Performance and Design of Dehumidifier Wheels

Abstract

A new theoretical model is presented for the performance of dehumidifier wheels. The model is aimed at providing design guidance for manufacturers and selection and operation advice for HVAC system designers. To characterize the performance of dehumidifier wheels, water vapor effectiveness, ∊_w, and water vapor mass ratio, Δw/Δw*, are defined. The theoretical model uses the transient response characteristics of the flow channel in the wheel matrix to predict the base case physical characteristics for fully developed laminar flow through the matrix where the heat transfer characteristics are first decoupled from the water vapor transfer. The simple algebraic equations, deduced for this base case of a dehumidifier wheel water vapor effectiveness, ∊_w, and water vapor mass ratio, Δw/Δw*, show that the mass rate of the supply and regenerator flows should be equal and that both ∊_w and Δw/Δw* go toward zero as the wheel speed decreases to low values. Corrections are made to these base case performance factors, which account for the coupling of the heat and water vapor transfer, as well as other smaller factors caused by entrance, heat conduction, carryover, and flow channel variation effects. It is concluded that more dehumidifier wheel performance data, along with a thorough analysis of uncertainties, will permit researchers to decrease the range of physical factor coefficients used in this model.