Exergy and entransy analyses in air-conditioning system part 2-Humid air handling process

Humid air handling process is an important component of the air-conditioning system. In the present study, air handling process between air and water or liquid desiccant are investigated from the perspectives of exergy and entransy analyses. Choosing typical inlet air states as examples, exergy destructions ΔEx,des and entransy dissipations ΔEn,dis are represented in the (1-T0/T)-Q diagram and the T-Q diagram respectively. Unmatched coefficient ξ is defined as the index to depict the uniformity of driving force (ΔT or Δω), which is always higher than or equal to 1. Reasons leading to ΔEx,des and ΔEn,dis are then clarified with the help of ξ. It's indicated that dissipations or destruction occurred during the heat and mass transfer processes are mainly due to the limited transfer capability and the unmatched properties. The heat and mass transfer process approaching to the saturation line is recommended between air and water, with an unmatched coefficient approaching to 1 and a least destruction or dissipation resulted from ξ. Case studies are carried out with emphasis on reducing the unmatched exergy destruction. The water is recommended to be heated for humidification rather than the air in the humidifier and similarly the solution should be heated for regeneration, lowering the unmatched exergy destruction. The present research is beneficial for performance optimization of the humid air handling process in the air-conditioning system.