How about this one!
Dryer heat exchanger
"performance is quite good. Access holes for a digital thermometer in the top two compartments show air from the dryer between 110 to 130 F degrees on "medium" heat setting while the preheated air back to the air box measures 112 to 122 degrees F. Another test run with a small load of towels on "high" heat measured 113 to 120 Deg. F to the air box and 123 to 148 Deg. F from the dryer."
I like the nice compact arrangement.
Gary