The effects of capillary grooves on surface wetting and evaporation have been analysed. An attempt has been made to obtain expressions which approximately describe the increase in heat transfer in order to select for given properties and temperature differences a groove of optimum design. For this purpose, it is assumed that the heat transfer mechanism is determined by thermal resistance of the liquid layers inside the grooves. From a numerical evaluation of linearized equations, heat transfer rates have been computed for grooves with triangular, semicircular, and square cross sections.
A wetted-wall column was used to measure liquid flow rates in capillary grooves on vertical surfaces. The test facility contained interchangeable grooved surfaces (2-in. OD) which contacted a liquid reservoir in such a way that the test surfaces were partially wetted by capillary action. The wetted portion was exposed to a forced-convection air stream, so that surface evaporation took place because of the different partial pressures of the vapor at the liquid-vapor interface and at the center of the air stream. All data were obtained in steady-state and nearly isothermal conditions. Experimental results with carbon tetrachloride on brass surfaces were in agreement with approximate predictions, which were computed for evaporative heat transfer and then related to mass transfer by using Reynolds analogy for pipe flow.
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