A mathematical model based on the Lucas-Washburn equation has been developed to address the relationships between capillary height,capillary radius and heat flux in a capillary loop.The stability criteria at the interface are studied in detail by introducing a small perturbation to the interfaces of the capillary loop.The formulae deduced as a consequence are used to analyze the influence of height of the capillary wick and the stability in a capillary loop undergoing phase changes.
Distribution expressions of total gas pressure and partial water vapor pressure along the channel direction were established based on lumped model by analyzing pressure loss in the channel and gas diffusion in the layer. The mechanism of droplet formation in the flow channel was also analyzed. Effects of the relative humidity, working temperature and stoichiometry on liquid water formation were discussed in detail. Moreover, the force equilibrium equation of the droplet in the flow channel was deduced, and the critical flow velocity for the water droplet removal was also addressed. The experimental results show that the threshold position of the liquid droplet is far from the inlet with the increase of temperature, and it decreases with the increase of the inlet total pressure. The critical flow velocity decreases with the increase of the radius and the working pressure.
