Liquid temperature gradient estimation for screen channel liquid acquisition device bubble point tests in liquid nitrogen

The LAD screen utilizes surface tension forces in microgravity environments to allow liquid to flow through the screen while blocking vapor ingestion up to a certain pressure differential across the screen. The limiting pressure differential of LAD screen operation prior to bubble breakthrough is known as the bubble point pressure (APBP). Previous cryogenic APBP studies have identified how noncondensable pressurization decreases the interface temperature within the pores of a LAD screen via evaporative cooling and how autogenous pressurization increases the interface temperature within a LAD screen via condensation heating. The temperature gradient in the liquid side boundary layer near the screen caused by these effects has not been previously quantified. This study provides an order of magnitude analysis to show how certain variables can influence the liquid side temperature gradient during APBP tests in liquid nitrogen (LN2) using noncondensable pressurization. Furthermore, cryogenic LN2 APBP data is taken for a 325x2300 Dutch Twill and 200x600 Dutch Twill screen with liquid side temperature measurements collected at varying distances away from the screen using dewar pressures ranging from & SIM; 0 -8 psig ( & SIM; 101.3 -156.5 kPa absolute). It has been shown that measuring the liquid screen side temperature 1/8 & DPRIME;(3.2 mm) away from the screen can result in a liquid side surface tension value that is & SIM; 10 -12.5% lower than the actual surface tension value at the interface for GHe tests in LN2. An empirical correlation is provided based on experimental temperature gradient data to correct historical and future APBP data for the liquid screen side diode placement.

Automated summary

The LAD screen allows liquid to flow while blocking vapor by utilizing surface tension forces in microgravity. This study analyzes the effects of noncondensable pressurization and autogenous pressurization on the temperature gradient in the liquid side boundary layer near the screen during APBP tests. Experimental data is provided for the liquid screen side temperature at varying distances from the screen using different dewar pressures in cryogenic conditions. An empirical correlation is developed to correct APBP data based on the temperature gradient.