Heat transfer of glycol vs water in the same pipe

[solarbair]

I am interested in the effects of propylene glycol anti freeze on heat transfer in hydronic heating systems, baseboard and radiant floor heating. I have information on viscosity, density, Reynolds number, Prandtl number, Nusselt number and thermal conductivity for both fluids. I have used the Dittus-Boelter correlation for tubulant flow but am unsure of my results. Any information or sources would be appreciated.

 

[btrueblood]

Your numbers at nominal room temp. to boiling look about right. But dunno about comparisons below 32 F/ 0 C - isn't water no longer solid there, so comparisons of antifreeze solution to water lose meaning?

The only reason to add glycol is if there is a risk the system will be exposed to temp's. below freezing. At higher temp's. glycol may reduce vapor pressure/boiling/cavitation concerns. I have had people tell me they add glycol antifreeze for the corrosion protection...but why not just add corrosion inhibitors to pure water?

 

[Bribyk]

If you can run inhibited water you'll have better heat transfer characteristics. There's tons of info on the web comparing water, EG and PG.