Direct measurement of heat flux from cooling lake thermal imagery

摘要

Laboratory experiments show a linear relationship between the total heat flux from a water surface to air and thestandard deviation of the surface temperature field, a, derived from thermal images of the water surface over a range ofheat fluxes from 400 to 1800 Wm~(-2). Thermal imagery and surface data were collected at two power plant cooling lakesto determine if the laboratory relationship between heat flux and a exists in large heated bodies of water. The heat fluxescomputed from the cooling lake data range from 200 to 1400 Wm~(-2). The linear relationship between a and Q is evidentin the cooling lake data, but it is necessary to apply band pass filtering to the thermal imagery to remove camera artifactsand non-convective thermal gradients. The correlation between a and Q is improved if a correction to the measured σ ismade that accounts for wind speed effects on the thermal convection. Based on more than a thousand cooling lakeimages, the correlation coefficients between σ and Q ranged from about 0.8 to 0.9.