Flow and Heat Transfer in a Pinched Helical Coil

Abstract

In a laminar flow regime, heat transfer performance of a helical coil is better than straight pipes due to secondary flows. This advantage of helical coil over straight pipe however vanishes for a turbulent flow regime. Recently, a concept of pinched pipe has been proposed to enhance heat transfer in laminar as well as turbulent flow regimes. Here, a combination of these two passive methods of heat transfer augmentation, helical coil and pinching of pipes, (pinched helical coils) is proposed and computationally investigated for its performance in laminar as well as in turbulent flow regimes. Initially, a computational model was developed to solve fully developed flow and heat transfer in helical coils. The method was validated by reproducing published experimental results for a helical coil. The computational model was further used to investigate flow and heat transfer characteristics of a pinched helical coil. The simulations were carried out in laminar and turbulent regimes (Re range of 100–30,000). It was observed that in a turbulent regime, the heat transfer performance of a pinched helical coil is slightly better (10–20%) compared to a normal helical coil. The computational model and results will be useful for devising better passive intensification strategies.

Keywords:

• Pinched helical coil
• Pressure drop
• Heat transfer
• Computational Fluid Dynamics (CFD)

Acknowledgements

Authors are grateful to financial support for this work by CSIR through Indus MAGIC (CSC123) project.