紧凑传热管束受限空间内沸腾强化换热特性

ENHANCEMENT BOILING HEAT TRANSFER OF THE COMPACT HEATED TUBE ARRAIES

海水淡化装置以及太阳能或余热吸收式制冷机中的蒸发换热器，采用管排外降膜式蒸发方式，它具有很多优点，但管间距离较大，以致尺寸较大，供液方式较复杂。将传热管束紧凑排列置于饱和状态液体中，将其变为满液式蒸发换热器，利用传热管束间受限空间内早期沸腾强化机理，将中小热负荷条件下的自然对流换热转化为核沸腾换热，在间隙尺寸适宜时，其换热性能可能优于降膜式蒸发换热器。对紧凑传热管束在受限空间内沸腾强化换热进行实验研究，确认了满液式蒸发换热器具有良好的换热性能，在中小热负荷条件下甚至超过降膜式蒸发换热器。

Falling film evaporating heat exchangers have widely been used for desalinization because of their great heat transfer coefficient.However,a rather large distance between heated tubes is needed for falling liquid flow.In the otherhand,if submerging all heated tubes in saturated liquid then this type is called as full liquid type evaporating heat exchanger.In desalinization devices,heat fluxes of heated tubes are generally quite low and cannot cause water boiling for the case of great distances between tubes.But when the distance between tubes is very small,boiling of restricted spaces can occur and it can make greater heat transfer than falling film.This study investigated experimentally the effects of distances between tubes,locations of tubes and heating status on boiling of restricted spaces in the compact tube arraies.The experimental results are of a reference value to actual engineering devises.