Local heat transfer and flow distribution in a three-pass industrial heat exchanger

Local heat transfer from single tubes in an industrial-sized, three-pass he at exchanger of the inline tube bundle type was measured. The transversal a nd longitudinal pitches were 1.80 and 1.5D, respectively, the height of eac h pass was 30D and the Reynolds number was 20 000. The measurements were ma de using an electrically heated cylindrical probe of the metallic film type , an instrument normally used in small-scale laboratory setups to gain deta iled information about local heat transfer. The probe was positioned at var ious tube locations and rotated to yield the circumferential variation of t he local heat transfer. Depending on location, local mean heat transfer was less than half or more than twice the nominal mean value. These variations were related to the non-uniform flow distributions present inside the heat exchanger, evidenced by computational fluid dynamics calculations. Also. t he calculated velocities were used with an empirical correlation for the Nu sselt number, and the results agreed very well with the measured values. (C ) 2001 Elsevier Science Ltd. All rights reserved.