Ceramic element MVHR

[SteamyTea]

Just been over to Wadebridge to the Self Distruction show (not worth the 4 quid to get in) and looked at a single room, through the wall, MVHR unit.

Seemed to be a simple, reversible direction, fan with a not to intricately shaped ceramic element in a pipe.

The idea is that it sucks air out the room, heats the china up, then reversed the airflow, drawing in cool air, that then extracts the heat out the crockery.

I am sure, in the dim and distant past, we have collectively discussed these, but can't remember what the outcome was.

Anyone know anything about them?

[ProDave]

A variant of this type that work with a slowly rotating disc made up of fins can work well, as the fins pass through the exhaust sector, they get heated and as they pass the inlet sector they give up their heat.

 

But this "back and forth" variant.  Well while you are extracting you lower the pressure in the room.  Where is the air going to come from to make that up?  And when you blow the air into the room, you will raise the pressure.  Where will the air escape?

[SteamyTea]

33 minutes ago, ProDave said:

Where is the air going to come from to make that up?

I was wondering this too.

The unit may have a respectable efficiency in isolation, but in practice it may not be that great.

I do like the simplicity of the design, and easy to make one at home.

It would also make fitting one easy.

 

[Ed Davies]

50 minutes ago, ProDave said:

But this "back and forth" variant.  Well while you are extracting you lower the pressure in the room.  Where is the air going to come from to make that up?  And when you blow the air into the room, you will raise the pressure.  Where will the air escape?

 

There are variants of that scheme with two units which synchronize: one pushes while the other pulls then v-v. Not sure how the communicate, whether you need extra wires or not.

[Jeremy Harris]

1 hour ago, ProDave said:

A variant of this type that work with a slowly rotating disc made up of fins can work well, as the fins pass through the exhaust sector, they get heated and as they pass the inlet sector they give up their heat.

 

But this "back and forth" variant.  Well while you are extracting you lower the pressure in the room.  Where is the air going to come from to make that up?  And when you blow the air into the room, you will raise the pressure.  Where will the air escape?

 

 

The rotating drum full of fins heat exchangers seem to work very well at a large scale.  We had one fitted in the air handling system at the new lab and offices we built and IIRC the efficiency was very high, plus it had the advantage of reducing the amount of humidification needed.

[SteamyTea]

52 minutes ago, JSHarris said:

The rotating drum full of fins heat exchangers seem to work very well at a large scale

Yes, but not in a 4 inch, or 6 inch, pipe though the wall.

I prefer Ed's comment

1 hour ago, Ed Davies said:

synchronize: one pushes while the other pulls then v-v

These days it can be done pretty reliably wirelessly I think.  Make them as matched pairs.

[ProDave]

3 minutes ago, SteamyTea said:

I prefer Ed's comment

These days it can be done pretty reliably wirelessly I think.  Make them as matched pairs.

The 433MHz transmitter and receiver I just bought from China for an add on to my solar PV dump controller cost just under £3 for the pair and would do that function.

[SteamyTea]

4 minutes ago, ProDave said:

The 433MHz transmitter and receiver I just bought from China for an add on to my solar PV dump controller cost just under £3 for the pair and would do that function.

I have some ESP8266s kicking about, they should do it too, and can have other sensors on them.

May have to get my box of winter projects out.

 

Thinking about the ceramic element, the SHC is not too great.  Polyurethane is a lot higher, and easy to mould into interesting shapes.

The I value is about half of ceramic, but that just means it takes twice as long to warm up and cool down, but at such a small scale, it is pretty irrelevant.

 

[A_L]

Some products,

 

https://www.lunos.de/en/systems/

 

http://www.utilityfreeliving.co.uk/heat-recovery-ventilators/

 

https://renergise.ie/shop/energy-saving-products/ventilation/