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You searched for subject:(Gas assisted evaporation). Showing records 1 – 2 of 2 total matches.

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1. Narayanan, Shankar. Gas assisted thin-film evaporation from confined spaces.

Degree: PhD, Mechanical Engineering, 2011, Georgia Tech

A novel cooling mechanism based on evaporation of thin liquid films is presented for thermal management of confined heat sources, such as microprocessor hotspots. The underlying idea involves utilization of thin nanoporous membranes for maintaining microscopically thin liquid films by capillary action, while providing a pathway for the vapor generated due to evaporation at the liquid-vapor interface. The vapor generated by evaporation is continuously removed by using a dry sweeping gas keeping the membrane outlet dry. This thesis presents a detailed theoretical, computational and experimental investigation of the heat and mass transfer mechanisms that result in dissipating heat. Performance analysis of this cooling mechanism demonstrates heat fluxes over 600W/cm2 for sufficiently thin membrane and film thicknesses (~1-5µm) and by using air jet impingement for advection of vapor from the membrane surface. Based on the results from this performance analysis, a monolithic micro-fluidic device is designed and fabricated incorporating micro and nanoscale features. This MEMS/NEMS device serves multiple functionalities of hotspot simulation, temperature sensing, and evaporative cooling. Subsequent experimental investigations using this microfluidic device demonstrate heat fluxes in excess of 600W/cm2 at 90 C using water as the evaporating coolant. In order to further enhance the device performance, a comprehensive theoretical and computational analysis of heat and mass transfer at micro and nanoscales is carried out. Since the coolant is confined using a nanoporous membrane, a detailed study of evaporation inside a nanoscale cylindrical pore is performed. The continuum analysis of water confined within a cylindrical nanopore determines the effect of electrostatic interaction and Van der Waals forces in addition to capillarity on the interfacial transport characteristics during evaporation. The detailed analysis demonstrates that the effective thermal resistance offered by the interface is negligible in comparison to the thermal resistance due to the thin film and vapor advection. In order to determine the factors limiting the performance of the MEMS device on a micro-scale, a device-level detailed computational analysis of heat and mass transfer is carried out, which is supported by experimental investigation. Identifying the contribution of various simultaneously occurring cooling mechanisms at different operating conditions, this analysis proposes utilization of hydrophilic membranes for maintaining very thin liquid films and further enhancement in vapor advection at the membrane outlet to achieve higher heat fluxes. Advisors/Committee Members: Fedorov, Andrei (Committee Chair), Joshi, Yogendra (Committee Co-Chair), Bakir, Muhannad (Committee Member), Ghiaasiaan, Mostafa (Committee Member), Jang, Seung Soon (Committee Member).

Subjects/Keywords: Evaporation; Thermal management; Electronic cooling; Gas assisted evaporation; Hotspot; Extended meniscus; Capillary evaporation; Phase change cooling; High heat flux; MEMS; Microfluidic cooling; Thin film; Thin films; Evaporative cooling; Heat Transmission; Mass transfer; Electronics Cooling

…transfer using evaporation. The concept of gas assisted evaporative cooling (GAEC) for… …ANALYSIS OF GAS-ASSISTED THIN FILM EVAPORATION A theoretical analysis of thin film evaporation is… …69 5.2.3 Gas-assisted thin-film evaporative cooling… …interface. The vapor generated by evaporation is continuously removed by using a dry sweeping gas… …x28;e.g. FC72) should offer performance superior to water in gas-assisted evaporative… 

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APA (6th Edition):

Narayanan, S. (2011). Gas assisted thin-film evaporation from confined spaces. (Doctoral Dissertation). Georgia Tech. Retrieved from http://hdl.handle.net/1853/42780

Chicago Manual of Style (16th Edition):

Narayanan, Shankar. “Gas assisted thin-film evaporation from confined spaces.” 2011. Doctoral Dissertation, Georgia Tech. Accessed July 16, 2019. http://hdl.handle.net/1853/42780.

MLA Handbook (7th Edition):

Narayanan, Shankar. “Gas assisted thin-film evaporation from confined spaces.” 2011. Web. 16 Jul 2019.

Vancouver:

Narayanan S. Gas assisted thin-film evaporation from confined spaces. [Internet] [Doctoral dissertation]. Georgia Tech; 2011. [cited 2019 Jul 16]. Available from: http://hdl.handle.net/1853/42780.

Council of Science Editors:

Narayanan S. Gas assisted thin-film evaporation from confined spaces. [Doctoral Dissertation]. Georgia Tech; 2011. Available from: http://hdl.handle.net/1853/42780

2. Erten, Edibe Seda. Characterization of aroma components of raw and roasted almonds and the effect of the oxidative state of the nut on roasted flavor formation.

