The design of equipment to carry out humidification and dehumidification operations depends upon the concepts of the direction of the transfer processes and their rates (determined by writing enthalpy) and material balance equations and rate equations by combining these equations into the applicable design equations. In this section, these concepts will be applied to the special conditions surrounding the operation of humidification and dehumidification equipment.
In a dehumidification process, a warm vapor gas mixture is contacted with a cool liquid. Vapor condenses from the gas phase, the gas phase cools, and the liquid is warmed. Both sensible and latent heat are transferred toward the liquid phase. In the normal convention, the gas phase is chosen as the system, and heat and mass-transfer rates and quantities are positive when transfer is toward the gas phase. This sign convention is equivalent to measuring distance in the direction toward the gas phase. Then, heat- and mass-transfer quantities for this physical situation will be negative.
In a water-cooling process, warm water is contacted by a cooler gas-vapor mixture. Mass and heat are transferred toward the gas phase. As a result, the signs of the driving-force terms and transfer rates are positive based upon the convention described above.
Figure
The design of equipment to carry out humidification and dehumidification operations depends upon the concepts of the direction of the transfer processes and their rates (determined by writing enthalpy) and material balance equations and rate equations by combining these equations into the applicable design equations. In this section, these concepts will be applied to the special conditions surrounding the operation of humidification and dehumidification equipment.
In a dehumidification process, a warm vapor gas mixture is contacted with a cool liquid. Vapor condenses from the gas phase, the gas phase cools, and the liquid is warmed. Both sensible and latent heat are transferred toward the liquid phase. In the normal convention, the gas phase is chosen as the system, and heat and mass-transfer rates and quantities are positive when transfer is toward the gas phase. This sign convention is equivalent to measuring distance in the direction toward the gas phase. Then, heat- and mass-transfer quantities for this physical situation will be negative.
In a water-cooling process, warm water is contacted by a cooler gas-vapor mixture. Mass and heat are transferred toward the gas phase. As a result, the signs of the driving-force terms and transfer rates are positive based upon the convention described above.
Figure
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