Forced Convection Heat Transfer of Nanofluids: A Review

2017 ◽  
Author(s):  
Aditya Kuchibhotla ◽  
Debjyoti Banerjee
Keyword(s):  
Heat Transfer ◽  
Experimental Data ◽  
Thermal Conductivity ◽  
Heat Capacity ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Specific Heat ◽  
Forced Convection ◽  
Convection Heat Transfer ◽  
Convection Heat

Stable homogeneous colloidal suspensions of nanoparticles in a liquid solvents are termed as nanofluids. In this review the results for the forced convection heat transfer of nanofluids are gleaned from the literature reports. This study attempts to evaluate the experimental data in the literature for the efficacy of employing nanofluids as heat transfer fluids (HTF) and for Thermal Energy Storage (TES). The efficacy of nanofluids for improving the performance of compact heat exchangers were also explored. In addition to thermal conductivity and specific heat capacity the rheological behavior of nanofluids also play a significant role for various applications. The material properties of nanofluids are highly sensitive to small variations in synthesis protocols. Hence the scope of this review encompassed various sub-topics including: synthesis protocols for nanofluids, materials characterization, thermo-physical properties (thermal conductivity, viscosity, specific heat capacity), pressure drop and heat transfer coefficients under forced convection conditions. The measured values of heat transfer coefficient of the nanofluids varies with testing configuration i.e. flow regime, boundary condition and geometry. Furthermore, a review of the reported results on the effects of particle concentration, size, temperature is presented in this study. A brief discussion on the pros and cons of various models in the literature is also performed — especially pertaining to the reports on the anomalous enhancement in heat transfer coefficient of nanofluids. Furthermore, the experimental data in the literature indicate that the enhancement observed in heat transfer coefficient is incongruous compared to the level of thermal conductivity enhancement obtained in these studies. Plausible explanations for this incongruous behavior is explored in this review. A brief discussion on the applicability of conventional single phase convection correlations based on Newtonian rheological models for predicting the heat transfer characteristics of the nanofluids is also explored in this review (especially considering that nanofluids often display non-Newtonian rheology). Validity of various correlations reported in the literature that were developed from experiments, is also explored in this review. These comparisons were performed as a function of various parameters, such as, for the same mass flow rate, Reynolds number, mass averaged velocity and pumping power.

Convective Heat Transfer Enhancement With Nanofluids: The Effect of Temperature-Variable Thermal Conductivity

2010 ◽  
Author(s):  
Sezer O¨zerinc¸ ◽  
Almıla G. Yazıcıog˘lu ◽  
Sadık Kakac¸
Keyword(s):  
Heat Transfer ◽  
Experimental Data ◽  
Thermal Conductivity ◽  
Heat Transfer Enhancement ◽  
Forced Convection ◽  
Convection Heat Transfer ◽  
Thermal Dispersion ◽  
Convection Heat ◽  
Transfer Enhancement ◽  
Experimental Values

A nanofluid is defined as the suspension of nanoparticles in a base liquid. Studies in the last decade have shown that significant amount of thermal conductivity and heat transfer enhancement can be obtained by using nanofluids. In the first part of this study, classical forced convection heat transfer correlations developed for pure fluids are used to predict the experimental values of heat transfer enhancement of nanofluids. It is seen that the experimental values of heat transfer enhancement exceed the enhancement predictions of the classical correlations. On the other hand, a recent correlation based on the thermal dispersion phenomenon created by the random motion of nanoparticles predicts the experimental data well. In the second part of the study, in order to further examine the validity of the thermal dispersion approach, a numerical analysis of forced convection heat transfer of Al2O3/water nanofluid inside a circular tube in the laminar flow regime is performed by utilizing single phase assumption. A thermal dispersion model is applied to the problem and variation of thermal conductivity with temperature and variation of thermal dispersion with local axial velocity are taken into account. The agreement of the numerical results with experimental data might be considered as an indication of the validity of the approach.

