FHV Sizing/Setting Helper Program

Mike T., Swampeast MO

Have only been able to work on it a few hours since last night but it's progressing reasonably.

Try as I might to avoid, I had to require that the user insert a constant (the "target" delta-t). Of course you can change the delta-t and everything will re-calculate.

Have most of the air temp modulating version table converted to equations and have all of the conversions (Danfoss table isn't available in "American" measures). Weight of water at different temperatures DOES matter by the way when converting the curves to equations.

Still have to look up a table for head loss through PEX and convert to equation. Once I have that done it will be easy to find the proper initial setting for the first room delta-p.

While I'm calling the delta-t a "constant", once you have multiple rooms, it will start adjusting the delta-t Up if flow through any individual FHV is too high) and down to try to keep all of the valves as close to possible to one of the flow balance curves. This will be the "magic" delta-p.

Danfoss told me that VERY few in this country use these devices. They're certainly more complicated to adjust properly than TRVs where you really do nothing more than make certain that the TRV is capable of handling your flow without noise/wear.

As long as your panel construction is very similar among the individual spaces (FHVs) served, this will produce an extremely well-balanced system with nearly identical delta-t and delta-p among loops of varying diameter and length.

Different constructions (say carpet instead of hard surfce) will (obviously) change the heat transfer factor of panel due to different r-value. As is normally done (I belive) you'll need to have a different supply temperature and different reverse-return manifold for the FHVs supplied in each panel type. Mixing them in the same manifold would result in the destruction of the "magic" delta-p.

Mike T., Swampeast MO

Thanks Mr. Sigenthaler!

Found the formula for actually computing head loss through tubing in one of your writings.

HL = (k * Le) * (f ^ 1.75)

where: HL = Head loss; k = constant depending on tube size type (you gave common values); Le = length (effective); and f = flow rate.

Couldn't find that anywhere else!

Mike T., Swampeast MO

Question about that formula

Two of the tables I found show a slightly decreasing pressure drop per foot of tube with increasing temperature.

I suppose it's that ugly, "How much does a gallon of water weigh?" answer rearing its' head.

Presumably, it's going to show up in that 1.75 exponent in the equation. Any guidance/links regarding how to compute this number? for fluids other than just water?

Jed_2

Mike, Your the only guy

I know who can complete a thread with your own postings!LOL

Jed

Mike T., Swampeast MO

Because I'll never claim to have the answer.