[ynot7201]

Originally Posted by Christ

This is exactly like an air to air intercooler, but will not be as efficient as a bar/plate design. Skin xfer of heat is limited to surface area, and the smaller your pipes are, the more surface area there is to xfer heat from one medium to the next. Bar and plate is one of the most efficient because there is a tradeoff between thermal xfer efficiency and pressure drop, and many of the best intercoolers on the market are borderline at 80% efficiency (of this type of design).

Also, keep in mind that the more heat you extract from your exhaust, the more you slow it down, making it more difficult for the intake fan to blow air through the dryer, and more difficult for the moisture to leave. The idea is to snake as much heat as you can right at the exhaust outlet so that there isn't a pressure increase slowing down flow.

Another way you might go about this is to minimize heat loss in all places except where you specifically want the heat to go. Insulate your exhaust and intake. If you want heat exchange from the exhaust to the intake, you don't want heat exchange anywhere else, so if you insulate the tubing, you can mitigate much of the heat loss, making the system more efficient than it would have been before, so your heat exchanger might have less of an impact on exhaust flow velocity.

Keep in mind, also, that you will need to periodically clean the heat exchange surfaces. If you don't, they will stop transferring heat. Lint is a great insulator.

thanks for the info regarind vent heat recovery. about 5-6 years ago I saw a system consising of a metal box with inlet 4" same for exhaust in the box was a fan on rear blowing the hot exhaust air forward to a foam like screen and a drip tray at the bottom this unit worked extremely well..but we are unable to find this sytem...any ideas ..thanks and have a great day.