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A study on the mechanism of dropwise condensation. 2nd report Condensation coefficient of water at low pressures.

1986; Japan Society Mechanical Engineers; Volume: 52; Issue: 477 Linguagem: Inglês

10.1299/kikaib.52.2214

0387-5016

Shigeo Hatamiya, Hiroaki Tanaka,

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Though an apparent difference in the number density of microscopic drops existed between gold and chromium condenser surfaces used, the heat-transfer coefficient was found to be almost of the same value. Then the distributions of drops by sizes down to 1μm in radius were experimentally determined. For the gold condenser surface on which small drops seemed to be densely populated, the measured drop-size distribution showed a satisfactory agreement with the theoretical prediction in the so-called equilibrium region of small drops. On the other hand, for the chromium surface, the number density of drops smaller than 7μm deviated clealy downward. Integrating the measured drop-size distribution weighted with the substantial condensation rate onto each droplet yields a heat-transfer coefficient, which should coincide with the actually measured one. From the comparison of the data for the both condenser surfaces, it is concluded that the condensation coefficient of water at pressures 1 and 3 kPa is 0.4.