Ethylene Propylene Glycol

Reference data and engineering information about ethylene propylene glycol for hvac systems applications.

ethylenepropyleneglycol

Overview

Engineering reference data for Ethylene Propylene Glycol in HVAC systems.

$Q = \dot{m} c_p \Delta T$

Heat causing temperature change.

$Q = \dot{m} h_{fg} \Delta\omega$

Heat causing moisture change.

$COP = Q_c / W$

Coefficient of performance.

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Comparison of Ethylene Glycol and Propylene Glycol as Antifreeze
Property	Ethylene Glycol	Propylene Glycol	Comments
Freeze point depression	more effective	less effective	More antifreeze is needed of propylene glycol to achieve the same freeze point.
Heat transfer efficiency/capability	better	less	Ethylene glycol has superior heat transfer efficiency due to lower viscosity - but more fluid must be circulated to transfer the same amount of energy since Propylene glycol has higher specific heat.
Viscosity	lower	higher	Propylene glycol increases major head loss in the systems. Pumps head increased.
Flammability	low	low
Chemical oxygen demand	low	higher
Biodegrading	degrades in 10 - 30 days	needs more than 20 - 30 days to degrade
Carcinogenic	no	no	A carcinogen is any substance or agent that promotes cancer.
Toxic	High level of acute when taken orally, targets the kidneys	Lower level of acute	Ethylene glycol should never be used in any drinking water or food processing system.
Skin irritant	low	low	Propylene glycol is used in small amounts in cosmetics.

Source: engineeringtoolbox.com

Toxicity: Ethylene glycol is highly toxic upon oral ingestion and targets the kidneys. It must never be used in systems associated with potable water or food processing. Propylene glycol has a lower level of acute toxicity.
Performance Trade-off: While ethylene glycol offers better heat transfer efficiency due to lower viscosity, propylene glycol has a higher specific heat capacity. This means more ethylene glycol fluid must be circulated to transfer the same amount of energy.
Environmental Impact: Ethylene glycol degrades faster (10-30 days) than propylene glycol (>20-30 days) and has a lower chemical oxygen demand, meaning less impact on aquatic oxygen levels.