Chris Lewis wrote:
According to Jeff Wisnia :

I wonder if it would be cost effective for some company to produce a
heat exchanger combined with a small circulating fan for recovering that
heat? The fan could be switched on by a thermostat so that it only ran
when the hot air from the dryer warmed the unit up.


I've been doing some research on this, and it appears that the
technology just seems to have not produced something economically
viable yet for residential class dryers. For multiple commercial
dryers (ie: laundramats) certainly, but not a single relatively
little used unit.

Coping with the lint is perhaps the major factor, otherwise,
standard heat recovery ventilators (ie: those in R2000 homes
are typically $500-$900) would be common already for this purpose.

The cheapest heat reclamation units I've seen suitable for dryers
are on the order of $3K at a bare minimum, and routine service
schedules (lint cleanout etc.) is apparently important. Significant
effectiveness and a reasonably short repayment period in a commercial
setting (especially when you share them amongst several units), but
not useful in a residence.

Sound similar to the thread here a while ago started by someone who was
wondering how he could recover the waste heat from warm shower water on
its way down the drain.

Even in my most parsimonious of moods I wouldn't expect you'd ever get a
payback of capital costs from doing something like that in a home.

Do they even do things like that in places like high school gym shower
rooms?

I do remember a friend who about 35 years ago had a city water cooled
air conditioning system in his home. The condenser was cooled by water,
not air. He had it plumbed so that he could route the discharge water to
his garden hose when he wanted to, but I expect those times were few and
far between and most of the time the water just went down the drain.

That was back when city water was ignorably cheap. I haven't recently
heard of any home air conditioning systems using water for condenser
cooling, do they still make them? (Don't bother telling me about setting
up a lawn sprinkler to spray the condenser of an air cooled unit. Same
general principle, but that's not what I was rambling about.)

Jeff

--
Jeffry Wisnia

(W1BSV + Brass Rat '57 EE)

"Truth exists; only falsehood has to be invented."