PASCO TD-8564 THERMAL EFFICIENCY APPARATUS - Manual (Page 8)

Thermal Efficiency Apparatus 012-05443A
4
PASCO scientific
Model TD-8564
THERMAL EFFICIENCY
APPARATUS
THERMISTOR
SELECT
PELTIER DEVICE
WATER PUMP
7.5 - 12 VDC
@500mA
COOLING
WATER HEATER 5 Ω± 1%
12 VDC MAX
2.0 Ω 1.0 Ω 0.5 Ω
THERMISTOR TABLE
K Ω
461
436
413
391
370
351
332
315
298
283
° C
-5
-4
-3
-2
-1
0
1
2
3
4
K Ω
269
255
242
230
218
207
197
187
178
169
° C
5
6
7
8
9
10
11
12
13
14
K Ω
161
153
146
139
133
126
120
115
109
104
° C
15
16
17
18
19
20
21
22
23
24
K Ω
100
95.4
91.1
87.0
83.1
79.4
75.9
72.5
69.3
66.3
° C
25
26
27
28
29
30
31
32
33
34
K Ω
63.4
60.7
58.1
55.6
53.2
51.0
48.9
46.8
44.9
43.0
° C
35
36
37
38
39
40
41
42
43
44
K Ω
41.2
39.6
37.9
36.4
34.9
33.5
32.2
30.9
29.7
28.5
° C
45
46
47
48
49
50
51
52
53
54
K Ω
27.4
26.4
25.3
24.4
23.4
22.5
21.7
20.9
20.1
19.3
° C
55
56
57
58
59
60
61
62
63
64
K Ω
18.6
17.9
17.3
16.6
16.0
15.5
14.9
14.4
13.8
13.4
° C
65
66
67
68
69
70
71
72
73
74
K Ω
12.9
12.4
12.0
11.6
11.2
10.8
10.4
10.1
9.76
9.43
° C
75
76
77
78
79
80
81
82
83
84
K Ω
9.12
8.81
8.52
8.24
7.96
7.70
7.45
7.21
6.98
6.75
° C
85
86
87
88
89
90
91
92
93
94
K Ω
6.53
6.33
6.12
5.93
5.74
5.56
5.39
5.22
5.06
4.91
° C
95
96
97
98
99
100
101
102
103
104
Ω
Out
In
Ohmmeter
Rubber
Hoses
9V Power
Supply In
Q
c
Q
h
T
c
Cold
Reservoir
Hot
Reservoir
Heat
Pump
W
Figure 3: Heat Pump
T
h
Figure 4: Thermal Efficiency Apparatus
This is similar to efficiency because it is the ratio of
what is accomplished to how much energy was ex-
pended to do it. Notice that although the efficiency is
always less than one, the COP is always greater than
one.
Maximum Coefficient of Performance
As with the maximum efficiency of a heat engine, the
maximum COP of a heat pump is only dependent on
the temperatures.
κ
max
=
T
C
T
H
– T
C
where the temperatures are in Kelvin.
Adjusted Coefficient of Performance
If all losses due to friction, heat conduction, radiation,
and Joule heating are accounted for, the actual COP
can be adjusted so it approaches the maximum COP.
Heat Pump (Refrigerator)
Introduction
A heat pump is a heat engine run in reverse. Normally,
when left alone, heat will flow from hot to cold. But a
heat pump does work to pump heat from the cold reser-
voir to the hot reservoir, just as a refrigerator pumps heat
out of its cold interior into the warmer room or a heat
pump in a house in winter pumps heat from the cold
outdoors into the warmer house.
In the case of the Thermal Efficiency Apparatus, heat is
pumped from the cold reservoir to the hot reservoir by
running a current into the Peltier device in the direction
opposite to the direction in which the Peltier device will
produce a current.
A heat pump is represented in a diagram such as Figure 3.
➤NOTE: The arrows are reversed compared to the
heat in Figure 2. By conservation of energy,
Q
C
+ W = Q
H
,
or in terms of power
P
C
+ P
W
= P
H
.
Actual Coefficient of Performance
Instead of defining an efficiency as is done for a heat
engine, a coefficient of performance (COP) is defined
for a heat pump. The COP is the heat pumped from the
cold reservoir divided by the work required to pump it
κ
= COP =
P
C
P
W
.