Conventional or Direct Membrane Emulsification

The pressure required for this process is determined by two effects. The first one is the pressure drop resulting from the flow of the disperse phase through the pores. It can be estimated by the Hagen-Poiseuille law (Equation 13.1) [8]. The pressure drop, Ap, depends on the viscosity of the disperse phase, p, the diameter and length of the pores, dp and Ip, and the flow velocity, v, in the pores  

The second effect is the capillary pressure. In order to create a new interface at the cylindrical pore opening, the capillary pressure according to Equation (13.2) has to be overcome [8]  

The capillary pressure, pc, depends on the interfacial tension, y, and the contact angle, 5, and it is inversely proportional to the pore diameter, dp. 

By using a pressure above the capillary pressure, a droplet starts to grow and is detached by the shear force of the continuous phase after reaching a critical droplet diameter. 

Among different forces interacting at the droplet in this state, Fy, is dominant, holding the droplet at the pore opening and can be calculated with Equation (13.3) [8]. Fy is determined by the time-dependent interfadal tension, y(t), and the droplet diameter. Since the interfadal tension is influenced by the emulsifier dynamics, droplet detachment can be influenced by the emulsifier used (8)  

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