gbwillson
Registered:1352981942 Posts: 2,311
Posted 1515712212
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#21
The only reason I could see the need for ducts is a short 12'"-18" stub at the exhaust so the air velocity can be more accurately measured. With 4 collectors, one should always be an empty box, while the other 3 units can try out various configurations to achieve the best BTU output. So the students will have to understand that there will be a tradeoff for having a long path through the collect. A longer path leads to higher output temps, at the cost of lower CFM/BTU output. I know you only have each group for a few weeks so time is limited, but once the group has discovered a design that gives the best BTU output, you might challenge them with the task of comparing that unit to other designs such as backpass, can or tube, and various matrix or screen type collectors. I know as a student at their age I loved classes such as yours. I remember learning about middle rockets by building and launching them during class time. Greg in MN
stmbtwle
Registered:1388591029 Posts: 2,877
Posted 1515721048
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#22
A length of flex might be good for demonstrating the effect duct resistance has on the collector, if you want to go that far.
__________________ Solar is like the wind. It may be free, but putting it to work isn't! Willie, Tampa Bay
Gordy
Registered:1362754383 Posts: 137
Posted 1515725612
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#23
I did not realize he only had them for a short time. So prolonged duct testing may not be possible, it does at least needs to be discussed as part of optimizing a successful solar collector build.
__________________ Gordy, Minnesota
matlocc
Registered:1420920295 Posts: 68
Posted 1515768147
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#24
I actually have 8 collectors. When this is the total focus of the class I can do all of that. Currently, I am easing this into the class. The regular class the students choose any topic that they want to learn about (within reason) and have seven weeks to learn the history, economic /environmental effects, how it has moved about the planet and provide a visual demonstration and or perform experiments. Then present a 10 minute presentation on their topic. Some of the topics that have been covered and were neat: catapults, solar panels, solar cookers, soap, dolls, shoes, makeup, chewing gum, crystal growth and (All of the previous the kids made their own to demonstrate) also the effect of air pressure in a basketball and how it affects shooting.
Gordy
Registered:1362754383 Posts: 137
Posted 1515780268
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#25
Sounds like a neat class. Should take away some of the boredom of the forced / mandatory curriculum.
__________________ Gordy, Minnesota
stmbtwle
Registered:1388591029 Posts: 2,877
Posted 1515794699
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#26
As solar is a growing industry, you might suggest that the school consider some more advanced courses in solar, as electives.
__________________ Solar is like the wind. It may be free, but putting it to work isn't! Willie, Tampa Bay
matlocc
Registered:1420920295 Posts: 68
Gordy
Registered:1362754383 Posts: 137
Posted 1516642618
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#28
Good job, look's like you got them thinking and engaged. It might be interesting for them to test the baffles as is, then paint them black. And see what kind of difference it makes. Also use a permanent marker on the blue tape.
__________________ Gordy, Minnesota
stmbtwle
Registered:1388591029 Posts: 2,877
Posted 1516654069
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#29
Interesting!
__________________ Solar is like the wind. It may be free, but putting it to work isn't! Willie, Tampa Bay
gbwillson
Registered:1352981942 Posts: 2,311
Posted 1516663258
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#30
I find it very interesting seeing how the students are thinking through the problem. If the tape is to help the baffles upright, the velcro isn't strong enough, or is weakening from the constant pulling. A suggestion for a future build might be to place a thin sheet of galvanized flashing on the back. And instead of velcro, attach 2 or 3 thin rare earth magnets to the bottom. The magnets are strong and will allow the baffles can be moved easily while firmly holding them in place. The grip won't weaken over time.https://www.amazon.com/X-bet-MAGNET-100-Ceramic-Magnets/dp/B018ITTFDM/ref=sr_1_9?ie=UTF8&qid=1516662865&sr=8-9&keywords=rare+earth+magnets Greg in MN