Convective Heat Transfer of Nanofluids (DI Water-Al2O3) in Micro-Channels

2007 ◽  
Author(s):  
Joohyun Lee ◽  
Roger D. Flynn ◽  
Kenneth E. Goodson ◽  
John K. Eaton
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Stainless Steel ◽  
Convective Heat Transfer ◽  
Convective Heat ◽  
Volume Concentration ◽  
Tube Wall ◽  
Steel Tube ◽  
Stainless Steel Tube ◽  
Micro Channels

The convection performance of nanofluids in microchannels has received relatively little attention. This work reports convective heat transfer experiments of deionized water/Al2O3 nanofluids using 200μm hydraulic diameter MEMs fabricated microchannel structures and a stainless steel tube with 250μm inside diameter. The tube wall is heated electrically producing a constant heat flux boundary condition and an infrared camera is used to measure the outside tube wall temperature. A full numerical conjugate analysis of the apparatus is used to infer the fluid thermal conductivity from the temperature measurements. The effective thermal conductivity of nanofluids increased only by 4% for 4% volume concentration nanofluids in the MEMs fabricated microchannel and 5% for 3% volume concentration in the stainless steel tube under laminar flow conditions. The effective viscosity of the nanofluids increased 12% for 2% volume concentration. A dynamic light scattering system was used to measure the effective particle diameter and particle size distributions of nanoparticles with various pH values and surfactants. The measured mean diameter of Al2O3 nanoparticle is 170 nm, which is larger than the 40–50 nm nominal size.

Convective Heat Transfer With Nanofluids in a Single 1.02-mm Tube

2006 ◽  
Author(s):  
W. Y. Lai ◽  
B. Duculescu ◽  
P. E. Phelan ◽  
R. S. Prasher
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Convective Heat Transfer ◽  
Convective Heat ◽  
Steel Tube ◽  
Deionized Water ◽  
Stainless Steel Tube ◽  
Al2o3 Nanoparticles ◽  
Fluid Temperature ◽  
Colloidal Solutions

Nanofluids are heat transfer liquids which contain small volume fractions of suspended nanoparticles, with sizes smaller than 100 nm, in colloidal solutions. Numerous experiments on the static thermal conductivity of these fluids have revealed a greater-than-expected effective thermal conductivity, and thus there is interest in utilizing nanofluids for heat transfer applications. The nanofluid thermal performance under convective heat transfer conditions is of even greater interest. Therefore, we report here our initial convection experiments with nanofluids. Our experimental test section consists of a single millimeter-size, stainless steel tube subjected to constant wall heat flux. The cooling nanofluids, flowed through the test tube, consist of Al2O3 nanoparticles and deionized water. Both wall temperature and fluid temperature are measured. Compared with base fluid, the Nu of 20-nm Al2O3-deionized water nanofluids had 8% enhancement for φ = 1 vol% but only 3% for φ = 0.5 vol% at Re = 270. Based on the results, the utility of convective heat sinks containing nanofluids are evaluated for contemporary uses.

Production Process and Heat Transfer Performance of 10/316 Clad Tube

2014 ◽  
Vol 1081 ◽  
pp. 270-274
Author(s):  
Zui Xian Yu ◽  
Xue Sheng Wang ◽  
Qin Zhu Chen
Keyword(s):  
Heat Transfer ◽  
Stainless Steel ◽  
Heat Transfer Coefficient ◽  
Carbon Steel ◽  
Transfer Coefficient ◽  
Heat Transfer Performance ◽  
Steel Tube ◽  
Stainless Steel Tube ◽  
Transfer Performance ◽  
Clad Tube

A new preparation technique of carbon steel/stainless steel clad tube was introduced, and the contact surface was well combined. Meanwhile, with the using of tube heat exchanger, the experiment on the heat transfer performance of the clad tube was done. Comparing the 10/316 clad tube and the 316 stainless steel tube, the effects on the heat transfer performance of 316 stainless steel tube attached to carbon steel was evaluated. It is showed that overall heat transfer coefficient of 10/316 clad tubes is higher than that of stainless steel tube. The average heat transfer coefficient of 10/316 clad tubes is about 18.7%~34.4% higher than that of stainless steel tube. Experimental investigation indicates that, by brazing and cold drawing, the 10/316 clad tube was well combined and the thermal conductivity was better than that of stainless steel tube.

