Reynolds-number-dependent entrance bias in temperature polarization of lab-scale membrane distillation
Abstract
Lab-scale membrane distillation (MD) modules are commonly used for membrane characterization and developing empirical heat-transfer correlations. Entrance-induced flow structures can introduce geometry-specific effects into measured temperature polarization (TP) and heat transfer. However, the dependence of these effects on module geometry and flow condition remains unclear. We performed three-dimensional computational fluid dynamics (CFD) simulations of direct contact membrane distillation (DCMD) over inlet Reynolds numbers of ℜin=10-$1000$, focusing on side-chamber length and main-channel height. We discovered that counter-rotating streamwise vortices formed near the main-channel entrance across all geometries, but their downstream persistence increased with ℜin. At lower ℜin, the vortices mostly decayed before mid-channel, while at higher ℜin they persisted farther downstream and produced pronounced spatial variations in TP. Increasing side-chamber length reduced the secondary-flow kinetic energy entering the main channel, and generally strengthened TP, whereas increasing main-channel height reduced the bulk velocity and streamwise kinetic energy, resulting in a thicker thermal boundary layer and stronger TP. For most geometries, the deviation from the straight-channel baseline changed from stronger TP at lower ℜin to weaker TP at higher ℜin. Entrance effects therefore vary in both magnitude and direction with operating condition and cannot be represented by a constant correction across the Reynolds-number range.
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BibTeX
@misc{kim2026reynoldsnumberdependent,
title = {{Reynolds-number-dependent entrance bias in temperature polarization of lab-scale membrane distillation}},
author = {Soyoung Kim and Tiezheng Tong and Yinuo Noah Yao},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2610.20470},
eprint = {2610.20470},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2610.20470},
note = {CC BY-NC-ND 4.0},
}
RIS
TY - UNPB
TI - Reynolds-number-dependent entrance bias in temperature polarization of lab-scale membrane distillation
AU - Soyoung Kim
AU - Tiezheng Tong
AU - Yinuo Noah Yao
PY - 2026
DA - 2026/10/14
PB - arXiv
DO - 10.48550/arxiv.2610.20470
UR - https://arxiv.org/abs/2610.20470
AB - Lab-scale membrane distillation (MD) modules are commonly used for membrane characterization and developing empirical heat-transfer correlations. Entrance-induced flow structures can introduce geometry-specific effects into measured temperature polarization (TP) and heat transfer. However, the dependence of these effects on module geometry and flow condition remains unclear. We performed three-dimensional computational fluid dynamics (CFD) simulations of direct contact membrane distillation (DCMD) over inlet Reynolds numbers of ℜ_in=10-$1000$, focusing on side-chamber length and main-channel height. We discovered that counter-rotating streamwise vortices formed near the main-channel entrance across all geometries, but their downstream persistence increased with ℜ_in. At lower ℜ_in, the vortices mostly decayed before mid-channel, while at higher ℜ_in they persisted farther downstream and produced pronounced spatial variations in TP. Increasing side-chamber length reduced the secondary-flow kinetic energy entering the main channel, and generally strengthened TP, whereas increasing main-channel height reduced the bulk velocity and streamwise kinetic energy, resulting in a thicker thermal boundary layer and stronger TP. For most geometries, the deviation from the straight-channel baseline changed from stronger TP at lower ℜ_in to weaker TP at higher ℜ_in. Entrance effects therefore vary in both magnitude and direction with operating condition and cannot be represented by a constant correction across the Reynolds-number range.
ER -