Heat Transfer Of Single-phase And Two-phase Flow In Vertical Narrow Rectangular Channel

Heat transfer in narrow channel has lots of advantages such as compact structure, low heat transfer temperature difference and high efficiency and so on. Therefore, this new technique of heat transfer enhancement is widely applied to various fields such as microelectronic heat sink, cryogenic industry, chemical industry and aeronautic & astronautic industry, etc. Especially in recent years, extensive attentions have been put on thermal-hydraulic characteristics and mechanism of the single-phase and two-phase flow in narrow channels.Published investigations of narrow channel are mainly focused on experimental research with annular channels, low latent heat work substance both at home and abroad. So far, reports on theoretical investigation are relatively few.In present work, experiments are carried out to investigate the single-phase convection heat transfer and two-phase flow boiling heat transfer of water in different narrow channels. An annular flow model was developed to predict thickness of liquid film and heat transfer of channels. And the heat transfer coefficient predicted by the model is compared with the experiment correlation. The experiment results show that single-phase convection heat transfer in vertical rectangular narrow channels is distinct from conventional tube, commonly used turbulent experience correlation of Dittus-Boelter couldn't be used in narrow channel. A correlation of single-phase convectional heat transfer within the range of the experiment parameter is: Nu = 10.7Re^0.1292Pr^{-1 .1189}w^-0.6382, the errors between the obtained data from this correlation and experiment data are 11.1%. Meanwhile, the results of single-phase convection heat transfer experiment show the heating method has very important effect on heat transfer. Average heat transfer coefficient increases with the increasing heat flux or decreasing mass flux at single heating, average heat transfer coefficient changes monotonously with heat flux or mass flux changing, which attributed the reason to the double heating interacted each other. The results of boiling heat transfer in vertical rectangular narrow channels show that the saturated boiling heat transfer coefficient decreases with increasing inlet pressure and channel gap, increases with heat flux, mass flux and increasing liquid quality within the range of the parameter of current experiment. The performance of saturated flow boiling in narrow rectangular channels differs from other regular channels. Nu = 21.33Re^0.2434Bo^-0.0238Pr^1.0392x^0.7146, which is...