Introduction to Heat Transfer
6th Edition
ISBN: 9780470501962
Author: Frank P. Incropera, David P. DeWitt, Theodore L. Bergman, Adrienne S. Lavine
Publisher: Wiley, John & Sons, Incorporated
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Chapter 7, Problem 7.56P
a.
To determine
The cost of lost heat.
b).
To determine
Savings associated with
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Air enters a 5 cm ID smooth-walled tube at 27°C with an average velocity of 3 m/s. The tube wall has a constant heatflux applied to it, qw = 380 W/m2K. Plot Tb(x) and Tw(x) until Tb reaches 38°C.
Water flows along a tube of diameter d = 6 mm with a velocity w = 0.4 m/s. The temperature of the tube wall t = 50°C. What should the length of the tube be to ensure a water outlet temperature tr2 = 20°C at a water inlet temperature twi = 10°C?
3.0 Consider two cases involving parallel flow of dry air at V=V= 1.5 m/s, T∞=T∞=45°C, and atmospheric pressure over an isothermal plate at Ts=Ts=20°C. In the first case, Rex,c=Rex,c=5 × 105, while in the second case the flow is tripped to a turbulent state at x=x=0 m. At what xx‐location, in m, are the thermal boundary layer thicknesses of the two cases equal? What are the local heat fluxes, in W/m2, at this location for the two cases?
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Introduction to Heat Transfer
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