Heat Transfer from Water Flowing Through a Chilled-Bed Open Channel

摘要

Observations and experiments have shown that the transfer is greater for waterflowing over ice than for water flowing over flat plates without melting. The mechanisms that contribute to this increased heat transfer are not completely understood. One possible cause is the density inversion of water at 4 C. In order to investigate this effect on heat transfer, a small open-channel flume was designed and constructed. Experiments were conducted with the flume bed at temperatures slightly above 0 C and at temperatures above 4 C. Bulk water temperatures ranged from 5 to 33 C. Flow data were obtained for 2500 < Re sub H < 100000. At high flow rates (fully developed turbulent flow) heat transfer correlations obtained from these experiments initially showed higher heat transfer rates than those obtained from experiments in larger flumes with ice present. This thought to be due to a difference in velocity profiles caused by the flume width. Once velocity corrections were made to the data, they agreed more closely with experiments from wider flumes. The results indicate that the density inversion of water could account for most of the increased turbulent heat transfer observed between melting and nonmelting systems. The heat transfer data at low flow rates are more qualitative than quantitative due to difficulty in obtaining accurate data. Keywords: Freshwater ice, Heat transfer, Ice covers, Water flows. (jhd)