DIY ventilation heat exchanger - Page 35

kostas · 01-20-13, 04:29 PM

Hi ham789, interesting experiment.
Have you tried putting fans on both of them?
Anyway, those heatsinks are quite expensive, I recon, so it seems not very convenient in the first place...

ham789 · 01-22-13, 06:24 AM

Yep, I did some bench experiments with controlled temperatures
and fans on both.
I picked these up cheap at garage sales. To get reasonable
efficiency, it would take at least three pair of 'em.

Some of the homemade heat-pipe stuff got posted here
about a year ago. Maybe by AC_HACKER.

I never found a cost effective method (cheap) of sealing 'em.

I'm not highly motivated, because the coroplast HRV is working
well enough.

kostas · 01-22-13, 07:31 AM

Quote:

Originally Posted by ham789

I'm not highly motivated, because the coroplast HRV is working
well enough.

I totally agree with that

Another issue that I'll have to handle is the RH output.
During this month of testing I noticed that inhouse RH never raised over 35%, and that's not a big deal.
I was thinking of using a humidifier placed in the inlet plenum.
There are two alternatives:

A vaporizer, cheap and easy to use, but very high current consumption (at least 1200W)

An Ultrasonic humidifier, more expensive, delicate to use and not so healthy, as it creates water drops that carry impurities that are in the reservoir, including minerals from hard water (which then forms a difficult to remove white dust on nearby objects and furniture), and pathogens growing in the stagnant tank.

Any other ideas?

Piwoslaw · 01-22-13, 02:49 PM

Quote:

Originally Posted by kostas

Any other ideas?

How about the ingoing air blowing over a small pan of water? This would catch some of the evaporation, increasing RH a bit. Also, the more humid the air, the less water vapor it will pick up. The up side is that it's cheap and won't increase power consumption. The water in the pan could come from the condensation going on inside the HX, so it will be more or less distilled.
Just an idea

kostas · 01-22-13, 04:32 PM

Yes, I was thinking about something like that, too. Welding that pan directly to the post heating exchanger would be best. My only concern is messing up with the good fellas like legionella or worse. Adding a UVC germicidal lamp above it could be a definitive solution?

ham789 · 01-22-13, 09:04 PM

Here in Oregon, the outside humidity is very high in winter.
I use an ultrasonic humidifier on the occasions that it gets too
low for comfort. Put a little bleach in it to keep the diseases at bay.
Don't have much problem with hard water.

My little hrv takes out a lot of water. Depending on current humidity,
I just don't run the stove
vent or the bathroom fan to keep the released moisture inside.

Never thought much about it and assumed an steam generator used
a lot of energy. But...if it takes just as much energy to vaporize
a cc of water at 70F as it does at 212F, maybe it doesn't matter.
And if all that heat stays in the environment, the only difference
is the cost of electricity vs cost of primary heat source.

I experimented with wet towels on the bathroom rack over
the heater vent. Seemed to help, but conflicts with the primary
purpose of the towel...to dry things.

And condensation inside the HRV should give back some percentage
of the energy it took to create the humidity in the first place.
Yes???
Next time I'm bored, I'll run a thermocouple down the coroplast
and see where the dew point is located.

I keep running into diminishing returns. It just doesn't get that cold
here. Was 23F this morning, but up near 40F during the day.
Over the last 577 cycles of the gas heater, I've averaged 7,440
BTU/Hour.

AC_Hacker · 01-22-13, 09:27 PM

Quote:

Originally Posted by ham789

...I use an ultrasonic humidifier on the occasions that it gets too low for comfort... Depending on current humidity,
I just don't run the stove vent or the bathroom fan to keep the released moisture inside... And condensation inside the HRV should give back some percentageof the energy it took to create the humidity in the first place.
Yes???

Sounds like you're having trouble with low humidity.

Somewhere in this forum there is a link to a guy who made a HRV HX out of cardboard, to send the humidity back into the house.

Might try that.

-AC

ham789 · 01-23-13, 02:57 AM

Problems with cardboard include...
I don't much like stuff that stays wet forever.
Structural integrity may be a problem with wet cardboard.
Outgoing air condenses at the dew point.
But incoming air needs to be above the dew point to
get significant evaporation. That means moisture has to
move backwards. I can't figure out how to arrange it to
happen reliably in cardboard.

I haven't been able to convince myself that the thermodynamics
works. The outgoing air gives up heat as the moisture condenses,
but you have to put it back to evaporate it in the input air stream.
My gut tells me that it's more efficient to add moisture by evaporating
water at inside air temp instead of starting at the dew point.
The math may be the same, but the practical aspects of getting the
heat where it's needed suggest not to try to reclaim the outgoing
moisture.

I'm gonna have to rethink how the desiccant wheels work.
Seems like desiccation must take much less energy than condensation/evaporation.

Discussion??

AC_Hacker · 01-23-13, 09:45 AM

Quote:

Originally Posted by ham789

...Problems with cardboard include... Discussion??

