DIY ventilation heat exchanger

[Xringer]

I was thinking of using something like a hair-dryer or a weak heat gun
on the warm air input 'port' and a cool air fan on the 'heat-pick-up' port.

Maybe let the warmed-up air blow out on a strip of copper,
so the temperature can be easily measured with the IR Pistola.?.

I'll have to check my stock of 4mm coroplas and see if there is enough
available to make a small X-block exchanger.
~
Yeah, I have some left-over sheets of white, blue and yellow,
and two larger un-cut sheets of yellow, if it comes to that..

Yeah, it looks like I could use it all and make an 8x8x8 core..

Wow, I was just looking at the specs for the Airiva units and they are using a 12x12 core that's 11.25" tall..

It's 74 12x12 (4mm thick) sheets..

Maybe a little DIY 8x8x8 core could be used in a practical application after
testing is complete.. (If it has good heat transfer)..

[NiHaoMike]

How about use a pair of car radiators and a pump to circulate a water/coolant mixture through it?

[AC_Hacker]

Originally Posted by Xringer

Maybe let the warmed-up air blow out on a strip of copper, so the temperature can be easily measured with the IR Pistola.?.

Aren't you the guy that built a data logger? This would be a perfect application for it.

And, I think that a thermistor just hanging in the air stream would be great. Thermistors are pretty quick to respond and most of them have a midrange close to the temperatures you're working with.

You're going to have to do some research to be able to calculate efficiency, but with a data logger and thermistor, you could at least rank various test configurations. That would be pretty useful in itself.

I'm trying to build a hydronic floor that doesn't weigh a ton (literally), and I tried testing several different materials using a data logger and a ranking scheme, and I really learned a lot. I'm still not ready to build, but I know what NOT to build.

-AC_Hacker

[Xringer]

I have the hardware, but not the software.. And I'm getting too old to program..

I do have a couple of probe type thermometers that should work,
and if the core seems like it can handle the job,
I could build a fan case and give the core a practical use test.
Even a little 8" core might be enough to provide a bit of fresh air to the basement..
Too bad I don't have more coroplas, I could build the box from it..

Spare time is the problem these days. Right now, it's in short supply..
The Honey-Do list never seems to shorten..

[AC_Hacker]

Originally Posted by Xringer

I have the hardware, but not the software.. And I'm getting too old to program..

Yeah, hardening of the brain, I guess...

If your data logger will output a comma-separated or tab-separated or space-separated text file, you could pick it up in Excel and use Excel's graphing capabilities.

Don't know if you know Excel, but it's far easier than traditional programming.

That's what I did with mine. Worked good enough for my purposes.

-AC_Hacker

[AC_Hacker]

As long as active minds & hands are involved with DIY HRV/ERV, I thought it would be a good idea to post some links regarding HVAC industry approved levels of room air replacement. They boil it down to Air Changes per Hour (AKA: ACH). This takes into consideration the Cubic Feet Per Minute, and also the volume of the room.

Here's a link to a page that clearly explains how to do the claculation.

And here is a link to a PDF that has the industry-approved air change rates, and also the formulas used to calculate the air change rate. (* download & save *).

Interesting to note that the Passive House standard is different and lower, and has a per-person standard or a per-area standard.

Early Passive Houses were able to hit the stringent heat-retention targets that were saught, but people complained that the Passive Houses were "stuffy". After rentless Germanic testing the following ventilating level was determined:

• Passive House per-person = 15 CFM per person.
• Passive House per-area = 15 CFM per 377 square feet floor area.

This works out to 0.3 ACH for a house. This works out to 1/20 to 1/67 of the recommended ASHRE standards. Interesting, huh?

I know that the Americans pretty much invented the science of air conditioning and ventilating, but the Germans should not be lightly dismissed.

Anyway I read an interview with one of the most prominent European Passive House spokesmen, and the question was raised as to whether or not a HRV would really pay for itself, and he essentially said that you should begin your design with Heat Recovery Ventilating.

I'm sold.

-AC_Hacker

[Xringer]

My wife is printing out pages on the Laser printer. Since it's about 2 feet from me,
I'm getting Ye Olde Laser Air right now.. Stinky!

So, right now, I'm thinking almost any amount of fresh air, is going to be better than none at all..

If I can build something that brings in some fresh air, without too much loss
of indoor heat (or cool air), it would be an improvement.

If we were talking a very minor improvement, then forget it.
But, if it were a noticeable improvement.?. Might be fun to build..

[Piwoslaw]

The standard for house ventilation systems is:

• Fresh air goes into "clean" rooms (bedroom, livingroom),
• Used air gets sucked out of "dirty" rooms (bathroom, kitchen).

Since the "dirty" rooms are getting their air from the rest of the house, in many circumstances those rooms don't even need their own heating/cooling.
As for air flow, I believe the minimum is 0.5 house volumes per hour, the maximum is either 2 or 4 house volumes per hour (don't remember). When replacing more than 2 (or 4) house volumes per hour the heating/cooling/recovery system may not be able to keep up, leading to noticeable drafts and energy loss. Also, the ducts should be sized to keep air speed below 5 m/s to keep noise down.

[AC_Hacker]

I called a sign-supply shop and ordered some Coroplast, or more correctly the same product made under another name.

There was a difference in price with regard to color...

White was about $13 per 4 ft x 8 ft sheet.

Black was about $17 per 4 ft x 8 ft sheet.

I went with black even though it was a bit more expensive, because I think that carbon is probably the pigment used and is likely to improve thermal transfer.

I bought 2 4x8 sheets. Since I don't have a van or truck, I had them cut into 12" x 12" squares (slightly less because they use a saw and kerf allowances were needed).

There was a small charge for cutting.

I still have the problem of if and how to join the pieces...

-AC_Hacker

[AC_Hacker]

Originally Posted by Piwoslaw

The standard for house ventilation systems is:

• Fresh air goes into "clean" rooms (bedroom, livingroom),
• Used air gets sucked out of "dirty" rooms (bathroom, kitchen).

Since the "dirty" rooms are getting their air from the rest of the house, in many circumstances those rooms don't even need their own heating/cooling.
As for air flow, I believe the minimum is 0.5 house volumes per hour, the maximum is either 2 or 4 house volumes per hour (don't remember). When replacing more than 2 (or 4) house volumes per hour the heating/cooling/recovery system may not be able to keep up, leading to noticeable drafts and energy loss. Also, the ducts should be sized to keep air speed below 5 m/s to keep noise down.

Comparing your figures with ASHRE figures helps explain why the US uses 2 times as much energy per person, compared to Europe!

-AC_Hacker