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Engineering Nanofluids for Heat Transfer Applications
KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Functional Materials, FNM.
2014 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Nanofluids (NFs) are nanotechnology-based colloidal dispersion prepared by dispersing nanoparticles (NPs) in conventional liquids, as the base liquid. These advanced fluids have displayed potential to enhance the performance of conventional heat transfer fluids. This work aims at providing an insight to the field of NFs by investigating in detail the fabrication and evaluation of physico-chemical, thermo-physical and heat transfer characteristics of NFs for practical heat transfer applications. However, in order to utilize NFs as heat transfer fluids in real applications there are some challenges to overcome. Therefore, our goal is not only to optimize the thermo-physical properties of NFs with the highest thermal conductivity (TC) and minimal impact of NPs on viscosity, but also on preparing NFs with good stability and the best heat transfer performance. In the first stage, detailed studies were carried out to engineer NFs with good stability and optimal thermo-physical properties. In this work we investigated the most important factors, and the dependence of thermo-physical properties of NFs, including NP composition and concentration, NF stability, surface modifiers, particle size (NP size and particle with micron size), NF preparation method (two-step vs one-step method) and base liquid was studied. We also demonstrated, for the first time, the role of crystal structure, exemplified by alpha- and beta- SiC particles, on thermo-physical properties of NFs. For these purposes several NFs were fabricated using different nanostructured materials and various base liquids by one-step and two-step methods. An optimization procedure was designed to keep a suitable control in order to reach the ultimate aim where several stages were involved to check the desired characteristics of each NF system. Among several NFs systems studied in the first stage evaluation, a particular NF system with 9 wt% concentration, engineered by dispersing SiC NPs with alpha- crystal structure in water/ethylene glycol as based liquid exhibited the optimal thermo-physical properties. This NF was the only case which could pass the all criteria involved in the optimization procedure by exhibiting good stability, TC enhancements of ~20% with only 14% increase in viscosity at 20 oC. Therefore, this engineered NF was considered for next phase evaluation, where heat transfer coefficient (HTC) tests were designed and carried out to evaluate the thermal transport property of the selected alpha- SiC NF. A HTC enhancement of 5.5% at equal pumping power, as realistic comparison criteria, was obtained indicating the capability of this kind of NFs to be used in industrial heat transfer applications. These findings are among the few studies in the literature where the heat transfer characteristics of the NFs were noticeable, reproducible and based on a realistic situation with capability of commercializing as effective heat transfer fluid.  

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2014. , xiii, 65 p.
Series
TRITA-ICT/MAP AVH, ISSN 1653-7610 ; 2014:03
Keyword [en]
nanofluid, thermal conductivity, viscosity, heat transfer, heat transfer coefficient, HTC, SiC nanoparticles, Cu nanoparticles, mesoporous silica, CNT, microwave synthesis
National Category
Engineering and Technology
Research subject
Chemistry
Identifiers
URN: urn:nbn:se:kth:diva-144217ISBN: 978-91-7595-056-3 (print)OAI: oai:DiVA.org:kth-144217DiVA: diva2:712511
Public defence
2014-05-30, Sal D, KTH-Forum, Isafjordagatan 39, Kista, 10:30 (English)
Opponent
Supervisors
Projects
Nanohex
Note

QC 20140416

Available from: 2014-04-16 Created: 2014-04-15 Last updated: 2014-05-12Bibliographically approved
List of papers
1. Novel Nanofluids Based on Mesoporous Silica for Enhanced Heat Transfer
Open this publication in new window or tab >>Novel Nanofluids Based on Mesoporous Silica for Enhanced Heat Transfer
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2011 (English)In: Journal of nanoparticle research, ISSN 1388-0764, E-ISSN 1572-896X, Vol. 13, no 11, 6201-6206 p.Article in journal (Refereed) Published
Abstract [en]

