Simulations and analyses of experimental data from leaks from high-pressure hydrogen storage systems will require knowledge of the stagnation state time histories and stream properties exiting the orifices.An analytical ideal-gas model based on the ideal gas state equation and a computer program making use of the NIST standard reference database(REFPROP)were developed to model the entire process of leaks from high-pressurized hydrogen gas containers.The results obtained by the two methods agree with each other well.As the gas behavior departs from the ideal gas properties at high pressures,the actual stagnation pressure and temperature decay more rapidly than with the ideal-gas assumption.
Condensation of humid air along a vertical plate was numerically investigated, with the mathematical model built on the full boundary layer equations and the film-wise condensation assumption. The velocity, heat and mass transfer characteristics at the gas-liquid interface were numerical analyzed and the results indicated that it was not reasonable to neglect the condensate film from the point of its thickness only. The condensate film thickness, interface temperature drop and the interface tangential velocity affect the physical fields weakly. However, the subcooling and the interface normal velocity were important factors to be considered before the simplification was made. For higher wall temperature, the advective mass transfer contributed much to the total mass transfer. Therefore, the boundary conditions were the key to judge the rationality of neglecting the condensate film for numerical solutions. The numerical results were checked by comparing with experiments and correlations.
The temperature overshooting phenomenon in one-dimensional nanoscale heat conduction in thin films is studied for various boundary conditions.The results show that when ballistic heat transport strongly affects the heat transport process,temperature overshooting is more likely to occur.A sudden increase of temperature on only one surface of a thin film cannot trigger temperature overshooting,while symmetric boundary temperature perturbations lead to the largest temperature overshooting.Twodimensional heat conduction is also studied in a nanoscale area.The analytic results show that Fourier’s law may severely underestimate the temperatures in nanofilms as well as in nanoareas when temperature overshooting occurs.
