Sealing Strips in Tubular Heat Exchangers

This paper presents design data relating to sealing strips for tubular heat exchangers. Sealing strip shapes, locations, and gap widths (the distance between the sealing strip and the nearest tube) are evaluated as to the pressure drop they create and, more importantly, as to their heat transfer characteristics. Velocity data were collected using a laser-Doppler anemometry system for which the fluid within the test model flow loop was refractive index matched with the pyrex rods that made up the tube bundle. A normalized heat transfer coefficient for each test has been inferred from the local velocity field. Unexpected trends were found in the heat transfer and pressure drop results of the gap width tests. It was concluded that the rectangular sealing strip located at the seventh row with a gap equal to the difference between the tube pitch and the tube diameter was the most effective. The successful application of LDA in the test program introduces a powerful measuring technique for the flow field in and around tube banks. From the measurements, pressure drops and heat transfer coefficients may be deduced. In addition, the technique will prove to be of great value in the field of flow-induced vibrations where detailed velocity data are required.