Heat transfer from a square tube bank with different hydraulic diameters at unsteady turbulent flow

The purpose of this study is heat transfer from a square tube bank with different hydraulic diameters at unsteady turbulent flow using numerical methods. By placing the smaller cylinders on larger cylinders upstream of a square tube bank, vorticity control of the flow through the cylinders, as well as its effect on drag force, pressure drop and heat transfer have been investigated. By reducing the longitudinal and transverse distance between the cylinders and resizing the smaller cylinders, six different arrangements of tube banks have been created that the comparison has been made with a tube bank of equal tubes. Unsteady turbulent incompressible flow is 40000 Reynolds. The finite volume method and FLUENT software have been used to solve Navier -Stokes and energy equations. The results show that the unequal tubes and reduce of longitudinal distance between them result in significant reduction of drag coefficient and flow Nusselt increase, but little change takes place in pressure drop.