Experimental study of the velocity field in a vortex-flow heat exchanger with isothermal conditions

Abstract

The velocity field in a vortex heat cell was investigated experimentally using laser Doppler velocimetry for a wide range of flow conditions. Experimental results point out the three dimensionality of the exchanger's flow, which is composed into a main vortex flow developing along the side walls. The strength of the flow increases up to a limiting value reached for a Reynolds number ranging between 15,000 and 30,000; a secondary flow, caused by interaction between centrifugal and inertial forces, extends perpendicularly to the main flow and remains Reynolds number dependent. It is composed of multiple counter-rotating structures occurring at the exchanger periphery with low inlet Reynolds numbers, thus reducing the rate of centripetal momentum transfer. With increasing inlet Reynolds number, the secondary flow extends across the whole exchanger radius, thus increasing the rate of mixing of the treated fluid. The appearance of so-called Taylor–Gortler vortices tends to reduce the z- and r-axis vorticity transfer.