matlocc
1420920295
Posted 1516727155
Reply with quote #1
Ok, so the kids figured the panels are 2.4 cubic /ft. The anemometer is showing 530 ft/min so does that mean the air is changing 220 times a minute? 530/2.4 not sure what I am doing wrong.
gbwillson
1352981942
Posted 1516735050
· Edited
Reply with quote #2
Normally we don't calculate the actual CF inside a collector, as it doesn't figure in performance numbers. Although a smaller space inside a collector will heat up marginally faster, it also means the airflow is closer to the cold glazing. We DO, however, calculate the CFM for the airflow. To do that you need to convert the LFM(linear feet per minute). Here is a link to calculate your own numbers. Just be sure to enter the proper duct size.http://www.calculatoredge.com/optical%20engg/air%20flow.htm As you can see below, there is roughly 46CFM of air passing through the collector. So divide the air passing through by the space inside the collector to find the exchange rate. 46.25 / 2.4 = 19.27 air changes per minute.
matlocc
1420920295
Posted 1516738625
Reply with quote #3
Thanks Greg. I figured that out after I posted. I start with the inside volume just to see how they are with measuring and simple math! Then they get an idea of how much air they are heating without fans and then we go from there. Without fans they are getting about 3-5 percent effiecency. Then they work up.
gbwillson
1352981942
Posted 1516741919
Reply with quote #4
I like to focus more on BTU output than efficiency. I have several small electric space heaters that know the BTU output, so I have a specific output for perspective and comparison. BTU output is also easier and quicker to calculate.
Garage_Hermit
1359070732
Posted 1517265806
Reply with quote #5
Hi, matlocc,https://www.builditsolar.com/References/Measurements/CollectorPerformance.htm
(1) "Heat goes from hot to cold, there is no directional bias"
