Chapter 15 Steady Heat Conduction3-48 A thin copper plate is sandwiched between two epoxy boards. The error involved in the total thermal resistance of the plate if the thermal contact conductances are ignored is to be determined. Assumptions1Steady operating conditions exist. 2Heat transfer is one-dimensional since the plate is large. 3 Thermal conductivities are constant. PropertiesThe thermal conductivities are given to be k= 386 W/m⋅°C for copper plates and k= 0.26 W/m⋅°C for epoxy boards. The contact conductance at the interface of copper-epoxy layers is given to be hc= 6000 W/m2⋅°C. Analysis The thermal resistances of different layers for unit surface area of 1 m2are C/W00017.0)mC)(1.W/m6000(1122ccontact°=°==cAhRRLkAplate2m(386 W / m. C)(1 m )C/W==°=×°−0 00126 106..RLkAepoxy2m(0.26 W / m. C)(1 m )°=°00050 01923..The total thermal resistance is C/W03914.001923.02106.200017.02226epoxyplatecontacttotal°=×+×+×=++=−RRRRThen the percent error involved in the total thermal resistance of the plate if the thermal contact resistances are
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