Development of heat transfer and evaporation model of LNG covered by Hi-Ex foam. (November 2016)

• Record Type: Journal Article
• Authors: Ye, Congliang; Hua, Min; Pan, Xuhai; He, Baolong; Jiang, Juncheng
• Is Part Of: Journal of loss prevention in the process industries. Volume 44(2016:Nov.)
• Page Start: 564
• Page End: 572
• Publication Date: 2016-11
• Subjects: Liquid nitrogen -- High expansion foam -- Experimental methods -- Heat transfer -- Evaporation rate -- Safety; Chemical industries -- Safety measures -- Periodicals; 660.2804
• DOI: 10.1016/j.jlp.2016.09.014
• Languages: English
• ISSNs: 0950-4230

Abstract

Abstract: Natural gas is a kind of clean, efficient green energy source, which is used widely. Liquefied natural gas (LNG) is produced by cooling natural gas to −161 °C, at which it becomes the liquid. Once LNG was released, fire or explosion would happen when ignition source existed nearby. The high expansion foam (Hi-Ex foam) is believed to quickly blanket on the top of LNG spillage pool and warm the LNG vapor to lower the vapor cloud density at the ground level and raising vapor buoyancy. To identify the physical structure after it contacted with LN2 and to develop heat transfer model, the small-scale field test with liquid nitrogen (LN2 ) was designed. In experiment, three layers including frozen ice layer, frozen Hi-Ex layer and soft layer of Hi-Ex foam were observed at the steady state. By characterizing physical structure of the foam, formulas for calculating the surface of single foam bubble and counting foam film thickness were deduced. The micro heat transfer and evaporation model between cryogenic liquid and Hi-Ex foam was established. Indicating the physical structure of the frozen ice layer, there were a certain number of icicles below it. The heat transfer and evaporation mathematical model between the frozen ice layer and LNG was derived. Combining models above with the heat transfer between LNG, ground and cofferdam, the heat transfer and evaporation mathematical model of LNG covered by Hi-Ex foam was developed eventually. Finally, LN2 evaporation rate calculated by this model was compared with the measured evaporation rate. The calculated results are 1.2–2.1 times of experimental results, which were acceptable in engineering and proved the model was reliable. Highlights: Small scale field test (LN2 ) was designed to observe the phenomena and get data. Physical structure of Hi-Ex foam was built to deduce the thickness of foam cell. Heat transfer and evaporation model of LNG covered by Hi-Ex foam was developed by physical structure and formulas. LN2 evaporation rate calculated by this model was compared with the measured evaporation rate to revise it.