Water Desalination using Vacuum Membrane Distillation - Essay Example

Of course, it can also be used for water desalination [5]. Vapor migrates from the membrane surface to the permeate side. How this process occurs varies with the different configurations, depending on the feed solution which is treated [3, 11, 16]. All the configurations have advantages and disadvantages, depending on their applications. In Direct Contact Membrane Distillation, for instance, the membrane is in direct contact with the water only during liquid phases. According to classical heat transfer theory, a thermal boundary is formed when liquid is in direct contact with a solid surface when their temperatures differ.

This thermal boundary stays next to the solid surface, where the liquid exhibits its temperature fluctuations. The process of heat and mass transfer illustrates the membrane distillation process, wherein a microporous membrane separates two fluids of differing temperatures (membrane thickness of). The feed temperature decreases from at its bulk to at the membrane’s surface. Accordingly, the permeate temperature increases from at its bulk to at the membrane’s surface. Two thermal boundary layers appear at the feed side (with the thickness of) and the permeate side (with the thickness of) of the membrane respectively, as shown in Fig. 3. where is the mass transfer flux through the membrane and is the latent heat of the volatile component.

Here, is only a small part of the energy transferred through the membrane in the form of latent heat. The temperature difference between the two sides of the membrane also conducts heat through the membrane and the gas that fills the pores with flux, written as The equation illustrates the temperature difference between the two sides of the hydrophobic membrane. Accounting for the vapor pressure difference is illustrated by, which is the driving force for mass transfer through the membrane.

Three mechanisms regulate the mass transfer through the membrane: The mass transfer mechanism