Elastic Wall Deformation of Flexible Microchannels Caused by Inside Condensation Flow

Abstract The elastic deformation of a flexible microchannel caused by condensation heat transfer of refrigerant FC-72 is experimentally investigated. The microchannel has a rectangular cross-sectional shape with a hydraulic diameter of 0.13 mm. The deformation of the elastic channel wall is measured using a white light confocal coaxial displacement sensor. The cooling temperature of 10–40 °C and the mass flow rate of 200 and 300 kg/(m2·s) are tested. The elastic wall deformation increased with decreasing cooling temperature and increasing mass flow rate. Surprisingly, the channel wall tends to thicken when sequential bubbles flow through. This phenomenon can be explained by the local fluid pressure decrease caused by condensation which is strong enough to cause the bubble to shrink quickly. This shrinking may leave a temporary vacuum in the liquid slug connecting two adjacent bubbles. In channels with soft wall, the vacuum pulls the flexible wall moving towards the inside of the channel, which is wall deformation observed in the experiments. Therefore, this wall deformation comes from condensation. The outcomes may support the design and optimization in soft device thermal management.