Experimental Convective Heat Transfer With Nanofluids

2008 ◽  
Author(s):  
S. Kabelac ◽  
K. B. Anoop
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Convective Heat Transfer ◽  
Convective Heat ◽  
Turbulent Regime ◽  
Heat Transfer Characteristics ◽  
Forced Convective Heat Transfer ◽  
Transfer Characteristics

Nanofluids are colloidal suspensions with nano-sized particles (<100nm) dispersed in a base fluid. From literature it is seen that these fluids exhibit better heat transfer characteristics. In our present work, thermal conductivity and the forced convective heat transfer coefficient of an alumina-water nanofluid is investigated. Thermal conductivity is measured by a steady state method using a Guarded Hot Plate apparatus customized for liquids. Forced convective heat transfer characteristics are evaluated with help of a test loop under constant heat flux condition. Controlled experiments under turbulent flow regime are carried out using two particle concentrations (0.5vol% and 1vol %). Experimental results show that, thermal conductivity of nanofluids increases with concentration, but the heat transfer coefficient in the turbulent regime does not exhibit any remarkable increase above measurement uncertainty.

Nucleate Boiling Heat Transfer of Binary Mixtures at Low to Moderate Heat Fluxes

1999 ◽  
Vol 121 (2) ◽  
pp. 365-375 ◽  
Author(s):  
R. J. Benjamin ◽  
A. R. Balakrishnan
Keyword(s):  
Heat Transfer ◽  
Stainless Steel ◽  
Binary Mixtures ◽  
Boiling Heat Transfer ◽  
Heating Surface ◽  
Nucleate Boiling ◽  
Steel Tube ◽  
Heat Fluxes ◽  
Stainless Steel Tube ◽  
Turbulent Natural Convection

A model for nucleate pool boiling heat transfer of binary mixtures has been proposed based on an additive mechanism. The contributing modes of heat transfer are (i) the heat transferred by microlayer evaporation, (ii) the heat transferred by transient conduction during the reformation of the thermal boundary layer, and (iii) the heat transferred by turbulent natural convection. The model takes into account the microroughness of the heating surface which has been defined quantitatively. The model compares satisfactorily with data obtained in the present study and in the literature. These data were obtained on a variety of heating surfaces such as a vertical platinum wire, a horizontal stainless steel tube and flat horizontal aluminium, and stainless steel surfaces (with various surface finishes) thereby demonstrating the validity of the model.

Investigations on Transient Natural Convection in Boron Nitride-Mineral Oil Nanofluid Systems

2012 ◽  
Author(s):  
Shijo Thomas ◽  
C. B. Sobhan ◽  
Jaime Taha-Tijerina ◽  
T. N. Narayanan ◽  
P. M. Ajayan
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Heat Transfer Coefficient ◽  
Natural Convection ◽  
Boron Nitride ◽  
Transfer Coefficient ◽  
Convective Heat Transfer ◽  
Convective Heat ◽  
Convective Heat Transfer Coefficient ◽  
Mineral Oil

Nanofluids are suspensions or colloids produced by dispersing nanoparticles in base fluids like water, oil or organic fluids, so as to improve their thermo-physical properties. Investigations reported in recent times have shown that the addition of nanoparticles significantly influence the thermophysical properties, such as the thermal conductivity, viscosity, specific heat and density of base fluids. The convective heat transfer coefficient also has shown anomalous variations, compared to those encountered in the base fluids. By careful selection of the parameters such as the concentration and the particle size, it has been possible to produce nanofluids with various properties engineered depending on the requirement. A mineral oil–boron nitride nanofluid system, where an increased thermal conductivity and a reduced electrical conductivity has been observed, is investigated in the present work to evaluate its heat transfer performance under natural convection. The modified mineral oil is produced by chemically dispersing boron nitride nanoparticles utilizing a one step method to obtain a stable suspension. The mineral oil based nanofluid is investigated under transient free convection heat transfer, by observing the temperature-time response of a lumped parameter system. The experimental study is used to estimate the time-dependent convective heat transfer coefficient. Comparisons are made with the base fluid, so that the enhancement in the heat transfer coefficient under natural convection situation can be estimated.

Numerical Study on the Surface Convective Heat Transfer of Mass Concrete Structure

2015 ◽  
Vol 723 ◽  
pp. 992-995
Author(s):  
Biao Li ◽  
Fu Guo Tong ◽  
Chang Liu ◽  
Nian Nian Xi
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Flow Velocity ◽  
Convective Heat Transfer ◽  
Convective Heat ◽  
Air Flow ◽  
Convective Heat Transfer Coefficient ◽  
Concrete Surface ◽  
Mass Concrete ◽  
Air Flow Velocity

The surface convective heat transfer of mass concrete is an important element of concrete structure temperature effect analysis. Based on coupled Thermal Fluid governing differential equation and finite element method, the paper calculated and analyzed the dependence of the concrete surface convective heat transfer on the air flow velocity and the concrete thermal conductivity coefficient. Results show that the surface convective heat transfer coefficient of concrete is a quadratic polynomial function of the air flow velocity, but influenced much less by the air flow velocity when temperature gradient is dominating in heat transfer. The concrete surface convective heat transfer coefficient increases linearly with the thermal conductivity of concrete increases.

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