Forced Convection Heat Transfer for Helium Gas Under Exponentially Decreasing Flow Condition

2017 ◽  
Author(s):  
Qiusheng Liu ◽  
Li Wang ◽  
Makoto Shibahara ◽  
Katsuya Fukuda
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Forced Convection ◽  
Flow Rate ◽  
Convection Heat Transfer ◽  
Convection Heat ◽  
Rate Condition ◽  
Initial Flow ◽  
Helium Gas

Knowledge of the heat transfer phenomenon during flow decay transient condition is important for the safety assessment of very high temperature reactor (VHTR) during the loss of coolant accident. In this study, transient heat transfer from a horizontal cylinder to helium gas under exponentially decreasing flow rate condition was experimentally studied. The experiment was performed by using a forced convection heat transfer test loop. A flow control value with its control system was used to realize the flow decay condition. Helium gas was used as coolant and platinum cylinder with 1 mm in diameter was used as the test heater. A uniform heat generation rate was added to the cylinder by a power source. The cylinder temperature was maintained at an initial value under a definite initial flow rate of the helium gas. Then, the mass flow rate of the helium gas starts to decrease exponentially with different time constants ranged from 4.3 s to 15.4 s. The initial flow velocity ranged from 10 m/s to 4 m/s. The surface temperature, heat flux, and heat transfer coefficient were measured during the flow decay transient process under wide experimental conditions such as initial flow rate, flow decay time constant. It was found that the temperature of the test heater shows rapid increase during this process, the increasing rate of the temperature is higher for a shorter time constant. The heat transfer coefficient versus time during the flow rate decreasing process was also obtained. The transient heat transfer process during exponentially decreasing flow rate condition was clarified based on the experimental data.

Estimation of transient wall and flow temperature distributions in a circular duct using an inverse approach

2007 ◽  
Vol 221 (11) ◽  
pp. 1353-1361
Author(s):  
S D Masouros ◽  
K Mathioudakis
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Forced Convection ◽  
Convection Heat Transfer ◽  
Convection Heat ◽  
Convection Heat Transfer Coefficient ◽  
Circular Duct ◽  
Inverse Approach ◽  
Forced Convection Heat Transfer

Inverse methods have become a useful tool for estimating parameters that cannot be measured or calculated directly in engineering applications. Parameters characterizing unsteady heat convection in circular duct flows are associated with numerous uncertainties. This fact renders the inverse approach appropriate for the determination of these parameters. An inverse problem for transient turbulent thermally developing and thermally developed forced-convection flow in a circular duct is formulated and discussed, and a simplified direct thermal model is presented. Parameters of the model are estimated by solving a minimization problem, using temperature data from the wall surface and/or the flow. A multivariable optimization algorithm is employed for this purpose. Furthermore, a model for the forced-convection heat-transfer coefficient is proposed and its effect on the results is discussed. The validity of the proposed method is assessed using data from two different circular duct flows. The method is shown to provide a good prediction capability in computationally demanding transient heat-data sequences of different duct flows, both in terms of duct and of flow characteristics. Results show that a hyperbolic axial distribution of the forced-convection heat-transfer coefficient in the developing region of the flow is essential for good adaptation of the method to the test data.

Forced Convection Heat Transfer of a Phase Change Material (PCM) Nanoemulsion

2013 ◽  
Author(s):  
Ryan Anderson ◽  
Masahiro Kawaji ◽  
Kenichi Togashi ◽  
Ravi Ramnanan-Singh
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Phase Change ◽  
Transfer Coefficient ◽  
Forced Convection ◽  
Latent Heat ◽  
Thermal Energy ◽  
Heat Storage ◽  
Convection Heat Transfer ◽  
Convection Heat

Phase Change Materials (PCM) are suitable for use in Thermal Energy Storage (TES) systems as they can store and release both sensible heat and latent heat during phase change. This investigation examines the thermophysical properties and heat transfer properties of a beeswax nanoemulsion during forced convection in a circular tube. First, the beeswax nanoemulsion was synthesized using surfactants and water, which possesses a relatively low viscosity to enhance pumpability, as well as a high beeswax percentage by mass for greater latent heat storage capacity. The test section was a circular stainless steel tube, 11.3 mm in diameter and heated uniformly using an Ohmic heating method. To determine the heat transfer coefficient, the inlet and exit nanoemulsion temperatures and tube wall temperatures were measured at several axial locations. The forced convection heat transfer coefficient results were first compared to water in order to verify the setup accuracy as well as the degree of success of the PCM in heat storage ability. The experimental results indicate suitable heat transfer coefficients for a stable beeswax nanoemulsion, making it a potential candidate for charging and discharging thermal energy in thermal storage applications.

