An electric resistance heater is embedded in a long cylinder of diameter 30mm. When water with a temperature of 25 C and velocity of 1m/s flows crosswise over the cylinder, the power per unit length required to maintain the surface at a uniform temperature of 90 C is 28kW/m. When air, also at 25 C, but with a velocity of 10m/s is flowing, the power per unit length required to maintain the same surface temperature is 400W/m. Calculate and compare the convection coefficients for the flows of water and air.

An electric resistance heater is embedded in a long cylinder of diameter 30mm. When water with a temperature of 25 C and velocity of 1m/s flows crosswise over the cylinder, the power per unit length required to maintain the surface at a uniform temperature of 90 C is 28kW/m. When air, also at 25 C, but with a velocity of 10m/s is flowing, the power per unit length required to maintain the same surface temperature is 400W/m. Calculate and compare the convection coefficients for the flows of water and air.

Principles of Heat Transfer (Activate Learning with these NEW titles from Engineering!)

8th Edition

ISBN:9781305387102

Author:Kreith, Frank; Manglik, Raj M.

Publisher:Kreith, Frank; Manglik, Raj M.

Chapter7: Forced Convection Inside Tubes And Ducts

Section: Chapter Questions

Problem 7.4P

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