Turbulent Heat and Mass Transfer Across a Hollow Fiber Membrane Tube Bank in Liquid Desiccant Air Dehumidification

The fluid flow and conjugate heat and mass transfer across a hollow fiber membrane tube bundle used for liquid desiccant air dehumidification are investigated. In this process, humid air flows across the fiber bank and salt solution flows inside the fibers packed in a shell. They exchange heat and moisture through the membranes. To overcome the difficulties in the direct modeling of the whole tube bundle, a representative cell, which comprises of a single fiber, a solution stream inside the fiber, and an air stream flowing across the fiber, is selected as the calculation domain. The liquid flow inside the fibers is assumed to be laminar due to the low Reynolds numbers, while the air flow across the bank is considered to be turbulent as a result from the disturbances from the numerous fibers. The governing equations for fluid flow and heat and mass transfer in the two flows and in the membrane are coupled together and solved numerically with a self-built code. Experimental work on hollow fiber membrane-based liquid desiccant air dehumidification is performed to validate the model. The fundamental data on friction factor, Nusselt and Sherwood numbers on both the shell and the tube sides are then obtained for Re = 300–600.