Ethylene Glycol Heat-Transfer Fluid

Freezing point, viscosity, specific gravity and specific heat capacity of ethylene glycol based heat-transfer fluids, or brines

Ethylene Glycol based water solutions are common in heat-transfer applications where the temperature in the heat transfer fluid can be below 32oF (0oC). Ethylene glycol is also commonly used in heating applications that temporarily may not be operated (cold) in surroundings with freezing conditions - such as cars and machines with water cooled engines.

Ethylene Glycol is the most common antifreeze fluid for standard heating and cooling applications. Ethylene glycol should be avoided if there is a slightest chance of leakage to potable water or food processing systems. Instead solutions based on propylene glycol are commonly used.

Specific heat capacity, viscosity and specific weight of a water and ethylene glycol solution vary significantly with the percent of ethylene glycol and the temperature of the fluid. Properties differs so much from clean water that heat transfer systems with ethylene glycol should be calculated thoroughly for actual temperature and solution.

Freezing Point of Ethylene Glycol based Water Solutions

Freezing points of ethylene glycol based water solutions at various temperatures are indicated below

Freezing Point
Ethylene Glycol Solution
(% by volume)
0102030405060
Temperature (oF) 32 25.9 17.8 7.3 -10.3 -34.2 -63
(oC) 0 -3.4 -7.9 -13.7 -23.5 -36.8 -52.8

Due to possible slush creation, ethylene glycol and water solutions should not be used in conditions close to freezing points.

Dynamic Viscosity of Ethylene Glycol based Water Solutions

Dynamic viscosities - μ- of ethylene glycol based water solutions at various temperatures are indicated below

Dynamic Viscosity - μ - (centipoise)
TemperatureEthylene Glycol Solution (% by volume)
(oF)(oC)253040506065100
0 -17.8 1) 1) 15 22 35 45 310
40 4.4 3 3.5 4.8 6.5 9 10.2 48
80 26.7 1.5 1.7 2.2 2.8 3.8 4.5 14
120 48.9 0.9 1 1.3 1.5 2 2.4 7
160 71.1 0.65 0.7 0.8 0.95 1.3 1.5 3.8
200 93.3 0.48 0.5 0.6 0.7 0.88 0.98 1.4
240 115.6 2) 2) 2) 2) 2) 2) 1.8
280 137.8 2) 2) 2) 2) 2) 2) 1.4
  1. below freezing point
  2. above boiling point

Note! The dynamic viscosity of an ethylene glycol based water solution is increased compared with the dynamic viscosity of clean water. As a consequence the head loss in the a piping system with ethylene glycol is increased compared to clean water.

Specific Gravity of Ethylene Glycol based Water Solutions

Specific gravity - SG - of ethylene glycol based water solutions at various temperatures are indicated below

Specific Gravity- SG -
TemperatureEthylene Glycol Solution (% by volume)
(oF)(oC)253040506065100
-40 -40 1) 1) 1) 1) 1.12 1.13 1)
0 -17.8 1) 1) 1.08 1.10 1.11 1.12 1.16
40 4.4 1.048 1.057 1.07 1.088 1.1 1.11 1.145
80 26.7 1.04 1.048 1.06 1.077 1.09 1.095 1.13
120 48.9 1.03 1.038 1.05 1.064 1.077 1.082 1.115
160 71.1 1.018 1.025 1.038 1.05 1.062 1.068 1.1
200 93.3 1.005 1.013 1.026 1.038 1.049 1.054 1.084
240 115.6 2) 2) 2) 2) 2) 2) 1.067
280 137.8 2) 2) 2) 2) 2) 2) 1.05
  1. below freezing point
  2. above boiling point

Note! The specific gravity of ethylene glycol based water solutions are increased compared with specific gravity of clean water.

Specific Heat Capacity of Ethylene Glycol based Water Solutions

Specific Heat - cp - of ethylene glycol based water solutions at various temperatures are indicated below

Specific Heat - cp - (Btu/lb.oF)
TemperatureEthylene Glycol Solution (% by volume)
(oF)(oC)253040506065100
-40 -40 1) 1) 1) 1) 0.68 0.703 1)
0 -17.8 1) 1) 0.83 0.78 0.723 0.7 0.54
40 4.4 0.913 0.89 0.845 0.795 0.748 0.721 0.562
80 26.7 0.921 0.902 0.86 0.815 0.768 0.743 0.59
120 48.9 0.933 0.915 0.875 0.832 0.788 0.765 0.612
160 71.1 0.94 0.925 0.89 0.85 0.81 0.786 0.64
200 93.3 0.953 0.936 0.905 0.865 0.83 0.807 0.66
240 115.6 2) 2) 2) 2) 2) 0.828 0.689
280 137.8 2) 2) 2) 2) 2) 2) 0.71
  1. below freezing point
  2. above boiling point
  • 1 Btu/(lbmoF) = 4,186.8 J/(kg K) = 1 kcal/(kgoC)

Note! The specific heat capacity of ethylene glycol based water solutions are less than the specific heat capacity of clean water. For a heat transfer system with ethylene glycol the circulated volume must be increased compared to a system with clean water.

In a 50% solution with operational temperatures above 36 oF the specific heat capacity is decreased with approximately 20%. The reduced heat capacity must be compensated by circulating more fluid.

Note! The density of ethylene glycol is higher than water - check the specific gravity (SG) table above, so the net impact on the heat transport capacity is reduced. Example - the specific heat of an ethylene glycol water solution 50% / 50% is 0.815 at 80 oF (26.7 oC). Specific gravity at the same conditions is 1.077. The net impact can be estimated to 0.815 * 1.077 = 0.877.  

Automobile antifreeze solutions should not be used in HVAC systems because they contain silicates that may cause fouling. Silicates in automobile antifreeze are used to protect aluminum engine parts.

Note! Distilled or deionized water should be used for ethylene glycol solutions. City water may be treated with chlorine which is corrosive.

Systems for automatic makeup water should not be used since a leakage would contaminate the environment and dilute the antifreeze protection of the system.

Boiling Points Ethylene Glycol Solutions

Boiling Point
Ethylene Glycol Solution
(% by volume)
0102030405060708090100
Temperature (oF) 212 214 216 220 220 225 232 245 260 288 386
(oC) 100 101.1 102.2 104.4 104.4 107.2 111.1 118 127 142 197

Increase in Flow required for a 50% Ethylene Glycol Solution

Increase in circulated flow for 50% ethylene glycol solutions compared with clean water are indicated in the table below

Fluid TemperatureFlow Increase
(%)
(oF)(oC)
40 4.4 22
100 37.8 16
140 60.0 15
180 82.2 14
220 104.4 14

Pressure Drop Correction and Combined Pressure Drop and Volume Flow Correction for 50% Ethylene Glycol Solution

Pressure drop correction and combined pressure drop and flow increase correction for 50% ethylene glycol solutions compared with clean water are indicated in the table below

Fluid TemperaturePressure Drop Correction with Flow Rates Equal
(%)
Combined Pressure Drop and Flow Rate Correction
(%)
(oF)(oC)
40 4.4 45 114
100 37.8 10 49
140 60.0 0 32
180 82.2 -6 23
220 104.4 -10 18

Related Topics

  • Air Conditioning - Air Conditioning systems - heating, cooling and dehumidification of indoor air for thermal comfort
  • Material Properties - Material properties - density, heat capacity, viscosity and more - for gases, fluids and solids

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