紧凑管束蒸发换热器内水的沸腾强化换热特性

设计了一种新式满液型蒸发换热器,利用水平传热管管束间狭窄受限空间内早期沸腾强化换热机理和同一管束中两管缝隙强化沸腾换热机理,将中小热负荷条件下的自然对流换热转化为充分发展核态沸腾换热,其换热性能大大优于传统的满液型蒸发换热器.对水平传热管管束在受限空间内沸腾强化换热的实验研究表明,这种水平管蒸发换热器具有良好的换热性能;管束距离和传热管在管束中的位置对各个传热管换热特性都有很大影响,且存在着一个最佳管束距离;随着压力增加,受限空间内沸腾强化换热的强化效果显著增强.

Boiling Heat Transfer Enhancement Characteristics of Water on Smooth Tubes in a Compact In-Line Tube Bundle

In desalinization devices and some heat exchangers making use of low-quality heat energy, both wall temperatures and wall heat fluxes of the heated tubes are generally quite low, hence they can not cause boiling in flooded tube-bundle evaporators with common large tube spacing. However, when the tube spacing is very small, the incipient boiling in restricted spaces can occur and results in higher heat transfer than that of pool boiling at the same heat flux. This paper investigated experimentally the effects of tube spacing, positions of tubes and test pressures on the boiling heat transfer of water in restricted spaces of the compact in-line bundles consisting of smooth horizontal tubes. The experimental results show that the tube spacing and tube position have significant effect on the boiling heat transfer in a compact tube bundle. There is an optimum tube spacing, which provides the largest heat transfer coefficient at the same heat flux.