I wish I remembered where the link to the cardboard HX was...

[EDIT: Thanks to Kostas the link is HERE and also HERE]

As I recall, the user reported that he had been using it for two years. Seems a stretch to me. I think that a permeable non-organic material would be better, but off the top of my head, I can't think of a readily available cheap material that would fit that bill.

But the corrugated cardboard thing definitely has its charm... as a proof of concept, it would be a dirt cheap project.

I suspect that dirt cheap projects would be ok.

I think the guy was using the cross flow configuration. I think your configuration is much better.

BTW, you doing anything today? I could drop by and show you the Fine-Wire HX that fell into my evil possession.

-AC

kostas · 01-23-13, 10:07 AM

Here it is

Izdelava kartonskega izmenjevalca | PodSvojoStreho

(woz here)

01-20-13, 04:29 PM	#341
kostas Helper EcoRenovator Join Date: Dec 2012 Location: Venice, Italy Posts: 89 Thanks: 15 Thanked 41 Times in 19 Posts	Hi ham789, interesting experiment. Have you tried putting fans on both of them? Anyway, those heatsinks are quite expensive, I recon, so it seems not very convenient in the first place...

01-22-13, 06:24 AM	#342
ham789 Helper EcoRenovator Join Date: Dec 2011 Location: tigard, oregon Posts: 42 Thanks: 0 Thanked 4 Times in 4 Posts	Yep, I did some bench experiments with controlled temperatures and fans on both. I picked these up cheap at garage sales. To get reasonable efficiency, it would take at least three pair of 'em. Some of the homemade heat-pipe stuff got posted here about a year ago. Maybe by AC_HACKER. I never found a cost effective method (cheap) of sealing 'em. I'm not highly motivated, because the coroplast HRV is working well enough.

01-22-13, 04:32 PM	#345
kostas Helper EcoRenovator Join Date: Dec 2012 Location: Venice, Italy Posts: 89 Thanks: 15 Thanked 41 Times in 19 Posts	Yes, I was thinking about something like that, too. Welding that pan directly to the post heating exchanger would be best. My only concern is messing up with the good fellas like legionella or worse. Adding a UVC germicidal lamp above it could be a definitive solution?

01-22-13, 09:04 PM	#346
ham789 Helper EcoRenovator Join Date: Dec 2011 Location: tigard, oregon Posts: 42 Thanks: 0 Thanked 4 Times in 4 Posts	Here in Oregon, the outside humidity is very high in winter. I use an ultrasonic humidifier on the occasions that it gets too low for comfort. Put a little bleach in it to keep the diseases at bay. Don't have much problem with hard water. My little hrv takes out a lot of water. Depending on current humidity, I just don't run the stove vent or the bathroom fan to keep the released moisture inside. Never thought much about it and assumed an steam generator used a lot of energy. But...if it takes just as much energy to vaporize a cc of water at 70F as it does at 212F, maybe it doesn't matter. And if all that heat stays in the environment, the only difference is the cost of electricity vs cost of primary heat source. I experimented with wet towels on the bathroom rack over the heater vent. Seemed to help, but conflicts with the primary purpose of the towel...to dry things. And condensation inside the HRV should give back some percentage of the energy it took to create the humidity in the first place. Yes??? Next time I'm bored, I'll run a thermocouple down the coroplast and see where the dew point is located. I keep running into diminishing returns. It just doesn't get that cold here. Was 23F this morning, but up near 40F during the day. Over the last 577 cycles of the gas heater, I've averaged 7,440 BTU/Hour.

01-23-13, 02:57 AM	#348
ham789 Helper EcoRenovator Join Date: Dec 2011 Location: tigard, oregon Posts: 42 Thanks: 0 Thanked 4 Times in 4 Posts	Problems with cardboard include... I don't much like stuff that stays wet forever. Structural integrity may be a problem with wet cardboard. Outgoing air condenses at the dew point. But incoming air needs to be above the dew point to get significant evaporation. That means moisture has to move backwards. I can't figure out how to arrange it to happen reliably in cardboard. I haven't been able to convince myself that the thermodynamics works. The outgoing air gives up heat as the moisture condenses, but you have to put it back to evaporate it in the input air stream. My gut tells me that it's more efficient to add moisture by evaporating water at inside air temp instead of starting at the dew point. The math may be the same, but the practical aspects of getting the heat where it's needed suggest not to try to reclaim the outgoing moisture. I'm gonna have to rethink how the desiccant wheels work. Seems like desiccation must take much less energy than condensation/evaporation. Discussion??

01-23-13, 10:07 AM	#350
kostas Helper EcoRenovator Join Date: Dec 2012 Location: Venice, Italy Posts: 89 Thanks: 15 Thanked 41 Times in 19 Posts	Here it is Izdelava kartonskega izmenjevalca \| PodSvojoStreho (woz here)