Ethylene Glycol Heat-Transfer Fluid
Freezing point, viscosity, specific gravity and specific heat capacity of ethylene glycol based heat-transfer fluids - brines
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Ethylene Glycol based water solutions are common in heat-transfer systems where the temperature in the heat transfer fluid can be below 32oF (0oC). Especially this is the situation for cooling systems where the fluid operates with temperatures below the water freezing point. Ethylene glycol is also common in heating applications that temporarily may not be operating (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 must be avoided in applications where there are a slightest chance of leakage to potable water or food processing systems. Instead solutions based on propylene glycol are commonly used.
The specific heat capacity, viscosity and specific weight of water and ethylene glycol solutions varies significantly with the percent of ethylene glycol and the temperature of the fluid. The properties differs so much from clean water that a heat transfer systems with ethylene glycol should be calculated thoroughly for the actual temperatures and solutions.
Freezing Point of Ethylene Glycol based Water Solutions
Freezing point of ethylene glycol based water solutions at various temperatures:
| Freezing Point | ||||||||
| Ethylene Glycol Solution (% by volume) |
0 | 10 | 20 | 30 | 40 | 50 | 60 | |
| Temperature | (oF) | 32 | 23 | 14 | 2 | -13 | -36 | -70 |
| (oC) | 0 | -3 | -8 | -16 | -25 | -37 | -55 | |
Due to possible slush creation, ethylene glycol and water solutions should not be used in a condition close to the freezing points.
Dynamic Viscosity of Ethylene Glycol based Water Solutions
Dynamic viscosity - μ- of ethylene glycol based water solutions at various temperatures:
| Dynamic Viscosity - μ - (centpoise) | ||||||||
| Temperature | Ethylene Glycol Solution (% by volume) | |||||||
| (oF) | (oC) | 25 | 30 | 40 | 50 | 60 | 65 | 100 |
| 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 |
- below freezing point
- 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 piping system increase.
Specific Gravity of Ethylene Glycol based Water Solutions
Specific gravity - SG - of ethylene glycol based water solutions at various temperatures:
| Specific Gravity- SG - | ||||||||
| Temperature | Ethylene Glycol Solution (% by volume) | |||||||
| (oF) | (oC) | 25 | 30 | 40 | 50 | 60 | 65 | 100 |
| -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 | 1.049 |
| 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 |
- below freezing point
- above boiling point
Note! The specific gravity of an ethylene glycol based water solution is increased compared with the specific gravity of clean water.
Specific Heat Capacity of Ethylene Glycol based Water Solutions
Specific Heat Capacity - cp - of ethylene glycol based water solutions at various temperatures:
| Specific Heat Capacity - cp - (Btu/lb.oF) | ||||||||
| Temperature | Ethylene Glycol Solution (% by volume) | |||||||
| (oF) | (oC) | 25 | 30 | 40 | 50 | 60 | 65 | 100 |
| -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 |
- below freezing point
- above boiling point
- 1 Btu/(lbmoF) = 4,186.8 J/(kg K) = 1 kcal/(kgoC)
Note! The specific heat capacity of an ethylene glycol based water solution is less than the specific heat of clean water. For a heat transfer system the circulated volume must be increased.
In a 50% solution with operational temperatures above 36 oF the specific heat capacity is decreased with aprox. 20%. The reduced specific heat capacity must be compensated by circulating more fluid.
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 is often treated with chlorine, which is corrosive, and should be avoided.
Automatic makeup water systems must not be used. A leakage will contaminate the environment and dilute the antifreeze protection of the systems.
Boiling Point Ethylene Glycol Solution
| Boiling Point | ||||||||
| Ethylene Glycol Solution (% by volume) |
0 | 10 | 20 | 30 | 40 | 50 | 60 | |
| Temperature | (oF) | 212 | 214 | 216 | 220 | 220 | 225 | 232 |
| (oC) | 100 | 101.1 | 102.2 | 104.4 | 104.4 | 107.2 | 111.1 | |
Flow Increase Needed for 50% Ethylene Glycol Solution
Flow increase for 50% ethylene glycol solution compared with water is indicated in the table below:
| Fluid Temperature | Flow 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 solution compared with water is indicated in the table below:
| Fluid Temperature | Pressure 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 |
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