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Unformatted text preview: Chapter 15 Steady Heat Conduction Critical Radius Of Insulation 383C In a cylindrical pipe or a spherical shell, the additional insulation increases the conduction resistance of insulation, but decreases the convection resistance of the surface because of the increase in the outer surface area. Due to these opposite effects, a critical radius of insulation is defined as the outer radius that provides maximum rate of heat transfer. For a cylindrical layer, it is defined as where k is the thermal conductivity of insulation and h is the external convection heat transfer coefficient. r k cr = / h h 384C It will decrease. 385C Yes, the measurements can be right. If the radius of insulation is less than critical radius of insulation of the pipe, the rate of heat loss will increase. 386C No. 387C For a cylindrical pipe, the critical radius of insulation is defined as r k cr = / . On windy days, the external convection heat transfer coefficient is greater compared to calm days. Therefore critical radius of external convection heat transfer coefficient is greater compared to calm days....
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This note was uploaded on 01/14/2012 for the course PHY 4803 taught by Professor Dr.danielarenas during the Fall '10 term at UNF.
 Fall '10
 Dr.DanielArenas
 Thermodynamics, Resistance, Convection, Mass, Heat

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