Freeze-protection point and the density, specific-heat, viscosity, heat-capacity, flow and pressure-drop correction factors for an aqueous ethylene- or propylene-glycol mix, by interpolation of published property tables on the % by volume axis.
Freeze (pumpable) protection, NOT burst protection. Verify to project spec and the fluid manufacturer's data.
For design guidance only. Always verify with a qualified engineer.
About this glycol properties calculator
This free glycol and antifreeze properties calculator works out the freeze-protection point and the property correction factors for an aqueous ethylene- or propylene-glycol mixture, density, specific heat, viscosity, heat capacity, pump flow and friction pressure drop, each expressed relative to plain water. It is aimed at UK building-services engineers, heating and chilled-water designers and installers who need to know how much a glycol charge derates a system and how cold it stays pumpable. Enter the glycol type, the concentration by volume (the figure a refractometer or hydrometer reads) and the lowest expected fluid temperature.
How the glycol properties are calculated
Each property is read from a published table by linear interpolation on the % by volume axis, clamped at the table ends. The freeze point follows the ASHRAE Handbook—Fundamentals (Chapter 31, Physical Properties of Secondary Coolants) freeze-point-depression data, corroborated against DOWFROST propylene data; the density, specific-heat and viscosity rows come from the same ASHRAE basis plus CORECHEM (ethylene) and Engineers Edge (propylene) tables. Ratios divide each property by its 0% (water) datum. The heat-capacity factor is density × specific-heat ratio (the ρ·cp that carries heat in Q = ρ·V̇·cp·ΔT), the flow correction factor is its reciprocal: the extra volumetric flow needed for the same duty at the same ΔT, and the pressure-drop factor is density^0.75 × viscosity^0.25, the turbulent Darcy–Weisbach friction multiplier from the Blasius equation. The verdict reports freeze (pumpable) protection, not burst protection.
Frequently asked questions
Ethylene or propylene glycol. Which should I use?
Ethylene glycol gives slightly better heat transfer and lower viscosity, so it derates a system less, but it is toxic. Propylene glycol is the low-toxicity choice required wherever the fluid could contact potable water or food, at the cost of a higher viscosity and pump-flow penalty.
Is the freeze point burst protection?
No. The result is the freeze (pumpable) protection temperature, the point at which ice crystals start to form and the fluid stops flowing. Burst protection, where the slush can no longer rupture pipework, typically extends roughly 6–8 °C colder and uses a separate table that is out of scope here.
Why does glycol need a bigger pump?
Glycol is denser and far more viscous than water, so the same volumetric flow costs more friction (the pressure-drop factor) and carries less heat per litre (the heat-capacity factor). To deliver the same duty you must push more flow, the flow correction factor. Which is why a glycol system usually needs the pump and pipework checked at the design concentration.