Download LAB 50: CONCENTRATING ENERGY

LAB 55 B: THERMOELECTRIC GENERATOR
5/3/2017
OVERVIEW
A thermoelectric module may be used as a heater or a refrigerator. When a current is run
through the wires, heat is transferred from one body to the other body. The direction of
heat flow depends on the direction of the current flow. This is shown in Figure 3. TE
modules are used in this way to heat or cool small surfaces. When used this way to cool,
the TE module is often, referred to as a solid state refrigerator. When used this way to
heat, it is an oven.
In lab 55-B, you will transfer heat by driving a current through the module. You will use
water stored in the holes of the aluminum blocks as the two objects; one to lose heat and
one to gain heat. The quantity of heat transferred can be determined by knowing the
density and specific heat of water, and measuring its volume and change of temperature.
OBJECTIVE: Use a thermoelectric module to transfer heat from one object to another.
EQUIPMENT
Thermoelectric Generator Device
Universal Lead Set
Beaker
Two Thermometers, Scaled
Support Stand Set:
--Mechanical Breadboard
--Two 24" Support Rods with Bases
--14.5" Crossbar
Two Hook Sleeves
Digital Stopwatch
Two Digital Multimeters
High Current Power Supply
30-cm Ruler
Water
PROCEDURE
PART A: Apparatus Assembly
Figure 1 shows the setup for this experiment.
1. Set up the equipment as shown in Figure 1 for Lab 55-B.
2. Make sure the high current power supply is off. Refer to Figure 1 for the following
connections. Connect the black wire of the TE module to the ammeter. Connect the
negative (common) terminal of the Ammeter to the negative terminal of the power
supply, in the 10 A or 20 A range. Connect the red wire of the TE module to the positive
terminal of the power supply.
3. Set the power supply meter to read "volts".
4. Select the 0-24 VDC range on the power supply.
5. Set the stopwatch to zero.
6. Fill the two chambers of the aluminum blocks with room temperature water to about
'/s inch of the top of each chamber. Don't let the water overflow or you will have to dry
the module and start over again.
7. Lower the thermometers into the chambers. The two chambers must be initially at the
same temperature. Check to be sure that the two thermometers read equal temperatures.
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LAB 55 B: THERMOELECTRIC GENERATOR
5/3/2017
PART B: Using TE module to transfer heat
1. On the high current supply, pre-set the voltage control for zero output. Turn the power
supply on and adjust to about 3 volts. (The current should not exceed 7.5 A)
2. When the voltmeter reads 3 volts, start the stopwatch. At the same time, record the
temperature of each chamber, and the voltage and current readings.
3. Record these values in the table at 30 second intervals. Adjust the sensitivity of the
ammeter, if needed, to obtain accurate readings.
4. After 10 minutes have elapsed, turn off the power supply. Disconnect the electrical
connections.
5. Take your lab setup apart.
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LAB 55 B: THERMOELECTRIC GENERATOR
5/3/2017
PART C: CALCULATIONS
1. Find the volume of each hole using the equation below. Record your answer on the
report form.
Volume:
V=
𝑫𝟐 𝒉
𝟒
or = 𝒓𝟐 𝒉
2. Use the initial and final voltage to calculate the average voltage as indicated below,
and record as Vag in the space below the data table.
𝟏
Vavg = 𝟐(Vi + Vf)
3. Use the initial and final current to find the average current, and record as Iavg in the
space below the data table. (This is similar to finding the average voltage as in step 2.)
Show your work and results for the following calculations in the space below the
questions on the Analysis page.
4. Find the average electrical power dissipated in the TE module. Pavg = Vavg Iavg
Record this value in Watts.
5. Calculate the total electrical energy input to the TE module. Eelec = Pavg•t The power
in Watts multiplied by the time in seconds will give energy.in Joules. Record this value.
It represents the energy input to the system.
6. Convert the volume of water in the chambers to mass in grams, using the known
density of water.
m = •V
(The mass density of water is 1.0 g/cm3)
7. Calculate the increase in temperature of the water in the warming chamber.
T = Tf - Ti in C°
Find the gain of heat energy by the water in the heated chamber, using the equation
below. Record the heat energy in calories.
H = mcT
(Specific heat of water: c = 1 cal/ (gm• C°)
8. Convert calories to Joules, and record on the report form. 1 cal = 4.185 J
This is the energy transferred to the water in the heated chamber.
9. In the first analysis question, you are treating the TE module, as a heater or "oven".
The output energy is the energy transferred to the water (calculation 8 above). The input
energy is the electrical energy from calculation 5 above.
𝐇
Efficiency: = 𝐄𝐞𝐥𝐞𝐜 x 100%
Discuss the remaining analysis questions with your lab partners, and complete the report
form.
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