Modeling of Heat and Mass Transfer in a TEC-Driven Lyophilizer

Dewatering of wet waste during space exploration missions is important for crew safety as it stabilizes the waste. It may also be used to recover water and serve as a preconditioning step for waste compaction. A thermoelectric cooler (TEC)- driven lyophilizer is under development at NASA Ames Research Center for this purpose. It has three major components: (i) an evaporator section where water vapor sublimes from the frozen waste, (ii) a condenser section where this water vapor deposits as ice, and (iii) a TEC section which serves as a heat pump to transfer heat from the condenser to the evaporator. This paper analyses the heat and mass transfer processes in the lyophilizer in an effort to understand the ice formation behavior in the condenser. The analysis is supported by experimental observations of ice formation patterns in two different condenser units. INTRODUCTION This paper describes modeling efforts carried out to develop an energy efficient condenser for a lyophilization system for solid waste dewatering and recovery for space exploration missions. Wet wastes are projected to be a significant issue for these missions [1] and processing of these wastes for resource recovery can reduce overall system mass impacts. For short-term missions, solid waste stabilization and water recovery are desirable but conversion of organic waste to CO