Evaporative Heat Transfer Characteristics in a Vertical Channel with Obstructions

An experimental study of evaporative heat transfer in a vertical channel with obstructions was conducted. Tests that encompass a range of mass fluxes of 37-220 klbm/ft2-s (50-300 kg/m2-s), heat fluxes of 960-8000 Btu/ft2-h (3-25 kW/m2), and inlet qualities of 0.2-0.8 were performed with the working fluid R-134a. For both upward and downward flow, both convective and nucleate boiling were observed. At higher mass fluxes, both flow configurations yield the same heat transfer performance. As mass flux decreases, upward flow has higher heat transfer performance relative to downward flow. The upward flow configuration suppresses nucleate boiling when compared to the downward flow configuration. Upon inspection of the data, there appears to be a discontinuity in heat transfer performance which may be attributed to a flow transition. There are no correlations in the literature that accurately describe the experimental heat transfer data present here.

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