PASCO ET-8782 Energy Transfer– Thermoelectric - Manual (Page 20)

Energy Transfer –Thermoelectric Load Resistance and Efficiency
20 ®
5. Connect the output load jumper to terminal D. This bypasses all of the resistors and reduces
the load resistance to almost zero. Note that the resistance is not exactly zero because the
wires and traces on the board have some resistance.
6. Place both insulators on the blocks.
7. Set the switch to Heat Pump mode. Watch the difference in temperature between the two
blocks (
∆T). You are waiting for ∆T to reach 35 °
C, which will take about one minute.
8. When
∆T reaches 35 °
C, change the switch to Heat Engine Mode. The temperature difference
will start to decrease. When
∆T drops below 35 °
C, DataStudio will automatically start
recording. You will see data appear on the graph of Power Generated vs.
∆T.
9. When
∆T drops below 5 °
C, data recording will stop automatically.
10. Change the name of the data run to indicate the load resistance.
11. Click Start. DataStudio will display temperature data, but it won’t start recording yet.
12. Remove the insulators and use the fan and heat sink to cool the blocks to within a few degrees
of room temperature.
13. Change the output load to 3
Ω (connect the jumper to terminal C).
14. Replace the insulators and repeat the cycle of heating and cooling. (Go back to step 7.)
15. Repeat the cycle again for the following values of output load:
• 7
Ω (Connect the jumper to B, but also connect a shorting jumper from C to D.)
• 10
Ω (Connect the jumper to B.)
• 20
Ω (Connect the jumper to A, but also connect a shorting jumper from B to D.)
• 30
Ω (Connect the jumper to A.)
When you are finished, you will have acquired power and temperature data for six different
values of output load resistance.
Analysis
From the data that has been recorded you will extract the data needed to plot a graph of Power
Generated (P) versus Load Resistance (R
L
) at
∆T = 30 °
C.
On the graph of P vs.
∆T use the smart cursor to read the power generated at ∆T = 30 °
C for each
value of load resistance. (Use the zoom select tool to change the scale of the graph and enlarge the
area around the data at 30
°
C in order to read the data precisely.)
Enter the values in the Power vs. Load table. As you enter data into the table, they will be plotted
on the Power vs. Load Resistance graph.
1) At what value of R
L
is the maximum power generated?