Exergetic Relationship between the Thermal Properties of Direct Contact Membrane Distillation
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Direct contact membrane distillation (DCMD) is a process that has shown promise within the field of desalination due to its less energy intensive methods and widespread applications. DCMD is a thermally driven microfiltration separation process that operates on the principle of vapor-liquid equilibrium conditions where heat and mass transfer occur simultaneously. Fundamentally, DCMD is based on a porous hydrophobic membrane separating the hot solution (feed) from the cold solution (permeate) where desalinated water condenses. The temperatures at the membrane interface determine the vapor pressure difference across the membrane. Molecular simulation has been used to identify trends between the various parameters of the distillation process by holding one property constant to study the effect on the other components of the system. However, DCMD still requires more concentrated research to determine what is required of all vital system components to produce an ideal and maximized output. In this work, a direct simulation Monte Carlo analysis is employed to investigate how the exergy of the system relates to other key thermal properties, namely, the temperature polarization coefficient and the thermal efficiency, as other parameters are changed, such as feed temperature, flow speed, and membrane porosity. Through molecular simulation, phase equilibrium was 1 2 reached by calculating the chemical potential at the membrane interface and the entropy of the system was found. Since exergy is a function of entropy, enthalpy, and temperature, the amount of useful work was calculated. Finally, exergy was compared to the TPC and TE as the flow rate and porosity was varied. We demonstrate that with these exergy calculations and the thermal relationship between microscopic and macroscopic scales, a probabilistic range for all parameters will improve future experimental work.
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Perdue, Dani Monique. "Exergetic Relationship between the Thermal Properties of Direct Contact Membrane Distillation." (2018) Master’s Thesis, Rice University. https://hdl.handle.net/1911/105921.