Advances in technology miniaturization with increasing power density call for new technologies for enhancing heat transfer. Enhancement of heat transfer with the use of nanofluids has been a hectic topic of research and development since the term “nanofluid” was first used in 1995, mainly because the thermophysical properties of nanofluids in most reports in the literature showed supremacy or improvement over their base fluids, which may not allow fulfillment of the present cutting-edge technology needs. Significant progress in this field has been made in the past two decades. This review summarizes a variety of the experimentally measured thermal properties of common nanofluids, the enhancement mechanisms discovered or hypothesised, the models used for properties and heat transfer characteristics, and the applications of nanofluids for enhancing heat transfer. The model of an artificial neutral network is particularly emphasized. Applications to cooling technology, renewable energy and energy systems, and building technology are detailed. Challenges and areas for future research are identified.

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A review on heat transfer enhancement with nanofluids

This article is a review of literature on heat transfer enhancement research published in 2018 in the English language. A topic search using “heat transfer” in the Web of Science resulted in about 17,000 articles published in 2018, of which nearly 4600 were relevant to heat transfer augmentation. Thus, some selection is inevitable. The included studies are grouped into the fields identified in the Aims and Scope of the Journal of Enhanced Heat Transfer, which considers a wide range of scholarly articles related to the subject of \"enhanced heat and mass transfer\" in natural and forced convection, phase-change heat transfer, conduction and radiative heat transfer, and the general topic of \"high performance\" heat transfer concepts, devices, or systems (e.g., heat exchangers and heat pipes).

Heat transfer enhancement − a brief review of 2018 literature

A current common topic of study among scientists and engineers is how to reduce energy usage. As the loading power of engineering devices is constantly upgrading, while they are becoming more and more compacted according to the market demand and in terms of less material consumption, thermal management is getting more complicated. Accordingly, three techniques are proposed to enhance heat transfer including passive, active, and compound (combination of passive and active) methods. Active methods enjoy external power sources, while passive methods mostly rely on modification of heat exchange surfaces without the need for any auxiliary tools. In the current paper, an extensive literature review is conducted for three widely used passive techniques including porous media, nanofluids, and microorganisms. Based on studies reviewed here, although hybrid (combination of more than one heat transfer enhancement method) passive methods could accelerate the rate of heat transfer, their productivity depends on whether the heat transfer enhancement acquired compensates the further induced pressure drops or not. Also, although an inconsistency was observed among published articles about the role of microorganisms’ presence in heat transfer intensification of nanofluid flow inside the porous medium, the overwhelming majority of studies proved the contributing role of microorganisms on heat transfer enhancement. There is a great deal of innovative thinking incorporated throughout this review article regarding future studies, and it concludes with key questions for further investigations. 

A critical review of heat transfer enhancement methods in the presence of porous media, nanofluids, and microorganisms

An experimental study on explosive boiling of superheated droplets in vacuum spray flash evaporation

A comprehensive review on computational studies of falling film hydrodynamics and heat transfer on the horizontal tube and tube bundle

Low temperature thermal desalination (LTTD) process involves flash evaporation of a seawater at 28–29°C in a single-stage evaporator maintained at a vacuum of around 25–27 m bar (abs). The seawater was splashed inside an evaporator through a 0.1 m diameter upward facing nozzles of around 24 nos arranged evenly throughout the evaporator and generated vapour was condensed in the shell and tube condenser using cooling water available at 12–13°C sucked from the deep sea through a long HDPE pipe. The main objective of this study was to find out the effect of geometry of the upward facing nozzles on the flash evaporation rate as well as on the non-equilibrium temperature difference (NETD) of the flashing process. Two different spout nozzle geometries with 0.37–0.87 m height were used in the experiment. The study indicated that the flashing rate increased by 0.9% (average) and and the NETD (Two – Tsat) decreased by 0.7°C (average), respectively, when nozzle height was increased by 0.87 m. Mechanism that ...

Experimental study on the effect of feed water nozzles on non-equilibrium temperature difference and flash evaporation in a single-stage evaporator and an investigation of effect of process parameters on the liquid flashing in a LTTD desalination process

A review of the role of passive techniques on heat transfer enhancement of horizontal tube falling film and flooded evaporators

\n This paper discusses about the effect of tube geometry and liquid feeder height on the heat transfer performance of falling film evaporation over the horizontal heated plain tubes. To investigate this, a two-dimensional computational fluid dynamics (CFD) model was developed, compared, and validated with published data available in the literature. A numerical simulation was carried out for varying liquid load, tube diameter, liquid feeder height, and corresponding changes in the heat transfer co-efficient (HTC), and mass transfer rate was recorded and analyzed. An attempt was also made to measure the thickness of the film around the tubes from the simulation model. Mechanisms that control the factors such as HTC, film thickness, and mass transfer were numerically investigated and discussed in this work. Numerical results indicated that low value of liquid film thickness appears approximately at the angular position of the range between 90 deg and 125 deg. Also the numerical investigation revealed that liquid film thickness decreases and HTC and mass transfer rate increases with the increase of feeder height. No remarkable change in film thickness was observed with increase in the tube diameter. This numerical study also proved that the prediction of thermally developed boundary region on the circumference of the tube could be possible in terms of mass transfer rate. It was also observed from the numerical study that the highest mass transfer rate takes place between the angle 135–165 deg near to the bottom of the tube.

Numerical Investigation on the Effect of Tube Geometry and Feeder Height on the Heat Transfer Performance of Horizontal Tube Falling Film Evaporation

The objective of this paper is to present a methodology to predict vacuum load theoretically and to compare those results with the experimental values for validation especially the non-condensable ...

Experimental study on the vacuum load of low-temperature thermal desalination plant

This paper discusses about the effect of feeder height and heat flux on the heat transfer characteristics of horizontal tube falling film evaporation in the thermal regimes. In order to investigate...

D. Balaji

Papers

Experimental study on the effect of feed water nozzles on non-equilibrium temperature difference and flash evaporation in a single-stage evaporator and an investigation of effect of process parameters on the liquid flashing in a LTTD desalination process

A review of the role of passive techniques on heat transfer enhancement of horizontal tube falling film and flooded evaporators

Numerical Investigation on the Effect of Tube Geometry and Feeder Height on the Heat Transfer Performance of Horizontal Tube Falling Film Evaporation

Experimental study on the vacuum load of low-temperature thermal desalination plant

Numerical studies on the thermal regimes of the horizontal tube falling film evaporation under varying feeder height