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PASCO TD-8564, Инструкция по эксплуатации

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012-05443A

Thermal Efficiency Apparatus

23

➅

Calculate the power input to the hot side, P

H

 = I

H

V

H

, and the power dissipated by the load

resistor, 

P

L

=

V

W

2

R

. Calculate the efficiency, 

e =

P

L

P

H

. Record all these values in Table 5.1.

➆

Adjust the power input to the hot side to keep the temperature of the hot reservoir at the
same temperature as it was for the 0.5 

Ω

 resistor while Steps 1 through 6 are repeated for the

other possible load resistances: 1, 1.5, 2, 2.5, 3, and 3.5 ohms.

Questions

➀

For which load resistor is the efficiency a maximum?

➁

If you have done experiment 2: How does the load resistance for optimum efficiency
compare with the internal resistance measured in that experiment?

Содержание TD-8564

Страница 1: ...25 26 27 28 29 30 31 32 C 25 26 27 28 29 30 31 32 K 63 4 60 7 58 1 55 6 53 2 51 0 48 9 46 8 K 63 4 60 7 58 1 55 6 53 2 51 0 48 9 46 8 C 35 36 37 38 39 40 41 42 C 35 36 37 38 39 40 41 42 K 41 2 39 6 37...

Страница 2: ......

Страница 3: ...of Performance 4 MEASUREMENTS USING THE THERMAL EFFICIENCY APPARATUS Direct Measurements 5 Temperatures 5 Power Delivered to the Hot Reservoir PH 6 Power Dissipated by the Load Resistor PW 6 Indirect...

Страница 4: ...operly packed to prevent damage and shipped postage or freight prepaid Damage caused by improper packing of the equipment for return ship ment will not be covered by the warranty Shipping costs for re...

Страница 5: ...known since the 1800 s but has only become practical since the recent devel opment of semiconductors In 1821 the Russian German physicist Thomas Johann Seebeck discovered that when a junction of diss...

Страница 6: ...gine Introduction Actual Efficiency Carnot Efficiency Measurements Using the Thermal Efficiency Apparatus Direct Measurements Temperatures Power to the Hot Reservoir Power Used by the Load Resistor Ex...

Страница 7: ...es at which energy is transferred or used by the Thermal Efficiency Apparatus all measurements will be power rather than energy So PH dQH dt and then the equation QH W QC becomes PH PW PC and the effi...

Страница 8: ...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 C...

Страница 9: ...ance of the thermistor imbedded in the hot or cold block To do this connect an ohmmeter to the terminals located as shown in Figure 4 The switch toggles between the hot side and the cold side The ther...

Страница 10: ...culated it is necessary to calculate the internal resistance This is accomplished by measuring the voltage drop across the Peltier device when an external load is applied First run the Thermal Efficie...

Страница 11: ...at which heat is delivered to the hot reservoir PH minus the rate at which work is being done PW Figure 3 Figure 7 No Load The work can be measured directly but the heat delivered to the hot reservoir...

Страница 12: ...experiments are written in worksheet form Feel free to photocopy them for use in your lab NOTE The first paragraph in each experiment lists all the equipment needed to perform the experiment Be sure t...

Страница 13: ...4 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 P...

Страница 14: ...ch to switch the ohmmeter to each side Record the readings in Table 1 1 Convert the resistances to temperatures using the chart on the front of the device or Table 1 as explained in the Measurements s...

Страница 15: ...actual efficiency increase or decrease as the temperature difference increases The Carnot efficiency represents the best that a perfect heat engine can do Since this heat engine is not perfect the ac...

Страница 16: ...Thermal Efficiency Apparatus 012 05443A 12 Notes...

Страница 17: ...be coming out of the rubber hose marked out Plug the ohmmeter into the thermistor terminals Modes of Operation To obtain all the necessary data for the heat engine it is necessary to run the Thermal E...

Страница 18: ...ents section E Record the voltage VH across the heating resistor the current IH and the voltage across the load resistor VW in Table 2 1 Open A Disconnect the patch cord from the load resistor so no c...

Страница 19: ...adjusted efficiency the total work done in terms of power is PW PW IW 2 r VW 2 R IW 2 r where IW VW R Calculate IW for the 2 load and record in Table 4 B Second the heat input must be adjusted The he...

Страница 20: ...match the Carnot efficiency which assumes no energy loss The adjusted efficiency is eadjusted PW PH PW IW 2 r PH PH open Calculate the internal resistance r using the equation r VP VW VW R which is d...

Страница 21: ...CIENCY experiment to get the data necessary to determine the internal resistance of the Peltier device To complete the measurements for this experiment use the following instructions to run the appara...

Страница 22: ...of Performance Calculate the actual COP using the data taken in the Heat Engine experiment PC PW PH OPEN PW PW Record this result in Table 3 1 Maximum Coefficient of Performance Calculate the maximum...

Страница 23: ...decrease Calculate the rate of change in entropy for the system which includes the hot and cold reservoirs Since the reservoirs are at constant temperature the rate of change in entropy is S t Q t T...

Страница 24: ...al Efficiency Apparatus the Peltier device has 71 couples and each couple consists of 2 elements so there is a total of 142 elements which conduct heat Figure 9 Each element has a length to area ratio...

Страница 25: ...istance of the Peltier device So the power can be expressed in terms of the Seebeck voltage the internal resistance and the load resistance P Vs r R 2 R Assuming the Seebeck voltage remains constant i...

Страница 26: ...ously vary the load resistance However it will be necessary to measure the resistance of the load Allow the system to come to equilibrium so that the hot and cold temperatures are constant This may ta...

Страница 27: ...input to the hot side to keep the temperature of the hot reservoir at the same temperature as it was for the 0 5 resistor while Steps 1 through 6 are repeated for the other possible load resistances...

Страница 28: ...Thermal Efficiency Apparatus 012 05443A 24 Notes...

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