Modeling and Simulation of the Drying of Cabin Solid Waste in Long-Term Space Missions

Arquiza, J. M. R. Apollo; Hunter, Jean B.; Morrow, Robert C.; Remiker, Ross

doi:10.4271/2008-01-2194

Cited by 2 publications

(2 citation statements)

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“…As the materials dry, the governing mass transfer resistance switches from external to internal 6 . A transient continuum model for trash drying based on conservation equations for energy and moisture has been reported previously by the authors 5 . In order to simplify this complex process we have represented partial adiabatic drying in the vessel empirically, as a combination of equilibrium adiabatic drying and air bypass as shown in Fig.…”

Section: Model For Drying Efficiency: the Bypass Fractionmentioning

confidence: 99%

“…The water vapor produced can also be recovered by a condenser. A prototype of a closed air-loop, heat-pump dryer and condenser system (DRYER) for astronaut cabin waste has been designed, fabricated, and tested 4,5 . The DRYER consists of a blower, air heater, wet material container, a gravity-independent Porous Membrane Condensing Heat Exchanger(PMCHX), thermoelectric heat pump cooler, and waste heat recovery module.…”

Section: Introductionmentioning

confidence: 99%

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Modeling of a Closed-loop, Forced-convection, Heat-pump Drying System for Space Operations

Arquiza

Hunter

Weinschenk

et al. 2011

41st International Conference on Environmental Systems

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Humans living in space generate wet trash which includes food residues, moist hygiene wipes and wet paper towels. For long-term space missions, these wastes must be treated to control microbial growth and avoid associated health hazards. Recovery of water in the trash will also reduce payload mass and resulting lift costs. These problems are solved by a closed-loop, forced-convection, heat-pump drying system which stops microbial activity by both pasteurization and desiccation, and recovers moisture in a gravity-independent porous media condensing heat exchanger. A computational model of the system consisting of the air heater, dryer vessel, condenser, and thermoelectric heat-pump coolers has been developed. The simulation uses a bypass factor to model drying efficiency and to predict the properties of the humid air leaving the drying vessel. The conservation equations for mass, energy, and fluid flow were applied to the condenser to give a system of partial differential equations that was solved numerically by the finite element method. The thermodynamic efficiency and power load of the thermoelectric cooler and heaters were computed for different dryer and condenser conditions. Simulation values were compared with experimental data to validate the model for various operating conditions at sea-level pressure and unit gravity. The model predicts the system performance, energy use per unit of recovered water, and effectiveness of enthalpy recovery options. This can be used to optimize the performance of the drying system for various space habitat conditions. NomenclatureC p,ave = average heat capacity of moist air c v = concentration of water vapor D v = mass diffusivity of water vapor g = acceleration due to gravity H = humidity ratio k ,ave = average thermal conductivity of moist air p = total pressure R = universal gas constant T = temperature T in = temperature of moist air entering condenser T plate = temperature at surface of plate u = x-component of velocity v = y-component of velocity v in = inlet velocity  = density  = viscosity

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Section: Model For Drying Efficiency: the Bypass Fractionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%