Author(s): Steven F. Daly; Edward W. Kempema
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Abstract: A power plant intake located 1200m offshore of the western coastline of Lake Michigan in 8m water depth experienced 15 blockage events during December 2008 and January 2009. The most likely cause of the blockages was frazil ice co llect ing on intake debris screens. Divercollected video from a January 2008 blockage confirm that this intake is suscept ible to frazil blockage. The majority of blockage events occurred between 2000 and 0600 hours (8pm to 6am) but several occurred in late morning and one at 1600 hours (4pm). Hourly meteorological data covering December 2008 and January 2009 was available from a nearby airport. Hourly lake level informat ion was also available. Air temperatures during blockage events ranged between -2°C and -20°C. Wind speeds varied between 2 and 12 ms-1, the average was 8ms-1. The wind direct ion was exclusively offshore during blockages, blowing from the land onto the water. Lake levels were variable during blockage events but were invariably falling, probably in response to the offshore winds. The hourly heat transfer between the water surface and the atmosphere was estimated based on calculat ions of the sensible, latent, short-wave and long-wave heat transfer. The calculations assumed a surface water temperature of 0°C and ice free condit ions. The heat t ransfer rates and total heat transfer pr ior to and at the time of blockages are described. Implicat ions for predict ing blockage occurrences are discussed.
Year: 2010