Numerical investigation of flow and heat transfer in axially-finned in-line tube banks

Numerical analysis of heat and fluid flow over tube bank heat exchangers with axial fins is performed in this work. Finite volume method is used to solve the governing equations numerically. Simulations are carried out in the range of 400-1500 Reynolds number. To ensure the numerical model reliability, unfinned in-line tube bank is simulated and compared with results from the literature. It is shown that the results are in accordance with the experimental studies in the literature. Heat transfer and pressure loss computations are carried out for four different axial and transversal pitch ratios; namely, $$s_L<^>{\rm{*}} = 3$$sL & lowast;=3 and $$s_T<^>{\rm{*}} = 1.5$$sT & lowast;=1.5, $$s_L<^>{\rm{*}} = 3$$sL & lowast;=3 and $$s_T<^>{\rm{*}} = 2$$sT & lowast;=2, $$s_L<^>{\rm{*}} = 5$$sL & lowast;=5 and $$s_T<^>{\rm{*}} = 1.5$$sT & lowast;=1.5, $$s_L<^>{\rm{*}} = 5$$sL & lowast;=5 and $$s_T<^>{\rm{*}} = 2$$sT & lowast;=2. Air and water are used as working fluids for determined mass flow rates where Prandtl numbers are 0.7 and 7, respectively. Moreover, velocity streamlines and temperature contours along the flow field are given. Effects of axial ($$s_L<^>{\rm{*}}$$sL & lowast;) and transversal ($$s_T<^>{\rm{*}}$$sT & lowast;) pitch ratios and fin lengths on the average Nusselt number and friction factor are also presented in graphical forms. It is found that the maximum average Nusselt number is observed at Re = 1500 for the pitch ratios of $$s_L<^>{\rm{*}} = 5$$sL & lowast;=5 and $$s_T<^>{\rm{*}} = 1.5$$sT & lowast;=1.5 where fin length equals to 2D mm. Besides, adding axial-fins to in-line tube bank results in a decrement in friction factors.