Simultaneous Heat and Mass Transfer in a Wetted Heat Exchanger, Part II: Modeling

An analytical model for a condenser with a wetted surface is developed by applying the governing conservations and rate equations and invoking the heat and mass transfer analogy. The heat exchanger is discretized in both the airflow and refrigerant-flow directions for a cross-flow configuration. Axial conduction along the tube walls is neglected and uniform distribution of water is assumed at the heat exchanger front fin surface. Any water not evaporated in a finite control volume is assumed to flow into the downstream control volume, and the model is applicable for dry, partially wet, or fully wet surface conditions. Mass and energy balances are applied to each discretized volume (node) to examine the local heat and mass transfer. The model is capable of predicting local heat/mass transfer, wetness condition as well as pressure losses throughout the heat exchanger. The physics-based model is developed to handle a variety of operating conditions and heat exchanger geometries. Correlations for pressure drop and heat transfer coefficients can be easily replaced or modified for different air-side configurations. The tube-side analysis can also be easily adapted to accommodate different working fluids or tubeside designs. The general framework of the model is robust and flexible. The model is validated with the experimental data presented in a companion paper, “Simultaneous heat and mass transfer in a wetted heat exchanger, part I: experiments.”