A critical review on convective heat transfer correlations of nanofluids

Sarkar, Jahar

doi:10.1016/j.rser.2011.04.025

Cited by 299 publications

(79 citation statements)

References 26 publications

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“…The PCM nanofluids reach higher Nu than water with an equal Re in both laminar and turbulent regimes, and the deviation increases with increasing concentration. Similar behavior has also been widely reported in literature for nanofluids, nanoemulsions and PCM fluids [5][6][7][8]12,19,[21][22][23][24]34]. However, this presentation method has been criticized in several recent publications, since it does not take the pumping power into account [21][22][23][24][25][26].…”

Section: Convective Heat Transfersupporting

confidence: 70%

“…However, the convection performance of such fluids containing nano-sized PCM particles has not been experimentally evaluated so far. The nanoscale might provide notable benefits over microscale, since suspensions containing solid nano-sized particles (nanofluids) or liquid droplets (nanoemulsions) have previously shown significantly enhanced convective heat transfer in several studies [6][7][8][9][10][11][12]19]. In addition, the smaller scale of particles may improve the stability of the fluids.…”

Section: Introductionmentioning

confidence: 99%

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Thermal properties and convective heat transfer of phase changing paraffin nanofluids

Mikkola

Puupponen

Saari

et al. 2017

International Journal of Thermal Sciences

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THERMAL PROPERTIES AND CONVECTIVE HEAT TRANSFER PERFORMANCE OF SOLID-LIQUID PHASE CHANGING PARAFFIN NANOFLUIDSWe aim to combine these two concepts for the first time by studying fluids containing nano-sized phase changing particles. In this study, the convective heat transfer performance and the thermal properties of solidliquid phase changing paraffin nanofluids are experimentally examined. Three water-based paraffin nanofluids with particle mass fractions of 5-10% are prepared and measured with an annular tube heat exchanger. The heat transfer measurements cover both laminar and turbulent regimes with Reynolds numbers varying in the range of 700-11000. The measurements also include pressure losses in order to study the suitability of the fluids for practical forced convection applications. In addition, the fluids are characterized: latent heats, specific heats, viscosities, thermal conductivities, densities and particle size distributions are all determined experimentally. In agreement with previous studies, the nanofluids are found to exhibit Nusselt numbers clearly higher than water when compared on the basis of equal Reynolds numbers. However, the differences in Prandtl numbers are shown to explain these deviations in Nusselt numbers. Indeed, the well-known Gnielinski correlation is able to explain the results quite adequately and thus, significant anomalies in the convection heat transfer caused by neither the melting of the phase change material nor the presence of the nanoparticles are observed. However, the nanofluids have systematically slightly higher Nusselt numbers than the correlation would predict, but the deviations are within the accuracy of the correlation (10%). When compared by using equal pumping powers, the nanofluids exhibit heat transfer performance poorer than that of water. The positive impact of the latent heat is outweighed by the negative effects of the increased viscosity and decreased specific heat.

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Section: Convective Heat Transfersupporting

confidence: 70%

Section: Introductionmentioning

confidence: 99%

Thermal properties and convective heat transfer of phase changing paraffin nanofluids

Mikkola

Puupponen

Saari

et al. 2017

International Journal of Thermal Sciences

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“…Nano-fluids: Nano-fluids are a colloidal mixture of base fluid containing nano-sized particles such as oxide ceramics, nitride ceramics, carbide ceramics, metals, semiconductors, carbon nanotubes and composite materials such as alloyed nanoparticles etc and have predominant characteristics because of nanoparticles' small size and high surface area [79]. Research studies on advanced high temperature heat transfer fluids by incorporation of metallic nanoparticles of copper, Al2O3, etc in concentrations of about ~5% by volume into conventional heat transfer fluids have been reported to be significantly improving the thermal transport properties of the HTFs [80,81]. Appreciable increase in thermal conductivity over the base fluids to the tune of about 20% at a 2 vol.% particle loading has been reported.…”

Section: High Temperature Collectorsmentioning

confidence: 99%

Recent Developments in Heat Transfer Fluids Used for Solar Thermal Energy Applications

