Thermodynamics HW Solutions 619

Thermodynamics HW Solutions 619 - Chapter 7 External Forced...

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Chapter 7 External Forced Convection 7-89 The plumbing system of a plant involves some section of a plastic pipe exposed to the ambient air. The pipe is to be insulated with adequate fiber glass insulation to prevent freezing of water in the pipe. The thickness of insulation that will protect the water from freezing more than 20% under worst conditions is to be determined. Assumptions 1 Heat transfer is transient, but can be treated as steady at average conditions. 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 The water in the pipe is stationary, and its initial temperature is 15 ° C. 5 The thermal contact resistance at the interface is negligible. 6 The convection resistance inside the pipe is negligible. Properties The thermal conductivities are given to be k = 0.16 W/m °C for plastic pipe and k = 0.035 W/m °C for fiberglass insulation. The density and specific heat of water are to be
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This note was uploaded on 01/22/2012 for the course PHY 4803 taught by Professor Dr.danielarenas during the Fall '10 term at UNF.

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