5. Conclusion
Heat transfer enhancement in a double pipe heat exchanger
made of corrugated outer and inner tubewas reported in this paper.
The main scope of the present study was to compare a double pipe
heat exchanger made of corrugated inner tube and smooth outer
tube with a double pipe heat exchanger made of corrugated inner
tube and corrugated outer tube. Besides, new various arrangements
of convex and concave corrugated tube were investigated. The results
of this study were provided as Nusselt number, friction factor,
effectiveness and thermal performance factor. Findings indicated
that the use of corrugated tubes is advantageous to enhance the
Nusselt number and performance of heat exchanger. Arrangement
type of corrugated tubes (concave and convex) had significant effect
on thermal and frictional characteristics. Depending on arrangement type and Reynolds number, the use of corrugated tube
as the inner tube of the double pipe heat exchanger increased the
Nusselt number and friction factor about 10e52% and 150e190%
respectively. When both of the inner and outer tubes were corrugated,
the Nusselt number and friction factor increased about
23e117% and 200e254%.