Nanofluids, which are liquids with engineered nanometer-sized particles suspensions, have drawn remarkable attraction from the researchers because of their enormous potential to enhance the efficiency in heat-transfer fluids. In the present study, water-based calcined mesoporous silica nanofluids were prepared and characterized. The commercial mesoporous silica (MPSiO2) nanoparticles were dispersed in deionized water by means of pH adjustment and ultrasonic agitation. MPSiO2 nanoparticles were observed to have an average particle size of 350 ± 100 nm by SEM analysis. The concentration of MPSiO2 was varied between 1 and 6 wt%. The physicochemical properties of nanofluids were characterized using various techniques, such as particle size analyzer, zeta-potential meter, TEM, and FT-IR. The thermal conductivity was measured by Transient Plane Source (TPS) method, and nanofluids showed a higher thermal conductivity than the base liquid for all the tested concentrations.

Keyword
Mesoporous Silica, Nanofluid, Thermal conductivity, Viscosity
National Category
Nano Technology
Identifiers
urn:nbn:se:kth:diva-124206 (URN)10.1007/s11051-011-0404-1 (DOI)000297351600067 ()2-s2.0-84857059450 (Scopus ID)
Conference
International Conference on Nanostructured Materials, Rome, Italy, September 13-17, 2010
Note

QC 20140416

Available from: 2013-06-27 Created: 2013-06-27 Last updated: 2017-12-06Bibliographically approved
2. Shelf stability of nanofluids and its effect on thermal conductivity and viscosity
Open this publication in new window or tab >>Shelf stability of nanofluids and its effect on thermal conductivity and viscosity
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2013 (English)In: Measurement science and technology, ISSN 0957-0233, E-ISSN 1361-6501, Vol. 24, no 10, 105301- p.Article in journal (Refereed) Published
Abstract [en]

This study proposes a method and apparatus to estimate shelf stability of nanofluids. Nanofluids are fabricated by dispersion of solid nanoparticles in base fluids, and shelf stability is a key issue for many practical applications of these fluids. In this study, shelf stability is evaluated by measuring the weight of settled solid particles on a suspended tray in a colloid versus time and correlated with the performance change of some nanofluid systems. The effects of solid particle concentration and bath sonication time were investigated for selected nanofluids. The results show the applicability of this simple method and the apparatus to evaluate nanofluid shelf stability. Furthermore, it shows that Stokes' law is not valid for determining the settling time of the tested nanoparticles probably due to their complicated shape and presence of surface modifiers. The effect of shelf stability on thermal conductivity and viscosity was illustrated for some nanofluids. Experimental results show that water-based Al2O3 nanofluids have quite good shelf stability and can be good candidates for industrial applications.

Keyword
Al 2O3, balance, CeO2, china clay, Nanofluid, sedimentation, shelf stability, sonication
National Category
Engineering and Technology
Identifiers
urn:nbn:se:kth:diva-133188 (URN)10.1088/0957-0233/24/10/105301 (DOI)000324621900032 ()2-s2.0-84884851197 (Scopus ID)
Note

QC 20131028

Available from: 2013-10-28 Created: 2013-10-28 Last updated: 2017-12-06Bibliographically approved
3. Design and Evaluation of Carbon Nanotube Based Nanofluids for Heat Transfer Applications
Open this publication in new window or tab >>Design and Evaluation of Carbon Nanotube Based Nanofluids for Heat Transfer Applications
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2013 (English)In: MRS Spring 2013 Proceedings: Symposium on Nanoscale Heat Transport—From Fundamentals to Devices, Materials Research Society, 2013Conference paper, Published paper (Refereed)
Abstract [en]

