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Thermodynamics HW Solutions 16
Course: PHY 4803, Fall 2010School: UNF
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1 Chapter Basics of Heat Transfer 1-37E A copper block and an iron block are dropped into a tank of water. Some heat is lost from the tank to the surroundings during the process. The final equilibrium temperature in the tank is to be determined. Assumptions 1 The water, iron, and copper blocks are incompressible substances with constant specific heats at room temperature. 2 The system is stationary and thus the...
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1 Chapter Basics of Heat Transfer
1-37E A copper block and an iron block are dropped into a tank of water. Some heat is lost from the tank
to the surroundings during the process. The final equilibrium temperature in the tank is to be determined.
Assumptions 1 The water, iron, and copper blocks are incompressible substances with constant specific
heats at room temperature. 2 The system is stationary and thus the kinetic and potential energy changes are
zero, KE = PE = 0 and E = U .
Properties The specific heats of water, copper, and the iron at room temperature are Cp, water = 1.0
Btu/lbmF, Cp, Copper = 0.092 Btu/lbmF, and Cp, iron = 0.107 Btu/lbmF (Tables A-3E and A-9E).
Analysis We take the entire of contents the tank, water + iron + copper blocks, as the system. This
is a closed system since no mass crosses the system boundary during the process. The energy balance on
the system can be expressed as
Ein E out
1 24
43
Net energy transfer
by heat, work, and mass
=
E system
1 24
43
Change in internal, kinetic,
potential, etc. energies
WATER
Qout = U = U copper + U iron + U water
or
Iron
Qout = [mC (T2 T1 )]copper + [mC (T2 T1 )]iron + [mC (T2 T1 )]water
Copper
Using specific heat values at room temperature for simplicity and
substituting,
600Btu = (90lbm)(0.092Btu/lbm F)(T2 160)F + (50lbm)(0.107Btu/lbm F)(T2 200)F
+ (180lbm)(1.0Btu/lbm F)(T2 70)F
T2 = 74.3 F
1-16
600 kJ
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UNF - PHY - 4803
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UNF - PHY - 4803
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UNF - PHY - 4803
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UNF - PHY - 4803
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UNF - PHY - 4803
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UNF - PHY - 4803
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UNF - PHY - 4803
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UNF - PHY - 4803
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UNF - PHY - 4803
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UNF - PHY - 4803
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UNF - PHY - 4803
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UNF - PHY - 4803
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UNF - PHY - 4803
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UNF - PHY - 4803
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UNF - PHY - 4803
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UNF - PHY - 4803
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UNF - PHY - 4803
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UNF - PHY - 4803
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UNF - PHY - 4803
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UNF - PHY - 4803
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UNF - PHY - 4803
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UNF - PHY - 4803
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UNF - PHY - 4803
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UNF - PHY - 4803
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UNF - PHY - 4803
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UNF - PHY - 4803
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UNF - PHY - 4803
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UNF - PHY - 4803
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UNF - PHY - 4803
Chapter 1 Basics of Heat Transfer1-140 . . . 1-144 Design and Essay Problems1-77