Abstract:
Due to design limitations or system upgrade, heat exchangers
are required to operate in the laminar-to-turbulent transition
region in order to achieve a high heat transfer with low pressure
drop. The present research investigates the effect of vertical
upflow with heating on the single-phase heat transfer in the
transitional flow regime of a vertical tube. The experimental
setup consists of a swinging test bench which allows for
horizontal flow and vertical upflow direction under constant heat
flux boundary condition. A smooth circular tube with inner
diameter of 5.1 mm and a heated length of 4.52 m was used as
the test section with water at Prandtl number ranging between 5
to 7 as working fluid. The experiment covers Reynolds number
range of 1 000 to 10 000 at horizontal and vertical orientations
of the test section using a squared-edged inlet geometry. For
fully developed vertical upflow direction, transition is delayed
when compared to horizontal flow direction where the effect of
secondary flow increases the laminar flow heat transfer and
causes transition to occur much earlier. The width of transition
region for vertical tubes is significantly smaller than that of the
horizontal tubes.
Description:
Papers presented at the 13th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, Portoroz, Slovenia on 17-19 July 2017 .
