Bubble-assisted film evaporation correlation for saline water at sub-atmospheric pressures in horizontal-tube evaporator

Handle URI:
http://hdl.handle.net/10754/594136
Title:
Bubble-assisted film evaporation correlation for saline water at sub-atmospheric pressures in horizontal-tube evaporator
Authors:
Shahzad, Muhammad Wakil; Myat, Aung; Chun, Won Gee; Ng, Kim Choon ( 0000-0003-3930-4127 )
Abstract:
In falling film evaporators, the overall heat transfer coefficient is controlled by film thickness, velocity, liquid properties and the temperature differential across the film layer. This article presents the heat transfer behavior for evaporative film boiling on horizontal tubes, but working at low pressures of 0.93-3.60 kPa (corresponding solution saturation temperatures of 279-300 K) as well as seawater salinity of 15,000 to 90,000 mg/l or ppm. Owing to a dearth of literature on film-boiling at these conditions, the article is motivated by the importance of evaporative film boiling in the desalination processes such as the multi-effect distillation (MED) or multi-stage flashing (MSF): It is observed that in addition to the above-mentioned parameters, evaporative heat transfer of seawater is affected by the emergence of micro-bubbles within the thin film layer, particularly when the liquid saturation temperatures drop below 298 K (3.1 kPa). Such micro bubbles are generated near to the tube wall surfaces and they enhanced the heat transfer by two or more folds when compared with the predictions of conventional evaporative film boiling. The appearance of micro-bubbles is attributed to the rapid increase in the specific volume of vapor, i.e., dv/dT, at low saturation temperature conditions. A new correlation is thus proposed in this article and it shows good agreement to the measured data with an experimental uncertainty of 8% and regression RMSE of 3.5%. © 2012 Elsevier Ltd. All rights reserved.
KAUST Department:
Water Desalination and Reuse Research Center (WDRC)
Citation:
Shahzad MW, Myat A, Chun WG, Ng KC (2013) Bubble-assisted film evaporation correlation for saline water at sub-atmospheric pressures in horizontal-tube evaporator. Applied Thermal Engineering 50: 670–676. Available: http://dx.doi.org/10.1016/j.applthermaleng.2012.07.003.
Publisher:
Elsevier BV
Journal:
Applied Thermal Engineering
Issue Date:
Jan-2013
DOI:
10.1016/j.applthermaleng.2012.07.003
Type:
Article
ISSN:
1359-4311
Appears in Collections:
Articles; Water Desalination and Reuse Research Center (WDRC)

Full metadata record

DC FieldValue Language
dc.contributor.authorShahzad, Muhammad Wakilen
dc.contributor.authorMyat, Aungen
dc.contributor.authorChun, Won Geeen
dc.contributor.authorNg, Kim Choonen
dc.date.accessioned2016-01-19T13:22:26Zen
dc.date.available2016-01-19T13:22:26Zen
dc.date.issued2013-01en
dc.identifier.citationShahzad MW, Myat A, Chun WG, Ng KC (2013) Bubble-assisted film evaporation correlation for saline water at sub-atmospheric pressures in horizontal-tube evaporator. Applied Thermal Engineering 50: 670–676. Available: http://dx.doi.org/10.1016/j.applthermaleng.2012.07.003.en
dc.identifier.issn1359-4311en
dc.identifier.doi10.1016/j.applthermaleng.2012.07.003en
dc.identifier.urihttp://hdl.handle.net/10754/594136en
dc.description.abstractIn falling film evaporators, the overall heat transfer coefficient is controlled by film thickness, velocity, liquid properties and the temperature differential across the film layer. This article presents the heat transfer behavior for evaporative film boiling on horizontal tubes, but working at low pressures of 0.93-3.60 kPa (corresponding solution saturation temperatures of 279-300 K) as well as seawater salinity of 15,000 to 90,000 mg/l or ppm. Owing to a dearth of literature on film-boiling at these conditions, the article is motivated by the importance of evaporative film boiling in the desalination processes such as the multi-effect distillation (MED) or multi-stage flashing (MSF): It is observed that in addition to the above-mentioned parameters, evaporative heat transfer of seawater is affected by the emergence of micro-bubbles within the thin film layer, particularly when the liquid saturation temperatures drop below 298 K (3.1 kPa). Such micro bubbles are generated near to the tube wall surfaces and they enhanced the heat transfer by two or more folds when compared with the predictions of conventional evaporative film boiling. The appearance of micro-bubbles is attributed to the rapid increase in the specific volume of vapor, i.e., dv/dT, at low saturation temperature conditions. A new correlation is thus proposed in this article and it shows good agreement to the measured data with an experimental uncertainty of 8% and regression RMSE of 3.5%. © 2012 Elsevier Ltd. All rights reserved.en
dc.publisherElsevier BVen
dc.subjectDesalinationen
dc.subjectFalling film evaporationen
dc.subjectHeat transfer coefficienten
dc.subjectHorizontal tubes evaporatorsen
dc.subjectLow pressure evaporationen
dc.subjectSalinityen
dc.titleBubble-assisted film evaporation correlation for saline water at sub-atmospheric pressures in horizontal-tube evaporatoren
dc.typeArticleen
dc.contributor.departmentWater Desalination and Reuse Research Center (WDRC)en
dc.identifier.journalApplied Thermal Engineeringen
dc.contributor.institutionDepartment of Mechanical Engineering, National University of Singapore, 9 Engineering Drive 1, Singapore 117576, Singaporeen
dc.contributor.institutionDepartment of Nuclear and Energy Engineering, Cheju National University, 66 Jejudaehakno, Jejusi, South Koreaen
kaust.authorNg, Kim Choonen
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