Propylene Glycol Correction Factor Question
Propylene Glycol Correction Factor Question
(OP)
I’m sizing a pump for a heat pump cooling water loop and have a question about propylene glycol correction factors.
I determined the required flow rate for the heat load based on properties of 40% PG (Spht and SG).
I determined the required pump head based properties of 40% PG (Friction factor based on Reynolds number which is based on 40% PG viscosity).
When viewing pump curves to make a selection, do I need any additional correction factors or am I good since I used 40% PG properties to determine the pump flow rate and head?
My understanding is the correction factors are used when your calculation uses water as the fluid. Working with propylene glycol is new to me and I want to make sure I’ve accounted for all required corrections.
I determined the required flow rate for the heat load based on properties of 40% PG (Spht and SG).
I determined the required pump head based properties of 40% PG (Friction factor based on Reynolds number which is based on 40% PG viscosity).
When viewing pump curves to make a selection, do I need any additional correction factors or am I good since I used 40% PG properties to determine the pump flow rate and head?
My understanding is the correction factors are used when your calculation uses water as the fluid. Working with propylene glycol is new to me and I want to make sure I’ve accounted for all required corrections.
Kevin Connolly, PE
www.TheEngineeringSurvivalGuide.com





RE: Propylene Glycol Correction Factor Question
http://fluidh.com/cmsAdmin/uploads/cih-taco5aselec...
The corrections become larger as the fluid temperature decreases.
For the purposes of scheduling the pump and reviewing the submittal, stating requirements in terms of performance when circulating pure water is easier.
Communicating expectations to the balancing contractor, and reviewing the TAB report may be less straightforward.
Balancing contractors may be unaccustomed to using or documenting correction factors when measuring flow rates through balancing valves that were calibrated for water, or for pressure gauges when measuring pump heads and reporting the values in feet (of what - pure water or glycol solution, at _?_°F?).
Where you "determined the required pump head," is this expressed in terms of "feet of 40% PG solution at the density for the flowing temperature?"
This may be interesting:
http://www.taco-hvac.com/wizard_pumps.html
It is not clear to me whether the "Design head" input field at the link above is in terms of "feet of water" or "feet of fluid." The selection program might expect the user to make corrections externally if the "fluid" is a glycol solution.
RE: Propylene Glycol Correction Factor Question
Though no information on correcting the NPSHR curve was found in the link below, one might expect variation in the head and efficiency curves, in addition to BHP curve, based on the procedure here:
http://www.mcnallyinstitute.com/14-html/14-04.htm
RE: Propylene Glycol Correction Factor Question
Based on the first linked article I need 3 corrections.
1. Flow rate - Check
2. Piping Friction Head - Check
3. Pump Performance - Need to use the tables in the linked article.
Items 1 and 2 determine my design point, then I need to inflate those in accordance with the tables (depending on temp and %) when reviewing pump curves based on pure H2O.
Kevin Connolly, PE
www.TheEngineeringSurvivalGuide.com
RE: Propylene Glycol Correction Factor Question
RE: Propylene Glycol Correction Factor Question
RE: Propylene Glycol Correction Factor Question
how exactly did you calculate friction with the glycol? You also need ot adjust for temperature. hot Glycol will be similar to standard water, but cold Glycol will have much more friction (and less efficient pump)
RE: Propylene Glycol Correction Factor Question
RE: Propylene Glycol Correction Factor Question
Note that NPSHR on a pump curve is feet of liquid, not feet of water (yes, the NPSHR is determined using water but the NPSHR is feet of your liquid, not feet of water). Take a look at the vapor pressure of the solution entering the pump and the suction pressure. The difference, converted to feet of 40% PG, is your NPSHA.
http://www.lyondellbasell.com/techlit/techlit/2514...
The above link would suggest that the viscosity of 40% PG isn't going to be greater than say 10 cP. I wouldn't expect any significant corrections to be needed to a pump curve.
RE: Propylene Glycol Correction Factor Question
RE: Propylene Glycol Correction Factor Question
http://www.eng-tips.com/viewthread.cfm?qid=390423