The present work investigates the fabrication, thermal conductivity (TC) and rheological properties of water based carbon nanotubes (CNTs) nanofluids (NFs) prepared using a two-step method. As-received (AR) CNTs heated and the effect of heat treatment was studied using X-ray diffraction and thermogravimetric analysis. The AR-CNTs and heat-treated CNTs (HT-CNTs) were dispersed with varying concentration of surface modifiers Gum Arabic (GA) and TritonX-100 (TX) respectively. It was found that heat treatment of CNTs effectively improved the TC and influenced rheological properties of NFs. Scanning electron microscopy analysis revealed TX modified NFs showed better dispersion ability compared to GA. Surface modification of the CNTs was confirmed by Fourier Transformation Infrared (FTIR) analysis. Zeta potential measurement showed the stability region for GA modified NFs in the pH range of 5-11, whereas pH was between 9.5-10 for TX NFs. The concentration of surface modifier plays an extensive role on both TC and rheological behavior of NFs. A maximum TC enhancement of 10% with increases in viscosity around 2% for TX based HT-CNTs NFs was measured. Finally comparison of experimental TC results with the predicted values obtained from a model demonstrated inadequacy of the predictive model for CNT NFs system.

Place, publisher, year, edition, pages
Materials Research Society, 2013
Series
MRS Proceedings, 1543
National Category
Other Natural Sciences
Identifiers
urn:nbn:se:kth:diva-123989 (URN)10.1557/opl.2013.676 (DOI)2-s2.0-84893397176 (Scopus ID)
Conference
MRS-2013 Spring Conference, April 1-5, 2013 San Francisco, California
Projects
NANOHEX
Note

QC 20140225

Available from: 2013-06-24 Created: 2013-06-24 Last updated: 2017-03-01Bibliographically approved
4. Thermal and rheological properties of micro- and nanofluids of copper in diethylene glycol: as heat exchange liquid
Open this publication in new window or tab >>Thermal and rheological properties of micro- and nanofluids of copper in diethylene glycol: as heat exchange liquid
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2013 (English)In: Nanoscale Thermoelectric Materials: Thermal and Electrical Transport, and Applications to Solid-state Cooling and Power Generation, Cambridge: Cambridge Scholars Publishing, 2013, , 6 p.165-170 p.Conference paper, Published paper (Refereed)
Abstract [en]

This study reports on the fabrication of nanofluids/microfluids (NFs/MFs) with experimental and theoretical investigation of thermal conductivity (TC) and viscosity of diethylene glycol (DEO) base NFs/MFs containing copper nanoparticles (Cu NPs) and copper microparticles (Cu MPs). For this purpose, Cu NPs (20-40 nm) and Cu MPs (0.5-1.5 urn) were dispersed in DEG with particle loading between 1 wt% and 3 wt%. Ultrasonic agitation was used for dispersion and preparation of stable NFs/MFs, and thus the use of surfactants was avoided. The objectives were investigation of impact of size of Cu particle and concentration on TC and viscosity of NFs/MFs on DEG as the model base liquid. The physicochemical properties of all particles and fluids were characterized by using various techniques including Transmission Electron Microscopy (TEM), Scanning Electron Microscopy (SEM) and Dynamic Light Scattering (DLS) techniques. Fourier Transform Infrared Spectroscopy (FTIR) analysis was performed to study particles' surfaces. NFs and MFs exhibited a higher TC than the base liquid, while NFs outperformed MFs showing a potential for their use in heat exchange applications. The TC and viscosity of NFs and MFs were presented, along with a comparison with values from predictive models. While Maxwell model was good at predicting the TC of MFs, it underestimated the TC of NFs, revealing that the model is not directly applicable to the NF systems.

