General Effects of Operating Variables

Among the operating parameters of a membrane system, the fluid temperature, transmembrane pressure (TMP) and feed concenu ation play important roles in determining the permeate flux. 

Transmembrane pressure. The driving force for membrane permeation is the transmembrane pressure or transmembrane pressure difference 

If the pressure drop along the membrane length is large such that the inlet and outlet pressures p and p2 on the feed side are significantly different, the arithmetic mean should be replaced by the logarithmic mean. 

Tcmpgrature. The effect of operating temperature on the permeate flux is usually significant due to the change of fluid viscosity with temperature. In liquid-phase processing, the permeate flux increases as the temperature increases primarily due to viscosity or solid solubility. Liquid viscosity generally decreases as the temperature increases. Furthermore, the solubility of suspended solids also typically increases with increasing temperature. 

On the contrary, the viscosity of gas at low density increases with increasing temperature. Therefore, as the temperature rises, the gas permeation rate becomes lower. 

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