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The dual membrane gas trap filter is utilized in the internal thermal control system (ITCS) as part of the pump package assembly to remove non-condensed gases from the ITCS coolant. This improves pump performance and prevents pump cavitation. The gas trap also provides the capability to vent air that is Ingested into the ITCS during routine maintenance and replacement of the International Space Station (ISS) system orbital replacement units. The gas trap is composed of two types of membranes that are formed into a cylindrical module and then encased within a titanium housing. The non-condensed gas that is captured is then allowed to escape through a vent tube in the gas trap housing.

The Internal thermal control system (ITCS) for the International Space Station Alpha (ISSA) employs a dual-membrane gas trap to remove and vent noncondensed gases entrained in the water-cooling loop. The removal of noncondensed gas bubbles is significant because the gases impede the performance of the centrifugal pump, interfere with the coolant flow, and affect instrumentation readings. The gas trap utilizes hydrophobic and hydrophilic membrane tube pairs to vent separated gases to ambient. Bench-top tests of the current configuration have demonstrated removal of nitrogen at concentrations up to 8 percent by volume at a 3000 lbm/hr water flow rate. Optimization studies to maximize the removal of noncondensed gases from the water-cooling loop with minimal pressure drop have been performed to determine the ideal membrane configuration. The flight test design uses one hydrophobic hollow fiber per membrane tube pair to minimize water vapor loss.

A gas trap is being developed for use in the internal thermal control system (ITCS) of Space Station Freedom. The function of the gas trap is to remove and vent noncondensed gases (NCG) that may be entrained in the ITCS water loop. Noncondensed gas bubbles in excessive concentrations can cause the performance of the centrifugal pump to degrade, block coolant flow in remote components, and cause inaccuracies in instrumentation readings. A design has been created utilizing polypropylene hydrophobic and nylon hydrophilic membranes. The hydrophobic membrane allows gas transfer from the water/gas mixture across the membrane to ambient, and blocks liquid flow at the expected ITCS pressure levels. The hydrophilic membrane permits ITCS water to flow through the membrane, and blocks noncondensed gas at the expected water pressure differential. The water leaving the hydrophilic membrane is degassed and exits from the gas trap.