Place, publisher, year, edition, pages
Cambridge: Cambridge Scholars Publishing, 2013. 6 p.
Series
Materials Research Society Symposium Proceedings, ISSN 0272-9172 ; 1543
Keyword
Copper, Nanofluid, diethylene glycol, Thermal conductivity, Viscosity
National Category
Nano Technology
Research subject
SRA - Energy
Identifiers
urn:nbn:se:kth:diva-124180 (URN)10.1557/opl.2013.675 (DOI)2-s2.0-84893372647 (Scopus ID)9781605115207 (ISBN)
Conference
2013 MRS Spring Meeting; San Francisco, CA; United States; 1 April 2013 through 5 April 2013
Projects
NanoHex
Funder
EU, FP7, Seventh Framework Programme
Note

QC 20140225

Available from: 2013-06-27 Created: 2013-06-27 Last updated: 2017-03-02Bibliographically approved
5. Experimental investigation on thermo-physical properties of copper/diethylene glycol nanofluids fabricated via microwave-assisted route
Open this publication in new window or tab >>Experimental investigation on thermo-physical properties of copper/diethylene glycol nanofluids fabricated via microwave-assisted route
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2014 (English)In: Applied Thermal Engineering, ISSN 1359-4311, E-ISSN 1873-5606, Vol. 65, no 1-2, 158-165 p.Article in journal (Refereed) Published
Abstract [en]

This study investigates the fabrication, thermal conductivity and rheological characteristics evaluation of nanofluids consisting of copper nanoparticles in diethylene glycol base liquid. The fabricated Cu nanofluids displayed enhanced thermal conductivity over the base liquid. Copper nanoparticles were directly formed in diethylene glycol using microwave-assisted heating, which provides uniform heating of reagents and solvent, accelerating the nucleation of metal clusters, resulting in monodispersed nanostructures. Copper nanoparticles displayed an average primary particle size of 75 ± 25 nm from SEM micrographs, yet aggregated to form large spherical particles of about 300 nm. The physicochemical properties including thermal conductivity and viscosity of nanofluids were measured for the nanofluids with nanoparticle concentration between 0.4 wt% and 1.6 in the temperature range of 20-50 C. Proper theoretical correlations/models were applied to compare the experimental results with the estimated values for thermal conductivity and viscosity of nanofluids. For all cases, thermal conductivity enhancement was higher than the increase in viscosity showing the potential of nanofluids to be utilized as coolant in heat transfer applications. A thermal conductivity enhancement of ∼7.2% was obtained for nanofluids with 1.6 wt% nanoparticles while maximum increase in viscosity of ∼5.2% was observed for the same nanofluid.

Keyword
Copper nanoparticles, Microwave synthesis, Nanofluids, Thermal conductivity, Viscosity
National Category
Engineering and Technology
Identifiers
urn:nbn:se:kth:diva-142326 (URN)10.1016/j.applthermaleng.2014.01.003 (DOI)000335099100017 ()2-s2.0-84893161468 (Scopus ID)
Funder
EU, FP7, Seventh Framework Programme, 228882
Note

QC 20140305

Available from: 2014-03-05 Created: 2014-02-28 Last updated: 2017-12-05Bibliographically approved
6. Fabrication, Characterization and Thermo-physical Property Evaluation of SiCNanofluids for Heat Transfer Applications
Open this publication in new window or tab >>Fabrication, Characterization and Thermo-physical Property Evaluation of SiCNanofluids for Heat Transfer Applications
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2014 (English)In: Nano-Micro Letters, ISSN 2150-5551, Vol. 6, no 2, 178-189 p.Article in journal (Refereed) Published
Abstract [en]

