VMC double flow: power and exchange surface?

[Christophe]

Following this topic: https://www.econologie.com/forums/vmc-fabric ... t6023.html and this post in particular https://www.econologie.com/forums/post176397.html#176397 , I open this topic to try to find the physical characteristics of a double flow CMV, the datasheets of the manufacturers that I have found for the moment only speak of efficiency ("theoretical"), flow rates, pressure drops and electricity consumption ...

Here is an example of a datasheet with some curves but nothing specific about the exchanger: Zehnder ComfoAir 200

Voila if someone has more specific about the exchanger, it will interest the world ...

[dedeleco]

To solve the problem of heat exchange in this type of exchanger, it is good to look at past work and theses!
So it is good to read the Nusselt number or in other words, the specialists hide in this number all the complexity of the flows and heat exchanges:
http://en.wikipedia.org/wiki/Nusselt_number
and also for plates:
http://www.cheresources.com/convection.shtml#flat

Finally read this interesting thesis, especially figure 19 of chapter chapter 2-3 which gives usable quantitative measured values.
http://www.unige.ch/cyberdocuments/thes ... these.html
which gives for 2m / s of air speed between 2 plates spaced a distance between 0,5cm and 20cm a heat exchange speed between 6 and 9 W / m2. ° K
and for 10m / s between 25 and 50 W / m2. ° K
it is roughly linear with the speed of the air.
The heat exchange being better for the little spaced plates, but a multiplication by 10 of this space only generates a reduction of a factor 2 of the heat exchange, thanks to the turbulence.
So if we multiply the surface by 2 we can take a large space or large diameter tubes !!

and it only remains to calculate the exchanger with these experimental data !!! In particular what is the best choice of surface, length of the plates, space between plates and number of plates.
We can take tubes, but it will require a comparable surface and it seems more difficult to achieve than plates ??
plates:



tubes:

[dedeleco]

Free online courses to read to correctly calculate an exchanger, with examples:


mit-heat-transfert-BON-page book 352 of 762
http://web.mit.edu/lienhard/www/ahttv131.pdf
GOOD - exchanger-calculation mode
http://web.mit.edu/16.unified/www/FALL/ ... 0000000000

http://web.mit.edu/16.unified/www/FALL/ ... node5.html

interseasonal heating
http://www.icax.co.uk/thermalbank.html

Articles on Interseasonal Heat Transfer
http://www.icax.co.uk/articles.html


Then it remains only to calculate in his particular case !!
Otherwise, at random, we risk mistakes.

It is necessary to fix the air flow and the desired output, to find the size and the length according to the diameter of the pipes or the interval between plates.
It is also necessary to know the thickness and nature of the pipes or plates, as well as the thermal conductivity of the material of the pipe or plates.