Heat transfer augmentation by swirl generators inserted into a tube with constant heat flux

On the role of inserts in forced convection heat transfer augmentation

“…This shows that the performance efficiency or the role played by an insert would be the same in different flow regimes based on the fact that the rates of increase in the rate of change of internal energy and heat transfer rate are uniform throughout the transitional and turbulent flow regimes. This is contradictory to the widely held axiom that the role of the insert becomes less significant when Reynolds number is increased whereby the effect induced by the insert on the heat transfer augmentation diminishes in the turbulent flow regime [26,[36][37][38][39][40]. In such case, it would be appropriate to claim that the performance efficiency of a particular insert is identical in different flow regimes based on the evaluation by the rate of change of internal energy, which is the intrinsic total energy of a thermodynamic system.…”

“…However, it is observed that the heat transfer augmentation decreases with Reynolds number, showing that the role of the insert becomes less significant when Reynolds number is increased. Therefore, the effect induced by the insert on the heat transfer augmentation diminishes in the turbulent flow regime [26,[36][37][38][39][40]. The reason behind this is yet to be explained and the present study is aimed to reason out the explanation of this phenomenon based on the physical interpretation of the pertinent parameters involved in the convection heat transfer as we shall discuss later on.…”

“…For the laminar flow regime, the effects of pressure drop and heat transfer of inserts have been investigated [9,[11][12][13][14][15][16][17][18][19]. While most of the previous studies on inserts concerned the turbulent flow regime [20][21][22][23][24][25][26][27][28], such investigations in the transitional flow regime [9,[29][30][31] are relatively scarce. Based on the fact that the two differing mechanisms proposed to explain the role of the insert in forced convection heat transfer enhancement are not clearly apprehended, we empirically analyze this type of problem by characterizing and quantifying the role of an insert in convective heat transfer enhancement.…”

Heat transfer characteristics of dual swirling flame impinging on a flat surface

“…Amount of heat transfer around the stagnation point depends on swirling intensity. Low stagnation point heat fluxes were observed at high swirl intensities due to flow diversion and formation of low velocity area around the stagnation point [17,18,27,28]. Location of peak heat transfer has been shifted away from the stagnation point at increased swirling intensities due to displacement of maximum velocity region away from the jet axis [20,25,29].…”

Heat transfer performance for turbulent flow through a tube using double helical tape inserts

“…Eiamsa-ard and Promvonge [3] studied on the heat transfer characteristics in a tube fitted with helical screwtape with/without core-rod inserts. Kurtbas et al [4] investigated the performances of heat transfer and pressure drop through a tube with different swirl generators for Reynlods number range of 10,000 to 35,000 under a constant heat flux condition. Sarkar et al [5] experimentally studied the heat transfer in turbulent flow through a tube with wire-coil inserts.…”