Pressure drop and heat transfer augmentation due to coiled wire inserts during laminar flow of oil inside a horizontal tube

An experimental study on heat transfer and pressure drop of MWCNT–water nano-fluid inside horizontal coiled wire inserted tube

“…It should be noted that the following conditions are considered to present Eqs. (12) and (13). 10; 000bReb20; 000 4:5b Prb6:5 1:70bp=db2:83 0:113be=db0:170…”

“…Chandrasekar et al [11] observed 21.5% heat transfer enhancement with wire coiled insert pitch of 3 for 0.1% of Al 2 O 3 /water nanofluid in a tube under fully developed laminar flow. Akhavan-Behabadi et al [12] studied six coiled wires by using engine oil as test fluid to study the enhancement in heat transfer coefficient inside a horizontal tube. They obtained 2.3 fold enhancement in Nusselt number for the specified coil insert compared to that of the plain tube.…”

Thermal performances of turbulent tubular flows enhanced by ribbed and grooved wire coils

“…In the Re range of 600-850, f remains constant; but the full domain laminar model fails due to the onset of turbulent outbreaks as Re > 850 [18]. Due to the weakened swirling effects caused by raising P/d of the wire coils, f decreases as P/d increases [16,[18][19]. In particular, as the critical Re triggering the laminar-to-turbulent transition in the tube with a twisted tape inserts are above than those of the smooth tube [20]; whereas the wire coil inserts bring forward the critical Re for laminar-to-turbulent transition [16], the HTE comparison between wire coils and twisted tape inserts has shown that wire coils perform better than twisted tapes in the low Re range about 700 6 Re 6 2500 [21][22].…”

“…Twisted tapes [1][2][3][4][5][6][7]20], extended surfaces [8][9][10], inserted meshes [11], displaced elements [12] and coil wires [13][14][15][16][17][18][19][21][22][23][24][25][26][27][28][29] are summarized as the mainstream of passive Heat Transfer Enhancement (HTE) methods in [1][2]. The simple fabrication with low cost, fouling mitigation and expediency for retrofit applications with small additional pressure drops [13][14] serve as the major advantages for wire coils.…”

“…As well as a reconfirmation [24], P/d and e/d were the dominant geometrical parameters characterizing the thermo-hydraulic behavior in the tubes fitted with wire coils [23]. Instead of using the round coil wires [13][14][15][16][17][18][19][21][22][23][24], Gunes et al [25] utilized the equilateral triangular sectioned coil wire which was inserted separately from the tube wall to study the thermal performances at turbulent conditions. This study reported that Nu increased with the increase of Re and wire thickness, but decreased by increasing P/d [25]; while the HTE ratios attributed to the wire coil inserts decreased as Re increased [26].…”