Comparison analysis of entropy and entransy under various conditions of a hollow fiber membrane humidifier (HFMH)

Abstract

The hollow fiber membrane heat and moisture transfer model is converted equivalently into a series of parallel-plate membranes stacked along the z-axis to simplify the model. A detailed modeling process is described based on the concept of finite difference method. The comparison of experimental values with calculated values ensures the validity of the model. Subsequently, an entransy dissipation model for the heat and moisture transfer process in a hollow fiber membrane humidifier (HFMH) is developed by analogizing heat and moisture conduction to electrical conduction. The variation of heat/moisture transfer capability within the HFMH is investigated from the perspective of “heat/moisture potential energy”. In addition, an entropy generation model for the HFMH is established to study the irreversible losses in the heat and moisture transfer process caused by irreversibility. The performance, entropy generation rate, and entransy dissipation rate of the HFMH under different conditions are comparatively analyzed. It can be found that the heat/moisture transfer performance of the humidifier can be improved by adjusting the operating conditions to increase the heat/moisture transfer driving force. However, the irreversible losses increase due to a higher heat/moisture transfer energy grade. The sensible and latent effectiveness can be enhanced by 20.9%–85.2 %, while the equivalent resistance can be reduced by 16.2%–42.0 % via optimizing the geometry structures and membrane properties. In the hot-dry region, the heat and moisture transfer increase by 25.9%–89.8 %, while the equivalent resistances decrease by 20.8%–66.0 %. In addition, the minimum equivalent resistances correspond to the optimal HFMH performance. The entransy analysis avoids the “paradox” of entropy analysis.