Abstract
In this study, a simplified two-dimensional axisymmetric finite element analysis (FEA) model was developed, using COMSOL Multiphysics® software, to simulate the water vapor separation in a moisture-selective hollow-fiber membrane for the application of air dehumidification in wood drying processes. The membrane material was dense polydimethylsiloxane (PDMS). A single hollow fiber membrane was modelled. The mass and momentum transfer equations were simultaneously solved to compute the water vapor concentration profile in the single hollow fiber membrane. A water vapor removal experiment was conducted by using a lab-scale PDMS hollow fiber membrane module operated at constant temperature of 35 °C. Three operation parameters of air flow rate, vacuum pressure, and initial relative humidity (RH) were set at different levels. The final RH of dehydrated air was collected and converted to water vapor concentration to validate simulated results. The simulated results were fairly consistent with the experimental data. Both experimental and simulated results revealed that the water vapor removal efficiency of the membrane system was affected by air velocity and vacuum pressure. A high water vapor removal performance was achieved at a slow air velocity and high vacuum pressure. Subsequently, the correlation of Sherwood (Sh)–Reynolds (Re)–Schmidt (Sc) numbers of the PDMS membrane was established using the validated model, which is applicable at a constant temperature of 35 °C and vacuum pressure of 77.9 kPa. This study delivers an insight into the mass transport in the moisture-selective dense PDMS hollow fiber membrane-based air dehumidification process, with the aims of providing a useful reference to the scale-up design, process optimization and module development using hollow fiber membrane materials.
Highlights
Fast developing and cutting-edge membrane separation technology has been widely used in environmental remediation, food, chemical, and pharmaceutical industries
We explored the potential application of moisture-selective polydimethylsiloxane (PDMS) membrane in the steam-kiln wood drying process since a considerable amount of water vapor and thermal energy is stored in exhaust air [7]
It was observed that a significant drop of relative humidity (RH) occurred in the first five minutes and the RH remained constant at a lower value
Summary
Fast developing and cutting-edge membrane separation technology has been widely used in environmental remediation, food, chemical, and pharmaceutical industries. We explored the potential application of moisture-selective polydimethylsiloxane (PDMS) membrane in the steam-kiln wood drying process since a considerable amount of water vapor and thermal energy is stored in exhaust air [7]. Recycling and reusing such waste thermal energy would improve the energy efficiency of the kiln-drying process. Compared with a plate-frame membrane module, the hollow-fiber membrane module was chosen due to its compact size and the extremely large surface area per unit volume of the membrane module [2,8]
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