Degree: PhD, Food Science & Human Nutrition, 2016, University of Illinois – Urbana-Champaign

Almond is the most produced tree nut in the US. Along with potential health related studies, popularity of almonds has been rising among consumers in the last few decades. Furthermore, consumer liking the flavor of both raw and roasted almonds plays a role in its increasing popularity. However, because of its high unsaturated fat content almond is prone to lipid oxidation during storage that leads to flavor and quality changes. Predominant aroma-active compounds in almonds were identified and the effect of oxidative state of raw almonds on roasted aroma was observed in this study. Volatile components of raw, dry roasted and oil roasted almonds were isolated by solvent extraction-solvent-assisted flavor evaporation and the predominant aroma-active compounds were identified by gas chromatography-olfactometry (GCO) and aroma extract dilutions analysis (AEDA), and by GC-mass spectrometry determination of odor-activity values (OAVs). Results demonstrated the importance of lipid-derived volatile compounds such as ketones and aldehydes in raw almond aroma. Meanwhile, volatile compounds derived via the Maillard reaction, lipid degradation/oxidation and sugar degradation were predominant aroma compounds in dry and oil roasted almonds. These compounds were mainly pyrazines, pyridines, pyrrolines, aldehydes and furanones. Aroma changes of stored raw (SR) and stored raw-then-roasted (SRTR) almonds were investigated by gas chromatography-olfactometry (GCO) and aroma extract dilutions analysis (AEDA) and GC-mass spectrometry (GC-MS). Raw almonds were stored at either room temperature (24±1°C), 37°C or 4°C for 18, 9 or 12 months, respectively. Based on their relatively high flavor dilution (FD) factors and OAVs, the predominant aroma compounds in stored raw almonds were identified as 1-octen-3-one, hexanal and acetic acid. Aldehydes and acids were found in highest abundance in raw almonds. Storage of raw almonds resulted in an increase in the total concentration of aroma compounds at all storage temperatures. In SRTR almonds, methional, Furaneol, 3-methylbutanal and 2-acetyl-3,4,5,6 (& 1,4,5,6)-tetrahydropyridine were the predominant aroma compounds, while aldehydes, nitrogen-containing compounds and acids were found in highest overall abundance. Total concentration of aroma compounds increased in SRTR almonds stored at RT and 37°C, whereas they decreased in almonds stored at 4°C. Concentrations of nitrogen-containing aroma compounds, responsible for roasted notes, increased in the SRTR almonds throughout the storage period. Results of this study indicate that storing raw almonds prior to roasting affects the levels of thermally generated aroma compounds formed during roasting. Advisors/Committee Members: Cadwallader, Keith R (advisor), Engeseth, Nicki J (Committee Chair), Lee, Soo-Yeun (committee member), Lee, Youngsoo (committee member).

Subjects/Keywords: raw almonds; roasted almonds; aroma-active compounds; storage; lipid oxidation; solvent-assisted flavor evaporation (SAFE); gas chromatography-olfactometry (GCO); aroma extract dilution analysis (AEDA)

…isolation efficiency factor RI retention index SAFE solvent-assisted flavor evaporation SR… …roasted almonds by gas chromatographyolfactometry… …then-roasted (SRTR) almonds by gas chromatographyolfactometry… …dilution GC-MS gas chromatography-mass spectrometry GCO gas chromatography-olfactometry IEF… …volatiles and the identification of compounds was based on mass spectra and/or gas chromatographic… 

Record DetailsSimilar RecordsGoogle PlusoneFacebookTwitterCiteULikeMendeleyreddit

APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6th Edition):

Erten, E. S. (2016). Characterization of aroma components of raw and roasted almonds and the effect of the oxidative state of the nut on roasted flavor formation. (Doctoral Dissertation). University of Illinois – Urbana-Champaign. Retrieved from http://hdl.handle.net/2142/92850

Chicago Manual of Style (16th Edition):

Erten, Edibe Seda. “Characterization of aroma components of raw and roasted almonds and the effect of the oxidative state of the nut on roasted flavor formation.” 2016. Doctoral Dissertation, University of Illinois – Urbana-Champaign. Accessed July 16, 2019. http://hdl.handle.net/2142/92850.

MLA Handbook (7th Edition):

Erten, Edibe Seda. “Characterization of aroma components of raw and roasted almonds and the effect of the oxidative state of the nut on roasted flavor formation.” 2016. Web. 16 Jul 2019.

Vancouver:

Erten ES. Characterization of aroma components of raw and roasted almonds and the effect of the oxidative state of the nut on roasted flavor formation. [Internet] [Doctoral dissertation]. University of Illinois – Urbana-Champaign; 2016. [cited 2019 Jul 16]. Available from: http://hdl.handle.net/2142/92850.

Council of Science Editors:

Erten ES. Characterization of aroma components of raw and roasted almonds and the effect of the oxidative state of the nut on roasted flavor formation. [Doctoral Dissertation]. University of Illinois – Urbana-Champaign; 2016. Available from: http://hdl.handle.net/2142/92850

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