Laminar flow and heat transfer of water/NDG nanofluid on tube banks with rhombic cross section with different longitudinal arrangements

Abstract

In present numerical study, water/NDG (nitrogen-doped graphene) nanofluid flow in different arrangements of rhombic tube banks is investigated in a two-dimensional space. Water/NDG nanofluid is considered in mass fractions of 0, 1, 2, 4 and 6% and Re numbers of 10, 100 and 450 as cooling fluid. The arrangements of tube banks are considered as ET (equilateral triangle), RS (rotated square) and ES (equal spacing) arrangements. Results revealed that the enhancement of mass fraction causes heat transfer enhancement which is due to the increase in thermal conductivity coefficient of cooling nanofluid compared to base fluid. The increase in Re causes the enhancement of average Nu which is due to better mixture of fluid layers with the enhancement of fluid velocity in higher Re which causes the reduction in temperature gradients among fluid layers away from tubes and homogeneous temperature distribution in these areas. Among investigated arrangements, RS has the highest Nu. Also, ET arrangement, compared to ES arrangement, has higher Nu. In all of the studied arrangements, the increase in Re causes the reduction in friction factor and the maximum values of friction factor are related to RS and ET arrangements, respectively.