Spring 2006
1
ME 201
Thermodynamics
Homework 15 Solution
1. A Carnot heat engine produces power of 2.5 kW. It rejects heat to a river that is
flowing at 2 kg/s, resulting in a temperature increase of 2
°
C. The average
temperature of the river is 20
°
C. Determine
(a) the heat transfer input required for the heat engine
(b) the efficiency of the heat engine
(c) the temperature at which heat transfer occurs to the engine
Solution:
We begin with our interaction diagram for a heat engine.
Our appropriate equations are:
η
th
net
H
=
W
Q
°
°
°
°
°
Q
= W
+ Q
H
net
L
η
Carnot
L
H
= 1
T
T
We note that we have 2 parameters given,
K
293
=
T
and
kW
2.5
=
W
L
net
°
, and four
unknowns,
and
,
T
,
Q
,
Q
th
H
L
H
η
°
°
. Clearly with just three equations we have a poorly
posed problem. In these cases we need to see if we can determine a heat transfer rate
High Temperature Reservoir
at T
H
Low Temperature Reservoir
at T
L
Heat Engine
Q
H
Q
L
W
net
This preview has intentionally blurred sections. Sign up to view the full version.
View Full Document
ME 201 Thermodynamics
Spring 2006
2
from a 1
st
law analysis on one of the heat reservoirs. For this problem the most likely
This is the end of the preview.
Sign up
to
access the rest of the document.
 Spring '06
 SOMERTON
 Thermodynamics, Heat, Heat engine, Heat Pump, Wnet

Click to edit the document details