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本文主要研究了制冷剂R134a.在水平矩形(截面为1 mm×1 mm)微槽道内的流动沸腾换热特性。通过可视化手段观察到流动沸腾过程中的流型变化。同时得到了质量流速在60~1100 kg/(m~2s)、热流密度在33~120 kW/m~2时的流动沸腾换热系数,并对R134a的沸腾曲线作了讨论。通过可视化结果,发现了从泡状流到干涸流的7种流型。换热系数随着热流密度的增加而增加,干涸流的出现会导致换热系数迅速减小。核态沸腾传热在受限气泡到弹状流阶段得到增强。在搅混-环状流到环状流阶段,R134a的传热系数稳定在一个较高的值。此外,质量流速越大,CHF值越高。
In this paper, we mainly study the flow boiling heat transfer characteristics of refrigerant R134a in a micro-channel with a horizontal rectangle (1 mm × 1 mm section). Flow pattern changes during flow boiling were observed visually. At the same time, the flow boiling heat transfer coefficients of mass flow rate at 60 ~ 1100 kg / (m ~ 2s) and heat flux at 33 ~ 120 kW / m ~ 2 were obtained. The boiling curve of R134a was also discussed. From the visualization results, seven patterns of flow from bubble to dry flow were found. The heat transfer coefficient increases with the increase of heat flux, and the appearance of dry flow will lead to the rapid decrease of heat transfer coefficient. Nucleate boiling heat transfer is enhanced at the stage of confined bubbles to slug flow. The heat transfer coefficient of R134a stabilized at a higher value during the mixing-annular flow to the annular flow. In addition, the higher the mass flow rate, the higher the CHF value.