Ethylene glycol, 30 % by volume
A 30 % by volume ethylene glycol solution, freeze protection to about −15 °C — lower viscosity than propylene at the same protection, and toxic.
| Phase | Liquid |
| Temperature range | -10 to 100 °C |
| Freeze protection | about -15 °C |
| Source | ASHRAE Handbook—Fundamentals, Ch. 31 (Secondary Coolants), interpolated from published tables |
Validated from -10 to 100 °C.
| Density | 1,041 kg/m³ |
| Dynamic viscosity | 2.4 mPa·s |
| Specific heat | 3.7 kJ/(kg·K) |
| Thermal conductivity | 0.464 W/(m·K) |
| Kinematic viscosity ν = µ/ρ | 2.3055 mm²/s |
| Prandtl number Pr = cpµ/k | 19.14 |
Every fluid property in these opens already filled, all from the same state — so a density and a viscosity in one calculation always describe the same fluid at the same temperature.
Glycol Loop Heat Transfer (Capacity Derate)
ρ = 1,041c = 3.7
Reynolds Number
ρ = 1,041μ = 2.4
Prandtl Number
μ = 2.4cₚ = 3.7k = 0.464
Learning zone
Ethylene glycol is the better heat transfer fluid of the two and the more dangerous. At equal freeze protection it is less viscous and has higher thermal conductivity than propylene glycol, so it pumps easier and transfers better: at 20 °C this mixture is 2.4 mPa·s against 3.4 for PG 30 %, and 0.464 W/(m·K) against 0.445.
It is also acutely toxic — sweet-tasting, readily drunk by animals and children, and lethal in small quantities through kidney failure. That rules it out of any loop with a credible path to potable water, food or open contact, which in practice means double-wall heat exchangers wherever it approaches domestic water. Chillers, closed process loops and automotive systems still use it because the thermal advantage is real and the containment is controllable.
At 30 % the penalties against water are moderate: specific heat down 12 % to 3.70 kJ/(kg·K), thermal conductivity down 22 %, viscosity up 2.4-fold at 20 °C. As with propylene, the numbers to design against are the ones at the coldest operating temperature, not at room temperature.