Analyses of Cryogenic Propellant Tank Pressurization based upon Experiments and Numerical Simulations
The active-pressurization of cryogenic propellant tanks for the launcher application was analyzed in this study. Therefore, ground experiments, numerical simulations and analytical studies were performed with the following important results: In order to minimize the required pressurant gas mass, a higher pressurant gas temperature is advantageous or the application of helium as pressurant gas. Numerical simulations of the pressurant gas mass using Flow-3D show good agreement to the experimental results. The dominating heat transfer during pressurization appears from the injected pressurant gas to the axial tank walls and the predominant way of phase change during the active-pressurization phase depends on the type of the pressurant gas. After the end of the pressurization phase, a significant pressure drop occurs. A theoretical model is presented for the analytical determination of this pressure drop.
Experiences with Pressurized Discharge of Liquid Oxygen from Large Flight Vehicle Propellant Tanks
Liquid propellant missiles and space vehicles require pressurization of the propellant containers during flight to provide sufficient net positive suction head for the pumps and structural rigidity for the tanks. It is important in this application that the pressurization system be of light weight and that it use a pressurant compatible with the propellant. The problem of determining the pressurant requirements for cryogenic propellants is being studied extensively by various groups in the cryogenics and rocket vehicle field. Mathematical models describing the internal thermodynamics of pressurization systems are being devised for this purpose. Unfortunately, most of the experimental studies are confined to small-model tests, the results of which have to be applied to tank systems several orders larger in capacity.
Condensation heat transfer and pressure drop of refrigerant R-410A flow in a vertical plate heat exchanger
Heat transfer and associated frictional pressure drop in the condensing flow of the ozone friendly refrigerant R-410A in a vertical plate heat exchanger (PHE) are investigated experimentally in the present study. In the experiment two vertical counter flow channels are formed in the exchanger by three plates of commercial geometry with a corrugated sinusoidal shape of a chevron angle of 60°. Downflow of the condensing refrigerant R-410A in one channel releases heat to the upflow of cold water in the other channel. The effects of the refrigerant mass flux, imposed heat flux, system pressure (saturated temperature) and mean vapor quality of R-410A on the measured data are explored in detail. The results indicate that the R-410A condensation heat transfer coefficient and associated frictional pressure drop in the PHE increase almost linearly with the mean vapor quality, but the system pressure only exhibits rather slight effects. Furthermore, increases in the refrigerant mass flux and imposed heat flux result in better condensation heat transfer accompanying with a larger frictional pressure drop. Besides, the imposed heat flux exhibits stronger effects on the heat transfer coefficient and pressure drop than the refrigerant mass flux especially at low refrigerant vapor quality. The friction factor is found to be strongly influenced by the refrigerant mass flux and vapor quality, but is almost independent of the imposed heat flux and saturated pressure. Finally, an empirical correlation for the R-410A condensation heat transfer coefficient in the PHE is proposed. In addition, results for the friction factor are correlated against the Boiling number and equivalent Reynolds number of the two-phase condensing flow.