boiling and Condensation Co-Existing Phase Change Heat Transfer Characteristics

给出了在低热流密度下沸腾-凝结面间距(相变腔高度)对沸腾凝结共存相变传热规律影响的实验研究结果。沸腾工质为去离子水,相变腔由水平朝上且具有薄膜延展面的紫铜沸腾面、抛光且朝下的冷凝面以及玻璃管侧壁面组成。高度为48 mm的相变腔对应充液高度分别为10 mm、14 mm、18 mm、22 mm、26 mm、30 mm和34 mm;高度为18 mm的相变腔对应充液高度分别为6 mm、8 mm、10 mm和12 mm。实验观察和测试结果表明,在所给定的有限空间范围内沸腾和凝结之间存在明显的相互作用,沸腾和凝结之间的这种相互作用及程度是引起传热变化的主要原因。随着液面高度的增加,沸腾和凝结表面传热系数均先增加后减小,同时,在本文研究所涉及的范围内,均存在一个使沸腾和凝结表面传热系数最大的充液高度,这说明沸腾-凝结面距离对沸腾凝结共存相变传热规律的影响具有一定的普遍性。

The experimental results of the influences of the boiling-condensation surface spacing on boiling and condensation co-existing phase change heat transfer characteristics in confined space under low heat flux conditions are presented.The working medium is de-ionized water,the phase change chamber consists of a copper surface with an extended thin film to restrain the edge effect as the boiling surface,a polished cooling cooper surface as the condensation surface and the transparent glass tube as the side wall.The liquid thickness of the confined chamber with a 48 mm spacing is set at 10 mm,14 mm,18 mm,22 mm,26 mm,30 mm and 34 mm,respectively;and the liquid thickness of the confined chamber with a 18 mm spacing is set at 6 mm,8 mm,10 mm and 12 mm,respectively.Experimental observation and results show that the liquid thickness has strong influences on the boiling and condensation inside the chamber,as well as their interactions.The interactions have direct effects on the heat transfer characteristic.The results and observations also disclose that there always exists an optimum water filling amount at which both the boiling and the condensation heat transfer coefficient acquire their maximum value for different spacings.