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Seatec

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Posts: 219
Reply with quote  #11 
Mine is kestrel, one of the cheaper ones! blue in colour! very sensitive.
Another instrument I use a lot is a meter for measuring the power of the sun in watts per sq meter. A good day is from 1000-1100 watts.

Wayne

solardan1959

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Posts: 1,845
Reply with quote  #12 
Well,
   Wrong again, did not do any research and did not see how a meter could measure CFM because it would not know the area of the flow it is measuring.  Magic or do you tell it the size and shape of the pipe?

  That's okay, not the first time and won't be the last.

Quote:
23 oz Arizona green tea cans
  That's a relief, at least it not those finicky pop cans.

Big collector, seems like a lot of heat for Georgia but I guess you guys are used to it.
Dan
Rick Stone

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Posts: 121
Reply with quote  #13 
   The concept  of a Zero Pass heater is not mine. Maybe someone that knows can give credit where it is due. The frame for the mirrors is just pieces of bed frame that I had laying around. The design for it was not something that was easy for a fly by the seat of the pants engineer. The concept comes from the flying buttress architectural design that is very old and I adapted it and made some changes. It took me about a 2 weeks to design and complete.
   Enclosed is a drawing that I hope will give you an idea of the structural design and the way that it works and why. It plays compressing of the bottom angle iron against outward tension of the stainless rod. It is something that is hard for me to describe but something that I can easily visualize where the stresses and tensions are. Maybe someone here with some engineering background can explain it better.
Rick Stone

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Posts: 121
Reply with quote  #14 
Quote:
Originally Posted by Rick Stone
   The concept  of a Zero Pass heater is not mine. Maybe someone that knows can give credit where it is due. The frame for the mirrors is just pieces of bed frame that I had laying around. The design for it was not something that was easy for a fly by the seat of the pants engineer. The concept comes from the flying buttress architectural design that is very old and I adapted it and made some changes. It took me about a 2 weeks to design and complete.
   Enclosed is a drawing that I hope will give you an idea of the structural design and the way that it works and why. It plays compressing of the bottom angle iron against outward tension of the stainless rod. It is something that is hard for me to describe but something that I can easily visualize where the stresses and tensions are. Maybe someone here with some engineering background can explain it better.

Attached Images
jpeg Drawing_.jpg (136.29 KB, 108 views)

Rick Stone

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Posts: 121
Reply with quote  #15 
Anemometer update.  I made some measurements with my anemometer  and using the online calculator (http://www.calculatoredge.com/optical%20engg/air%20flow.htm )                                 to see what cfm the fan was producing and what cfm was I getting at my outlet.

The fan specs said that it was a 133 cfm fan, but they all lie and I expected less when it was measured but no..

177.3 cfm coming out of the fan at the end of a 5 ft hose. I found that if I tried to measure directly at the fan it had a dead spot in the middle and a hot spot where the fan blades were.

141.96 cfm coming from the outlet

So the difference is 35.34 cfm drop which is 20% loss due to the heater and air duct resistance.

I have nothing to reference that to other solar heaters. Is that good, bad or fair ?  What percentage of loss are other people here getting?
gbwillson

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Posts: 2,224
Reply with quote  #16 

Hi Rick-

How great that your fan is more powerful than you thought. Different fan types are important too. Inline fans don't operate very well with much resistance. There are no hard rules  for how much airflow will decrease due to ducting as no two systems are the same. I do know that ducting elbows add a lot of resistance. For example, a 90 degree elbow adds as much resistance as 6' of ducting. Flex ducting adds a lot too. If you do use it, keep it as straight and stretched out as possible. Over the weekend there was a discussion about how turning up your fan could increase efficiency as much as 40%. The cooler the output air, the more efficient the collector is running. While the air coming out of your heater may feel lukewarm, as long as the airflow is warmer than the air in the room, you will be adding heat to the room. But I wouldn't want what feels like a cool breeze blowing on me. If you happen to have too much CFM for you liking, you can either limit air intake, or get a speed control for you fan. Being able to adjust the fan speed would allow you to "dial in" the perfect fan setting.

Greg, MN[wave]

Seatec

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Posts: 219
Reply with quote  #17 
Correction,mine measures in fpm. The chart I use has cfm written beside it and I was think of that.
This is what I get out of mine the last day we had sun.
580fpm out of a 5in pipe, measured in the center which is 79.09 cfm . Temp rise of 55f gives me 4071 btus,
60 f rise gives 4441 btus, does this sound right.

Wayne
Seatec

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Posts: 219
Reply with quote  #18 
I may have made a mistake, it may be 97.09 cfm, will have to check when I go to my shop.

Wayne
Julian Jameson

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Posts: 152
Reply with quote  #19 
The velocity method formula for sizing ducts is:

A=144q/v

Where:
A = duct cross sectional area (sq.in.)
 
q = air flow rate (cfm)
 
v= air speed (fpm)


You can solve for cfm on that formula if you know A and fpm (which sounds like what you're doing Wayne)

Rearranging the formula and solving for cfm gives:

q=a*v/144
or
cfm=duct area(sq.in.) * fpm / 144

PI*(5/2)^2 * 580 / 144 =79.09 cfm

http://www.engineeringtoolbox.com/sizing-ducts-d_207.html
Seatec

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Posts: 219
Reply with quote  #20 
I just go my chart I have printed out, never could do algebra in school, was a mystery to me, just could not do a simple one, geometry I would make 90 on exams, algebra about 5.

Wayne
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