Phase change analysis of an underwater glider propelled by the ocean's thermal energy

The phase change characteristic of the power source of an underwater glider propelled by the ocean＇s thermal energy is the key factor in glider attitude control. A numerical model has been established based on the enthalpy method to analyze the phase change heat transfer process under convective boundary conditions. Phase change is not an isothermal process, but one that occurs at a range of temperature. The total melting time of the material is very sensitive to the surrounding temperature. When the temperature of the surroundings decreases 8 degrees, the total melting time increases 1.8 times. But variations in surrounding temperature have little effect on the initial temperature of phase change, and the slope of the temperature time history curve remains the same. However, the temperature at which phase change is completed decreases significantly. Our research shows that the phase change process is also affected by container size, boundary conditions, and the power source＇s cross sectional area. Materials stored in 3 cylindrical containers with a diameter of 38ram needed the shortest phase change time. Our conclusions should be helpful in effective design of underwater glider power systems.

Mass transfer analysis for microwave hot in-place recycling of asphalt pavements

In order to realize mass transfer analysis for microwave hot in-place recycling of asphalt pavements, a volume element is established including asphalt mixtures, liquid water and vapor. A mass transfer control model is built by the theory of multiphysics, phase transformation and diffusion. The model contains continuity equation, energy conservation equation, movement equation and vapor diffusion equation. To gain the solution of the mass transfer model, the formulas are simplified to one-dimensional differential equations. And then a mathematical model of boundary conditions is established. The mass transfer velocity and dissipative energy are obtained in different moisture contents through simulation of asphalt pavements recycling. The result indicates that when initial moisture content is certain, mass transfer velocity is almost uniform in depth direction at the same heating time and enertrv absorbed by water i,~ descendino with denletion of moisture.

One-Dimensional Analysis of Melting in an External Artery Heat Pipe

Melting in an external artery heat pipe was observed experimentally in art earth-based system which simulated the micro- or zero-gravity environment in space. The melting process was analyzed with an one-dimensional model. Heat transfer in the heat pipe shell was assumed to be sufficiently greater than in the melting working fluid that temperature variations in the shell could be neglected. Melting of the working fluid was successfully analyzed using the one-dimensional model to track the location of the melting front and to predict the temperature distribution within the fluid. The predictions compared well to both the experimental data and results from a two-dimensional model[1]. The final solid temperature and the melting time are given for various values of the applied heat flux and the radius of the frozen working fluid channel.