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Entropy generation analysis of cylindrical heat pipe using nanofluid
KTH, School of Industrial Engineering and Management (ITM), Energy Technology.
KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
2015 (English)In: Thermochimica Acta, ISSN 0040-6031, E-ISSN 1872-762X, Vol. 610, 37-46 p.Article in journal (Refereed) Published
Abstract [en]

Thermal performance of cylindrical heat pipe with nanofluid is studied based on the laws of thermodynamics. The objective of the present work is to investigate nanofluids effect on different sources of entropy generation in heat pipe caused by heat transfer between hot and cold reservoirs and also frictional losses and pressure drop in the liquid and vapor flow along heat pipe. An analytical study was performed to formulate all sources of entropy generation and the predicted results are compared with experimental ones. Cylindrical miniature grooved heat pipes of 250 mm length and 6.35 mm outer diameter were fabricated and tested with distilled water and water based TiO2 and Al2O3 nanofluids at different concentrations as working fluids. Analytical and experimental results revealed that the entropy generation in heat pipes decreases when nanofluids are used as working fluids instead of basefluid which results in improved thermal performance of the heat pipes with nanofluids.

Place, publisher, year, edition, pages
2015. Vol. 610, 37-46 p.
Keyword [en]
Heat pipe, Nanofluid, Thermodynamics, Entropy generation, Thermal resistance
National Category
Energy Engineering
Identifiers
URN: urn:nbn:se:kth:diva-169951DOI: 10.1016/j.tca.2015.04.028ISI: 000355707700006Scopus ID: 2-s2.0-84929461189OAI: oai:DiVA.org:kth-169951DiVA: diva2:826894
Note

QC 20150626

Available from: 2015-06-26 Created: 2015-06-25 Last updated: 2017-12-04Bibliographically approved
In thesis
1. Investigation of Thermal Performance of Cylindrical Heatpipes Operated with Nanofluids
Open this publication in new window or tab >>Investigation of Thermal Performance of Cylindrical Heatpipes Operated with Nanofluids
2017 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Nanofluids as an innovative class of heat transfer fluids created by dispersing nanometre-sizedmetallic or non-metallic particles in conventional heat transfer fluids displayed the potential toimprove the thermophysical properties of the heat transfer fluids. The main purpose of this study is toinvestigate the influence of the use of nanofluids on two-phase heat transfer, particularly on thethermal performance of the heat pipes. In the first stage, the properties of the nanofluids were studied,then, these nanofluids were used as the working fluids of the heat pipes. The thermal performance ofthe heat pipes when using different nanofluids was investigated under different operating conditionsexperimentally and analytically. The influences of the concentration of the nanofluids, inclinationangles and heat loads on the thermal performance and maximum heat flux of the heat pipes wereinvestigated.This study shows that the thermal performance of the heat pipes depends not only on thermophysicalproperties of the nanofluids but also on the characteristics of the wick structure through forming aporous coated layer on the heated surface. Forming the porous layer on the surface of the wick at theevaporator section increases the wettability and capillarity and also the heat transfer area at theevaporator of the heat pipes.The thermal performance of the heat pipes increases with increasing particle concentration in all cases,except for the heat pipe using 10 wt.% water/Al2O3 nanofluid. For the inclined heat pipe, irrespectiveof the type of the fluid used as the working fluid, the thermal resistance of the inclined heat pipes waslower than that of the heat pipes in a horizontal state, and the best performance was observed at theinclination angle of 60o, which is in agreement with the results reported in the literature. Otheradvantages of the use of nanofluids as the working fluids of the heat pipes which were investigated inthis study were the increase of the maximum heat flux and also the reduction of the entropy generationof the heat pipes when using a nanofluid.These findings revealed the potential for nanofluids to be used instead of conventional fluids as theworking fluid of the heat pipes, but the commercialization of the heat pipes using nanofluids for largescale industrial applications is still a challenging question, as there are many parameters related to thenanofluids which are not well understood.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2017. 103 p.
Series
TRITA-REFR, ISSN 1102-0245 ; 17/01
Keyword
Nanofluid, heat pipe, thermal resistance, heat transfer coefficient, evaporator, condenser, wick, porous layer, heat flux, inclination angle, thermal conductivity, viscosity
National Category
Engineering and Technology
Research subject
Energy Technology
Identifiers
urn:nbn:se:kth:diva-202566 (URN)978-91-7729-291-3 (ISBN)
Public defence
2017-03-17, F3, Lindstedtsvägen 26, Stockholm, 14:00 (English)
Opponent
Supervisors
Note

QC 20170228

Available from: 2017-02-28 Created: 2017-02-28 Last updated: 2017-03-01Bibliographically approved

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