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gbwillson

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Reply with quote  #21 
Random thoughts...

Being these are for experimentation and learning only, do you really need the polyiso? Silicone to seal any air leaks would be handy. So would foil tape. How are you holding the glazing in place? And as far as glazing, would cheap plastic film be good enough? You may want some sort of weatherstrip or seal to make the cover airtight. Screws or rivets to assemble the steel studs. Paint?

Greg in MN

matlocc

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Reply with quote  #22 
I forgot paint and screws!
I planned on using velcro or magnets to hold the glazing on. This idea has gotten much bigger than I thought.  What would be good computer interfaced thermometers for them to work with to gather data?
stmbtwle

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Reply with quote  #23 
The DS18b20 sensor works well; you can put several on the same lead and read them individually. Work well with an Arduino, and they're inexpensive.

https://www.amazon.com/Vktech-DS18b20-Waterproof-Temperature-Transmitter/dp/B00CHEZ250/ref=sr_1_8?ie=UTF8&qid=1508243207&sr=8-8&keywords=digital+temperature+sensor

Also on ebay.

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Willie, Tampa Bay
Rick H Parker

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Reply with quote  #24 
If you want to compare the productivity of different configurations your need to measure more then temperature alone, your need to measure air flow also.

 The objective of a collector is to harvest Thermal energy. Which is measured in Joules or British thermal Units (BTU). Joules and BTUs are quantities of energy. Temperature is not a quantity of energy, it is a differential measurement, the average Kinetic energy in reference to a datum.

A collector with a higher temperature gain can be more productive or it can be less productive then a collector with a lower temperature gain.

To measure the productivity of a collector you need to calculate the rate in which Thermal energy is transferred to the collector and compare it to the rate Thermal energy is transferred from the collector.

This equation is not exact but it is close enough for your purpose.

Where:
CFM = Air flow in Cubic Feet per Minute.
1.08 is a constant based on the industry standard assuming, 0.075 lb/cu ft density for air, 0.24 specific heat and the conversion of CFM to CFH.
Delta T (ΔT)   = The change in temperature in degrees Fahrenheit, T1 being the output temperature, T2 being the input temperature.

BTUs/hour = CFM * 1.08 * ΔT.

 


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Rick H Parker
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gbwillson

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Reply with quote  #25 
I'd skip the data tracking for now as it could blow your limited budget, but could be added later as the budget allows. Digital probe thermometers are cheap($7) and can be easily mounted in the air stream to capture the air temps. I also makes the Padawan learners chart the results on paper or in a spreadsheet. I'd invest in an anemometer so you can capture the output CFM. The only way to directly compare the performance results of two collectors is to have identical CFM flowing through them. Once the two units CFM matches, the one with the higher Delta T is the winner.

Greg in MN
stmbtwle

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Reply with quote  #26 
Seems to me you could compare different CFM collectors just as easily.

What you are looking for is a function of CFM x dT (per sq ft) so a collector with a higher flow and a lower dT could be compared with one with lower flow and a higher temperature difference. One could even compare different sized collectors, or collectors in series.

Add a speed control or damper to the fan and one could hunt for that "sweet spot" of greatest efficiency.

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Solar is like the wind. It may be free, but putting it to work isn't!
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matlocc

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Reply with quote  #27 
Great thought on the anemometer.  Quick question, I am going to get some stuff to do a partial build to show my principal after work today.  would a clear shower curtain work for glazing?  That would cut costs a bunch.
Rick H Parker

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Reply with quote  #28 
Window shrink film will withstand temperatures of 240 - 340°F
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Rick H Parker
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gbwillson

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Reply with quote  #29 
You probably could get away with it. 

Most are made of vinyl or PVC and would soften a great deal when heated. But you likely won't get too warm as long as you have a fan moving the air. You could also consider the window film you place over windows in the winter.  Good luck in making your presentation!

Greg in MN


stmbtwle

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Reply with quote  #30 
I think the window shrink film woulld work well. With a little creativity one could even "double glaze" with it.
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Solar is like the wind. It may be free, but putting it to work isn't!
Willie, Tampa Bay
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