DIY ventilation heat exchanger - Page 24

Fornax · 12-11-12, 02:09 PM

Mikesolar,

Indeed, given enough coroplast the efficiency might be high enough.
When just rotating whole plates 90 degrees you'll have surfaces that are not totaly flat pressed against eachother thus making a lousy contact with eachother. Not only will you have a double amount of coroplast between the cold and warm airstreams, they are separated with a thin layer of insulating air, this is not ideal.

A while back I wondered why use coroplast at all? To me plastics aren't known for their great transfer of heat. But of course if it's a thin sheet with a large surface this is hardly a problem.
Actual numbers: Coroplast 0.20W/m*K, Aluminum 237W/m*K
I found a study where a HRV is build and tested with Coroplast, along with calculations.
I replaced the value for coroplast with the one for aluminum in one of the formulas for -that- heatexchanger-core and the result changed from 12.7 W/m2*K to 13.2 W/m2*K, which is only about 4% higher for aluminum (if used in -that- specific HX).
Link: http://www.ewp.rpi.edu/hartford/user...0Exchanger.pdf

Fornax · 12-11-12, 02:54 PM

I just checked my email,

The aluminium plates I ordered are send and supposed to be delivered tomorrow.

I ordered 72 plates of 25x50cm (say 10x20 inches), 0.8mm thickness which is, erm, <grabs calculator> 0.03125 inch or exactly 1/32".

The HX-core will be 30 centimeters thick. Using 72 sheets that will separate them by 3.4mm (4.3/32"). So the dimensions will be 25X50X30cm (10x20x15").

When these arive (in good shape) I'll order the 2 fans to be used.
I work in shifts, I plan on starting the build in my next weekend which is about a week from now, I'll be sure to take pictures.

Update, the next day:

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Piwoslaw · 12-11-12, 03:55 PM

Ooooo, this project will be fun!

Quote:

Originally Posted by Fornax

When these arive (in good shape) I'll order the 2 fans to be used.

I think I recall reading that using ECM squirrel cage motors is the most efficient and quietest solution, though not the cheapest. Not sure what kind of airflow you will be needing, but maybe some cheap 140mm computer fans would work for testing?

Fornax · 12-13-12, 05:35 AM

I'll be needing 2 fans and I have some demands.
They need to be:
- available to me
- somewhat affordable
- able to move the right amount of air
- be reasonably silent while doing that
- economical on energy use.

Airflow in the lowest setting will be around 50-75 m^3/hr (30-44CFM) depending on the resistance in the ducting, filters and HX. I asume this resistance will be quite low. In the middle setting airflow will be up to 150 m^3/hr (88CFM).

With those airvolumes you are in the range of wholehouse ventilators where most types are fairly large, have multiple connections and cost from 200-450 euros. I did find a smaller and cheaper one with only 1 in- and outtake, perfect for me.

It's the Comair Solo 44Y which is of course 230 volt for us in Europe.
Specsheet of the series (in dutch) is at http://www.ventilair.nl/Repository/S...20811A4web.pdf

Specs:

As you can see in the lowest setting it is stated to use around 8W (times 2) which is conveniently low.
Our current wholehouse ventilator is using around 40W, replacing it with the HRV using about half of that will safe me 40 euros on electricity a year alone.

.

MN Renovator · 12-13-12, 07:14 AM

Panasonic Whispergreen bathroom fans are the most energy efficient ways of moving air as long as you are okay with the form factor of the air collector. All sorts of CFM settings and they adjust themselves to speed up to blow the right CFM under pressure.

kostas · 12-13-12, 09:12 AM

@ Fornax I'm going to use the Nicotra direct driven motors for my project. Most HRV producers use Nicotra's motors in Europe (at least that's what I was told).
The DDM 120/126 model has a 45W consumption and gives over 400 qm/h at 100Pa
That's more than enough for a 100sqm house.
Have a look:
nicotra-gebhardt.com/front_content.php?idart=106]Catalogues
Maybe you can find a local dealer in the Netherlands, too.

