A 1-in.-diam, 6-in.-long transite rod (k = 0.56 Btu/(hr ft ?F), = 100 lb/cu ft, c

A 1-in.-diam, 6-in.-long transite rod (k = 0.56 Btu/(hr ft ?F), ρ = 100 lb/cu ft, c = 0.20 Btu/(lb ?F) on the end of a 1-in.-diam wood rod at a uniform temperature of 212?F is suddenly placed into a 60?F, 100 ft./s air stream flowing parallel to the axis of the rod. Estimate the average center line temperature of the transite rod 8 min after cooling starts. Assume radial heat conduction, but include radiation losses, based on an emissivity of 0.90, to black surroundings at air temperature.GIVENTransite rod on the end of a wood rod with air flowing parallel to the axisTransite propertiesThermal conductivity (kt) = 0.56 Btu/(hr ft?F)Density (ρt ) = 100 lb/ft3Specific heat (ct) = 0.20 Btu/(lb?F)Rod diameter (D) = 1 in = 1/12 ftTransite rod length = 6 in = 0.5 ftInitial temperature (To) = 212?F = 672 RAir temperature (T??) = 60?F = 520 RAir speed (U??) = 100 ft/sRod emissivity (ε) = 0.90ASSUMPTIONSRadial heat conduction only ?? neglect end effectsWood rod acts as an insulator and only provides support for the transiteSurroundings behave as a black body at the ambient temperatureConvective heat transfer can be approximated as a flat plateConstant thermal properties of the rod and theair

Transcribed Image Text:

L-0.5 ft Alr U.= 100 fVe T.= 60°F D=1 In Wood Transite