Enhancing thermal conductivity of fluids with nano-particles
01 Jan 1995-Vol. 231, pp 99-105
About: The article was published on 1995-01-01 and is currently open access. It has received 7263 citations till now. The article focuses on the topics: Thermal conductivity & Nanoparticle.
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TL;DR: In this paper, the effects of Al2O3/water nanofluid on the hydrodynamics and convective heat transfer of a counter flow double-tube heat exchanger were investigated.
Abstract: Double-tube heat exchanger is primarily adapted to high-temperature, high-pressure applications due to their relatively small diameters. An experimental study performed to investigate the effects of Al2O3/water nanofluid on the hydrodynamics and convective heat transfer of a counter flow double-tube heat exchanger. The nanofluid was used as hot fluid and passed through the inner tube of the heat exchanger considering fully developed turbulent flow regime. Experiments were conducted at the nanofluid flow rates of 7, 9, and 11 L min−1, nanofluid inlet temperatures of 45, 55, and 65 °C, and dilute nanoparticle concentrations of 0.05 and 0.15 vol%. Local convective heat transfer coefficient in double-tube heat exchanger has been measured experimentally for the first time. Results showed that nanofluids had higher Nusselt number than pure water. Also, the Nusselt number increased by increasing particles volume fraction, flow rate as well as temperature of nanofluid. However, increasing the convective heat transfer coefficient of the nanofluids was not sensible with increasing the concentration. In addition, the ratio of the heat transfer coefficient of nanofluid to that of the base fluid decreased by increasing Reynolds number. Adding γ-Al2O3 nanoparticles to the base fluid increased the friction factor. In this study, the greatest enhancement in the heat transfer coefficient and the friction factor obtained at 0.15 vol% concentration of nanoparticles which were 23 and 25 %, respectively.
77 citations
Cites background from "Enhancing thermal conductivity of f..."
...This type of fluid was called nanofluid for the first time by Choi [1]....
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TL;DR: The results of the present model indicate that the nanofluid Nusselt number increases with increasing concentration of nanoparticles and decreasing diameter, and the enhancement of the fluid heat transfer becomes better at high Re in laminar flow with the addition of nanoparticle.
Abstract: In this article, laminar flow-forced convective heat transfer of Al2O3/water nanofluid in a triangular duct under constant wall temperature condition is investigated numerically In this investigation, the effects of parameters, such as nanoparticles diameter, concentration, and Reynolds number on the enhancement of nanofluids heat transfer is studied Besides, the comparison between nanofluid and pure fluid heat transfer is achieved in this article Sometimes, because of pressure drop limitations, the need for non-circular ducts arises in many heat transfer applications The low heat transfer rate of non-circular ducts is one the limitations of these systems, and utilization of nanofluid instead of pure fluid because of its potential to increase heat transfer of system can compensate this problem In this article, for considering the presence of nanoparticl: es, the dispersion model is used Numerical results represent an enhancement of heat transfer of fluid associated with changing to the suspension of nanometer-sized particles in the triangular duct The results of the present model indicate that the nanofluid Nusselt number increases with increasing concentration of nanoparticles and decreasing diameter Also, the enhancement of the fluid heat transfer becomes better at high Re in laminar flow with the addition of nanoparticles
77 citations
Cites background or methods from "Enhancing thermal conductivity of f..."
...Based on the studies carried out to evaluate the thermal conductivity of the nanofluids [5,6,42-45], the theoretical models cannot predict the thermal conductivity of nanofluids....
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...The thermophysical properties of nanofluid in the Equations 13-14 were calculated from nanoparticles and water properties using the following correlation at the mean bulk temperature [5,35,41]:...
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...Choi [5] was the first person to have created fluids containing suspension of nanometer-sized particles which are called the nanofluids and disclosed their significant thermal properties through the measurement of the convective heat transfer coefficient of those fluids....
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...the working fluid and hence the heat transfer capability [5-12]....
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TL;DR: It is found that the dispersion characteristics and thermal conductivity performance of copper-based nanofluids exhibited excellent dispersion in the presence of SDBS, which can be directly related to the particle/agglomerate size of the copper nanoparticles in water, as determined from dynamic light scattering.