(edit)
Here it is:
NETHERLANDS
Rucon Ventilatoren B.V.
Postbus 263
3840 AG Harderwijk (Netherlands)
Phone 0031 341 439-100
Fax 0031 341 439-190
E-mail verkoop@rucon.nl
wwwrucon.nl

Fornax · 12-13-12, 12:22 PM

I already ordered the fans I mentioned.

MN Renovator, those Panasonic fans look good indeed and several models on amazon are reasonably priced.

Kostas, that DDM120/126 is rated for a high capacity, more than I need, but did you notice it will make a noise of at least 61dB in the 'low' setting? If the noise is acceptable depends on your situation but for me it would not.

kostas · 12-14-12, 02:59 AM

Fornax, yes I noticed that, I don't think that this is an issue as I won't need 380 qm/h but only the half of it in daily basis. Also noise insulated ducts will help.
The problem is the price, over €170 each!

TimSmall · 12-14-12, 10:24 AM

I see you can buy some EBM Papst DV6424/2TDP fans used from Sun rack-mount computers for around 25 euros. You'll need to supply them with 24v DC. These are mixed flow (i.e. hybrid axial / centrifugal fans). They seem to be a custom high-power version for Sun (either 80w, or 110w depending on model), but are easily PWM controlled. At 40w, the fan curve looks like the below:

Student 07 · 12-14-12, 11:41 AM

Hi,
I have heard that Fantech also makes some very good (quiet) fans. Insulation will definitely help reduce noise, but I think TimSmall may be on to something: If you could use PWM to control the speed- a variable speed motor could easily be adjusted to an acceptable level that meets both noise and efficiency requirements. A lot of the noise will depend on the design of the system; large insulated ducts allow more flow at less noise.
I really like the idea of using aluminum plates, they should increase efficiency.

I still have a problem with HRVs. Even at 80% efficiency you are venting warm air and replacing it with cooler air. If the house is at 68*F you would be venting that air and replacing it with 61*F air. You would be cooling your house in the winter.
In link #163 Piwoslaw drew a picture of what I think would be the solution. Some people may say that the HP would use more energy than the HRV alone; however, when you have 61*F air coming into the house something is required to bring that air up to 68* to keep the house warm, either your central heating system or a small auxiliary heater. A small heat pump IMHO would be the best auxiliary heater.
I have some concerns about combining the HRV with a HP (which would be a hacked dehumidifier or AC unit): most HRV are rated at 150-350CFM while an Air Source Heat pump requires a lot of air. My 4 1/2 ton unit flows about 3500CFM. If I design it to make the HRV more efficient (small gap between plates) then the HP won't get much air flow, and if the plates of the HRV are spaced farther apart to increase flow for the HP, then the HRV is less efficient. I read an article on Build it Solar about DIY HRVs and it states that the airflow should be slow to increase heat transfer. Which is the opposite of what a HP needs

I suppose there would have to be a compromise between what they need. Does anybody know how much a small (say 1 ton) dehumidifier flows- CFM?
Every time I think about needing a HRV I come back to this, eventually I will have to make it.

12-11-12, 02:09 PM	#231
Fornax Helper EcoRenovator Join Date: Oct 2012 Location: Beuningen (Gld), the Netherlands Posts: 64 Thanks: 4 Thanked 19 Times in 16 Posts	Mikesolar, Indeed, given enough coroplast the efficiency might be high enough. When just rotating whole plates 90 degrees you'll have surfaces that are not totaly flat pressed against eachother thus making a lousy contact with eachother. Not only will you have a double amount of coroplast between the cold and warm airstreams, they are separated with a thin layer of insulating air, this is not ideal. A while back I wondered why use coroplast at all? To me plastics aren't known for their great transfer of heat. But of course if it's a thin sheet with a large surface this is hardly a problem. Actual numbers: Coroplast 0.20W/mK, Aluminum 237W/mK I found a study where a HRV is build and tested with Coroplast, along with calculations. I replaced the value for coroplast with the one for aluminum in one of the formulas for -that- heatexchanger-core and the result changed from 12.7 W/m2K to 13.2 W/m2K, which is only about 4% higher for aluminum (if used in -that- specific HX). Link: http://www.ewp.rpi.edu/hartford/user...0Exchanger.pdf Last edited by Fornax; 12-13-12 at 03:24 AM..

