HEAT TRANSFER ENHANCEMENT IN LAMINAR FORCED CONVECTION: NANOFLUIDS, MICROCHANNELS, STRUCTURED SURFACES

2009 ◽  
Author(s):  
Renato M. Cotta ◽  
Carlos A. A. Mota ◽  
Carolina P. Naveira-Cotta ◽  
Helcio R. B. Orlande ◽  
Jeziel S. Nunes ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Enhancement ◽  
Forced Convection ◽  
Transfer Enhancement ◽  
Structured Surfaces ◽  
Laminar Forced Convection

Effects of Particle Shape on Nanofluids Laminar Forced Convection in Helically Coiled Tubes

2017 ◽  
Author(s):  
Fang Liu ◽  
Yang Cai
Keyword(s):  
Heat Transfer ◽  
Pressure Drop ◽  
Heat Transfer Enhancement ◽  
Forced Convection ◽  
Particle Shape ◽  
Spherical Nanoparticles ◽  
Transfer Enhancement ◽  
Two Phase ◽  
Laminar Forced Convection ◽  
Shape And Size

In this study, effects of particle morphology (shape and size) on nanofluids laminar forced convection in helically coiled tubes are investigated numerically using Eulerian-Lagrangian two-phase approach. The laminar forced convective heat transfer and pressure drop of Al2O3-water nanofluids containing nanoparticles with various particle shapes (sphere, platelet, blade, cylinder and brick) and sizes at different volume fractions in the developing and fully developed regions are investigated using the validated two-phase model. It is found that the nanofluids containing platelet particle shape has the highest heat transfer enhancement, which is followed by nanofluids containing cylinder, blade, sphere and brick nanoparticle shapes, respectively. Non-spherical nanoparticles with larger aspect ratio, small particle size and a suitable particle volume concentration are beneficial for heat transfer enhancement of forced convection. Heat transfer efficiency reaches minima at Re of 1250 for laminar forced convection with 1% volume fraction. The correlations of Nusselt number and pressure drop with nanoparticle shape and size were developed to predict convective heat transfer of nanofluids containing spherical nanoparticles and non-spherical nanoparticles.

A Numerical Study of the Thermal Performance of Two Stationary Insert Designs in Internal Compressible Flows

2009 ◽  
Author(s):  
Emad Y. Tanbour ◽  
Ramin K. Rahmani
Keyword(s):  
Heat Transfer ◽  
Pressure Drop ◽  
Heat Transfer Enhancement ◽  
Forced Convection ◽  
Thermal Performance ◽  
Compressible Flows ◽  
Convection Heat Transfer ◽  
Convection Heat ◽  
Transfer Enhancement ◽  
Stationary Heat Transfer

Enhancement of the natural and forced convection heat transfer has been the subject of numerous academic and industrial studies. Air blenders, mechanical agitators, and static mixers have been developed to increase the forced convection heat transfer rate in compressible and incompressible flows. Stationary inserts can be efficiently employed as heat transfer enhancement devices in the natural convection systems. Generally, a stationary heat transfer enhancement insert consists of a number of equal motionless segments, placed inside of a pipe in order to control flowing fluid streams. These devices have low maintenance and operating costs, low space requirements and no moving parts. A range of designs exists for a wide range of specific applications. The shape of the elements determines the character of the fluid motion and thus determines thermal effectiveness of the insert. There are several key parameters that may be considered in the design procedure of a heat transfer enhancement insert, which lead to significant differences in the performance of various designs. An ideal insert, for natural conventional heat transfer in compressible flow applications, provides a higher rate of heat transfer and a thermally homogenous fluid with minimized pressure drop and required space. To choose an insert for a given application or in order to design a new insert, besides experimentation, it is possible to use Computational Fluid Dynamics to study the insert performance. This paper presents the outcomes of the numerical studies on industrial stationary heat transfer enhancement inserts and illustrates how a heat transfer enhancement insert can improve the heat transfer in buoyancy driven compressible flows. Using different measuring tools, thermal performance of two different inserts (twisted and helix) are studied. It is shown that the helix design leads to a higher rate of heat transfer, while causes a lower pressure drop in the flowfield, suggesting the insert effectiveness is higher for the helix design, compared to a twisted plate.

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