Quantification of Thermal Energy Delivery to Water-Membrane Interface in Membrane Distillation

Membrane Distillation (MD) is an attractive technology for treatment of high salinity waters (e.g. waste brines, produced water, saline ground waters) that can take advantage of low grade heat or solar thermal energy, reducing its operational costs. However, the MD process performance (i.e. flux, water recovery, and thermal efficiency) which is governed by the heat transfer to the membrane-water interface cannot be directly quantified in experimental systems. Past efforts to quantify energy transport to the water-membrane interface have used thermal transport models that rely on bulk temperature and flow rate measurements, and the inaccuracies from this approach have led to high uncertainty in translating process performance from the bench to commercial scale. Herein, we demonstrate through analysis of literature and experimental data the effect of system size on MD performance, and current limitations in our ability to predict its performance. We present a novel approach that leverages our fundamental understanding of vapor transport to correct existing heat transport correlations and significantly reduce the uncertainty in estimated MD process performance.