Pumping criterion and dynamic measurements of an inverted U-shape heat driven pump using microchannels and miniature check valves

Abstract

We demonstrated an inverted U-shape heat driven pump consisting of a microchannel heat sink, two vertical branches and two miniature check valves. A new criterion, which is governed by the fluid physical properties, the geometry effect and the heat transfer rates at various oscillating stages, was developed. The theory can explain the operating range of the applied heating power. The dynamic measurements with a high speed data acquisition system shows that periodically a full cycle can be subdivided into a short liquid suction stage, a bulk boiling and a fluid discharge stage, followed by a pressure decrease stage with both of the valves closed. The average mass flow rate is small and can be computed by the energy conservation equation. The cycle period is shortened with increasing the applied heating power. The wall temperatures of the microchannel heat sink are oscillating with small amplitudes but they are slightly higher than the saturated temperature of the working fluid by several degrees. Deionized water was selected as the working fluid. Finally a closed loop heat driven pump design incorporating the microchannel heat sink and the condenser fin heat sink is proposed.