title: Water cycle and its management for plant habitats at reduced pressures.
abstract: Experimental and mathematical models were developed for describing and testing temperature and humidity parameters for plant production in bioregenerative life support systems. A factor was included for analyzing systems operating at low (10-101.3 kPa) pressure to reduce gas leakage and structural mass (e.g., inflatable greenhouses for space application). The expected close relationship between temperature and relative humidity was observed, along with the importance of heat exchanger coil temperature and air circulation rate. The presence of plants in closed habitats results in increased water flux through the system. Changes in pressure affect gas diffusion rates and surface boundary layers, and change convective transfer capabilities and water evaporation rates. A consistent observation from studies with plants at reduced pressures is increased evapotranspiration rates, even at constant vapor pressure deficits. This suggests that plant water status is a critical factor for managing low-pressure production systems. The approach suggested should help space mission planners design artificial environments in closed habitats.
authors.affiliation: University of Florida, Agricultural and Biological Engineering Department, Gainesville, FL 32611-0570, USA. vrygalov@aero.space.edu
authors.forename: Vadim Y
authors.initials: VY
authors.lastname: Rygalov
authors.forename: Philip A
authors.initials: PA
authors.lastname: Fowler
authors.forename: Raymond M
authors.initials: RM
authors.lastname: Wheeler
authors.forename: Ray A
authors.initials: RA
authors.lastname: Bucklin
mesh_terms: D001274:Atmospheric Pressure; D018504:Ecological Systems, Closed; D006813:Humidity; D008021:Life Support Systems; D008962:Models, Theoretical; D018526:Plant Transpiration / Q000502:physiology*; D010944:Plants; D013026:Space Flight; D013696:Temperature; D014867:Water / Q000737:chemistry*; D014893:Weightlessness
chemical_list: D014867:Water