Has anyone reused waste heat from a gas dryer?

[arttex]

I think the expensive part with heat exchangers is just the huge amount of surface area needed to make them efficient.  Seems like it would be a great project for DIY, if you have the materials, and an expert to double check it.

If they are counter flow (parallel) type, yes. To be efficient they need larger area for the fluids to pass trough. But with cross flow type of heat exchangers (cube like core, 90 degrees angle of the plates to each other), it can be done with smaller surface. Up to 60% of the temperature difference between two air streams (fresh air and dryer fumes) can be transferred to the fresh air.   

[Rockers]

As I have mentioned already in my earlier post there are heat exchangers available for gas dryers. This one is made in the UK by CPN for their Clean Burn dryer. Of course that dryer spits out already a lot less CO2 the any other dryer on the market and needs a lot less gas  due to the superior airflow system they have developed. So their heat exchanger might work only for their type of gas dryer but it shows you that if there is a will and demand, and there is in Europe for sure, this can be easily achieved and build by any equipment manufacturer.
See page 2 of the pdf for the heat exchanger.
http://www.cpnuk.com/Clean%20Burn%20Brochure%20-%20NEW%20June%202010.pdf

[BorisB]

We  use heat exchanger on both of our gas dryers. First I installed cube like model which worked air/air. I wasn't too happy because air from dryer is very hot (130-160 deg C) and you can have it two ways:
a) lousy percentage of energy won by not heating fresh air enough
b) make it efficient will either cost you a lot and/or give you lots of air with about 90-100 deg C,  which is difficult to use.

Later I installed heat exchanger that works air/water by heating water that's in central heating system. In winter this exchanger heats up 80m2 of office space. According to engineer installing it we win back something like 14-15kW of heating power from our 150cm x 300cm gas dryer. It was made rather primitive with total cost of around 1000 EUR. With this system I'm happy

Boris

[Gilligan]

Hook us up with some pictures!

[californiadreamin]

CleanBurn = "Green Marketing Bull$hitt" Carbon Tax Credits!
A 25+ year old design used in the screen print graphic arts side!
Built years ago by Natgraph, Trumax, and a few others
Cleanest Burner? Show me the data
Minimal gas consumption! Low Air Flow. A kitchen oven hardly any gas! Bingo, no airflow.
It is all about the amount of goods, coming out cured, in a specific amount of space, with a
specific amount of energy.
Clean Burn does NOT pass the muster! A Great Marketing Illusion.Period
winston
904.3430848
 

[mk162]

I thought the same thing when I saw their numbers.

[Gilligan]

Winston, you must have some ideas for recycling this energy though... I'd love to hear them.

[BorisB]

Hook us up with some pictures!

Here you go:



Catcher View



Boilerman View

Simple concept, we have manual choice of bypass for summer, or going through exchanger unit. We added pump plus two temp/pressure controlls and safety valve. Inside of Exchanger is the same as in any water heating oven. Hot fumes (in our case air only) passes  in long curvy way through container filled with water.


Boris

[californiadreamin]

Gilligan!
Heat recycling makes total sense! I saw this in more northern states 30 years ago.
It was being done on the screenprint graphic side more often where
average gas burners were one to two million btu's. In the USA 1/2 of the dryers
I see are under vented or vented incorectly!  A lot of printers opt for the cheapest
vent which doesn't pass NFPA codes, but do it any way. In Europe were the climate is
colder, shops have been using heat exchanger technology for years. They have different
tax credits for things like this! The amount of shops there is nothing , like the amount here!
There are printers who put some units out, but most are printing 300-400 per hour which
lets them use smaller dryers than here. A 48" wide belt is real wide there. Dryers built here
in the USA are better for Manufacturing than dryers built in Europe! We lose energy here
when we fail to maintain and keep our equipment in top notch condition no matter what the brand!
Saving/ reusing energy makes Total Sense but, needs do be done in a balanced sense with
Amount of energy saved and return on investment!

[californiadreamin]

The pictures that Borris B. put up are great!
These help show where to start!
Quality/Type of vent are also correct! They are not the average single wall vent
that is sold at Home Depot! It shows adjustable flaps for adjusting air returns,recirculation.