Critical Heat Flux of Boiling Heat Transfer in aModerate Narrow Space

Boiling heat transfer process is analyzed in a moderate narrow space consisted of two horizontal plates.The main difference between this process and the conventional unconfined pool boilillg is the liquidsupply mechanism which is absolutely prevented by the growth of coalescence bubble along with theheated surface in the narrow space. As a result, the macrolayer becomes thinner due to the evaportion of the individual bubbles within the macrolayer during the period of bubble coalescence, with orwithout dryout that depends on both the gap size of narrow space and the size of heated surface. Fora specified size of the heated surface, the initial thickness of the liquid layer has a critical value whichapproaches a constant while the space height is larger than a critical value. The individual bubblebehaviors and tlie heat transfer can be considered as the same as that in the unconfined pool boiling, ifthe space gap is large. However, the individual bubbles do not generate in the last period of the bubblecoalescence and a lower maximum heat fiux will be resulted if the space gap is reduced. In such a case,the macrolayer is dryout.