Why are some reciprocating compressors using glycol for their cooling system in the recycle gas compressor while other don't have such as net gas booster compressor?
Answers
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23/12/2019
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Sandeep Gupta, HPCL, sandeepkumar.gupta@hpcl.in
Ethylene glycol is primarily used in antifreeze formulations (50%) and as a raw material in the manufacture of polyesters such as polyethylene terephthalate (PET) (40%). Thus as a Coolant and heat transfer agent.The major use of ethylene glycol is as a medium for convective heat transfer in, for example, automobiles and liquid cooled computers. Ethylene glycol is also commonly used in chilled water air conditioning systems that place either the chiller or air handlers outside, or systems that must cool below the freezing temperature of water. In geothermal heating/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 (lake, ocean, water well) or dissipates heat to the sink, depending if 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. A 50/50 mix by mass has a specific heat capacity of about 3140 J/kg C (0.75 BTU/lb F) three quarters that of pure water, thus requiring increased flow rates in same system comparisons with water. The formation of large bubbles in i.c. engines cooling passages will seriously inhibit heat-flow (flux)from that area thus allowing nucleation (tiny bubbles) heat-transfer to occur is not advisable. Large bubbles in cooling passages will be self sustaining or grow larger, with virtually the complete loss of cooling in that spot. With pure MEG that hot spot has to get to 200*C.Cooling due other effects such as air draft from fan etc. (not considered in pure nucleation analysis) will assist in preventing large bubble formation.
Antifreeze[edit]
Ethylene glycol disrupts hydrogen bonding when dissolved in water. Pure ethylene glycol freezes at about −12 °C (10.4 °F), but when mixed with water, the mixture does not readily crystallize, and therefore the freezing point of the mixture is depressed. Specifically, a mixture of 60% ethylene glycol and 40% water freezes at −45 °C (−49 °F).[3]Diethylene glycol behaves similarly. It is used as a de-icing fluid for windshields and aircraft. The antifreeze capabilities of ethylene glycol have made it a component of vitrification (anticrystallization) mixtures for low-temperature preservation of biological tissues and organs. Mixture of ethylene glycol and water can also be chemically termed as Glycol Concentrate/ Compound/ Mixture/ Solution.
However, the boiling point for aqueous ethylene glycol increases monotonically with increasing ethylene glycol percentage. Thus, the use of ethylene glycol not only depresses the freezing point, but also elevates the boiling point such that the operating range for the heat transfer fluid is 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; there is no chemical stabilization against boiling of the liquid phase at intermediate compositions, as there is against freezing
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13/08/2019
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Abhay Raj Mishra, Iocl, mishraar@indianoil.in
Normally Compressor manufacturer suggest glycol for demineralized water circulation in reciprocating compressor jacket cooling. It help for lowering the freezing point and viscosity of circulating water . It is very useful in cold weather environment. We have changed glycol mix water in our one system and started circulation without glycol but no any abnormality observed in packing cooling system.
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12/08/2019
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Nitin Mittal, HPCL Mittal Energy Limited, mitnit73@yahoo.co.in
Glycol is added in cooling water to avoid freezing of cooling water.
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