Lab Report_ Coefficient of Performance.docx

Thermodynamics, MAE219 Lab Report: Coefficient of Performance 5/28/2022 Professor Ngabonziza Objective To measure the coefficient of performance of a reversible heat pump running in both refrigerator and heat pump mode. Introduction Heat pumps can pump heat out of a building (cooling the space) or into a building (heating the room). If a heat pump is working as an air conditioner or refrigerator, it is absorbing heat from the space to be cooled and rejecting it to the surrounding atmosphere (for example, the surrounding room where a refrigerator is). If a heat pump works as a heater, it absorbs heat from the surrounding cold atmosphere (outside) and uses it to warm the heated space (inside a house). Heat pumps and refrigerators are typically separate systems, but in this experiment, we will use a reversible heat pump that can be used as both a heater and an air conditioner. The amount of energy that a heat pump uses to move a certain amount of heat is called its coefficient of performance. Coefficient of performance of a refrigerator k = Q cold W ( cooling ) Coefficient of performance of a heat pump k = Q hot W ( heating ) 1

The software DataStudio was used to calculate and display heat flow, power, and work for a reversible heat pump in this experiment. The interface showed the values for the temperatures of the hot and cold blocks, the heating flowing into the hot block (Q hot ), and the heat flowing out of the cold block (Q cold) . Additionally, the real-time power vs. time graph was displayed and the area under this graph is equal to the work done by the peltier. Equipment  Thermal Efficiency Apparatus  Foam insulators  Banana patch cords  Temperature cables  DC Power Supply (5 V, 1 A minimum)  PASPORT Voltage/Current Sensor  PASPORT Quad Temperature Sensor Setup  Set the switch to the neutral position. Connect the power supply using banana patch cords to the input power terminals.  Attach the heat sink and insulator to the aluminum blocks.  Connect the cables from the temperature ports on the circuit board to the temperature sensor.  Connect the cables from the voltage ports and the current ports on the circuit board to the voltage/current sensor.  Connect the temperature sensor and the voltage/current sensor to the computer. Open DataStudio and launch the file “Coeff of Performance”. 2

Procedure Refrigerator  Before starting, the knife switch was moved to the neutral position, and the fan turned off.  The DC power was set to 5 volts.  The foam insulator was moved to the cold block, and the heat sink was moved to the hot block.  The program was started in DataStudio.  Once the temperatures of the blocks were within 0.1 ᵒ C, the knife switch was closed, and the program was allowed to run for 10-15 seconds. 3

 The values for power (W*s) and Q cold (J) were recorded. Heat pump  The foam insulator was moved to the hot block, and the heat sink was moved to the cold block.  The procedure outlined above for the refrigerator was repeated for the heat pump. Experimental Results and Discussion Refrigerator 1. Use your values for the heat pumped out of the cold block (Qcold) and the area under the Power versus time curve (W) to calculate the Coefficient of Performance, k, for your model refrigerator. Trial Q cold (J) W (W*s) k 1 1.05 0.11 9.55 2 1.05 0.12 8.75 3 1.05 0.14 7.5 Average 9 2. For real heat pumps k is usually expected to be greater than 1. Is this the case for your model? Yes, the coefficient of performance k was greater than one for all trials. 3. Your heat pump can also be thought of as a model air conditioner, a device used to keep the inside of a building cooler than the outside air. In terms of moving heat, what does 4

Your preview ends here

Eager to read complete document? Join bartleby learn and gain access to the full version

Access to all documents
Unlimited textbook solutions
24/7 expert homework help