PASCO TD-8564 THERMAL EFFICIENCY APPARATUS - Manual (Page 22)

Thermal Efficiency Apparatus 012-05443A
18
➁ Plug the 9V transformer into the wall socket and into the pump on the Thermal Efficiency
Apparatus. You should now hear the pump running and water should be coming out of the
rubber hose marked “out”.
➂
Disconnect the power supply to the hot side. Connect the power supply directly across the
Peltier device with no load resistance. See Figure 3.1
➃
Connect an ammeter and a voltmeter to the power supply.
Procedure
➀
Increase the voltage until equilibrium is reached at the same hot temperature as in the
previous experiment. The hot side is now being heated by heat pumped from the cold side
rather than the heater resistor.
➁ Record the resistances and convert them to degrees. Also record the voltage (V
W
) and the
current (I
W
) in Table 3.1.
Analysis
➀ Actual Coefficient of Performance: Calculate the actual COP using the data taken in the
Heat Engine experiment.
κ
=
P
C
P
W
=
P
H (OPEN)
– P
W
P
W
Record this result in Table 3.1.
➁
Maximum Coefficient of Performance: Calculate the maximum COP using
κ
MAX
=
T
C
T
H
– T
C
and record this result in Table 3.1.
➂
Adjusted Coefficient of Performance: Part of the power being applied to the Peltier device
is being dissipated in the Joule heating of the internal resistance of the device rather than
being used to pump the heat from the cold reservoir. Therefore, to adjust for this, I
2
r must
be subtracted from the power input to the Peltier device. Then the COP becomes the heat
pumped from the cold reservoir divided by work done to pump the heat, rather than divid-
ing by the work done to pump the heat and heat the internal resistance. In terms of the
power,
κ
ADJUSTED
=
P
H (OPEN)
– P
W
P
W
– I
W
r
2
Record this result in Table 3.1. Calculate the percent difference between the adjusted COP
and maximum COP:
% Difference =
κ
MAX
–
κ
ADJUSTED
κ
MAX
×
100%
and record in Table 3.1.