Energy Conservation Through Dryer Exhaust Air Recirculation

If your fresh inlet air is too cold and your exhaust air too hot, then a simple passive heat exchanger will help things a lot.

Google HVAC heat exchanger or passive heat exchanger.

Or have I missunderstood?

Gotta go...wife says she's just read that blogging isn't cool and I should be out in the garden!

You seem to be using industrial tumble dryers. Agricultural produce dryers have the same problem. a lot of heated air are released unused.

The moisture must however be removed between successive units.

The best way would be to use a heat exchanger to reduce the heat to allow for condensation and the removal of water. Remaining heat should then be used to preheat the air to the next unit.

I don't think it would be viable but it is worth investigating.

It depends also on how your existing dryer functions. If it is a modern refrigerated dehumidifier it probably reheats the air - and in terms of heat pump theory it could be more than 100% efficient anyway.

Please describe the dryer function for more info

When I worked for an industrial laundry, we visited this issue.

You must keep your input and exhaust airflows separate. Especially in a cleanroom where you are looking to exhaust your particulate matter.

The biggest drawback on the industrial side was sand from mats would eat away at any heat exchanger we would mount in the exhaust.

In a cleanroom, you will not have that issue.

I believe Cain Industries out of WI would be a good starting point.

Energenics is another vendor for these items.

Thanks for the ponters and sorry for the vague information. Yeap, these are industrial tumble dryers for cleanroom laundry with a draw of a max volumetric flow of 3000 cubic meter per hour of air each run.

Our current design is:

Fresh air at ambient temperature (27-30 degree C) is mixed with the recirculated hot exhaust air in a mixing chamber before being filtered through ULPA filters and re-supplied to the dryers. We also have a tee-off with a manual damper at the recirculation ducting to direct the exhaust air out in case this system doesn't work.

We do have concerns on particulate contamination and that's why we route them through ULPA filters again.

I agree with those above that a passive heat exchanger is probably your best bet. You'll be able to recycle a decent amount of heat and avoid the particulate and moisture problems.

Another possibility might be using the exhaust to provide some of the heat for the wash water. I'm not sure, but I wouldn't be surprised if you could get a higher efficiency heat transfer to the water and maybe save more energy. Heating water is by far the #1 use of electricity in laundry applications and isn't that far from lighting and AC overall (or so I've heard, I don't have a reference). If that is viable, you might want to look into solar water heaters as well. They are quite efficient and can save lots of electricity, in the right situation, and not that expensive to have installed or build yourself.

This is a realtively common application and condensation needs to be dealt with. There are a couple of companies that specialize in heat recovery air make up units. I would suggets you contact; Lahren James Inc (519)841-6464 and DesChamps Labs (540)291-1111. A lot of heat transfer companies can solve this problem for you but this is what Lahren James and Des Champs specialize in.

Delta T Heat Exchangers

Sir,

Can you pls. give some address and contact numbers who deals with such type of energy conservation measures from India.

regards

Sampath Kumar