05 Juni 2015

Easter Projects: Heat Exchanger and Bike Design

Hello, everyone! I have been busy doing my Easter term projects. So, a third year engineering student at Cambridge needs to do two projects after he/ she is done with exams. I chose bicycle design (because there are so many bikes in Cambridge!) and heat exchanger (because I took Thermodynamics, and Heat & Mass Transfer). I learnt a lot from these projects, and I had good team (thanks, team!).

The assembled heat exchanger! His name is Albert.

The heat exchanger one was quite interesting. We basically created a program on MATLAB to find the maximum heat transfer with the constraints given: 1. The mass should not exceed 1.1 kg, 2. The length should not exceed 0.5 m, 3. The inlet hot temperature is 60 degrees C, and the inlet cold temperature is 20 degrees C.

So, as you could see above, the heat exchanger of our team had 2 shell passes and 2 tube passes. The copper tubes are where the hot water is going to pass, and the cold water is passing in the shell. Actually, our team design was quite a gamble. It could transfer 20 kW, but the uncertainty was really high. In the end, the gamble did not pay off, and we ended up getting fourth place (yup, we're group B!). It is a little bit sad, but we were still happy that we did not get the last place, haha. I know Albert (the name of our heat exchanger) worked so hard.

Final results of heat exchanger competition. Only 10.9 kW in the end.
For my bike design, I mostly did stuff on my computer. The topic was materials selection for bicycle handlebar. This time, most of my project was based on Alex Wanner's paper about size limited, weight-minimizing design. If you have taken materials selection courses, you might be familiar with material indices to determine which materials are best for certain purposes. This time, I incorporated the maximum outer radius of handlebar, because if it's too large, it's going to be hard to grip. There are also two things that I need to consider: the stiffness, and the strength.

So, if I choose aluminium alloy as the reference material...

Comparison of different materials.
The rigid polymer foam, PVC, and plywood, cannot make the cutoff. This means, they cannot be used as handlebar in bicycle, because they are neither stiff nor strong. On the other hand, bamboo can be as strong as aluminium alloys, but it is not as stiff. There are several materials which can be used, for instance GFRP, but it is too heavy. The best one is CFRP, as you can see above.

So, for this project, I basically have pages of spreadsheet, so many MATLAB graphs (I've become quite good at plotting graphs in MATLAB, hooray!), and some readings to do.

Overall, I am glad I chose these two projects, because I learnt a lot and also made new friends in my teams. Thank you so much team-mates!

I am basically done with my third year (junior year), and I am so happy about it. I am going to India in two weeks for summer internship, and then heading home for few weeks before going back to the United States for my final year at MIT. This exchange year has been amazing so far, and I am glad I did it. Thanks for your support everyone :)

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