Thermal conductivity of ethylene glycol at various temperatures

Thermal conductivity of ethylene glycol at various temperatures

Junjie Chen

Contributor: Junjie Chen, ORCID: 0000-0001-5055-4309, E-mail address: [e-mail], Department of Energy and Power Engineering, School of Mechanical and Power Engineering, Henan Polytechnic University, 2000 Century Avenue, Jiaozuo, Henan, 454000, P.R. China

Ethylene glycol is mainly used for two purposes, as a raw material in the manufacture of polyester fibers and for antifreeze formulations. It is an odorless, colorless, flammable, viscous liquid. Ethylene glycol has a sweet taste, but it is toxic in high concentrations. Ethylene glycol is produced from ethylene, via the intermediate ethylene oxide. Ethylene oxide reacts with water to produce ethylene glycol. This reaction can be catalyzed by either acids or bases, or can occur at neutral pH under elevated temperatures. The highest yields of ethylene glycol occur at acidic or neutral pH with a large excess of water. Under these conditions, ethylene glycol yields of 90 percent can be achieved. The major byproducts are the oligomers diethylene glycol, triethylene glycol, and tetraethylene glycol. The separation of these oligomers and water is energy-intensive. Because the methanol is recycled, only carbon monoxide, hydrogen, and oxygen are consumed. The major use of ethylene glycol is as an antifreeze agent in the coolant in for example, automobiles and air-conditioning systems that either place the chiller or air handlers outside or must cool below the freezing temperature of water. In geothermal heating and cooling systems, ethylene glycol is the fluid that transports heat through the use of a geothermal heat pump. The ethylene glycol either gains energy from the source or dissipates heat to the sink, depending on whether the system is being used for heating or cooling. Pure ethylene glycol has a specific heat capacity about one half that of water. So, while providing freeze protection and an increased boiling point, ethylene glycol lowers the specific heat capacity of water mixtures relative to pure water. The freezing point depression of some mixtures can be explained as a colligative property of solutions but, in highly concentrated mixtures such as the example, deviations from ideal solution behavior are expected due to the influence of intermolecular forces. It's important to note that though pure and distilled water will have a greater specific heat capacity than any mixture of antifreeze and water, commercial antifreezes also typically contain an anti-corrosive additive to prevent pure water from corroding coolant passages in the engine block, cylinder heads, water pump and radiator. There is a difference in the mixing ratio, depending on whether it is ethylene glycol or propylene glycol. The use of ethylene glycol not only depresses the freezing point of aqueous mixtures, but also elevates their boiling point. This results in the operating temperature range for heat-transfer fluids being broadened on both ends of the temperature scale. The increase in boiling temperature is due to pure ethylene glycol having a much higher boiling point and lower vapor pressure than pure water, as is typical with most binary mixtures of volatile liquids. In the plastic industry, ethylene glycol is an important precursor to polyester fibers and resins. Polyethylene terephthalate, used to make plastic bottles for soft drinks, is prepared from ethylene glycol. Ethylene glycol is used in the natural gas industry to remove water vapor from natural gas before further processing.

Thermodynamic temperature (degrees kelvin), Thermal conductivity (watts per meter-kelvin)

0.2549          280

0.2563          290

0.2576          300

0.259            310

0.2603          320

0.2616          330

0.263            340

0.2643          350

0.2645          288.15

0.2609          293.15

0.2695          353.15