Bubble Columns for Condensation at High Concentrations of Noncondensable Gas: Heat-Transfer Model and Experiments

Carrier gas based thermodynamic cycles are common in water desalination applications. These cycles often require condensation of water vapor out of the carrier gas stream. As the carrier gas is most likely a noncondensable gas present in very high concentrations (60-95%), a large additional resistance to heat transfer is present. It is proposed to reduce the aforementioned thermal resistance by condensing the vapor-gas mixture in a column of cold liquid rather than on a cold surface using a bubble column heat exchanger. A theoretical predictive model for estimating the heat-transfer rates and new experimental data to validate this model are described. The model is purely physics based without the need for any adjustable parameters, and it is shown to predict heat rates within 0 to -20% of the experimental values. The experiments demonstrate that heat-transfer rates in the proposed device are up to an order magnitude higher than those achieved in existing state-of-the-art dehumidifiers. (C) 2013 American Institute of Chemical Engineers AIChE J, 59: 1780-1790, 2013