Engineering task and calculation objective
The GLYC module calculates the properties of the heat transfer and coolant brines Antifrogen® N, L, KF and SOL from the manufacturer Clariant. If you need to calculate the properties of glycol-water mixtures — for example for the design of coolant brine circuits, heat pumps, solar thermal systems or recooling plants — you obtain density, specific heat capacity, thermal conductivity, viscosity and further quantities as functions of temperature and composition or of the required frost protection.
Antifrogen N is an ethylene glycol-water mixture for closed industrial circuits; Antifrogen L is the physiologically safe alternative based on 1,2-propylene glycol for use near food and drinking water; Antifrogen KF is an aqueous solution of organic salts (formates) with low viscosity for low temperatures; and Antifrogen SOL is a special product of propylene glycol with higher-boiling alkylene glycols for solar thermal systems. The data basis is the product data sheets of Clariant GmbH.
From the basic quantities, the module derives the parameters needed for heat transfer and pressure drop calculations, including Prandtl number, thermal diffusivity and coefficient of thermal expansion, as well as the boiling point and saturation pressure of the mixture.
Standard and calculation basis: Clariant GmbH
Calculation workflow
- Choose the product and concentration: First, the Antifrogen product (N, L, KF or SOL) is selected. For N, L and KF, the composition is either specified directly as a mass or volume fraction, or indirectly via the required frost protection temperature, from which the module determines the necessary concentration. Antifrogen SOL, being a ready-mixed product of fixed composition, is evaluated as a function of temperature only.
- Set the operating temperature: The temperature — for instance the mean brine temperature in the heat exchanger or the lowest operating temperature of the circuit — is entered. It must lie within the permissible range for the selected concentration, above the setting-point curve.
- Calculate the properties: From the stored manufacturer data, the density, specific heat capacity, thermal conductivity, and dynamic and kinematic viscosity are interpolated as functions of temperature and concentration; in addition, the boiling point and vapor pressure of the mixture are output.
- Form derived quantities: Prandtl number, thermal diffusivity and coefficient of thermal expansion are calculated from the basic quantities. They enter directly into Nusselt correlations for heat transfer and into the sizing of expansion vessels.
- Use the results in the plant design: With the property values, the heat exchangers, pumps and piping of the brine circuit can be dimensioned — in particular, comparison with pure water shows how strongly the higher viscosity and lower heat capacity of the mixture change heat transfer and pressure drop.
Input quantities
| Quantity | Symbol | Unit |
|---|---|---|
| Temperature | ϑ ϑ | °C |
| Temperature | ϑ ϑ | °C |
| Weight fraction | 0 ≤ g ≤ 0.61 g g | -- |
| Weight fraction | 0 ≤ g ≤ 0.61 g g | -- |
| Volume fraction | 0 ≤ v ≤ 0.60 v v | -- |
| Volume fraction | 0 ≤ v ≤ 0.60 v v | -- |
| Density | ρ ρ | kg/m³ |
| Density | ρ ρ | kg/m³ |
| Specific heat capacity | cp cp | J/(kg·K) |
| Specific heat capacity | cp cp | J/(kg·K) |
| Dynamic viscosity | η η | mPa·s |
| Dynamic viscosity | η η | mPa·s |
| Kinematic viscosity | ν ν | m²/s |
| Kinematic viscosity | ν ν | m²/s |
| Thermal conductivity | λ λ | W/(m·K) |
| Thermal conductivity | λ λ | W/(m·K) |
| Prandtl number | Pr Pr | - |
| Prandtl number | Pr Pr | - |
| Coefficient of thermal expansion | β β | 1/K |
| Coefficient of thermal expansion | β β | 1/K |
| Boiling point | ϑs ϑs | °C |
| Boiling point | ϑs ϑs | °C |
| Vapour pressure | ps ps | Pa |
| Vapour pressure | ps ps | Pa |
Calculation options
Temperature
1,2-propylene glycol · Ethylene glycol · 3 · 4
Frequently asked questions
What is the difference between frost protection and the setting point?
Glycol-water mixtures do not freeze abruptly; they first form an ice slush of ice crystals in the remaining solution. The frost protection temperature denotes the temperature down to which the mixture remains free of frost bursting, because the ice slush is still pumpable or volumetrically tolerable; the setting point lies below it. For plant design, the decisive point is that the lowest operating temperature lies with sufficient margin above the ice formation limit of the selected concentration.
When should Antifrogen L be chosen instead of Antifrogen N?
Antifrogen N, based on ethylene glycol, has the more favorable properties (lower viscosity, higher thermal conductivity) and is the first choice for closed industrial circuits. Ethylene glycol is, however, harmful to health; wherever transfer into food, drinking water or process water is possible — the food industry, heat pumps with domestic hot water heating — the physiologically safe Antifrogen L based on propylene glycol is used. The price for this is a considerably higher viscosity at low temperatures and thus more pumping power and poorer heat transfer.
Why does the brine degrade heat transfer compared with pure water?
With increasing glycol content, thermal conductivity and specific heat capacity decrease while viscosity rises strongly — at low temperatures by a factor of several. The Prandtl number increases and the Reynolds number decreases at the same volume flow; in the unfavorable case, the flow changes from turbulent to laminar, which drastically reduces the heat transfer coefficient. The concentration should therefore be chosen only as high as the frost protection actually requires.
What distinguishes Antifrogen KF for low temperatures?
Antifrogen KF is not based on glycol but on aqueous solutions of organic salts (formates). At low temperatures, these brines have a much lower viscosity than glycol mixtures of the same frost protection, which makes heat transfer and pumping energy demand significantly more favorable — attractive for refrigeration applications down to about −50 °C. The different corrosion characteristics and the compatibility with sealing materials must be observed and checked against the manufacturer's specifications.