Chapter 1
Basics of Heat Transfer
134
A hot copper block is dropped into water in an insulated tank. The final equilibrium temperature of
the tank is to be determined.
Assumptions
1
Both the water and the copper block 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,
ΔΔ
KE
PE
==
0 and
E
U
=
.
3
The system is wellinsulated and thus there is no heat transfer.
Properties
The specific heats of water and the copper block at room temperature are
C
p, water
= 4.18
kJ/kg·
°
C and
C
p, Cu
= 0.386 kJ/kg·
°
C (Tables A3 and A9).
Analysis
We observe
that the volume of a rigid tank is constant We take the entire contents of the tank,
water + copper block, 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
EE
E
U
in
out
−=
=
Net energy transfer
by heat, work, and mass
system
Change in internal, kinetic,
potential, etc. energies
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 Fall '10
 Dr.DanielArenas
 Thermodynamics, Energy, Mass, Heat, 25 Min, 50 kg, 27.5°C

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