Development of a heat-driven pulse pump for spacecraft applications

The basic concept for the heat driven pulse pump (HDPP) is to use the fluid itself to create the pumping pressure head. The pump consists of a grooved cylinder, two check valves (one on the inlet and one on the outlet), a wick, and strip heaters. Three pumps are installed in parallel to provide continuous operation. For specified time, power is applied to a pump, and the liquid in the pump vaporizes, creating a pressure head exceeding the pressure drop in the system. This pressure head forces the liquid in the cylinder to be pushed out through the wick past the outlet check valve. As the liquid in the cylinder is displaced, the liquid in the grooves is wicked towards the heater and sustains vaporization until the heater is turned off. As the next pump in the series is heated, it forces the displaced liquid into the other previously emptied pump(s). A series of tests were made with heater powers from 30 to 70 Watts and with a timing sequence of 20 seconds. Each pump would be on for 20 seconds and off for 40 seconds with no overlapping. As one pump would empty, the other two would be filling. The flow rate generated by the three pumps in parallel would cycle up and down with the magnitude depending on heater power. For test periods of 30 minutes, the average flow rate varied from 5 grams/minute at 30 W to 71 g/m at 70 W. There are still a number of tests that need to be made to determine how well it will operate to meet actual spacecraft applications.