The Properties of Heat Transfer: Chang and Guo

The mechanisms of heat transfer enhancement due to a twisted tape include:

(1) a reduction of a hydraulic diameter causing resulting in an increase of flow velocity and curvature which in turn increases the shear stress at the wall and drives secondary motions,

(2) An increase of fluid mixing between the core and the near-wall flow regions and

(3) An extra heat transfer through thermal contact, probably.

A high cost of energy and material has resulted in an increased effort aimed at producing more efficient heat exchange equipment. The methods of improving convective heat transfer in the tubes of boiler have been widely investigated by many researchers. Coil insert or tape insert is one of the techniques of heat transfer enhancement which categorized under passive technique. In this study, the author will focus on the perforated-type of twisted tape insert on how it affects to the heat transfer enhancement.

Chang and Guo (2012) investigated the properties of heat transfer over developing and developed flow regimes, the pressure drop coefficients and the thermal performance factors (TPF) of tubular flows with the continuous and spiky twist tapes enhanced by perforated, jagged and notched winglets. It is founded that among of the type of twisted tape that have been investigated in the study, the V-notched spiky twisted tape offers the highest heat transfer enhancement impact with favorable TPF performance.

Nanan et. al (2014) experimentally studied perforated helical twisted tape on the heat transfer, friction loss and thermal performance characteristics under a uniform heat flux condition. From the result of the experiment, they have founded that perforated helical twisted tape contributes in the reduction of f...

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...ape insert on heat transfer, friction loss and thermal performance factor characteristics in a round tube. The results shows both heat transfer rate and friction factor in the tube equipped with the peripherally-cut twisted tapes were significantly higher than those in the tube fitted with the typical twisted tape and plain tube, especially in the laminar flow regime.

From all the paper discussed above, it is founded that coil plate inserts in the tubular heat exchange equipment significantly improve the heat transfer rate of the system. However, there is a room of improvement that can be done through this project. Thus, the main focus of this project is to enhance further the heat transfer rate of the system by implementing hole (perforated) on the coil plates. Experimental investigation will be done to come out new results and findings through this technique.