Liquid nitrogen wicking rate experiments for screen channel liquid acquisition devices

Abstract

A screen channel liquid acquisition device (LAD) commonly employed in microgravity space applications uses a finely woven mesh of metal wires along with capillary forces to separate liquid and vapor phases in storage tanks used for propellant transfer. Successful implementation of LADs in flight propulsion systems, particularly for cryogenic systems, depends on analytical design models that are anchored to experimental data. Screens are characterized using parameters such as bubble point pressure, flow-through-screen pressure drop, and wicking rate. The last parameter is especially important to cryogenic LAD systems due to the high propensity for screens to experience evaporation dry out during a mission. This paper presents new experimental wicking rate data for 12 screens covering a wide range of weave types, mesh counts, and metal type with liquid nitrogen (LN2) as a working fluid using a continuous flow method. The horizontal wicking rate data is used to validate the room temperature fluid-based wicking rate model from Grebenyuk and Dreyer (2016) with the gravitational term neglected. Results are examined parametrically, with respect to the effect of wicking rate direction, dewar test pressure, fineness of the screen, shute to warp wire ratio, warp wire orientation, and using cryogenic vs. room temperature fluid. The main takeaway from the current work is that the effective wicking diameter from cryogenic testing lies within experimental uncertainty as wicking diameters from room temperature data for all screens, implying that the room temperature based-model from Grebenyuk and Dreyer (2016) can be used to compute wicking velocities for cryogenic nitrogen for most screen types.