Session: 03-03: Energy Storage Separate from CSP: Thermal, Mechanical, Thermochemical

Paper Number: 130463

130463 - Elastic Wall Deformation of Flexible Microchannels Caused by Inside Condensation Flow 

Abstract: 

Many high-tech fields have put forward the demand for miniaturized and foldable integrated electric devices, which, with increasing requirement in high-efficient thermal management in compact area, has promoted the research on phase change flow in flexible microchannel heat exchangers. Some flexible devices need to work at a specific ambient temperature, such as flexible lithium batteries and flexible fuel cells. Restorative treatment with a new hydrogel skin patch requires heating to the excitation temperature of the drug. Some of the equipment itself needs to have heating or cooling functions, such as deep-sea exploration, aerospace personnel diving suit or space suit which require compact, lightweight and stable heating insulation. These application scenarios put forward requirements for flexible surface temperature regulation.

In this article, the elastic deformation of a flexible microchannel caused by condensation heat transfer of refrigerant FC-72 was experimentally investigated. The microchannel has a rectangular cross-sectional shape with a hydraulic diameter of 0.13 mm. The flow regime was observed by the high speed camera and the deformation of the elastic channel wall thickness was measured using a white light confocal coaxial displacement sensor. The cooling temperature of 15-25 °C and mass flow rate of 220, 250 and 300 kg/(m²·s) were tested. Results showed that the deformation of the elastic wall increased with decreasing cooling temperature and increasing mass flow rate. Surprisingly, the channel wall tended to thicken when sequential bubbles flow through. This phenomenon can be explained by the local fluid pressure decrease caused by condensation strong enough to lead bubble quickly shrinking. In a microchannel, surface tension and the gas-liquid interfacial shear stress dominate the two-phase flow which has been reported in the existing studies. Adding condensation, the elongated bubbles in microchannels shrink as increasing vapor transfers to liquid. This rapid shrinking may leave a temporary vacuum in the liquid slug connecting two adjacent bubbles. In rigid channels, this pressure sudden decrease may pull the upstream bubble to accelerate and downstream bubble to decelerate. While in channels with soft wall, this vacuum pull the flexible wall moving towards inside the channel, which is the wall deformation observed in the experiments. This condensation induced wall thickening is so strong, which indicates the condensation may induce a third force comparative to surface tension or shear stress in micro-scale. Therefore, this wall deformation comes from condensation, which has not been observed previously. The outcomes may support the design and optimization in soft device thermal management.

Presenting Author: Ziqi Liu China University of Petroleum Beijing

Presenting Author Biography: Liu Ziqi is studying in China University of Petroleum ( Beijing ). He is studying for a doctorate in power engineering and engineering thermophysics. The research direction is multiphase flow microchannel phase transition.

Authors:

Ziqi Liu China University of Petroleum Beijing
Ji Wang China University of Petroleum Beijing
Xingtao Li China National Oil and Gas Exploration and Development Co
Shengyang Yu China University of Petroleum Beijing