Title:
Heat Transfer and Pressure Drop During Condensation of Refrigerants in Microchannels

dc.contributor.advisor Garimella, Srinivas
dc.contributor.author Agarwal, Akhil en_US
dc.contributor.committeeMember Allen, Mark G.
dc.contributor.committeeMember Fuller, Tom
dc.contributor.committeeMember Ghiaasiaan, Mostafa
dc.contributor.committeeMember Graham, Samuel
dc.contributor.department Mechanical Engineering en_US
dc.date.accessioned 2007-03-27T18:27:33Z
dc.date.available 2007-03-27T18:27:33Z
dc.date.issued 2006-11-20 en_US
dc.description.abstract Two-phase flow, boiling, and condensation in microchannels have received considerable attention in the recent past due to the growing interest in the high heat fluxes made possible by these channels. This dissertation presents a study on the condensation of refrigerant R134a in small hydraulic diameter (100 < Dh < 160 mm) channels. A novel technique is used for the measurement of local condensation heat transfer coefficients in small quality increments, which has typically been found to be difficult due to the low heat transfer rates at the small flow rates in these microchannels. This method is used to accurately determine pressure drop and heat transfer coefficients for mass fluxes between 300 and 800 kg/m2-s and quality 0 < x < 1 at four different saturation temperatures between 30 and 60oC. The results obtained from this study capture the effect of variations in mass flux, quality, saturation temperature, hydraulic diameter, and channel aspect ratio on the observed pressure drop and heat transfer coefficients. Based on the available flow regime maps, it was assumed that either the intermittent or annular flow regimes prevail in these channels for the flow conditions under consideration. Internally consistent pressure drop and heat transfer models are proposed taking into account the effect of mass flux, quality, saturation temperature, hydraulic diameter, and channel aspect ratio. The proposed models predict 95% and 94% of the pressure drop and heat transfer data within ±25%, respectively. Both pressure drop and heat transfer coefficient increase with a decrease in hydraulic diameter, increase in channel aspect ratio and decrease in saturation temperature. A new non-dimensional parameter termed Annular Flow Factor is also introduced to quantify the predominance of intermittent or annular flow in the channels as the geometric parameters and operating conditions change. This study leads to a comprehensive understanding of condensation in microchannels for use in high-flux heat transfer applications.
dc.description.degree Ph.D. en_US
dc.format.extent 8953560 bytes
dc.format.mimetype application/pdf
dc.identifier.uri http://hdl.handle.net/1853/14129
dc.language.iso en_US
dc.publisher Georgia Institute of Technology en_US
dc.subject Microchannels en_US
dc.subject Condensation en_US
dc.subject Two-phase en_US
dc.subject Heat transfer en_US
dc.subject Pressure drop en_US
dc.subject Annular en_US
dc.subject Intermittent en_US
dc.subject.lcsh Heat Transmission en_US
dc.subject.lcsh Refrigerants en_US
dc.subject.lcsh Expansion (Heat) en_US
dc.subject.lcsh Heat exchangers en_US
dc.title Heat Transfer and Pressure Drop During Condensation of Refrigerants in Microchannels en_US
dc.type Text
dc.type.genre Dissertation
dspace.entity.type Publication
local.contributor.advisor Garimella, Srinivas
local.contributor.corporatename George W. Woodruff School of Mechanical Engineering
local.contributor.corporatename College of Engineering
relation.isAdvisorOfPublication 7c74399b-6962-4814-9d2a-51f8b9c41e1f
relation.isOrgUnitOfPublication c01ff908-c25f-439b-bf10-a074ed886bb7
relation.isOrgUnitOfPublication 7c022d60-21d5-497c-b552-95e489a06569
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