Abstract: We present an analysis of the dispersion characteristics and thermal conductivity performance of copper-based nanofluids. The copper nanoparticles were prepared using a chemical reduction methodology in the presence of a stabilizing surfactant, oleic acid or cetyl trimethylammonium bromide (CTAB). Nanofluids were prepared using water as the base fluid with copper nanoparticle concentrations of 0.55 and 1.0 vol.%. A dispersing agent, sodium dodecylbenzene sulfonate (SDBS), and subsequent ultrasonication was used to ensure homogenous dispersion of the copper nanopowders in water. Particle size distribution of the copper nanoparticles in the base fluid was determined by dynamic light scattering. We found that the 0.55 vol.% Cu nanofluids exhibited excellent dispersion in the presence of SDBS. In addition, a dynamic thermal conductivity setup was developed and used to measure the thermal conductivity performance of the nanofluids. The 0.55 vol.% Cu nanofluids exhibited a thermal conductivity enhancement of approximately 22%. In the case of the nanofluids prepared from the powders synthesized in the presence of CTAB, the enhancement was approximately 48% over the base fluid for the 1.0 vol.% Cu nanofluids, which is higher than the enhancement values found in the literature. These results can be directly related to the particle/agglomerate size of the copper nanoparticles in water, as determined from dynamic light scattering.
77 citations
TL;DR: In this article, the magnetohydrodynamic (MHD) flow of Powell-Eyring nanomaterial bounded by a nonlinear stretching sheet is studied and the effects of different pertinent parameters on velocity, temperature and concentration fields are studied and analyzed.
Abstract: This communication addresses the magnetohydrodynamic (MHD) flow of Powell–Eyring nanomaterial bounded by a nonlinear stretching sheet. Novel features regarding thermophoresis and Brownian motion are taken into consideration. Powell–Eyring fluid is electrically conducted subject to non-uniform applied magnetic field. Assumptions of small magnetic Reynolds number and boundary layer approximation are employed in the mathematical development. Zero nanoparticles mass flux condition at the sheet is selected. Adequate transformation yield nonlinear ordinary differential systems. The developed nonlinear systems have been computed through the homotopic approach. Effects of different pertinent parameters on velocity, temperature and concentration fields are studied and analyzed. Further numerical data of skin friction and heat transfer rate is also tabulated and interpreted.
77 citations
TL;DR: In this paper, the authors investigated the effect of mixed convection flow and heat transfer of some nanofluids, in which the thermal conductivity and viscosity vary nonlinearly with the volume fraction.
Abstract: The significance of the local skin friction as well as the heat transfer rate on the motion of water
$$ \left( {{\text{H}}_{2} {\text{O}}} \right) $$
and ethylene glycol
$$ \left( {{\text{C}}_{2} {\text{H}}_{6} {\text{O}}_{2} } \right) $$
conveying metallic and metallic oxide nanoparticles (e.g., Al, Cu, Zn, Al203, CuO and ZnO) along a vertical thin needle is needed to improve the performance of chemical reactors, heat exchangers, pharmaceutical equipment and hybrid-powered engines. This led to the investigation of mixed convection flow and heat transfer of some nanofluids, in which the thermal conductivity and viscosity vary nonlinearly with the volume fraction. For simplifying the present investigation, appropriate variables were introduced successfully in the mathematical formulation to convert the governing nonlinear partial differential equations to coupled ordinary differential equations (ODEs). Moreover, the resulting ODEs were solved numerically via a robust differential quadrature algorithm. Furthermore, a comparative study with the existing literature is found to be in an excellent agreement. The enhancement of heat transfer in nanofluids is ascertained by increasing the convection ratio. Generally, the maximum improvement in the local skin friction was perceived for the flows of zinc–water-based nanofluids (
$$ {\text{Zn}} $$
–
$$ {\text{H}}_{2} {\text{O}} $$
) with the upsurge in the volume fraction of the nanoparticles
$$ {\text{Zn}} $$
. On the contrary, the highest enhancement in the heat transfer rate was revealed for the flows of copper–ethylene glycol-based nanofluids (
$$ {\text{Cu}} $$
–
$$ {\text{C}}_{2} {\text{H}}_{6} {\text{O}}_{2} $$
) with the increase in the weight percent of the
$$ {\text{Cu}} $$
nanomaterial loading.
77 citations