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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.
