Effect of Gravity on Ice-Layer Growth in a Freezable Heat Exchanger

摘要

The effect of gravity on the onset of nucleation and growth rate of the ice layer within a water/ice-phase-change heat exchanger has been experimentally investigated. A compressible bladder within the tube-in-tube heat exchanger provided the room needed for volumetric expansion during the freeze of water to ice without causing structural damage. The pressure drop, water inlet and outlet temperatures, and tube outer wall temperatures were measured, from which the heat transfer rate and onset of ice formation could be determined. By altering the orientation of the water/ice heat exchanger in 1g, it is shown that the onset of freeze is delayed when the water flow is directed downward relative to horizontal and upward flow conditions, thus giving initial insight into the role of gravity in the ice formation process. Characterizing this behavior is important to the development of freeze-tolerant heat exchangers for use in spacecraft thermal control systems.