Warm pressurant gas bubble point experiments for coarse mesh screen channel liquid acquisition devices in liquid nitrogen

The most crucial aspect in screen channel liquid acquisition device (LAD) design is the bubble point pressure (APBP). Historically, results have shown that cryogenic liquid nitrogen (LN2) APBP values can be increased when using helium (GHe) pressurant and decreased when using gaseous nitrogen (GN2) pressurant due to evaporative cooling and condensation heating of the liquid-vapor interface within the screen, respectively. Historical results show a reduction in APBP performance when using warm pressurant, regardless of pressurant gas type. This paper presents warm pressurant APBP tests in LN2 using both GHe and GN2 with pressurant bulk gas temperatures (TGB) between (77 - 160) K for 14 screen types, focusing on coarser meshes. Results from this study show a degradation in GHe APBP but no degradation in GN2 APBP at elevated TGB, the latter of which contradicts historical trends. To help explain these results and to provide a level of physical background to the warm pressurant APBP experiments, a noncondensable pressurant sweat cooling heat and mass transfer model is developed as part of this study. Based on current and historical results, it is concluded that the flow velocities on the gas side of the screen could degrade APBP significantly, especially when warm pressurant is used.

Automated summary

The bubble point pressure (APBP) is the most crucial aspect in screen channel liquid acquisition device (LAD) design. Previous results have shown that using helium (GHe) pressurant can increase APBP values of cryogenic liquid nitrogen (LN2), while using gaseous nitrogen (GN2) pressurant can decrease APBP values. However, using warm pressurant always leads to a reduction in APBP regardless of the pressurant gas type. This study found a degradation in GHe APBP but no degradation in GN2 APBP at elevated pressurant bulk gas temperatures (TGB), contradicting historical trends.