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liquid flashing

English translation: An explanation of liquid flashing

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15:49 Apr 2, 2007
English to English translations [PRO]
Tech/Engineering - Mechanics / Mech Engineering / chillers
English term or phrase: liquid flashing
talking about the condenser

"The coils will have an integral subcooler circuit that provides sufficient subcooling to effectively eliminate the possibility of ***liquid flashing*** and increase the unit`s efficiency of 5-7% without increasing in power absorption."

(original text is probably a translation from German)

...could you explain what they mean by liquid "flashing"?? thanks
Elena Ghetti
Italy
Local time: 06:17
English translation:An explanation of liquid flashing
Explanation:
Hope this helps.

Liquid flashing phenomena holds an interest in many areas of science and engineering. As examples one can
mention: a) the accidental release of flammable and toxic pressure-liquefied gases in chemical and nuclear
industry; the failure of a vessel or pipe in the form of a small hole results in the formation of a two-phase jet
containing a mixture of liquid droplets and vapor, b) fuel atomization for improvement of fuel injector
technology, c) flashing mechanism occurrence in expansion devices of refrigerator cycles etc. Violent boiling
and aerodynamic fragmentation control the two-phase behavior of flashing flows. The initial, flashing stage of
the jet, where the system is furthest from equilibrium is least understood. To investigate theoretically these
source processes, knowledge of accurate and reliable data such as distribution of droplet size, velocity and
temperature is mandatory. These models are needed in design and safety assessment. This PhD study focuses on
the understanding of the source processes with emphasis on flashing release of flammable pressurized liquids,
characterize the two-phase jet after the release and the effects of initial conditions such as initial storage
pressure, temperature, geometrical effects of the release points.
The flashing phenomenon occurs when a liquid is out of thermodynamic equilibrium such as sudden changes in
the pressure or temperature of a liquid system. In the case of rapid depressurization, the liquid keeps its initial
temperature constant, so that, because of thermal inertia, the internal temperature finds itself above the saturation
temperature in the final condition. The meta-stable liquid will return violently to its equilibrium condition
through evaporation (i.e. consuming its superheat as latent heat). Evaporation will occur within the liquid
through bubble growth. This process can be extremely sudden and explosive. Because a maximum surface
exchange is crucial for evaporation, the jet will disintegrate into small droplets. Equilibrium will be reached
when partial vapor pressure at the interface equals to that far a way from the droplets.

See more at www.vki.ac.be/ea-dept/phd/04-05/yildiz.pdf
Selected response from:

Jack Doughty
United Kingdom
Local time: 05:17
Grading comment
thanks!
4 KudoZ points were awarded for this answer

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Summary of answers provided
3liquid reaching the flash point (see below)
Marie-Hélène Hayles
3An explanation of liquid flashing
Jack Doughty


Discussion entries: 1





  

Answers


46 mins   confidence: Answerer confidence 3/5Answerer confidence 3/5
An explanation of liquid flashing


Explanation:
Hope this helps.

Liquid flashing phenomena holds an interest in many areas of science and engineering. As examples one can
mention: a) the accidental release of flammable and toxic pressure-liquefied gases in chemical and nuclear
industry; the failure of a vessel or pipe in the form of a small hole results in the formation of a two-phase jet
containing a mixture of liquid droplets and vapor, b) fuel atomization for improvement of fuel injector
technology, c) flashing mechanism occurrence in expansion devices of refrigerator cycles etc. Violent boiling
and aerodynamic fragmentation control the two-phase behavior of flashing flows. The initial, flashing stage of
the jet, where the system is furthest from equilibrium is least understood. To investigate theoretically these
source processes, knowledge of accurate and reliable data such as distribution of droplet size, velocity and
temperature is mandatory. These models are needed in design and safety assessment. This PhD study focuses on
the understanding of the source processes with emphasis on flashing release of flammable pressurized liquids,
characterize the two-phase jet after the release and the effects of initial conditions such as initial storage
pressure, temperature, geometrical effects of the release points.
The flashing phenomenon occurs when a liquid is out of thermodynamic equilibrium such as sudden changes in
the pressure or temperature of a liquid system. In the case of rapid depressurization, the liquid keeps its initial
temperature constant, so that, because of thermal inertia, the internal temperature finds itself above the saturation
temperature in the final condition. The meta-stable liquid will return violently to its equilibrium condition
through evaporation (i.e. consuming its superheat as latent heat). Evaporation will occur within the liquid
through bubble growth. This process can be extremely sudden and explosive. Because a maximum surface
exchange is crucial for evaporation, the jet will disintegrate into small droplets. Equilibrium will be reached
when partial vapor pressure at the interface equals to that far a way from the droplets.

See more at www.vki.ac.be/ea-dept/phd/04-05/yildiz.pdf

Jack Doughty
United Kingdom
Local time: 05:17
Native speaker of: Native in EnglishEnglish
PRO pts in category: 143
Grading comment
thanks!

Peer comments on this answer (and responses from the answerer)
neutral  Richard Benham: "Phenomena" is plural...don't know too much about the rest.
15 hrs
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1 hr   confidence: Answerer confidence 3/5Answerer confidence 3/5
liquid reaching the flash point (see below)


Explanation:
Jack may well be right, but the first idea which came to my mind was that they mean when the liquid reaches its flash point, i.e. the (lowest) temperature at which it can form a combustible mixture with air. Obviously this would apply to flammable liquids only!

Marie-Hélène Hayles
Local time: 06:17
Native speaker of: English
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