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Date of Publication:2014-01-01

Journal:哈尔滨工程大学学报

Affiliation of Author(s):能源与动力学院

Issue:12

Page Number:1492-1496

ISSN No.:1006-7043

Abstract:In order to investigate the influence of tube spacing on horizontal tube falling film evaporation, an exper-imental study is conducted on the heat transfer and flow pattern with 19mm out-diameter Al-brass tubes by using water as working fluid.This study focuses on the effect of three different tube spacing on the flow pattern and heat transfer characteristics.The variations of flow patterns with different tube spacing in the range of Re from 35 to 347 were observed and the critical Re numbers of flow pattern transition of the horizontal tube were obtained.The aver-age and local heat transfer coefficients were obtained from the measured temperatures of tube surface and saturated vapor by thermocouples.The local and average heat transfer coefficients are analyzed with the variation of tube spac-ing.The results showed that there is no obvious difference of critical Re number for pattern transition at larger tube spacing, but the critical Re number at small tube spacing will be small for patterns transition from droplet-column to column and column to column-sheet.The average heat transfer coefficient decreases with decreasing of the tube spacing.As the tube spacing is 0.3 times of tube diameter, the average heat transfer coefficient will be not related with the spray density.In addition, the local heat transfer coefficient on the top of the tube peripherally decreases with the decreasing of tube spacing either.

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