Nanofluids (NFs) are nanotechnology-based colloidal suspensions fabricated by suspending nanoparticles (NPs) in a base liquid. These fluids have shown potential to improve the heat transfer properties of conventional heat transfer fluids. In this study we report in detail on the fabrication, characterization and thermo-physical property evaluation of SiC NFs, prepared using SiC NPs with different crystal structure, for heat transfer applications.  For this purpose, a series of SiC NFs containing SiC NPs with different crystal structure (α-SiC and β-SiC) were fabricated in a water (W)/ethylene glycol (EG) mixture (50/50 wt % ratio). Physicochemical properties of NPs/NFs were characterized by using various techniques such as powder X-Ray Diffraction (XRD), Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), Fourier Transform Infrared Spectroscopy (FTIR), Dynamic Light Scattering (DLS) and Zeta Potential Analysis were performed. Thermo-physical properties including thermal conductivity (TC) and viscosity for NFs containing SiC particles (α- and β- phase) were measured. The results showed among all suspensions, NF fabricated with α-SiC particles have more favorable thermo-physical properties compared to the NFs fabricated with β-SiC; the observed difference was attributed to combination of several factors, including crystal structure (β- vs. α-), sample purity, and residual chemicals exhibited on SiC nanoparticles. A TC enhancement of ~20% while 14% increased viscosity were obtained for a NF containing 9wt% of particular type of α-SiC NPs indicating promising capability of these kind of NFs for further heat transfer characteristics investigations. 

Keyword
SiC nanoparticles, Nanofluids, Thermal conductivity, Viscosity, Thermo-physical property
National Category
Engineering and Technology
Research subject
SRA - Energy
Identifiers
urn:nbn:se:kth:diva-144271 (URN)10.5101/nml.v6i2.p178-189 (DOI)000337033300010 ()2-s2.0-84958743111 (Scopus ID)
Funder
Swedish Research Council
Note

QC 20140416

Available from: 2014-04-15 Created: 2014-04-15 Last updated: 2017-03-01Bibliographically approved
7. Experimental study on preparation and base liquid effect on thermo-physical and heat transport characteristics of α-SiC nanofluids
Open this publication in new window or tab >>Experimental study on preparation and base liquid effect on thermo-physical and heat transport characteristics of α-SiC nanofluids
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2014 (English)In: International Communications in Heat and Mass Transfer, ISSN 0735-1933, E-ISSN 1879-0178, Vol. 55, 38-44 p.Article in journal (Refereed) Published
Abstract [en]

Nanostructured solid particles dispersed in a base liquid are a new class of nano-engineeredcolloidal solutions, defined with a coined name of nanofluids (NFs). These fluids have shownpotential to enhance heat transfer characteristics of conventional base liquids utilized in heattransfer application. We recently reported on the fabrication and thermo-physical propertyevaluation of SiC NFs systems, containing SiC particles with different crystal structure. In thisstudy, our aim is to investigate the heat transfer characteristics of a particular α-SiC NF withrespect to the effect of α-SiC particle concentration and different base liquids on the thermophysicalproperties of NFs. For this purpose, a series of NFs with various α-SiC NPsconcentration of 3, 6 and 9wt% were prepared in different base liquids of distilled water (DW)and distilled water/ethylene glycol mixture (DW/EG). Their thermal conductivity (TC) andviscosity were evaluated at 20 oC. NF with DW/EG base liquid and 9wt% SiC NPs loadingexhibited the best combination of thermo-physical properties, which was therefore selected forheat transfer coefficient (HTC) evaluation. Finally, HTC tests were performed and compared indifferent criteria, including equal Reynolds number, equal mass flow rate and equal pumpingpower for a laminar flow regime. The results showed HTC enhancement of NF over the baseliquid for all evaluation criteria; 13% at equal Reynolds number, 8.5% at equal volume flow and5.5% at equal pumping power. Our findings are among the few studies in the literature where theheat transfer enhancement for the NFs over its base liquid is noticeable and based on a realistic situation.

Keyword
Nanofluids, SiC nanoparticles, Thermal conductivity, Viscosity, Heat transfer coefficient, Pumping power
National Category
Engineering and Technology
Identifiers
urn:nbn:se:kth:diva-144273 (URN)10.1016/j.icheatmasstransfer.2014.04.011 (DOI)000337986600006 ()2-s2.0-84900313987 (Scopus ID)
Funder
Swedish Research Council, 2013-5647EU, European Research Council, 228882
Note

QC 20140805

Available from: 2014-04-15 Created: 2014-04-15 Last updated: 2017-12-05Bibliographically approved

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