19. Steady-state heat transfer occurs in the composite wall shown in the figure. A thin-foil heater is pictured in the figure. A thin-foil heater consists of a very thin wire through which an electric current passes. As the current passes through the wire, Ohmic heating occurs. In theory (not necessarily in practice) the heat is dissipated uniformly across the heater. The heater in the figure below is designed to dissipate thermal energy at a rate of 560.8 Btu/hr. Given data: A = 3.6 ft² ₁ = 2.1 inches = 3.6 inches 3 = 1.2 inches k₁ = 0.42 Btu/hr-ft-ºF k₂ = 0.12 Btu/hr-ft-°F k3 = 0.092 Btu/hr-ft-°F TA Tf.l = 45.1 °F T₁2 = 76.2 °F h₁= 4.3 Btu/hr-ft²-°F h₂=2.7 Btu/hr-ft²-ºF (a) What is the temperature of the heater? (b) What percentage of the total heat dissipated in the heater reaches fluid 2?

19. Steady-state heat transfer occurs in the composite wall shown in the figure. A thin-foil heater is pictured in the figure. A thin-foil heater consists of a very thin wire through which an electric current passes. As the current passes through the wire, Ohmic heating occurs. In theory (not necessarily in practice) the heat is dissipated uniformly across the heater. The heater in the figure below is designed to dissipate thermal energy at a rate of 560.8 Btu/hr. Given data: A = 3.6 ft² ₁ = 2.1 inches = 3.6 inches 3 = 1.2 inches k₁ = 0.42 Btu/hr-ft-ºF k₂ = 0.12 Btu/hr-ft-°F k3 = 0.092 Btu/hr-ft-°F TA Tf.l = 45.1 °F T₁2 = 76.2 °F h₁= 4.3 Btu/hr-ft²-°F h₂=2.7 Btu/hr-ft²-ºF (a) What is the temperature of the heater? (b) What percentage of the total heat dissipated in the heater reaches fluid 2?

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.

Chapter4: Numerical Analysis Of Heat Conduction

Section: Chapter Questions

Problem 4.3DP

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