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There are several parameters which affects the efficiency of membrane clarification of fruit juices, such as feed temperature, transmembrane pressure (TMP) and feed velocity. Pomegranate juice undergone the clarification process in a microfiltration unit at different feed canal heights (FCH; 0.4, 1.5 and 2 cm) to evaluate its effect on the permeate flux and fouling mechanism. Changes in permeate flux, main fouling mechanism and occurrence time of each fouling mechanism were evaluated. Results showed that increasing the FCH can increase permeate flux, total and irreversible fouling resistances duo to increase the feed volume on the membrane surface which can increase raw material of clarified juice. Also, cake formation was the dominant fouling mechanism in all membrane units; however, it occurs during the early stages of membrane processing at an FCH of 2 cm in contrast with 0.4 cm in which cake was produced at the steady state. PRACTICAL APPLICATIONSConcentration of nonclarified pomegranate juice caused off flavor because of burn large particles on the walls of the evaporator. Microfiltration can be used to clarify pomegranate juice. To increase the efficiency of the clarification process, the feed canal height (FCH) in the flat sheet module was increased. Results showed that the amount of clarified juice can be increased by increasing the FCH. Also, washing the membrane at high velocity can repair its efficiency after juice treatment; because of the cake formation was the main fouling mechanism.

A B S T R A C TBackground and Objectives: Pomegranate juice (PJ) contains large particles that stick to evaporator walls causing off flavors in the concentrate due to burning. Microfiltration is used to clarify PJ. Fouling is a limiting phenomenon that can prevent the industrialization of membrane clarification. Changes in the geometry of the membrane module such as using baffles are useful to decrease this problem. Computational fluid dynamics (CFD) is a powerful numerical tool used in modeling membrane processing. Materials and Methods:The effect of baffle geometry on the efficiency of membrane clarification of pomegranate juice in a flat-sheet module was simulated using computational fluid dynamics (CFD). The geometry of the membrane unit was plotted and meshed with Gambit software, and was solved using FLUENT software. A two-dimensional double-precision method at steady state was selected to simulate the membrane process. The convective terms were discretized with a standard first-order upwind scheme in computational solution. The RNG k-model was used due to its high accuracy in eddy flows with a low Reynolds number. The effects on the process performance of the number of baffles, their angle and the distance between the baffles and the membrane surface were evaluated. Results:The results showed that the configuration with the feed-channel height of 2 cm, the baffle angle of 90 o and the distance between the membrane surface and baffles of 2 mm had maximum permeate flux. Conclusions: Reducing the distance between the baffles and the membrane surface increased the permeate flux due to create an eddy flow near the membrane surface in the flat-sheet module and reduced the total and cakelayer resistances.

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