Heat Transfer and Pressure Drop for Flow Condensation Inside a Vertical Tube

概要

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Experimental data of the condensate film thickness and the local heat transfer coefficient are presented for steam condensing in down flow inside a vertical tube. On the basis of the data obtained, the relations between the condensate film thickness, local heat transfer coefficient, film Reynolds number of condensate and shear stresses at tube wall and vapor-liquid interface are investigated and compared with the theoretical predictions for tubulent and laminar film condensation. A brass tube with an inside diameter of 24 mm was used as the test tube. The ranges of variables covered by this experiment are: 40〜90m/sec for the inlet velocity of steam, 0.2〜0.8 for the exit dryness fraction and 500〜2000 for the condensate film Reynolds number. A prediction is also presented for the thickness of laminar sublayer from the experimental data of local heat transfer coefficient by assuming that the condensate film consists of two layers, a laminar sublayer and a turbulent layer. The result indicates that the laminar sublayer thickness of condensate film is considerably different from that of single phase full tube flow.