Abstract
The research presents a numerical analysis of laminar fully developed periodic flow and heat transfer in a constant temperature-surfaced circular tube with single twisted tape inserted. The twisted tape is introduced and inserted in the middle of the tested tube. The effects of twisted ratios (y/W = 1, 2, 3, 4, 5 and 6) are presented for Reynolds number (Re) values ranging from Re = 100 to 2000. The SIMPLE algorithm and periodic condition are used in the current study. The computational results are shown in the topology of flow, heat transfer and thermal improvement. It is found that the heat transfer in the circular tube with the twisted tape is more effective than that with no twisted tape inserted. The increase in the y/W ratio leads to decrease in the Nusselt number and friction factor. In addition, the numerical result shows that the reduction in the y/W ratio not only helps to create strong longitudinal vortex flows which enhance heat transfer, but also increase the pressure loss in the tested tube. The computed result reveals that the maximum value of the thermal enhancement factor, TEF is found to be 3.52 for using the twist tapes with y/W = 5 at the highest Reynolds number regime.
Highlights
The increasing necessity for saving energy and material imposed by the diminishing world resources and environmental concerns have prompted the development of more effective heat transfer equipment with improved heat transfer rates
The results present that the decrease in tape width lead to reduce of the pressure loss cause of the increase in flow area in the tested tube
The effects of Reynolds number on flow behavior and heat transfer are presented in terms of streamlines in the transverse planes, contours of temperature and Nux as Fig. 2 and 3
Summary
The increasing necessity for saving energy and material imposed by the diminishing world resources and environmental concerns have prompted the development of more effective heat transfer equipment with improved heat transfer rates. Heat must be transferred either to input energy into the system or to remove the energy produced in the system. Considering the rapid increase in energy demand world-wide, both to reducing energy lost due to ineffective use and enhancement of the energy transfer in the form of heat has become an increasingly important task for the design and operation engineers for such systems. Many techniques have been proposed for the enhancement of the heat transfer rate. These can be classified into two main groups: Passive technique not requiring additional power sources and active technique requiring additional external power inputs. In the case of the passive technique, convection heat transfer from surfaces with attachments of different solid shapes with different geometries, such as baffles, fins, ribs, twist tapes, have been exploited, especially; twisted tape which is widely used in many industries
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