Effects of Sweep Ratio on High-Pressure Membrane Dehumidifiers Available to Purchase

This study investigates the performance of high-pressure membrane dehumidifiers (MDs) over a wide range of sweep ratios and feed mass flow rates to emulate the operating conditions of the high-pressure section of an air cycle machine (ACM). A previously validated numerical model and experimental data were used to assess dehumidification efficiency, which exhibited asymptotic behavior with increasing sweep ratio. However, discrepancies between the model and experimental results are shown to emerge at higher feed mass flow rates. These discrepancies are likely due to compressible flow effects, which the model does not capture, coupled with flow choking on the sweep side. Additionally, the study reveals that while dehumidification efficiency tends to approach an asymptote, the dew point continues to decrease significantly with increasing sweep ratios and lower feed mass flow rates, underscoring the nonlinear relationship between dew point and humidity ratio. This behavior indicates that system designers must consider not only efficiency metrics but also dew point reductions in optimizing ACM performance. These findings highlight the need for both component-level and system-level considerations in ACM design incorporating MDs, particularly the use of additional membrane capacity, e.g., parallel membrane operation, to achieve lower dew points and improved overall system performance.