Combined active-passive heat transfer control using slotted fins and oscillation in turbulent flow: the cases of single cylinder and tube banks

TL;DR

This study investigates combined active-passive heat transfer control using slotted fins and oscillation in turbulent flow around cylinders and tube banks, achieving significant drag reduction and heat transfer enhancement through optimized fin design and tube oscillation.

Contribution

It introduces the use of slotted fins combined with tube oscillation to simultaneously reduce drag and enhance heat transfer in turbulent flows, validated by CFD simulations.

Findings

Slotted fins reduce drag coefficient by 23%.

Heat transfer increases up to 2.5 times with slotted fins and oscillation.

Optimal configurations yield 76% increase in Nusselt number.

Abstract

In heat transfer augmenting methods such as radial fins, the heat transfer enhancement commonly leads to the drag force increment. In the present paper, slots are inserted over the fins to simultaneously reduce the drag coefficient. Turbulent convection heat transfer around a cylinder, as well as oscillating bundle of tubes including the slotted radial fins have been investigated. The governing equations are solved in two-dimension utilizing OpenFOAM software based on k-{\omega} SST closure model. The cases with various slot location, slot width, the number of the slots, the fin height, and oscillation frequencies are examined. In all cases, the Reynolds number is taken to be equal to 5000. Presence of three slots on the fins reduces the drag coefficient by 23% and augments the Nusselt number by 76%. In order to enhance the heat transfer from the bundle of tube, oscillation of tubes and utilization of the slotted fins are applied. The optimum situation occurs for a sample with the oscillating third column that shows 3% increment in heat transfer relative to that of the fixed case. This is while adding the slotted fins to the oscillating tube bank increases the heat transfer up to 2.5 times.