Convective heat transfer for cold tube bundles with ice formations in a stream of water at steady state

Abstract

Experiments were conducted on cold-tube banks subjected to a cross-flow of water. The tubes were internally cooled below the freezing temperature and became enveloped in ice. The resulting ice shapes, which formed on the outside surfaces of the tubes, were allowed to stabilize, and their impact on the total steady-state rate of energy exchange between the tubes and the flowing water was investigated. Both in-line and staggered tube-bank geometries were considered, with tests conducted in the low to moderate Reynolds number range (Re d = 100−2,000) and for cooling-temperature ratio variations of 0.5 < Θ < 8. The ice formations were directly observed and photographed, and the total heat transfer rate for the tube bank was inferred from a simple energy balance on the system. The ice shapes that formed around the tubes were described by one of three distinct categories: ice formutions with no linkage occurring between any adjacent tubes; ice formations with partial linkage of some adjacent tubes; and, for the staggered tube bank, a complete linkage of a majority of the tubes. The experiments showed that the ice formations dramatically affected the convective heat transfer rate of the tube banks (when compared to nonicing tube banks at the same Re d) and that the change in heat transfer rate is dependent on the tube-bank geometry. In the no-link category, the ice formations were found to either increase or decrease the tube-bank heat transfer rate depending on the amount of ice-build accumulation, the staggered configuration showing a greater overall rise with Θ than the in-line geometry. Ice linkage between adjacent tubes was found to be detrimental to the heat transfer rate of the staggered bank; however, the same phenomenon on the in-line tube bank did not seriously impede its heat transfer rate. Correlations expressing the heat transfer behavior of both in-line and staggered tube banks with ice formations at steady state have been developed.