Course:ENPH257/Archive/2017St1/Lab

Preamble

Due to space and apparatus restrictions, you will work in groups of four. What you submit for marks will be a group effort.
There is one multi-part experiment.

Heat Transport Laboratory

Golden Rule

Shoes must be worn at all times in the lab – no sandals or otherwise open footwear.

1. Lab Goals:

(a) Observe and measure thermal waves in an aluminum rod by modulating the heating at one end. In particular, demonstrate that part of the rod can be cooling as another part is heating.
(b) Compare each measurement to your own simulations and extract the conductivity and heat capacity of this aluminum alloy, plus heat loss parameters
(c) Complete experimental part and interim report by Thursday June 16; final analysis report due Friday June 30, 17:00.

2. You are provided with:

• Aluminum rod and attachment screw
• Power resistor, thermal paste for coupling
• DC adjustable power supply
• Thermocouples, temperature sensors, thermometers
• Arduino board for data collection
• DMMs
• Vessels to immerse the rod
• Hot water, ice
• SolidWorks

3. Overview:

Modulate the power of the heater and measure the resulting temperatures at various points along the rod, both as a function of time and position. Based on what you learn, and by comparing to your simulations, you are to estimate the:
• thermal diffusivity of the rod material, and thus the thermal conductivity and the specific heat capacity
• emissivity of the rod material
• convective heat transfer coefficient for this system
• fraction of power generated by the thermal resistor flowing down the rod

4. Getting started:

(a) You are provided with TMP36 temperature sensors; look up the specs and build a circuit to connect them to the Arduino. You will need to download an arduino support package and Arduino drivers (from the Arduino site). The computers in the lab are slow but fine for data taking (in Matlab or Python). You probably want to use your own laptop for the simulations; your professor uses a 2008 Toshiba Portégé with an SSD hard drive, i.e. you don’t need the latest and fastest machine
(b) Make sure your power resistor is connected to convenient leads–solder some new wires if needed, and/or insulate leads with heat-shrink tubing. Look up the maximum temperature of your resistor, and make sure it never exceeds that. We’re can’t afford to replace a dozen blown resistors!
(c) Attach your resistor tightly to the end of the rod, using a dab of thermal paste. Only a dab! The small pot must be enough for everyone.
(d) Attach sensors where desired. The TMP36s can be surface mounted or set into the rod by means of a 13/64” hole. Your challenge is to choose positions and measure T vs. time for each, compare to simulations, and from this comparison estimate the quantities above. See appendix for tips on writing DAQ code.
(e) Put some power into the resistor (make sure it does not get too hot!) and see what happens. There is no reason or benefit to exceed 70C (pain threshold).
(f) Think carefully about how to make particular measurements that emphasize one parameter over the others.
(f) You may program cooling measurements overnight, but there must be no active heating after the lab closes at 17:00.

5. Lab journal

Keep a lab journal (electronic, yellow lab book or part thereof, you choose). A knowledgeable reader (i.e. your prof or TA) should be able to reconstruct what your group (not just you!) did during the lab period, when, and in what order. It is a simple requirement; it is not easy to fulfill.
• When deciding what to write, imagine you will have to defend your actions of today in a court of law 10y from now!
• Graph your data during the lab period and scotch-tape the graphs into your journal (if paper).
• Analyze as you go.
• At the end of the day, write a brief summary with a job list for the next lab period.
• No loose pieces of paper

6. Analysis report

This will consist of nothing but properly captioned diagrams, graphs and a table summarizing your numerical results and uncertainties. You will be coached on how to do this in the tutorials. A reader with knowledge of the task you were assigned should be able to assess the quality of your work from these diagrams and graphs alone.

Marking guide to the analysis report

Submission

• Interim report due Thursday June 16th 2017 at 17:00. One (only!) file named interim_analysis_group#.pdf to enph257@phas.ubc.ca
• Final report due Friday June 30th 2017 at 17:00. One (only!) file named final_analysis_group#.pdf to enph257@phas.ubc.ca

Appendix

Hints and useful bits of MATLAB code

Save data (including the raw voltages) in files with informative names and the date/time included.

ts = datetime('now');
DateString = datestr(ts,30);
filename = ['5Wpolished_horizontal' DateString '.xlsx'];

While taking data:
Plot the nominal temperatures on an updating graph with fixed and labelled axes.
Save raw voltages as you go (in case your experiment is interrupted an hour in).