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?

Elements Of Electromagnetics

7th Edition

ISBN:9780190698614

Author:Sadiku, Matthew N. O.

Publisher:Sadiku, Matthew N. O.

ChapterMA: Math Assessment

Section: Chapter Questions

Problem 1.1MA

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Concept explainers

Work and Heat Transfer

It is generally related to thermal engineering which tells about the use, creation, conversion and transfer of heat energy between the systems. It is also considered that to transfer heat from one source to another, transfer of masses is also required. There are various mechanisms by which, transfer of heat takes place i.e. thermal conduction, convection, radiation or by change of phase. All these mechanisms have their own specific features which sometimes occur simultaneously within the same system.

Question

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.
Tf,1
Given data:
A = 3.6 ft²
₁ = 2.1 inches
₂= 3.6 inches
03 = 1.2 inches
k₁ = 0.42 Btu/hr-ft-°F
k₂ = 0.12 Btu/hr-ft-°F
k3 = 0.092 Btu/hr-ft-°F
Tf1 = 45.1 °F
T₁.2 = 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?
1
2
3
Very Thin
Foil Heater
Tf2

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