Experimental Study On Convective Flow Boiling In Mini-channels And Micro-channels

With the wide use in Aero-Space, nucleation engineering and the cooling of the electronics etc, the flow boiling heat transfer in micro-channels and mini-channels has been a hot spot of heat and mass transfer. Flow pattern, heat transfer and pressure drop across the channels had been investigated through experiments.Experiments were conducted with the degassed deionized water driven by the con-stant flow pump which could keep the mass flux (61.9-605kg/m2s) be constant. Two different copper test pieces with a micro-channel of width ranging from 0.5 to 1mm, all with a depth of 1mm, were considered. Flow visualizations, the process of the transition from single phase to two phase and flow pattern, were performed with a high-speed dig-ital video camera while the wall temperature and pressure drop across the channels were simultaneously obtained through the T-type thermocouples located at the bottom of test section and pressure transducers fixed up at inlet and outlet of the channels respectively.Considering the effects of mass flux and channels size on the ONB, the four exist-ing correlations were evaluated with a variety of datas obtained from experiments. The ONB of flow boiling has been analyzed from mechanism. The applicability of the bal-ance mechanism between vapor-liquid interfaces has been proved in the process of flow boiling in mini-channels and micro-channelsA comprehensive flow pattern map has been developed through utilizing nondi-mensional parameters including Ca, Co and Bl. The effects of heat flux, mass flux and channels size on flow pattern have been investigated.The typical flow boiling curve is presented to analyze the relation between channel temperature and heat flux. The effects of mass flux and channel size on local heat transfer coefficient and pressure drop across the channel were analyzed and a new per-spective that the effects of mass flux and channel size on local heat transfer coefficient and pressure drop were dependent on the heat flux has been proposed. And the curves that present the relationship between pressure drop and heat flux were drawn when the inlet water was subcooled.