Location
Cocoa Beach, FL
Start Date
7-3-1966 8:00 AM
Description
This paper presents an engineering evaluation of the environmental parameters that affect man's comfort during shirtsleeve operation under conditions of weightlessness. To obtain a minimum weight system, the penalty for providing convective, radiative, and evaporative cooling was established. Mathematical expressions were developed to relate how the total metabolic heat generated by a crew member is divided among radiation, convection, and evaporation. These expressions included the vehicle design parameters — air temperature, relative humidity, air velocity, and mean radiant temperature (MRT), and the crew-oriented parameters of clothing thermal resistance and effective wetted surface area. A basic premise was that the system be designed so that the crew memberT s effective wetted skin is 10 percent of the total area, and the crew member is comfortable under these conditions. For fixed values of the MRT and clothing thermal resistance, the velocity required to provide sufficient convection and evaporation was found as a function of compartment air temperature. The equipment required to dehumidify the compartment and provide air circulation is affected by the relative amounts of heat lost by convection, radiation, and evaporation. Equipment weight and power penalties were established for each mode of heat transfer for fixed values of MRT and clothing thermal resistance and as a function of compartment air temperature. The total vehicle penalty was then obtained.
Before the system design point could be chosen, an examination of the system off-design performance was necessary. This was done by examining how much the effective wetted area increases as the metabolic load increases. The design metabolic loads examined were for maintenance activities and for exercising.
The sensitivity of the optimum design values to changes in crew clothing were investigated by establishing how they would change if the crew were to wear a minimum-thermal-resistance garment. Decreasing the clothing thermal resistance allows the use of lower design air velocities and higher MRT and results in lower vehicle weight penalties. Savings were obtained at the expense of flexibility in operating at off-design conditions.
This study demonstrates that one can find an optimum combination of design parameters of air velocity, air temperature, clothing thermal resistance; and MRT for a wide range of crew activities. Additional work is required to verify the predicted heat and mass transfer coefficients in space vehicles.
Optimization of Crew Comfort System
Cocoa Beach, FL
This paper presents an engineering evaluation of the environmental parameters that affect man's comfort during shirtsleeve operation under conditions of weightlessness. To obtain a minimum weight system, the penalty for providing convective, radiative, and evaporative cooling was established. Mathematical expressions were developed to relate how the total metabolic heat generated by a crew member is divided among radiation, convection, and evaporation. These expressions included the vehicle design parameters — air temperature, relative humidity, air velocity, and mean radiant temperature (MRT), and the crew-oriented parameters of clothing thermal resistance and effective wetted surface area. A basic premise was that the system be designed so that the crew memberT s effective wetted skin is 10 percent of the total area, and the crew member is comfortable under these conditions. For fixed values of the MRT and clothing thermal resistance, the velocity required to provide sufficient convection and evaporation was found as a function of compartment air temperature. The equipment required to dehumidify the compartment and provide air circulation is affected by the relative amounts of heat lost by convection, radiation, and evaporation. Equipment weight and power penalties were established for each mode of heat transfer for fixed values of MRT and clothing thermal resistance and as a function of compartment air temperature. The total vehicle penalty was then obtained.
Before the system design point could be chosen, an examination of the system off-design performance was necessary. This was done by examining how much the effective wetted area increases as the metabolic load increases. The design metabolic loads examined were for maintenance activities and for exercising.
The sensitivity of the optimum design values to changes in crew clothing were investigated by establishing how they would change if the crew were to wear a minimum-thermal-resistance garment. Decreasing the clothing thermal resistance allows the use of lower design air velocities and higher MRT and results in lower vehicle weight penalties. Savings were obtained at the expense of flexibility in operating at off-design conditions.
This study demonstrates that one can find an optimum combination of design parameters of air velocity, air temperature, clothing thermal resistance; and MRT for a wide range of crew activities. Additional work is required to verify the predicted heat and mass transfer coefficients in space vehicles.