One-Dimensional Numerical Investigation of a Cylindrical Micro Combustor

2009 ◽  
Author(s):  
A. Irani R. ◽  
M. Saediamiri ◽  
M. S. Saidi ◽  
M. H. Saidi ◽  
M. B. Shafii
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Convection Heat Transfer ◽  
Diffusion Reaction ◽  
Convection Heat ◽  
Convection Heat Transfer Coefficient ◽  
One Dimensional ◽  
Micro Combustor

In this paper, a one-dimensional numerical approach is used to study the effect of various parameters such as micro combustor diameter, mass flow rate and external convection heat transfer coefficient on the temperature and species mass fraction profiles. A premixed mixture of H2-Air with a multi-step chemistry (9 species and 19 reactions) is used and thermal conductivity of the mixture is considered as a function of species thermal conductivity and temperature by using a set of new relations. The transient gas phase energy and species conservation equations result in an Advection-Diffusion-Reaction system (A-D-R) that leads to two stiff systems of PDEs, which can not be solved by conventional Computational Fluid Dynamics (CFD) methods. In the present work, Strang splitting method, which is suitable for nonlinear stiff system of PDEs, is used. The results show that both convection heat transfer coefficient and micro combustor diameter have a significant effect on the combustion and heat transfer rates in the micro scales. Also, increasing the convective heat transfer coefficient and decreasing the diameter and inlet mixture velocity, decreases the temperature and active radicals along the micro combustor.

scholarly journals Forced Convection Nanofluid Heat Transfer as a Function of Distance in Microchannels

Materials ◽  
2021 ◽  
Vol 14 (11) ◽  
pp. 3021
Author(s):  
Saeid Vafaei ◽  
Jonathan A. Yeager ◽  
Peter Daluga ◽  
Branden Scherer
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Forced Convection ◽  
Convection Heat Transfer ◽  
Crystal Phase ◽  
Convection Heat ◽  
Effective Parameters ◽  
Forced Convection Heat Transfer ◽  
Base Liquid

As electronic devices become smaller and more powerful, the demand for micro-scale thermal management becomes necessary in achieving a more compact design. One way to do that is enhancing the forced convection heat transfer by adding nanoparticles into the base liquid. In this study, the nanofluid forced convection heat transfer coefficient was measured inside stainless-steel microchannels (ID = 210 μm) and heat transfer coefficient as a function of distance was measured to explore the effects of base liquid, crystal phase, nanoparticle material, and size on heat transfer coefficient. It was found that crystal phase, characteristics of nanoparticles, the thermal conductivity and viscosity of nanofluid can play a significant role on heat transfer coefficient. In addition, the effects of man-made and commercial TiO2 on heat transfer coefficient were investigated and it was found that man-made anatase TiO2 nanoparticles were more effective to enhance the heat transfer coefficient, for given conditions. This study also conducted a brief literature review on nanofluid forced convection heat transfer to investigate how nanofluid heat transfer coefficient as a function of distance would be affected by effective parameters such as base liquid, flow regime, concentration, and the characteristics of nanoparticles (material and size).

scholarly journals Determination of Heat Transfer Coefficient for the Air Forced Cooling Over a Flat Side of Coil

2019 ◽  
Vol 15 (1) ◽  
pp. 15-20 ◽  
Author(s):  
Payam Shams Ghahfarokhi ◽  
Ants Kallaste ◽  
Anouar Belahcen ◽  
Toomas Vaimann
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Forced Convection ◽  
Convection Heat Transfer ◽  
Convection Heat ◽  
Forced Convection Heat Transfer ◽  
Analytical Results ◽  
Flat Side

AbstractThe paper deals with the analytical and experimental determination of the forced convection heat transfer coefficients over the flat coil module. In the analytical part, the forced convection coefficients at different wind speeds are calculated based on various known equations of the forced convection heat transfer coefficient with unheated starting length. The experimental part presents the description of the test: loading the coil with DC current and measurements of the coil temperatures with thermal sensors while it was inside a wind tunnel. Based on the measurement, the convection coefficients were determined. In the final part, the experimental and analytical results are compared. It is found that the accuracy of the analytical results is more precise in highly turbulent flows.

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