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W A T L O WReference DataHeat Loss Factorsand GraphsHeat Losses at 21°C (70°F) AmbientHow to use the graph for moreaccurate calculationsConvection curve correctionfactors:For losses from Multiply convectiontop surfaces or curve value byfrom horizontal 1.29pipes2000180016001400Convection—Vertical SurfaceCombined Radiation and Convection—Oxidized AluminumRadiation—Black BodyCombined Radiation and Convection—Oxidized SteelHeat Losses from Uninsulated SurfacesFor side surfaces Use convectionand vertical curve directlypipesFor bottomsurfacesMultiplyconvection curvevalue by 0.63Radiation Curve Correction FactorsThe radiation curve shows lossesfrom a perfect blackbody and are notdependent upon position. Commonlyused block materials lose less heatby radiation than a blackbody, socorrection factors are applied. Thesecorrections are the emissivity (e) valueslisted to the right:Total Heat Losses =Radiation losses (curve value times e)+ Convection losses (top)+ Convection losses (sides)+ Convection losses (bottom)= Conduction losses(where applicable)Temperature of Surface—°F120010008006004002000.1 0.2 0.3 0.4 0.6 0.8 1 2 3 4 5 6 7 8 910 20 30 40 5060 80 100Losses—W/in 2Resources and InformationReference Data397