Abstract:
This study is focused on numerical analysis of the thermal
behavior within a scraped surface heat exchanger (SSHE) for
threshold fluids (Bingham fluids). An innovative SSHE is
considered which includes helical ribbon, instead of using
scrapers. Heat transfer simulations were carried out by means
of specific CFD code to solve the three dimensional form of
continuity, momentum and energy equations. In this work, the
influence of dimensionless numbers (rotational Reynolds, axial
Reynolds and Oldroyd numbers) on thermal behavior is
studied. Numerical results show that for low axial Reynolds
numbers compared to rotational Reynolds number (Reax/Rer
<1), there is opposition between the axial components of
velocity coming from the flow (ascending components) and
axial components at the helical ribbon due to the mixing effect
(descending components). However, for high axial Reynolds
numbers (Reax/Rer >1), a parabolic-like flow is generated,
indicating low degree of back mixing. Numerical results show
also that an important heated zone was observed near the blades
due to high blades rotating speed. The highest temperatures are
found at the thermal boundary layer periodically disturbed by
the helical ribbon. It appears that increasing the Oldroyd
number produces a slight rise in the temperature field.
Description:
Papers presented to the 12th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, Costa de Sol, Spain on 11-13 July 2016.
