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#511 |
Lurking Renovator
Join Date: Feb 2017
Location: Constanta, Romania
Posts: 1
Thanks: 0
Thanked 0 Times in 0 Posts
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![]() Hello,
I just register on this forum but I am reading for the last couple on months and found very interesting subjects and ideas. First of all I would like to thank you for all the post as they have helped me take some decisions. For one of those decisions I am writing this post. I have decided to make a ventilation system for my house with heat recovery. For the heat recovery unit I have already decided what to do based on your experiments/models/posts. Now I would like to know your opinion on two aspects: 1. Every room will have supply and extraction. I would like to add individual pipes for each room that will connect together in my attic in some kind of plenum and then to pass through the heat exchange. For all the system I will have CO2 and humidity sensors in order to increase or decrease fan speed. 2. Total ventilated volume. Accordingly to Romania standards I should have for my entire house 700mc/h. But there are different ventilation values depending the designation of the room. Is there going to be a problem if I will ventilate, let's say, from bedroom 50mc/h (required by standards 40mc/h) and from bathroom 20mc/h (required by standard 30mc/h)?. Hard to find my words, but what I would like to say that total ventilated volume will be as required even if it will not be as per standard from each room. |
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#512 | |
Apprentice EcoRenovator
Join Date: Aug 2012
Location: North Alabama
Posts: 167
Thanks: 0
Thanked 40 Times in 20 Posts
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#513 |
Lurking Renovator
Join Date: Mar 2017
Location: usa
Posts: 9
Thanks: 0
Thanked 0 Times in 0 Posts
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![]() I see of Heat Recovery Ventilators usually use a cross-flow cell, with the air paths crossing at a 90 degree angle. They usually have an efficiency of about 60% to 70%. I have seen write-ups of experiments done on cells that had a 180 degree cross-flow and the efficiency was increased to some degree (maybe 5% to 8%). Sorry, but I didn't book mark the studies.
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#514 |
Lurking Renovator
Join Date: Jan 2016
Location: The Netherlands
Posts: 11
Thanks: 5
Thanked 0 Times in 0 Posts
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![]() Hi people,
I was thinking about the idea of reversing the flow through the heat exchanger every N minutes, to regulate the moisture content of the air. It's an appealing idea, but I could not come up with a design that does not require at least 4 actuators. 2 for switching the air supply/exhaust on one side, 2 for switching them on the other sides and a pretty clunky maze of canals. The actuators are pretty costly, especially when you buy them in a store instead of on ebay. Am I missing some clever design idea that requires less actuators? Has anyone ever built this idea, is it applied in commercial HRV units? |
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#515 |
Apprentice EcoRenovator
Join Date: Apr 2012
Location: Phillips, WI
Posts: 109
Thanks: 10
Thanked 30 Times in 25 Posts
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![]() Google rotating heat exchanger. Rotating heat exchangers have very high efficiency and no actuators or dampers.
I don't know if frost in cold temperatures (-35 deg C) would be a problem, especially if it is designed for high efficiency. Be a great project to build one... |
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#516 | |
Supreme EcoRenovator
Join Date: Mar 2009
Location: Portland, OR
Posts: 4,004
Thanks: 303
Thanked 724 Times in 534 Posts
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The reversing work is done with electronics. In these HRVs the core has enough thermal mass, that: 1. a 'charge' of indoor air is blown out, thus warming the core, 2. there is some dwell time for the core to absorb the heat from the charge 3. a 'charge' of outdoor air is drawn into the core, to be warmed 4. there is some dwell time for the core to release heat 5. REPEAT If you are able to work with a micropressor like Arduino (or similar), the timing and duration can be finely optimized, depending on the thermal mass of the core, etc. The Arduino can be also programmed to continuously vary the fan speeds, and ramp-up or ramp-down rate, to maximize efficiency. Best, -AC_Hacker
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I'm not an HVAC technician. In fact, I'm barely even a hacker... |
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#517 | |
Lurking Renovator
Join Date: May 2017
Location: Romania
Posts: 1
Thanks: 0
Thanked 0 Times in 0 Posts
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![]() Hello, this is my first time writing on this forum. I just spent all this night reading this tread from begining, and seeing how much work you all have put into it.
I want to build a HRV core for 1200m3/h ventilation system, from aluminium sheets 0.3 mm thick. I saw that mainly coroplast (Is coroplast = celular polycarbonate panel ?) was used in similar proiects, but in my opinion there are too many layers between the two air streams that need to change heat) You can see attached my initial design option, but with that I still felt that there is too much material between the two air streams. There should be one thin wall. I want to build some kind of a roller setup that can make the "bumps" in the sheets, to act like spacers and turbulence generators. The flow will be 180 degree counterflow. I mostly know how to build it, I know how I can seal up the edges, my main problem is I don't know how to size it for 1200 m3/h, to have max. possible efficiency, and lowest possible pressure drop. My current thought is to size it for maintaining the fi315 inlet/outlet pipe's interior cross section area, thru the core, but don't know how long should be the section, where the two streams will flow in paralel(oposit directions). This is why I want to ask Kostas to share the design (and size) of this new "homemade countercurrent 600mm heat exchanger" that he mentioned in th below quote. Quote:
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#518 |
Helper EcoRenovator
Join Date: Dec 2012
Location: Venice, Italy
Posts: 89
Thanks: 15
Thanked 41 Times in 19 Posts
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![]() Hi guys, what goes around comes around, so here I am with the latest news: I finally finished my diy HRV system!To be honest I completed and installed it last February but only now I managed to make the video tutorial, as promised.
It is in Italian, as well as my blog, but I added some english subtitles so everyone can understand. I hope you enjoy! https://youtu.be/phIWQD5LAcA Btw, here's my blog if you want to see every part of the process, for I've made a video for every custom component: https://diyvmc.wordpress.com/ |
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#520 |
Helper EcoRenovator
Join Date: Aug 2014
Location: The Netherlands
Posts: 70
Thanks: 18
Thanked 26 Times in 14 Posts
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![]() Looks good.
Did you do any temperature measurements in/out and in/out? So what's the efficiency? |
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Tags |
erv, heat recovery, hrv |
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