This week-end I build a small solar heater of 1.2meter by 1.2meter. Basically a closed box with the back painted in black and front cover with a transparent plastic. I trying to know the rough performance of it but I get a bit lost on how to calculate it.
The numbers I have:
-The panel is 1.44 square meter ( not sure is required ). -The fan suck the outdoor air at 10 Celcius in the panel. -The fan push the air out from the panel at 50 Celcius at noon. -The rated fan CFM is 16Cubic Feet Minute. -I don't know the relative air humidity exactly. Let's say 40% but I don't use it for approximate result. I don't want to be so precise.
Here is my wrong calculation:
16 cfm = 0.45 cubic meter minute. air heat = 721 J/Kg * Celcius air density = 1.29 Kg per cubic meter temperature difference = 40Celcius 0.453 cubic meter of air = 0.45 cubic meter x 1.29Kg/cubic meter = 0.58 Kg 721J/ 0.58Kg * 40Celcius = 721J / 23.36 = 30.86J
It's where I get stuck. 30.86Joule is per minute ? So I have to multiply it by 60 to get it in hour ? 1800J ... so 0.5watt/hour? It's not look like correct to me for all that heat come out of my panel. Don't multiply it by 60 give me worst result.
If it's right , my panel have poor performance ! :)