If my exploration of the drawing is right then both airflows are straight through - each of the flat airspaces in each path are in parallel. When I'd previously looked at plate exchangers I'd assumed that the flow wiggled through each of the layers in turn - airspaces in series. Have I got it wrong? Parallel certainly makes the construction a lot simpler.

ST: have you given any thought to drainage? If the HR is working properly you should be getting condensation otherwise you're wasting quite a bit of latent heat in the outgoing air.

I'm not convinced that metal is justified for the plates. Though a plastic material will have a higher resistivity the layers are so thin that it doesn't really matter. The lowest conductivity for a solid (not foamed/expanded) plastic given in:

http://www.engineeringtoolbox.com/thermal-conductivity-d_429.html

is 0.1 W/(m·K) for polypropylene. A 2 mm thick sheet would have a U-value of 50 W/(m²·K). Air-to-surface interfaces tend to have U-values of around 10 W/(m²·K), or at least something like half to double that, depending on the orientation and airflow. Even at 20 W/(m²·K) for each of the two interfaces with the plastic we have thermal resistances:

Air/plastic: 0.05 m²·K/W.
Plastic: 0.02 m²·K/W
Plastic/air: 0.05 m²·K/W

Total: 0.12 m²·K/W

so the plastic only contributes one sixth of the total resistance. And 2 mm is probably a bit thick.

My plan is a very tall vertical flow exchanger in the porch area of the house. Connections to and from the house on each side at the top. Inlet from outside or, experimentally, from the greenhouse at the side at the bottom. Outflow just straight out the bottom (completely open) with a drip tray with drain underneath.

Easy disassembly for cleaning is, I think, a must.

I was thinking of making filters from reticulated foam sheet (or kitchen scourers), I used to make filters for mining and performance air filters for cars, there is nothing special about them.
What I like to find out is the performance per £ compared to bought units.

Ed
I cannot see any reason why a heat exchanger cannot be tall and thin, vertical or horizontal (allowing for drainage). The commercial units do seem a little constricted on design. Mentioned on another thread about fitting them between first floor floor and ground floor ceiling void (or any storey really) and between the roof timbers. It is really all down to surface area. Commercial ones seem to be about packing as much surface area into as small a space as possible regardless of cost.

Posted By: JSHarrisLooks interesting and worth playing with further. That corrugated plastic stuff so beloved by Estate Agents for signs (Correx) should work well, I'd have thought, although you'd probably need a big stack of sheets to get the flow resistance down to an acceptable level. You could probably recycle used signs as a source of heat exchanger material.

There is homemade one using just this on one of my earlier links - http://www.autoconstruction.info/techniques/energie-chauffage-isolation/la-fabrication-d-un-recuperateur - a block of 86 sheets 32cmx32cmx0.03cm , giving a surface area of around 18m2.

regs
Richard

Hi ST - the filter in my unit is made out of what seems to be a 300mm*200mm piece of white grease filter, used in cooker hood extractors. Its big so the air pressure drop across is it small. It's held rigid with a wire frame. You can buy big sheets of the stuff from ebay for £10.
As to the heat exchanger material - I agree that thin plastic is top. Its easy to get plastic thin enough to have a high enough U value that it transfers the heat. With copper or aluminium, you'll find the loss along the length of the plate will be high - and this is loss, coupling from hot to cold end of the exchanger. Thin steel is prob ok, being low conductivity... I see you painted it to stop rust :-)
Efficient fans may be quite hard to source - the ones in ours are centrifugal type, and quite big.
I think Viking house have it right by integrating humidity and CO2 sensors Inside, and controlling using these.
I have to say, that the better MVHR units are £1000+, and theres not a lot inside the box. It's all know- how and low supply&demand keeping the price high.
Luck !

That's called 'technical experience' and 'observations' and beats a pure theoretical approach hands (well, blades in your case) down...

Rgds

Damon

Posted By: SteamyTeaI am sure if I can make it just a little bigger it will work

Or I have this nice bridge. I'm sure your machine will work better if you buy my bridge and install your machine on it

Right
Done the RH chart for a full 24 hours.
Data sampled every 1 minutes then averaged to 6 minute intervals.

Had a fiddle about with the number and this is what seems to be happening. It is more a reflection on how often the unit is used, rather than an ultimate efficiency, or in English, real life.
I changed the efficiency calculation to better reflect what we want to know (it is temperature based not energy based, I have to find a way to work out the mass air flow yet, the fan manufacturer claims up to 85m^3.h^-1)
The efficiency is now calculated using the difference between the cold air entering and exiting the unit divided by the hot air entering the unit.
The time fraction (blue line) is just how often, and at what temperature, the air is entering the unit over the 24 hour test period. So for 0.4 (40%, 9 hours 40 minutes) of the time the air is between 17 and 17.5°C, 0.1of the time between 18 and 18.5°C. Two important numbers here are the mean temperature 17.8°C and the modal temperature 17.1°C. They describe the temperature entering the unit from the bathroom.
From the charts above you can see that during the night the temperature is lower and the fan is not on at all.
From this I can deduce that the mean efficiency of the unit is 0.15 (15%). I shall try running another test with the unit on for a couple of hours to see if this is confirmed.
If it is assumed that the fans can deliver 50% of there maximum 45m^3.h^-1, then the mass of air that is shifted is 50 kg.h^-1, with a mean temperature increase of 2.7°C. That works out at 0.9 kWh.day^-1 saved.

Your right Ed, I should be more precise, pure laziness on my behalf.
I had not thought about the scale (and I usually use Kelvin, so may redo it and see what what happens. I was getting some great efficiency figures when I used the old 'toolbox' equation for the efficiency, sometimes over 100%, so knew that could not be right.
Got it set up again and leaving it running for a couple of hours to see if it makes more sense. What I can say is that it does heat up the incoming air and if the temperature is right it condenses out the water.

Just for reference:
Hot In is from the bathroom to the exchanger
Hot out is from the exchanger to outside
Cold In is from outside to the exchanger
Cold Out is from the exchanger to the room

Had a quickish google about and I just cannot find a standard way of referring to the ins and outs of a heat exchanger

I tend to go along with that sentiment, but it is possibly the reason that we have a dreadful housing stock.
Lets face it, this forum cannot agree on much, be it EWI vs IWI, Heatstores or not, high or low thermal mass, manure or chemicals. The list goes on.

By posting results and methods up, errors can be highlighted. What it is all about.

''When I made the water turbine to power a row of reversing lights''. If you put the lights on forward did the wheel go the other way? :)

Oooooooh.

Right, MkII is up and running, even made a small video of it for you all. Please excuse the raspy voice, its always like that, especially after a cold.
It is uploading to UTwitFace or whatever it is, and will be fully loaded later all going well.
Here is the link:
http://youtu.be/F6XMp5AfitU

Only got as far as a quick chart, not worked out any efficiencies yet, shall try and do a longer test tomorrow.

Having watched Jinxy now I have had an attack of the Vapour and I am Turning Japanese, I really think so.