12-11-12, 02:54 PM	#232
Fornax Helper EcoRenovator Join Date: Oct 2012 Location: Beuningen (Gld), the Netherlands Posts: 64 Thanks: 4 Thanked 19 Times in 16 Posts	I just checked my email, The aluminium plates I ordered are send and supposed to be delivered tomorrow. I ordered 72 plates of 25x50cm (say 10x20 inches), 0.8mm thickness which is, erm, <grabs calculator> 0.03125 inch or exactly 1/32". The HX-core will be 30 centimeters thick. Using 72 sheets that will separate them by 3.4mm (4.3/32"). So the dimensions will be 25X50X30cm (10x20x15"). When these arive (in good shape) I'll order the 2 fans to be used. I work in shifts, I plan on starting the build in my next weekend which is about a week from now, I'll be sure to take pictures. Update, the next day: Last edited by Fornax; 12-13-12 at 03:28 AM..

12-13-12, 05:35 AM	#234
Fornax Helper EcoRenovator Join Date: Oct 2012 Location: Beuningen (Gld), the Netherlands Posts: 64 Thanks: 4 Thanked 19 Times in 16 Posts	I'll be needing 2 fans and I have some demands. They need to be: - available to me - somewhat affordable - able to move the right amount of air - be reasonably silent while doing that - economical on energy use. Airflow in the lowest setting will be around 50-75 m^3/hr (30-44CFM) depending on the resistance in the ducting, filters and HX. I asume this resistance will be quite low. In the middle setting airflow will be up to 150 m^3/hr (88CFM). With those airvolumes you are in the range of wholehouse ventilators where most types are fairly large, have multiple connections and cost from 200-450 euros. I did find a smaller and cheaper one with only 1 in- and outtake, perfect for me. It's the Comair Solo 44Y which is of course 230 volt for us in Europe. Specsheet of the series (in dutch) is at http://www.ventilair.nl/Repository/S...20811A4web.pdf Specs: As you can see in the lowest setting it is stated to use around 8W (times 2) which is conveniently low. Our current wholehouse ventilator is using around 40W, replacing it with the HRV using about half of that will safe me 40 euros on electricity a year alone. . Attached Thumbnails

12-13-12, 09:12 AM	#236
kostas Helper EcoRenovator Join Date: Dec 2012 Location: Venice, Italy Posts: 89 Thanks: 15 Thanked 41 Times in 19 Posts	@ Fornax I'm going to use the Nicotra direct driven motors for my project. Most HRV producers use Nicotra's motors in Europe (at least that's what I was told). The DDM 120/126 model has a 45W consumption and gives over 400 qm/h at 100Pa That's more than enough for a 100sqm house. Have a look: nicotra-gebhardt.com/front_content.php?idart=106]Catalogues Maybe you can find a local dealer in the Netherlands, too. (edit) Here it is: NETHERLANDS Rucon Ventilatoren B.V. Postbus 263 3840 AG Harderwijk (Netherlands) Phone 0031 341 439-100 Fax 0031 341 439-190 E-mail verkoop@rucon.nl wwwrucon.nl Last edited by kostas; 12-13-12 at 09:18 AM.. Reason: added info

12-13-12, 12:22 PM	#237
Fornax Helper EcoRenovator Join Date: Oct 2012 Location: Beuningen (Gld), the Netherlands Posts: 64 Thanks: 4 Thanked 19 Times in 16 Posts	I already ordered the fans I mentioned. MN Renovator, those Panasonic fans look good indeed and several models on amazon are reasonably priced. Kostas, that DDM120/126 is rated for a high capacity, more than I need, but did you notice it will make a noise of at least 61dB in the 'low' setting? If the noise is acceptable depends on your situation but for me it would not. Attached Thumbnails Last edited by Fornax; 12-13-12 at 12:41 PM..

