Special issue on advances in heat transfer enhancement – Part III
Heat transfer enhancement refers to the application of different methods to improve the rate of heating or cooling of a surface. Heat transfer enhancement in heat exchange devices is one of the key factors affecting energy savings and compact designs in wide variety of engineering applications. There are many different methods of improving heat exchange in thermal systems. These include both passive and active techniques, such as the application of magnetic fields, usage of oscillators and baffles, and use of nanofluids as working fluids.
In recent years, pioneering heat transfer research has led to the development of a new innovative fluids called “nanofluids” through the addition of nanoparticles (usually less than 100nm) to low thermal conductivity conventional fluids. It has been reported that the suspended metallic or non-metallic nanoparticles change the transport properties and heat transfer characteristics of the base fluid by a significant amount. Metallic nanofluids often refer to those containing metallic nanoparticles (such as Cu, Al, Zn, Ni, Si, Fe, Ti, Au and Ag), while nanofluids containing non-metallic nanoparticles, such as aluminium oxide (Al2O3), copper oxide (CuO) and silicon carbide (SiC), are often considered as non-metallic nanofluids. Nanofluids exhibit superior heat transfer properties compared to conventional heat transfer fluids. Investigators have recently reported on the use of hybrid nanofluids for further heat transfer enhancement in which there are two dissimilar types of nanoparticles.
Other important techniques for enhancing heat transfer include the change of geometry by introducing baffles. For example, in shell and tube heat exchangers that are widely used in power plants, chemical engineering, environment engineering and waste heat recovery, the cross flow through the banks is obtained by means of baffle plates, responsible for changing the direction of the flow and for increasing the heat exchange time between fluid and the heated surfaces. In addition, in many situations, the application of magnetic field to electrically conducting fluids has the tendency to improve the heat transfer such as in the case of liquid metals in channels with conducting or non-conducting walls because of the creation of enhanced turbulence and/or the increase in the velocity in the vicinity of the heated wall.
This special issue was initiated to focus on the advances in heat transfer enhancement methods and to address their use in engineering applications. Many papers were submitted, but only 52 were accepted. A total of 32 of them were already published in Part I and Part II of this special issue. The remaining 20 papers are published in this Part III. The contributions to this part of the special issue addressed various pertinent aspects of magnetohydrodynamics (MHD), baffles and nanofluids in terms of their models and applications. The accepted papers were mostly reporting numerical investigations. The topical coverage included MHD nanofluid convection because of a rotating cylinder in a 3-D enclosure with phase change material, MHD nanofluid convection in a cubic cavity with a conductive partition for various nanoparticle shapes; three-dimensional combined radiation-magneto-convection of low electrically conductive dielectric oxide melt, entropy generation of magneto-nanoliquids embedded with aluminium and titanium alloy nanoparticles in microchannel, natural nanofluid convection in a cavity containing rough elements, free convection of magnetizable micropolar nanofluid with non-uniform magnetic field, double diffusion convection in an enclosure filled with a nanofluid using Buongioro’s two phase model, external nanofluid flow over a bundle of cylinders with sharp wedge-shaped porous media, fluid–structure interaction of transient convection in a cavity containing inner solid cylinder and flexible wall, two-phase nanofluid over a rotating disk with exponential variable thickness, entropy generation and thermo-diffusion effects on unsteady chemically reactive slip flow between two rotating disks, heat transfer enhancement using multi-frequency heating, enhancement of the performance of bubble absorber using hybrid nanofluid, study of electro-kinetic effects for heat transfer in microchannel, analysis of the performance of LED water cooling system, analysis of best wall-mounted V-baffle configuration for optimal heat transfer for turbulent flow in a channel, investigation of partially wet surface condition on the performance of fin-tube heat exchanger, energetic–exergetic heat transfer of air handling unit, analysis of using ceiling fans on human thermal comfort and temperature identification of a heat source in conjugate heat transfer problems.
The guest editors of this special issue would like to express their deep appreciation and thanks to the editor-in-chief, Professor Roland Lewis for his diligent efforts and unique editorial skills, and the staff of the International Journal of Numerical Methods for Heat and Fluid Flow. Special thanks are also because of the various talented authors for their excellent original contributions and to the anonymous professional reviewers for their valuable time, comments and suggestions that significantly improved the quality of the accepted papers.
It is important to note here that while this special issue could not possibly cover all aspects and areas of heat transfer enhancement research and applications, it is hoped that it succeeded in providing a review of recent advances in specific fields and problems in nanofluids, MHD and internal and external flows with baffles and others. It is also hoped that this issue succeeded in providing motivation to researchers to fully engage in this important and emerging research area.
