Investigation of Condensing Ice Heat Exchangers for MTSA Technology Development

Metabolic heat regenerated Temperature Swing Adsorption (MTSA) technology is being developed for thermal and carbon dioxide (CO₂) control for a Portable Life Support System (PLSS), as well as water recycling. CO₂ removal and rejection is accomplished by driving a sorbent through a temperature swing starting at below freezing temperatures. The swing is completed by warming the sorbent with a separate condensing ice heat exchanger (CIHX) using metabolic heat from moist ventilation gas. The condensed humidity in the ventilation gas is recycled at the habitat. Designing a heat exchanger to efficiently transfer this energy to the sorbent bed and allow the collection of the water is a challenge since the CIHX will operate in a temperature range from 210 K to 280 K. The ventilation gas moisture will first freeze and then thaw, sometimes existing in three phases simultaneously. Analyses and experimental work is presented that investigates condensing and icing as applied to MTSA to enable higher fidelity modeling and assess the impact of geometry variables on CIHX performance for future CIHX design optimization.