Model experiment concerning the use of ambient heat with the help of the Peltier heat pump ENT 7.3

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Sophie Tate
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1 Model experiment concerning the use of ambient heat ENT Keywords Peltier effect, Peltier element, cooling engine (chiller), heat pump, thermogenerator, and geothermal energy Principle When direct current flows through a Peltier element, a temperature difference results: one side heats up and the other side cools down. The temperature on the hot side influences the temperature on the cold side and vice versa. If the hot side is held at a constant temperature by way of a reservoir, e.g. a water reservoir, the cold side cools more strongly than would be the case without the reservoir. In this experiment, the temperatures are measured over time when the thermogenerator is used without and with a "water reservoir" on the hot side. Equipment *1 Thermogenerator, Peltier element *1 Heat insulating sheet, felt Apparatus carrier with a fastening *1 magnet *1 Glass beaker, short, 250 ml *2 Glass beaker, short, 400 ml Additional equipment 1 Demo physics board with a stand Power supply, universal **1 Cobra4 Wireless Manager **1 Cobra4 Wireless-Link Cold water **1 Cobra4 Sensor-Unit 2x Temperature **1 Holder for hand-held meters Immersion probe, NiCr-Ni, stainless **2 steel **1 measure software for Cobra Connecting cable, 750 mm, red Connecting cable, 750 mm, blue PC, USB port, XP, Vista, Win7 * Included in the ENT 1 set ** Included in the Cobra4 extension set Fig. 1: Experiment set-up with a thermogenerator without a water reservoir P PHYWE Systeme GmbH & Co. KG All rights reserved 1

ENT Model experiment concerning the use of ambient heat Set-up - Set the experiment up as shown in Fig. 1.

- Insert the two temperature sensors into the holes of the thermogenerator that are intended for this purpose and connect the sensors to the Sensor-Unit 2x Temperature.

2 ENT Model experiment concerning the use of ambient heat Set-up - Set the experiment up as shown in Fig Place the heat insulating sheet onto the apparatus carrier and then the thermogenerator on top of it. - Connect the thermogenerator to the DC voltage output of the power supply unit. - Insert the two temperature sensors into the holes of the thermogenerator that are intended for this purpose and connect the sensors to the Sensor-Unit 2x Temperature. T1 shall be the temperature of the leg with the blue socket. - Fill the 250 ml beaker and the two 400 ml beakers up to the upper mark with water and keep them ready. Procedure - Start the PC and Windows. - Connect the Cobra4 Wireless Manager to the USB port of the PC. - Start the "measure" software package on the PC. - Connect the Cobra4 Wireless-Link to the Cobra4 Sensor-Unit. After it has been switched on, the Sensor-Unit will be automatically detected and an ID number will be assigned to the Cobra4 Wireless-Link. This number will be displayed. The communication between the Cobra4 Wireless Manager and the Cobra4 Wireless-Link is indicated by way of the data LED. - Switch the Cobra4 Wireless-Link with the connected Cobra4 Sensor-Unit 2x Temperature on. The Sensor-Unit and the quantities T 1 and T 2 are displayed as the measuring channels. - Load the experiment (Experiment > Open experiment > ). The program will now open all of the required presettings for the measurement data recording process (Fig. 2). Fig. 2: Measurement data recording 2 PHYWE Systeme GmbH & Co. KG All rights reserved P

3 Model experiment concerning the use of ambient heat ENT 1 st experiment: thermogenerator without a water reservoir (Fig. 1) - Adjust the current to 1 A and the voltage to approximately 3 V on the scale of the power supply unit. - Switch the power supply unit on. - Start the measurement data recording process in "measure". - The system will record a measurement value every 15 seconds. - Stop the measurement after approximately 5 minutes when the temperature T 2 does not change anymore. - Transfer the measurement values to the "measure" main program. - Switch the power supply unit off. - In order to cool the thermogenerator, place both sides of it into the 400 ml beakers that are filled with water. Wait until the temperature compensation is complete. 2 nd experiment: thermogenerator with a water reservoir on the hot side (Fig. 3) - Dry the thermogenerator. - Place the 250 ml beaker on the apparatus carrier. - Set up the thermogenerator so that the leg with the blue socket plunges into the beaker. - In order to perform a new measurement, switch over to "measure Cobra4". - Insert the two temperature sensors into the holes of the thermogenerator. T1 shall be the temperature of the negative pole (blue). - Switch the power supply unit on. - Start the measurement data recording process in "measure". - The measurement will be stopped automatically after 8 minutes. - Transfer the measurement values to the "measure" main program. - Switch the power supply unit off. Fig. 3: Experiment set-up with a thermogenerator with a water reservoir P PHYWE Systeme GmbH & Co. KG All rights reserved 3

4 ENT Model experiment concerning the use of ambient heat Observations and results When a water reservoir is used, the temperature on the hot side hardly increases at all. The temperature on the cold side is lower than in the case without a water reservoir. Evaluation Fig. 4: Measurement of the temperatures of the thermogenerator without a water reservoir Fig. 5: Measurement of the temperatures of the thermogenerator with a water reservoir on the hot side 4 PHYWE Systeme GmbH & Co. KG All rights reserved P

5 Model experiment concerning the use of ambient heat ENT Fig. 4 shows that, in the case of the thermogenerator (Peltier element) without a water reservoir, the temperature T 2 on the cold side remains constant after a certain time. This time can be determined with the aid of the graphical representation or by displaying the table. Time up to the temperature minimum: t 0 = 4.5 minutes (for the measurement in Fig. 4). Use the "Survey" function to determine the temperature decrease of T 2 from the start of the measurement (t = 0) until this moment of time. In order to compare the temperature, do the same with the curve T 2 in Fig. 5. Temperature change on the cold side of the thermogenerator after 4.5 minutes: Without a water reservoir With a water reservoir T 2 = 21.5 C 16.2 C = 5.3 K T 2 = 21.4 C 15.6 C = 5.8 K While, during the first experiment, the temperature remains constant after 4.5 minutes, it continues to decrease further in the second experiment. After 8 minutes, it reaches a value of 14.0 C, still showing a slightly falling tendency. With a water reservoir (8 minutes) T 2 = 21.4 C 14.0 C = 7.4 K Note For this experiment, the current should not be higher than 1 A. With higher current values, the Peltier element will heat up too strongly so that the temperature on the hot side will increase regardless of the water reservoir. As a result, the cooling differences with and without a water reservoir will be less pronounced. Application Cooling engines (chillers) or heat pumps are particularly effective when the hot or cold side is kept at a constant temperature by way of a large reservoir. These can be water reservoirs or underground reservoirs. Notes Corresponding student experiments TESS EN 7.5 Model experiment concerning the use of ambient heat (P ) For the execution of the experiment without a PC, the items on the list (page 1) that are marked with (**) must be replaced with the following items: Experiment P Cobra 4 Mobile-Link Cobra4 Sensor-Unit 2x Temperature Cobra4 Display-Connect, transmitter and receiver set Holder for hand-held meters Immersion probe, NiCr-Ni, stainless steel Large-scale display P PHYWE Systeme GmbH & Co. KG All rights reserved 5

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