Continued miniaturization and demand for high-end performance of electronic devices and appliances have led to dramatic increase in their heat flux generation. Consequently, conventional coolants and cooling approaches are increasingly falling short in meeting the ever-increasing cooling needs and challenges of those high heat generating electronic devices. This study provides a critical review of traditional and emerging cooling methods as well as coolants for electronics. In addition to summarizing traditional coolants, heat transfer properties and performances of potential new coolants such as nanofluids are also reviewed and analyzed. With superior thermal properties and numerous benefits nanofluids show great promises in fulfilling the cooling demands of high heat generating electronic devices. It is believed that applications of such novel coolants in emerging techniques like micro-channels and micro-heat pipes can revolutionize cooling technologies for electronics in the future.

A critical review of traditional and emerging techniques and fluids for electronics cooling

This paper summarizes the important results regarding the improvement in the thermophysical properties of nanofluids. The influence of important parameters like particle's (loading, material, size, and shape), base fluid type, temperature, additives and pH value has been considered. There are many conflicting reports on the influence of parameters on thermophysical properties and the literature in this field is widespread, so this article would be beneficial for investigators to have a precise screening of a broad range of studies in this field. Further literature review of the applications of nanofluids with a particular focus on the advantages of using nanofluids in solar collectors and as coolants in automotive heat exchangers. The authors hope that this review can help in the translation of nanofluid technology from the lab scale research to industrial applications in solar collectors and automotive sector. At last, the paper identifies the opportunities for future research.

A review on thermophysical properties of nanofluids and heat transfer applications

This paper presents a critical review of heat transfer applications of nanofluids. The effects of nanoparticle concentration, size, shape, and nanofluid flow rate on Nusselt number, heat transfer coefficient, thermal conductivity, thermal resistance, friction factor and pressure drop from numerous studies reported recently are presented. Effects of various geometric parameters on heat transfer enhancement of system using nanofluids have also been reviewed. Heat transfer devices covered in this paper include radiators, circular tube heat exchangers, plate heat exchangers, shell and tube heat exchangers and heat sinks. Various correlations used for experimental validation or developed in reviewed studies are also compiled, compared and analyzed. The pros and cons associated to the applications of nanofluids in heat transfer devices are presented in details to determine the future direction of research in this arena.

Recent advances in application of nanofluids in heat transfer devices: A critical review

Economic reasons (material and energy saving) leads to make efforts for making more efficient heat exchange. The heat transfer enhancement techniques are widely used in many applications in the heating process to make possible reduction in weight and size or enhance the performance of heat exchangers. These techniques are classified as active and passive techniques. The active technique required external power while the passive technique does not need any external power. The passive techniques are valuable compared with the active techniques because the swirl inserts manufacturing process is simple and can be easily employed in an existing heat exchanger. Insertion of swirl flow devices enhance the convective heat transfer by making swirl into the bulk flow and disrupting the boundary layer at the tube surface due to repeated changes in the surface geometry. An effort has been made in this paper to carry out an extensive literature review of various turbulators (coiled tubes, extended surfaces (fin, louvered strip, winglet), rough surfaces (Corrugated tube, Rib) and swirl flow devices such as twisted tape, conical ring, snail entry turbulator, vortex rings, coiled wire) for enhancing heat transfer in heat exchangers. It can be concluded that wire coil gives better overall performance if the pressure drop penalty is considered. The use of coiled square wire turbulators leads to a considerable increase in heat transfer and friction loss over those of a smooth wall tube.

Review of heat transfer enhancement methods: Focus on passive methods using swirl flow devices

The heat transfer characteristics of current fluids are tremendously improved by suspending nano-sized solid particles with diameter below 100 nm and are considered as prospective working fluids for the applications such as solar collectors, heat pipes, nuclear reactors, electronic cooling systems, automobile radiators etc. The present paper summarizes the current research in the nanofluid studies on convective heat transfer performance, thermo-physical properties, effect of fluid temperature, inlet velocity, use of surfactant for better stability of nanofluids, particle size, and volume concentration effects. The article also suggests the direction for future developments.

Heat transfer characteristics in nanofluid—A review

Experimental investigation of heat transfer coefficient and friction factor of ethylene glycol water based TiO2 nanofluid in double pipe heat exchanger with and without helical coil inserts

Experimental studies on thermal conductivity of blends of ethylene glycol-water-based TiO2 nanofluids☆

Thermal Conductivity Measurements of Ethylene Glycol Water Based TiO2 Nanofluids

Calotropis Gigantea (CG) is a shrub plant that grows rampantly in South Asia. Here we report the development of CG bast fibre yarns, which could yield replacements for artificial fibres in engineering applications. Most of the researchers concentrated only in the short form of natural fibres, this leads to dropping the fibre reinforcement in continuous and lengthy products. An attempt has been made in this research by taking CG fibre in the form of twisted yarn as reinforcement. The surface treatment is done to enhance the properties of the CG fibres and to reduce hydrophilic and hygroscopic behaviour using NaOH (aq.). Determining the appropriate NaOH concentration in the treatment solution is essential to reduce the hydrophilicity of the fibres while retaining its mechanical properties. Generally optimised NaOH concentration found by completing fibre characterization, which is a very lengthy and time-consuming process. In this research work, the optimum concentration of NaOH found by a quick and short process using simple techniques. Two techniques were used such as Contact angle measurement of fibre surface and microscopic observation of xylem structure to find an optimum concentration of NaOH in the aqueous solution. On treated CG fibres, the contact angle is found to be as high as 112° for 4 wt.% NaOH (aq.) concentration; indicating that the treatment renders the fibre hydrophobic and the observation of xylem structure (voids) confirms in a minimum amount in the same 4 wt.% NaOH treated fibre. The mechanism involved is rationalized using infrared/vibrational spectroscopy based measurements of untreated and treated sampled. The orientation of the fibre helps with optimization of the properties. The elastic modulus (measured as per ASTM standards) obtained are 4.18 GPa (along the fibres) and 3.05 GPa (perpendicular to the fibres).

Optimization of surface treatment in Calotropis Gigantea (CG)-fibre yarn by simple techniques and characterization of CG fibre yarn reinforced laminate

M. Chandra Sekhara Reddy

Papers

Experimental investigation of heat transfer coefficient and friction factor of ethylene glycol water based TiO2 nanofluid in double pipe heat exchanger with and without helical coil inserts

Experimental studies on thermal conductivity of blends of ethylene glycol-water-based TiO2 nanofluids☆

Thermal Conductivity Measurements of Ethylene Glycol Water Based TiO2 Nanofluids

Optimization of surface treatment in Calotropis Gigantea (CG)-fibre yarn by simple techniques and characterization of CG fibre yarn reinforced laminate

Enhancement of Thermal Energy Storage System Using Sensible Heat and Latent Heat Storage Materials