scholarly journals Nanofluid properties for forced convection heat transfer :a review

2015 ◽  
Vol 3 (1) ◽  
pp. 145 ◽  
Author(s):  
Mohsen Darabi ◽  
Reza Naeimi ◽  
Hamid Mohammadiun ◽  
Saeed Mortazavi
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Base Fluid ◽  
Convection Heat Transfer ◽  
Theoretical Models ◽  
Transfer Coefficients ◽  
Practical Applications ◽  
Heat Transfer Coefficients ◽  
The Stability

<p>The thermal conductivity of nanofluids depends on various parameters, such as concentration, temperature, particle size, pH, shape, material, and possibly on the manufacturing process of the nanoparticles. Data on the viscosity of nanofluids, available in the literature, are very limited. Theoretical models for the determination of the thermal conductivity and viscosity of nanofluids have been pursued. Experiments with nanofluids indicate that they higher heat transfer coefficients than the base fluid. No significant increase in a pressure drop is reported with nanofluids, compared with values with the base fluid. However, the stability of nanofluids with regard to settlement/agglomeration, especially at higher concentrations, is still a problem for practical applications.</p>

Determination of Local Convection Heat Transfer Coefficients Inside a Circular Pipe Using Pulsed Laser

2015 ◽  
Author(s):  
S.-C. Lin ◽  
S. Tambe ◽  
M.-C. Lai ◽  
S.-M. Jeng
Keyword(s):  
Heat Transfer ◽  
Numerical Study ◽  
Convection Heat Transfer ◽  
Finite Size ◽  
Pulsed Laser ◽  
Experimental Results ◽  
Convection Heat ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients

The determination of local convection heat transfer coefficients of pipe flow using pulsed laser heating (PLH) from a combination of experimental and numerical study is presented in this paper. The method is advantageous because it is fluid-independent, contact-free and high in spatial and temporal resolution. For simplicity, the experiment used water at different temperatures and flow rates inside two long circular tubes which were subject to radiation heating using a finite size (20 mm in diameter) pulsed laser beam. An infrared camera was used to image and measure its surface temperatures. Two correlations for convection heat transfer coefficient in the thermal/combined entry length region were used in this paper for comparison with the experimental results. The experimental results using the thermal circuit method processed by MATLAB® agree well with both correlations. To gain better insight and quantify the uncertainty, a 3-D conjugated heat transfer simulation was carried out using Fluent CFD. The implication of the accuracy and limitation of the PLH method on the determination of local heat transfer coefficients are also discussed in the analysis.

Determination of the Thermal Constants of the Heat Flow Equations of Electrical Machines

1969 ◽  
Vol 184 (9) ◽  
pp. 84-92 ◽  
Author(s):  
T. J. Roberts
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Heat Flow ◽  
Sheet Steel ◽  
Electrical Machine ◽  
Transfer Coefficients ◽  
Flow Equations ◽  
Heat Transfer Coefficients ◽  
Thermal Constants

One of the major problems in obtaining accurate predictions of temperature distribution within an electrical machine is the values of the thermal constants used in the solution of the heat flow equations. A line source method is developed for anisotropic materials and is used to determine the thermal conductivity of sheet steel laminations. Results are given for three typical sheet steels showing the effect of varying core clamping pressure. The thermal conductivity of high-voltage insulation is obtained from tests on production machine coils and values are given for typical insulation systems. A model test is described for the evaluation of the heat transfer coefficients from the cooling surfaces of the radial air ducts, based on the assumption of a uniform distribution of air across the duct entrance. The heat transfer coefficients from the other cooled surfaces within the machine are determined from full-scale temperature measurements on production machines. The limitation of this latter method of determination of heat transfer coefficient is evaluated.

Paper 1: Natural Convection in the Supercritical Region

1967 ◽  
Vol 182 (9) ◽  
pp. 1-5 ◽  
Author(s):  
J. D. Parker ◽  
T. E. Mullin
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Natural Convection ◽  
Convection Heat Transfer ◽  
Heat Transfer Process ◽  
Transfer Coefficients ◽  
Rapid Variation ◽  
Variable Property ◽  
Heat Transfer Coefficients ◽  
Fundamental Equations

In the region just above the thermodynamic critical point, the thermodynamic properties vary rapidly with small changes in temperature. The rapid variation of the physical properties exerts a strong influence on the natural convection heat transfer process. Relatively large heat transfer coefficients are experienced in this region. Consideration of the fundamental equations involving conservation of mass momentum and energy has led to the establishment of a set of significant parameters to be considered in this problem. The derivation is essentially an extension of the work of Sparrow and Gregg (I) and is more adaptable to actual solution of the general variable property problem. The technique allows for variation in density, specific heat, viscosity, and thermal conductivity. An important step in the development is the use of thermodynamic relationships to obtain derivatives of properties with respect to temperature. A demonstration of the technique is made for Freon 114 using a Martin (2) equation of state along with Sutherland and Bromley equations for viscosity and thermal conductivity, corrected for pressure (3) (4). The use of a reference temperature in the variable property problem is critically discussed.

Preparation and Characterisation of Graphene Nanofluid: To Be Used As Coolant

2020 ◽  
Author(s):  
Senthil Kumar Velukkudi Santhanam ◽  
Dolly Austen Thomas ◽  
Mystica Augustine Michael Duke ◽  
Viswanathan Doraiswamy
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Base Fluid ◽  
Solid Phase ◽  
Nano Particles ◽  
Planar Geometry ◽  
Phase System ◽  
Transfer Coefficients ◽  
Two Phase ◽  
The Stability

Abstract In the recent years, nanofluids embarked as a new class of fluids with improved thermophysical properties such as thermal conductivity, thermal diffusivity, viscosity, and convective heat transfer coefficients thus promoting better heat transfer. Nanofluids consists of two-phase system where the nano sized solid phase (nanoparticles) is dispersed into a base fluid. Graphene is a material which has two-dimensional planar geometry with thermal conductivity of the order of 5000 W/mK. Nanoparticles in the form of thin flakes as small as 50 nm, 100 nm has been used in this study. Two step technique is the used method for preparing nanofluids. Inclusion of additives in small quantity, enhance the durability of the nano particles inside the conventional base fluids. The stability of the solid nano particles inside the conventional base fluid is increased by using surfactants. The heat transfer capacity and stability of the fluids are considered as the basic properties for investigation. The nanofluids characterization studies were drawn from the SEM, XRD and thermal conductivity results. Hot wire method was used to determine the thermal conductivity of the nanofluids. The preparation and properties of graphene based nanofluids which can be used as coolant are studied in this work.

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