Chapter 3 Steady Heat Conduction3-153ESteam is produced in copper tubes by heat transferred from another fluid condensing outside the tubes at a high temperature. The rate of heat transfer per foot length of the tube when a 0.01 in thick layer of limestone is formed on the inner and outer surfaces of the tube is to be determined. Assumptions1Heat transfer is steady since there is no indication of any change with time. 2 Heat transfer is one-dimensional since there is thermal symmetry about the centerline and no variation in the axial direction. 3 Thermal properties are constant. 4 Heat transfer coefficients are constant and uniform over the surfaces. PropertiesThe thermal conductivities are given to be k= 223 Btu/h⋅ft⋅°F for copper tubes and k= 1.7 Btu/h⋅ft⋅°F for limestone. Analysis The total thermal resistance of the new heat exchanger is &&().QTTRRQnewtotal,newtotal,newnew4F210Btu/hh. F / Btu=−⎯→⎯=−=−°×=°∞∞12350 2500005
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This note was uploaded on 01/19/2012 for the course PHY 4803 taught by Professor Dr.danielarenas during the Fall '10 term at UNF.