Flow Visualization and Stream Temperature Measurement of Liquid Hydrogen Line Chill Down Experiments

A thermally representative tank-to-tank transfer line was designed and tested at SMiRF at NASA Glenn to simulate liquid hydrogen transfer from a Low Earth Orbit depot storage tank to a customer receiver tank. The line was equipped with three external skin silicon diode measurements, one internal stream temperature measurement, and a high speed imaging system to view flow profiles as the system chilled down from 250K to LH2 temperatures. Image: Two phase flow video stills correlated with temperature measurements shows the time evolution of chill down. Skin measurements indicate chill down is nearly complete within 20s due to annular flow and liquid layer along wall, but internal stream temperature doesn't bottom out until >140s due to bubbly flow. Majority of chill down is spent in annular and bubbly flow regimes. SD1-3 are successive skin diodes mounted along the transfer line.