Hi,
"I see I am not the only one who read "Sunspots"."
Right -- along with the Shurcliff "100 Inventions" book, its one of my favorites.
"All systems for fluid flow do better with smooth surfaces and large cross-section piping to transfer fluid. Gasses are considered fluids. Prediction of flow and velocities is "good guess-work" even by air-handling "experts", IMO."
Good point -- especially for the thermosyphon, smooth flow passages should have some payoff in better airflow. Large entry and exit vents definitely make a difference.
"Thermosyphon systems depend on solar radiation, a variable, positioning of panels, another variable, sun position and cloud cover, more varaibles, and the air handling "duct work", an unknown in this case. Fans are a great "CYA" method of insuring a working system."
My (slight) objection to fans and controllers is that its just more stuff to take care of, and people tend to just let things go when the fan stops working. The thermosyphon collectors just keep working.
The nice thing about fans is that you don't have to cut so many holes through your walls
"As all the temperatures and energy for calculation are in "Kelvin", one should realize using outside air may be a viable option. The reports I have read and on my own collectors, I have chosen this approach. Gary, however, has actually calculated, built and measured results."
I guess this depends a lot on climate, and what you want to use the air for, but it does not seem like a real good bet in Montana when is -20F outside
Gary