Srivastva¹,

Malhotra²,

Sc³

2015

J Fundam Renewable Energy Appl

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Solar thermal collectors are emerging as a prime mode of harnessing the solar radiations for generation of alternate energy. Heat transfer fluids (HTFs) are employed for transferring and utilizing the solar heat collected via solar thermal energy collectors. Solar thermal collectors are commonly categorized into low temperature collectors, medium temperature collectors and high temperature collectors. Low temperature solar collectors use phase changing refrigerants and water as heat transfer fluids. Degrading water quality in certain geographic locations and high freezing point is hampering its suitability and hence use of water-glycol mixtures as well as water-based nano fluids are gaining momentum in low temperature solar collector applications. Hydrocarbons like propane, pentane and butane are also used as refrigerants in many cases. HTFs used in medium temperature solar collectors include water, waterglycol mixtures -the emerging "green glycol" i.e., trimethylene glycol and also a whole range of naturally occurring hydrocarbon oils in various compositions such as aromatic oils, naphthenic oils and paraffinic oils in their increasing order of operating temperatures. In some cases, semi-synthetic heat transfer oils have also been reported to be used. HTFs for high temperature solar collectors are a high priority area and extensive investigations and developments are occurring globally. In this category, wide range of molecules starting from water in direct steam generation, air, synthetic hydrocarbon oils, nanofluid compositions, molten salts, molten metals, dense suspension of solid silicon carbide particles etc., are being explored and employed. Among these, synthetic hydrocarbon oils are used as a fluid of choice in majority of high temperature solar collector applications while other HTFs are being used with varying degree of experimental maturity and commercial viability -for maximizing their benefits and minimizing their disadvantages. Present paper reviews the recent developments taking place in the area of heat transfer fluids for harnessing solar thermal energy. Refrigerants/phase changing materials: These are low boiling point but high heat capacity substances used in the solar collectors to transfer heat in applications like solar space cooling and heating, refrigerators, air conditioning, etc [7]. These materials absorb heat from the solar collectors, produce work either by expanding in a turbo-generator of a vapor compression cycle or by dissociating the refrigerant from its absorbent in a vapor absorption cycle [8]. In some of the relatively high temperature applications, higher boiling point refrigerants are used as indirect heat transfer fluids, wherein the heat collected from the solar collectors is transferred to another fluid like water from where the refrigerants pick-up heat to do the required work in the turbo-generators [9,10]. Recent Developments in Heat Transfer

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“…It has been observed that the convective heat transfer improved Sarkar et al (2011) Heat transfer characteristics of nanofluids in forced and free convection flows, for pressure drop prediction of the nanofluids conventional friction factor correlation of base fluid for both laminar and turbulent flows in minichannel as well as in microchannel is studied Huminic et al (2012) Effective thermal conductivity, viscosity, Nusselt number, and application of nanofluids in numerous types of heat exchangers Vajjha et al (2012) Due to variations of density, specific heat, thermal conductivity and viscosity, the effects on the performance of nanofluids are studied Yu et al (2012) The comparison criteria of the thermophysical property-related heat transfer performance of nanofluids and their base fluids, the predictions of the heat transfer coefficients of nanofluids based on homogeneous fluid models by using nanofluid effective thermophysical properties, the enhancements of the heat transfer coefficients of nanofluids over their base fluids. in the laminar flow regime by the using of Al 2 O 3 nanoparticles which is dispersed in water.…”

Section: Experimental Studies On Forced Convective Heat Transfer Of Nmentioning

confidence: 99%

A comprehensive review of experimental investigations of forced convective heat transfer characteristics for various nanofluids

Gupta

Arora

Kumar

et al. 2014

Int J Mech Mater Eng

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Nanofluids are suspension of nanoparticles (less than 100 nm) in the conventional base fluids. The dispersed solid metallic or non-metallic nanoparticles change the thermal properties like thermal conductivity, viscosity, specific heat, and density of the base fluid. Past studies focused on measuring the thermal properties of nanofluids. These suspended nanoparticles effectively improve the transport properties and heat transfer characteristics of the base fluids. Recently, heat transfer augmentation using suspensions of nanometre-sized solid particles in base liquids have been investigated by various research groups across the world. This paper reviews the state-of-the-art nanofluid studies in the area of forced convection heat transfer enhancement. The results for the heat transfer characteristics in internal flow with constant heat flux and constant wall temperature boundary conditions reported by various researchers have been compiled and reviewed. Further, in heat exchangers, the real boundary conditions are different from the constant heat flux and constant wall temperature boundary conditions. Over a span of 2 decades, the literature in this field is widespread; hence, this review would be useful for researchers to have a precise screening of a wide range of investigations in this area.

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A critical review on convective heat transfer correlations of nanofluids

Cited by 299 publications

References 26 publications

Thermal properties and convective heat transfer of phase changing paraffin nanofluids

Thermal properties and convective heat transfer of phase changing paraffin nanofluids

Recent Developments in Heat Transfer Fluids Used for Solar Thermal Energy Applications

A comprehensive review of experimental investigations of forced convective heat transfer characteristics for various nanofluids

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