Thermal characterization of turbulent tube flows over diamond-shaped elements in tandem

On the role of inserts in forced convection heat transfer augmentation

“…With the incorporation of insert, the friction factor experimental results coincide with those of the plain channel. It was observed in some of the previous studies that the friction factor with insert is higher than that of a plain channel [9,[36][37][38][39][40]. The present results are distinct due to the fact that the insert is placed upstream of the test section and the turbulent flow is hydrodynamically fully developed before entering the test section.…”

“…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.…”

Numerical Investigation of Heat Transfer Enhancement in a Circular Tube with Rectangular Opened Rings

“…Heat transfer enhancement techniques play a vital role for laminar flow heat transfer since the heat transfer coefficients are generally low for laminar flow in plain tubes [5,9,31,32,42]. The heat transfer rate can be improved by introducing a disturbance in the fluid flow, which can be achieved by with the twisted tape/turbulator insert in circular tube.…”

“…Smith Eiamsa-ard and Pongjet Promvonge [9] have been conducted the experiments to investigate the heat transfer and friction factor characteristics of the fully developed turbulent Shashank S. Choudhari and S.G. Taji [10] have been studied the experimental investigation of the heat transfer and friction factor characteristics of a double pipe heat exchanger fitted with coil wire insert made up of three different material as copper, aluminum and stainless steel and different pitches for Reynolds number in range of 4000-13000.…”