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Ethylene Glycol Heat-Transfer Fluid Properties

Properties like freezing point, viscosity, specific gravity and specific heat of ethylene glycol based heat-transfer fluids, or brines.

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Ethylene Glycol based water solutions are common in heat-transfer applications where the temperature in the heat transfer fluid can be below 32 o F (0 o C) . 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, 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

Ethylene Glycol Water Solution Heat-Transfer Fluid - Freezing Point
Ethylene Glycol Solution
( % by volume )		01020304050608090100
Freezing Point ( o F) 32 25.9 17.8 7.3 -10.3 -34.2 -63 ≈ -51 ≈ -22 9
( o C) 0 -3.4 -7.9 -13.7 -23.5 -36.8 -52.8 ≈ -46 ≈ -30 -12.8

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

Water with ethylene glycol - freezing points

Dynamic Viscosity of Ethylene Glycol based Water Solutions

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

Ethylene Glycol Heat-Transfer Fluid - Dynamic Viscosity
TemperatureDynamic Viscosity - μ - (centiPoise)
Ethylene Glycol Solution (% by volume)
( o F) ( o C) 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 15.5
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 2.4
240 115.6 2) 2) 2) 2) 2) 2) 1.8
280 137.8 2) 2) 2) 2) 2) 2) 1.2
  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 (pressure 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

Ethylene Glycol Water Solution Heat-Transfer Fluid - Specific Gravity
TemperatureSpecific Gravity - SG -
Ethylene Glycol Solution (% by volume)
( o F) ( o C) 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 .

Densities of Ethylene Glycol based Water Solutions

Turn the screen to see the whole table.

Ethylene Glycol Water Solution Heat-Transfer Fluid - Density
Mass Fraction of Ethylene Glycol in SolutionDensity - ρ - (kg/m 3 )
Temperature - t - ( o C)
-48-35-25-14-8-4020406080100
0 1000 998 992 983 972 958
0.1 1019 1018 1014 1008 1000 992 984
0.2 1038 1037 1036 1030 1022 1014 1005 995
0.3 1058 1056 1055 1054 1046 1037 1027 1017 1007
0.4 1080 1077 1075 1073 1072 1063 1052 1041 1030 1018
0.5 1103 1100 1096 1093 1092 1090 1079 1067 1055 1042 1030
0.6 1127 1124 1120 1115 1112 1110 1107 1095 1082 1068 1055 1042

Example - Expansion Volume in a Heating System with Ethylene Glycol

A heating system with liquid volume 0.8 m 3 is freeze protected with 50% (by mass, mass fraction 0.5) ethylene glycol. The installation temperature of the system is down to 0 o C and the maximum medium operation temperature is 80 o C .

From the table above we see that the density of the solution at installation temperature can be as high as 1090 kg/m 3 - and the medium density at operation temperature can be as low as 1042 kg/m 3 .

The mass of the liquid at installation can be calculated as

m inst = ρ inst V inst (1)

= (1090 kg/m 3 ) (0.8 m 3 )

= 872 kg

where

m inst = mass of liquid at installation (kg)

ρ inst = density at installation (kg/m 3 )

V inst = liquid volume at installation (m 3 )

Mass of the liquid in the system during operation will be same as the mass in system during installation

m inst = m op (2)

= ρ op V op

where

m op = mass of liquid at operation (kg)

ρ op = density at operation (kg/m 3 )

V op = liquid volume at operation (m 3 )

(2) can be modified to calculate liquid operation volume as

V op = m inst / ρ op (2b)

= (872 kg) / ( 1042 kg/m 3 )

= 0.837 m 3

The required expansion volume to avoid pressure can be calculated as

ΔV = V op - V inst (3)

= (0.837 m 3 ) - (0.8 m 3 )

= 0.037 m 3

= 37 liter

where

ΔV = expansion volume (m 3 )

Expansion volume can be calculated as

ΔV = ( ρ inst / ρ op - 1 ) V inst (4)

Specific Heat of Ethylene Glycol based Water Solutions

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

Turn the screen to the whole table.

Ethylene Glycol Water Solution Heat-Transfer Fluid - Specific Heat
Ethylene Glycol Solution
(% by weight) 		Specific Heat - c p (Btu/lb o F)
Temperature (°C)
-50-40-30-20-100102030405060708090100
0 1.0038 1.0018 1.0004 0.99943 0.99902 0.99913 0.99978 1.0009 1.0026 1.0049 1.0076
10 0.97236 0.97422 0.97619 0.97827 0.98047 0.98279 0.98521 0.98776 0.99041 0.99318 0.99607
20 0.93576 0.93976 0.94375 0.94775 0.95175 0.95574 0.95974 0.96373 0.96773 0.97173 0.97572
30 0.89373 0.89889 0.90405 0.90920 0.91436 0.91951 0.92467 0.92982 0.93498 0.94013 0.94529 0.95044
40 0.84605 0.85232 0.85858 0.86484 0.87111 0.87737 0.88364 0.88990 0.89616 0.90243 0.90869 0.91496 0.92122
50 0.79288 0.80021 0.80753 0.81485 0.82217 0.82949 0.83682 0.84414 0.85146 0.85878 0.86610 0.87343 0.88075 0.88807
60 0.72603 0.73436 0.74269 0.75102 0.75935 0.76768 0.77601 0.78434 0.79267 0.80100 0.80933 0.81766 0.82599 0.83431 0.84264 0.85097
70 0.67064 0.67992 0.68921 0.69850 0.70778 0.71707 0.72636 0.73564 0.74493 0.75422 0.76350 0.77279 0.78207 0.79136 0.80065 0.80993
80 0.61208 0.62227 0.63246 0.64265 0.65285 0.66304 0.67323 0.68343 0.69362 0.70381 0.71401 0.72420 0.73439 0.74458 0.75478 0.76497
90 0.58347 0.59452 0.60557 0.61662 0.62767 0.63872 0.64977 0.66082 0.67186 0.68291 0.69396 0.70501 0.71606
100 0.53282 0.54467 0.55652 0.56838 0.58023 0.59209 0.60394 0.61579 0.62765 0.63950 0.65136 0.66321
  • Freezing point 100% ethylene glycol at atmospheric pressure is -12.8 o C (9 o F)
  • 1 Btu/(lb m o F) = 4,186.8 J/(kg K) = 1 kcal/(kg o C)

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

In a 50% solution with operational temperatures above 36 o F 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 o F (26.7 o C). 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

For full table with Boiling Points - rotate the screen!

Ethylene Glycol Water Solution Heat-Transfer Fluid - Boiling Point
Ethylene Glycol Solution
(% by volume) 		0102030405060708090100
Boiling Point ( o F) 212 214 216 220 220 225 232 245 260 288 386
( o C) 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

Increase in Flow required for a 50% Ethylene Glycol Solution
Fluid TemperatureFlow Increase
(%)
( o F) ( o C)
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

Ethylene Glycol Water Solution Heat-Transfer Fluid - Pressure Drop Correction vs. Temperature
Fluid TemperaturePressure Drop Correction with Flow Rates Equal
(%) 		Combined Pressure Drop and Flow Rate Correction
(%)
( o F) ( o C)
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
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