Best configuration for double panel hx
 

Hi,

I'm after some advice.

I have what is effectively a double panel air to water heat exchanger that is used to heat/cool a house via air ducts. The unit has a fan that draws air through the exchanger and blows it from the room vents.

What is the best direction for water vs air flow - the uncooled air passing through the coldest panel first, then the warmer panel or the reverse?

Acuario

If the temperature differences are not large, either way will work.

Steve

Counterflow if possible.

NiHao is correct, but the efficiency difference may be small. Try it both ways and see. The greatest heat flow (Q) is proportional to dt (delta t - temperature difference). So a counter flow system maximizes this with the coldest return air being exchanged for the warmest outflow water. There are many equations that model this, which is why I put in those terms above. You can find them in books on thermodynamics and also on the internet.

But you may have physical constraints that limit which pipe goes where. I suggest hooking it up as easily as possible (counter flow is best) and see how it works.

Let us know.

Steve

It depends on the temp drop in each direction but in general counterflow wins out every time. You will get the highest heat transfer. Flow rate is not that important for watts transferred as it is either going to be a high flow at low temp rise or vise versa. That said, the flow rate is determined by the desired output temp (and supply temp). If you need 35C, go slow and save fan/pump power but if you want 25C you may need to spend a bit more energy to do it.