Pumpless evaporative cooling of actively heated surfaces

In this paper we study the ability of a passive, evaporative pumping system to dissipate thermal energy from a constant heat flux source. For that, an instrumented experimental setup was built wherein a thin, flat porous membrane was placed on top of a circular copper made heater. Evaporation from the membrane continually drew distilled water from a reservoir through the system. The tests aimed to parametrically determine the effect of the heat flux dissipated by the membrane on the evaporation rate, heater temperature, and the suction pressure created by evaporation. The maximum suction pressure can ultimately be used to estimate the maximum pumping height differential between the evaporative surface and the free water surface of the reservoir. The results obtained indicated that there was a direct relationship between the heater power and the evaporation rate, within the range of parameters investigated. Also, the results showed that for a heat flux up to 2220 W/m2, which is more than twice the terrestrial solar irradiation, the heater temperature was roughly 45 °C, 28 °C below the temperature of an equivalent surface cooled purely by natural convection.

► A passive, evaporative pumping system dissipates thermal energy.
► Application to large scale thermal management (i.e., building HVAC assistance).
► Evaporation rate is a function of power and used to lower copper plate temperature.