CFD Analysis for Heat Transfer Enhancement inside a Circular Tube with Half-Length Upstream and Half-Length Downstream Twisted Tape

Table 1

The highest recorded heat transfer enhancement level estimated due to each enhancer, (Siddique et al. [3]).

Heat transfer enhancer type	(Heat transfer due presence of the enhancer/heat transfer in absence of the enhancer)
Fins inside tubes	2.0, [4]
Microfins inside tubes	4.0 for laminar, [5]
Porous media	≈12.0 (keff/kf), [6]
Nanofluids	3.5, [7]
Flexible seals	2.0, [8]
Flexible complex seals	3.0, [9]
Vortex generators	2.5, [10]
Protrusions	2.0, [11, 12]
Ultra high thermal conductivity composite materials	6, [13]