Abstract:
A higher heat transfer at relatively low energy cost in heat
exchangers used in various engineering applications is essential
towards achieving sustainable energy management in the
industries. This is achievable by enhancing and operating heat
exchangers in the transitional flow regime as compared with the
laminar flow regime. The Nusselt number results of an
experimental investigation on transition in a smooth tube
equipped with twisted tape insert of twist ratio 5 are presented
in this study. This experiment was performed under a constant
heat flux boundary condition of 2 kW⁄m2, using water as
working fluid over a range of 500 ≤ Re ≤ 11 000 and
3.9 ≤ Pr ≤ 6.7. In the enhanced tube transition from laminar to
turbulent occurred at a range of Reynolds numbers of 750 to
2 082, while the transition in smooth tube commenced and
ended at a Reynolds number of 2 700 and 3 187 respectively.
The commencement of the transitional flow regime inside the
tube with twisted tape insert was observed to be earlier as
compared with smooth tube counterpart. The heat transfer
coefficients with twisted tape insert tube are also higher than
the one in smooth tube in the all the flow regimes. This
investigation makes data available for both designers and
researchers of heat exchangers. Particularly in the transitional
flow regime, the heat transfer results are higher at low
Reynolds numbers. This increase is very useful in the industries
where higher heat transfer through heat exchangers at low
energy consumption and cost are required.
Description:
Papers presented to the 12th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, Costa de Sol, Spain on 11-13 July 2016.
