The flat tubes are necessary apparatus to design the modern heat exchangers. In this context, a CFD (computational fluid dynamics) study has been achieved to explore the influence of the flat tube size on the heat transfer characteristics in cross-flow over flat tube banks. The calculations are performed with the help of the computer software (Fluent) which is based on the finite volume method to solve the continuity, momentum and energy equations. The numerical investigations are achieved for laminar flow (Reynolds numbers changing from 50 to 800), two dimensional flows and incompressible fluids. Some predicted results are compared with available experimental data of the literature and a satisfactory agreement is observed. The obtained results show a decrease in the heat transfer coefficient with increased size of the flat tube. A new valuable empirical correlation is suggested for the prediction of heat transfer coefficients over a flat tube bank. The proposed correlation may be useful for engineers to predict the heat transfer rates in such devices without requirements of experimental measurements.

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Effects of blower shaped baffles on the fluid dynamics and filtration flux in a membrane tube are numerically explored. Both the staggered and inline arrangements of baffles are studied. The carbonate calcium suspensions with a concentration of 5 g/L were used as a working medium. The efficiency of filtration was determined via the calculation of velocity of fluid particles, wall shear stresses and static pressure. An increase in the shear stresses on the tube surface, as well as a formation of fluid eddies were observed with the presence an array of blower baffles, resulting thus in a significant improvement of the filtration performance. The case of the staggered baffles with pith ratio of L/D = 1 and Re = 15,000 achieved an increase in the filtration flux rate by 42% and 12%, compared with unbaffled and tube with baffle orientation angle of 180°, respectively.