Speaker
Description
Chill down of cryogenic transfer lines is a crucial part of cryogenic propulsion as chill down ensures transfer of single phase fluid to the storage tanks of cryogenic engine as well as also ensures single phase liquid flow during start of the engine. Chill down time depends on several parameters such as length of the pipe, pipe size, orientation, mass flux etc. For all these experiments, outer surface temperature is measured at different axial locations as well as in azimuthal planes. Studies are carried out at different inlet pressures and mass flux to understand the effect of these parameters. Two different pipe sizes are taken to study the effect of variation in diameter, stratification, chill down time and quantity of cryogen required. Different orientations are taken to understand its effect on the chill down time, heat transfer coefficient and critical heat flux for the same inlet pressure and mass flux. Pressure drop is also measured for all these cases and compared with the calculated value for each case. Pipe inner wall temperature, heat transfer coefficient for different pool boiling regimes and critical heat flux are calculated based on measured outer surface temperature history for each case. These results also give an insight for variation of heat transfer coefficient in different flow regimes for same mass flux and inlet pressure for different orientations.
A one dimensional energy conservation equation is solved for transient chill down process considering the constant mass flux and inlet pressure to predict the chill-down time. Temperature variation during chill down obtained from the numerical simulations are compared with the measured temperature history.
Keywords: Cryogenics, Chill down, Heat transfer Coefficient, Critical Heat Flux
