ISSN オンライン: 2688-7231
ISBN 印刷: 978-1-56700-497-7 (Flash Drive)
ISBN オンライン: 978-1-56700-496-0
Proceedings of the 25th National and 3rd International ISHMT-ASTFE Heat and Mass Transfer Conference (IHMTC-2019)
Numerical Investigations on Flow Regimes in Helical Coil Dry Evaporators
In any refrigeration system, the evaporator is one of the main
components. In dry type (DX) evaporators, part of the heat
transfer area is used for superheating of the refrigerant. The
helical coil heat exchanger is one of the passive heat transfer
enhancement devices. It enhances heat transfer performance
due to the action of centripetal force and secondary flows. In
the present study, DX evaporator of vertical helical coil type
is considered with refrigerant R134a flowing inside the tubes.
As the refrigerant liquid is flowing in the evaporator, it
undergoes phase change, which leads to the formation of
different flow regimes. This phase change phenomenon has
been investigated using the Volume of Fluid (VOF) method
with the help of commercial software ANSYS Fluent 18.1.
This study helps to identify the different flow regimes in DX
helical coil evaporator, which will be advantageous for
estimating the two-phase heat transfer rates and pressure
drops. From the simulation results, it was observed that
bubbly, plug, slug, wavy, and annular flow regimes have
occurred in phase change phenomenon, and the generated
vapour is always pushed towards the inner side of the helical
coil. Effects of heat flux and mass flux on pressure drop and
vapour quality have discussed. It was found that the vapour
quality increases with heat flux and decreases with mass flux.
Pressure drop increases with both heat flux and mass flux.