Dry-out limits of screen wicks vertically pumping against gravity above an acetone pool were determined in evaporation experiments. As the pumping height shortened, the increase in heat input at dry-out became less than that expected from a fully saturated wick layer. The receding of the evaporating boundary into a sublayer of the wick was postulated, based on the fact that the measured thermal resistance across the wick layer decreased as heat input increased. Such a recess seems to terminate at two layers above the heated wall. A new wicking model taking into account the receding of evaporation boundary could predict the experimental dry-out heat inputs within 10 percent.

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