Review on Comparative Study between Straight Tube Heat Exchanger and Helical Coil Heat Exchanger

Abstract

The main purpose of this study is to determine the relative advantage of using a helically coiled heat exchanger over a straight tube heat exchanger. It is found that the heat transfer in helical circular tubes is higher as compared to Straight tube due to their geometrical shape. Helical coils offer advantages over straight tubes due to their compactness and increased heat transfer coefficient. The increased heat transfer coefficients are a consequence of the curvature of the coil, which induces centrifugal forces to act on the moving fluid, resulting in the development of secondary flow. The curvature of the coil governs the centrifugal force while the pitch (or helix angle) influences the torsion to which the fluid is subjected to. The difference in velocity sets-in secondary flows. The fluid particles flowing at the core of the pipe have higher velocities than those flowing near to the pipe wall. Thus the fluid particles flowing close to the tube wall experience a lower centrifugal force than the fluid particles flowing in the tube core. This causes the fluid from the core region to be pushed towards the outer wall. This additional convective transport increases heat transfer and the pressure drop when compared to that in a straight tube.