Publikacje

Abstract:

Flow boiling heat transfer of FC-72 in a minichannel oriented vertically and horizontally was discussed where foil with micro- and mini-recesses distributed on one side acts as a microstructured heating surface. The temperature distribution was measured on the external side of the foil using liquid crystals. Flow structures were observed on the microstructured side of the foil, which was in direct contact with the fluid inside the minichannel. Temperatures of the two-dimensional heating surface, local fluid and saturation were measured and the examples of the resulting boiling curves and local transfer coefficient distributions were shown. Heat transfer mechanism was analyzed on the basis of all the experimental data. Simultaneous observations were used to identify flow structures and to plot flow pattern maps. Selected images of two-phase flow patterns were studied to determine void fraction and vapor quality. The influence of the channel spatial orientation and the microstructured surfaces on the issues being investigated was identified to find that spatial orientation had the greater effect. A comparison of experimentally determined total pressure drop with the data obtained from theoretical models shows that all of the predicted results fall within the range of ±30%, but only for the vertical minichannel.

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Heat transfer and pressure drop in minichanels with microstructured surface and various orientation