Modeling and experimental validation of direct contact crossflow packed beds condenser used in HDH desalination systems

Humidification and dehumidification (HDH) desalination systems are alternatives to reverse osmosis desalina-tion systems, especially for high salinity waters. A HDH system is essentially equipped with a humidifier (also called as evaporator) for air to pick up vapor from saline water, a dehumidifier (also called as condenser) to produce freshwater, and a heating source. HDH systems based on direct contact packed beds heat exchangers have remarkably lower costs than traditional HDH systems due to their inexpensive materials and simple con-figurations. This paper specifically focuses on direct contact crossflow packed beds condensers, in which cooling water vertically drips through the packed beds, directly contacting the horizontal air-vapor flow. A two-dimensional mathematical model that solves for the enthalpy values of the working fluids is proposed in this paper, and the PDEs are solved using finite differences. To validate the model, an experimental condenser was built and tested. Water temperatures inside the test section at twenty-nine locations were measured, as well as the air vapor temperatures of five locations at the outlet. The measured water and air-vapor temperatures agree with the simulation results with less than 10 % error in most of the compared domain.

Automated summary

Humidification and dehumidification (HDH) desalination systems provide a cost-effective alternative for high salinity waters. This study focuses on direct contact crossflow packed beds condensers in HDH systems. A mathematical model is proposed to solve for the enthalpy values of the working fluids, and the model is validated with experimental data. The results show good agreement between the measured and simulated temperatures.