P08451 Prototype Thermoelectric Heat Exchanger

Transcription

1 P08451 Prototype Thermoelectric Heat Exchanger Special Operating Procedure Prepared by: Jacob LaManna Sections 1) Assembly of prototype 2) Installing prototype in test stand 3) Running tests 1

2 Section 1: Assembly of Prototype To begin assembly a) Decide on appropriate setup for test: select desired fins and module types. b) (If fins are not needed for the current test setup, then skip to next step in procedure) With the duct in a fully dismantled state, apply thermal paste to dove-tail surface on the fins and slide the fins into each duct half. c) To begin assembly of the duct, start by bolting the duct halves together. If fins are used make sure to tighten the bolts enough to allow for the fins to compress against each other as this will help to minimize contact resistance. d) To assemble the duct sections together, place insolating insulation pieces between mating surfaces of each section and bolt together. 2

3 e) To ensure a proper mounting surface for the thermoelectric modules, it will be necessary to check the surface for flatness. Using a straight edge, check that all three duct surfaces line up with each other on both sides of the duct. If gaps are found between duct sections it may be necessary to loosen some of the bolts to allow the duct to assume a flat position. f) To finish the assembly of the duct, bolt the end tanks on to each end of the duct. Use only four bolts to secure the end tank to the duct section. Remember to place a Teflon gasket between the end tank and the duct during assembly. g) Select appropriate thermoelectric module insulation insert and place onto the duct. 3

4 h) Apply thermal paste to the duct surface in thermoelectric module locations marked out in the insulation insert. i) Apply thermal paste to each surface of the thermoelectric modules. j) Apply thermal paste on the surface of the cold plates in the locations that the thermoelectric modules will meet with the cold plate. k) Assemble the entire unit from the bottom up. Begin by placing the bolts (head down) with Belleville springs into the bottom compression plate and setting this on a level surface. Now place the bottom cold plate (thermal paste side up) onto the compression plate. Place thermoelectric modules on the cold plate (lip face down if equipped) and space them appropriately and place the insulation around them. Place duct on top of the modules. Apply other insulation piece to top face of the duct and place the thermoelectric modules into each location on the insulation (lip face up if equipped). Set second cold plate (thermal paste side down) onto the thermoelectric modules. The top compression plate is placed on top of the top cold plate. 4

5 l) Slide thermocouple probes into the grooves that correspond to areas beneath the modules. m) Place a Belleville spring over the end of each bolt and tighten each bolt finger tight. 5

6 n) Torque to specified value in shown pattern o) Insert sidewall and bolt insulation. 6

7 Section 2: Installation of Prototype in Test Stand a) Mate exhaust flanges and bolt into test stand. Make sure to place exhaust flange gaskets between flanges during bolt up. Bolt up can be made easier with the help of jack stands placed under the prototype to help support the load. b) Connect the water lines to the Y junctions coming from the cold plates. The supply water line feeds into the side closest to the edge of the able (right side if looking down the heat exchanger towards the heater) and the return line connects on the blower side of the prototype. 7

8 c) Connect modules in desired pattern. This connection pattern is dependant on test setup requirements and the number of modules used. The patterns can be any combination of series and parallel connections. d) Run voltage sensing lines from each zone to its respective rheostat on the measurement box. It is optional to run a multi-meter in ammeter mode to collect the current measurements in addition to the load voltage drop measured in LABview. e) Install thermocouple module and measurement box to DAQ. f) Connect thermocouple leads to corresponding thermocouple. The numbering scheme is as follows: The first number in the 3 digit sequence after the C represents what zone the thermocouple corresponds to, the second two digits represents the thermocouple number for that zone. i.e. tag number C109 is thermocouple 9 in Zone 1 and C312 is thermocouple 12 in Zone 3. 8

9 Section 3: Running Tests a) Open the LABview program designated P08451 DAQ final. b) Reset the chassis to insure that data readings will be correct. c) Using LABview program a. The LABview interface is setup to provide distinction between the different measurements and thermal zones of the prototype. The numerical indicators labeled C101-C312 represent the temperature readings of the thermocouples in the each of the zones of the prototype. The graphs below these indicators graph the hot side and cold side temperatures to aid in determining if steady-state has been achieved. The numerical indicators to the top right of the screen labeled A1- A5 represent the five thermocouple temperature readings on the test stand. Below these indicators are numerical indicators for both water and air flow rates. b. To set the interface up to output to Microsoft Excel files, the operator will need to select an existing file and rename the file in the output location selection bar. Selecting an existing file is necessary as LABview will return a directory does not exist error if the file is just typed in. Once the location is selected, it will be necessary to select the number of points to acquire and at what time delay. In the box labeled as number of data points, input the number of data points desired for the analysis, i.e. 50. Now set the time delay in the box labeled time delay between data points. This box sets the interval between when each data point is written, i.e. 2 seconds. c. All electrical inputs and outputs are found at the bottom of the interface. The bottom most left corner of the interface has two columns of 4 numerical inputs 9

10 were the calculated load resistances and the open circuit voltages are inputted. Following these two columns are two more columns consisting of numerical indicators that output the internal impedance (which is only calculated when the calculate bottom is depressed) and the measured voltage drop across the load resisters. The voltages are also displayed on graphs to help in determining steadystate conditions. d) Start test stand and ramp to desired conditions following test stand specific operating procedures. e) Achieve steady state. This is seen as stable temperatures that graph horizontally in the LABview program. f) Collecting electrical data: Electrical data is collected using a combination of multimeters and voltage measurements performed by LABview. The multimeters are used to collect Open Circuit Voltages (OCV) and current readings for each zone during a test. a. Once steady state is achieved, set the multimeters to measure DC voltage and measure the OCV for each zone. Allow ample time for the reading to reach steady state as heat flows within the modules change when current doesn t flow. Record these values in a logbook. b. Unplug the multimeters and set them to appropriate current measurement setting. Plug on measurement line into the multimeter and the other into on plug of the rheostat. Use a short Banana plug extension line to connect the open terminal of the rheostat to the open terminal of the multimeter. Allow time for the modules to reach steady state. Then record the current quantity in a logbook for each zone. 10

11 c. Now move back to the LABview interface to take the voltage readings. Record in the logbook the values for the voltage drop across each rheostat. d. Calculate the load resistance of each rheostat by dividing the voltage dropped across the resister by the current. Record this value in the logbook. e. Input the calculated load resistance and the OCV values into the respective numerical inputs in the interface. Once all values have been inputted, click on the ok to calculate button. The program will now calculate the internal impedance of the thermoelectric modules. Record these values in the logbook. g) Collecting temperature data. a. Once all of the electrical data has been collected and the temperatures are steady, click the ok to record button at the top of the interface. Allow the program enough time to collect all data points. The program will run slower and choppier while it is collecting data. Once the green light in the button goes out all data has been collected. h) Once data has been collected at the current point, ramp to the next condition and repeat steps (d) through (g). 11