Drag reducing solutions can reduce turbulent pressure loss by
nearly 90% and can decrease pumping energy requirements and
increase flow rates in fluid flow systems. Unfortunately, drag
reduced flow is accompanied by lower convective heat transfer
coefficients, which is undesirable in district heating and cooling
systems, heated tube bundles for undersea petroleum production,
and other recirculating heat transport systems.
In this study, three different rotating agitators were installed
inside the inner tube of a concentric tube heat exchanger to enhance
heat transfer in a surfactant drag reducing solution. An
earlier mathematical model for heat transfer in scraped surface
heat exchangers was adapted for this application so that the effectiveness
of agitators with different geometries could be compared
quantitatively. In addition, an enhancement efficiency factor was
defined to compare power efficiency with previous methods. It
was found that agitation can increase the inner heat transfer coefficient
to exceed that of pure water; heat transfer reduction compared
to water was reduced from 60% to -20%. In addition, the
enhancement can be more energy-efficient than that of previously
studied static mixers.
Papers presented to the 12th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, Costa de Sol, Spain on 11-13 July 2016.