Last week the article covered pressure drop correction calculations. Today we offer you some handy charts to use for second glycol correction pressure drop.

 

Pressure Drop Corrections for Glycol/Water Solutions
	Percent Propylene Glycol				Percent Ethylene Glycol
Average Temperature	30%	40%	50%		30%	40%	50%
35F	1.56	1.78	2.00		1.37	1.47	1.60
45F	1.46	1.63	1.90		1.30	1.39	1.51
50F	1.41	1.56	1.80		1.27	1.36	1.47
80F	1.20	1.29	1.45		1.11	1.18	1.27
100F	1.10	1.19	1.30		1.04	1.10	1.17
130F	1.01	1.07	1.15		0.96	1.01	1.06
150F	0.96	1.01	1.07		0.92	0.96	1.01
170F	0.93	0.97	1.02		0.89	0.92	0.96

Glycol Pressure Drop Correction Example

Let’s assume we have a primary variable chilled water system with a 40% Dowfrost fluid. The system is designed for a 45⁰F average temperature. The engineer’s calculations would be more detailed, but this will get the point across as an example.

 

ITEM	WATER BASED PD (FEET)	GLYCOL BASED PD (FEET)
Chiller		28
Mechanical room equipment	10
Distribution piping	33
Pipe fittings (25%)	8
Farthest (controlling) AHU		16
Control valve	12
AHU piping and valves	4
Totals	67	44
Glycol correction factor	1.63	1.0
Correction head	109	44
Total before safety	153
Pump head with 15% safety factor	176

 

You can see the correction factors add up quickly. Not something you want to miss. We hope this short R. L. Deppmann Monday Morning Minutes will help you in your determination of glycol based system pump head.