System design and performance assessment of hollow fiber membrane-based humidifier for HVAC applications

Abstract

Recently, hollow-fiber membrane technology has emerged as a clean and energy-efficient humidification system for air-conditioning, utilizing indirect air–water contact. This study proposed a water-to-air cross-flow hollow fiber membrane module, featuring cylindrical shell-and-tube bundles in a rectangular block, as an air humidifier for air-conditioning systems. Two-dimensional heat and mass transfer equations governing water-to-air interactions were numerically solved. Key operating parameters, including inlet water temperature and water flow ratio, and a design parameter, the number of mass transfer units of the membrane (NTUm), were analyzed. A parametric study was conducted to evaluate the effects of these factors on humidifier performance. The simulation results demonstrated that the inlet water temperature (1–48.4 °C) and NTUm (0.15–2.35) ranges required to achieve the target air humidity ratio (0.008–0.011 kg/kg). Furthermore, to achieve performance comparable to isothermal humidification, it is recommended to operate the humidifier with a water temperature in the range of 35.5 –47 °C and NTUm between 0.15 and 0.45.