12-13-12, 07:14 AM	#235
MN Renovator Less usage=Cheaper bills Join Date: Nov 2010 Location: Minneapolis, MN Posts: 939 Thanks: 41 Thanked 116 Times in 90 Posts	Panasonic Whispergreen bathroom fans are the most energy efficient ways of moving air as long as you are okay with the form factor of the air collector. All sorts of CFM settings and they adjust themselves to speed up to blow the right CFM under pressure.

12-14-12, 02:59 AM	#238
kostas Helper EcoRenovator Join Date: Dec 2012 Location: Venice, Italy Posts: 89 Thanks: 15 Thanked 41 Times in 19 Posts	Fornax, yes I noticed that, I don't think that this is an issue as I won't need 380 qm/h but only the half of it in daily basis. Also noise insulated ducts will help. The problem is the price, over €170 each!

12-14-12, 10:24 AM	#239
TimSmall Geek about the house Join Date: Dec 2012 Location: Brighton, Great Britain Posts: 17 Thanks: 0 Thanked 0 Times in 0 Posts	I see you can buy some EBM Papst DV6424/2TDP fans used from Sun rack-mount computers for around 25 euros. You'll need to supply them with 24v DC. These are mixed flow (i.e. hybrid axial / centrifugal fans). They seem to be a custom high-power version for Sun (either 80w, or 110w depending on model), but are easily PWM controlled. At 40w, the fan curve looks like the below: Attached Thumbnails

12-14-12, 11:41 AM	#240
Student 07 Helper EcoRenovator Join Date: Dec 2011 Location: Gresham OR Posts: 35 Thanks: 0 Thanked 3 Times in 3 Posts	Looking for solution Hi, I have heard that Fantech also makes some very good (quiet) fans. Insulation will definitely help reduce noise, but I think TimSmall may be on to something: If you could use PWM to control the speed- a variable speed motor could easily be adjusted to an acceptable level that meets both noise and efficiency requirements. A lot of the noise will depend on the design of the system; large insulated ducts allow more flow at less noise. I really like the idea of using aluminum plates, they should increase efficiency. I still have a problem with HRVs. Even at 80% efficiency you are venting warm air and replacing it with cooler air. If the house is at 68F you would be venting that air and replacing it with 61F air. You would be cooling your house in the winter. In link #163 Piwoslaw drew a picture of what I think would be the solution. Some people may say that the HP would use more energy than the HRV alone; however, when you have 61F air coming into the house something is required to bring that air up to 68 to keep the house warm, either your central heating system or a small auxiliary heater. A small heat pump IMHO would be the best auxiliary heater. I have some concerns about combining the HRV with a HP (which would be a hacked dehumidifier or AC unit): most HRV are rated at 150-350CFM while an Air Source Heat pump requires a lot of air. My 4 1/2 ton unit flows about 3500CFM. If I design it to make the HRV more efficient (small gap between plates) then the HP won't get much air flow, and if the plates of the HRV are spaced farther apart to increase flow for the HP, then the HRV is less efficient. I read an article on Build it Solar about DIY HRVs and it states that the airflow should be slow to increase heat transfer. Which is the opposite of what a HP needs I suppose there would have to be a compromise between what they need. Does anybody know how much a small (say 1 ton) dehumidifier flows- CFM? Every time I think about needing a HRV I come back to this, eventually I will have to make it.