Introduction to heat transfer

The field of nanofluids has received interesting attention since the concept of dispersing nanoscaled particles into a fluid was first introduced in the later part of the twentieth century This is evident from the increased number of studies related to nanofluids published annually The increasing attention on nanofluids is primarily due to their enhanced thermophysical properties and their ability to be incorporated into a wide range of thermal applications ranging from enhancing the effectiveness of heat exchangers used in industries to solar energy harvesting for renewable energy production Owing to the increasing number of studies relating to nanofluids, there is a need for a holistic review of the progress and steps taken in 2019 concerning their application in heat transfer devices This review takes a retrospective look at the year 2019 by reviewing the progress made in the area of nanofluids preparation and the applications of nanofluids in various heat transfer devices such as solar collectors, heat exchangers, refrigeration systems, radiators, thermal storage systems and electronic cooling This review aims to update readers on recent progress while also highlighting the challenges and future of nanofluids as the next-generation heat transfer fluids Finally, a conclusion on the merits and demerits of nanofluids is presented along with recommendations for future studies that would mobilise the rapid commercialisation of nanofluids

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An updated review of nanofluids in various heat transfer devices

The thermal management of the flow of the hybrid nanofluid within the conical gap between a cone and a disk is analyzed. Four different cases of flow are examined, including (1) stationary cone rotating disk (2) rotating cone stationary disk (3) rotating cone and disk in the same direction and (4) rotating cone and disk in the opposite directions. The magnetic field of strength [Formula: see text] is added to the modeled problem that is applied along the z-direction. This work actually explores the role of the heat transfer, which performs in a plate-cone viscometer. A special type of hybrid nanoliquid containing copper Cu and magnetic ferrite Fe3O4 nanoparticles are considered. The similarity transformations have been used to alter the modeled from partial differential equations (PDEs) to the ordinary differential equations (ODEs). The modeled problem is analytically treated with the Homotopy analysis method HAM and the numerical ND-solve method has been used for the comparison. The numerical outputs for the temperature gradient are tabulated against physical pertinent variables. In particular, it is concluded that increment in volume fraction of both nanoparticles [Formula: see text] effectively enhanced the thermal transmission rate and velocity of base fluid. The desired cooling of disk-cone instruments can be gained for a rotating disk with a fixed cone, while the surface temperature remains constant.

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Hybrid nanofluid flow within the conical gap between the cone and the surface of a rotating disk.

The main objective of this research is to study the effects of nanoparticle shape on the entropy generation characteristics of boehmite alumina nanofluid flow in a horizontal double-pipe heat exchanger The examined boehmite alumina nanofluids include dispersed cylindrical, brick, blade, platelet and spherical nanoparticles in a mixture of water/ethylene glycol The nanofluid and water flow through the tube side and annulus side of the heat exchanger, respectively Two-phase mixture model is applied to precisely simulate the behavior of nanofluid The effects of the various Reynolds numbers, nanoparticle concentrations and nanoparticle shapes on the frictional, thermal and total entropy generation rates as well as the Bejan number are numerically investigated The results indicated that the highest and lowest frictional entropy generation rate belongs to the nanofluids with platelet shape and spherical shape nanoparticles, respectively, while the nanofluid containing spherical shape and platelet shape nanoparticles represented the maximum and minimum thermal and total entropy generation rates Furthermore, it was inferred that the frictional entropy generation rate is enhanced with an increase in nanoparticle concentration, whereas except for nanofluid with spherical shape nanoparticles, the opposite is true for thermal and total entropy generation rates and Bejan number

Second law analysis of turbulent convection flow of boehmite alumina nanofluid inside a double-pipe heat exchanger considering various shapes for nanoparticle

In the current investigation, the heat transfer development with the turbulent flow of novel metal oxide-based ternary composite nanofluids of ZnO + Al2O3+TiO2/DW at varying wt.% concentrations (0.025, 0.05, 0.075, and 0.1) in a square heat exchanger below constant heat flux conditions was discussed. The new ternary composite nanofluids were synthesized by using the sonochemical technique. The ZnO + Al2O3+TiO2/DW based ternary composite nanofluids with their respective wt. % reveals an enhancement in effective thermal conductivity and heat transfer coefficient local and average with Reynolds numbers varying from 4550 to 20,367. The extreme growth in overall effective thermal conductivity was noticed up to 1.149 W/m-K at 0.1 wt% for ternary hybrid composite nanofluids at a maximum temperature 45 °C. Similarly, at 0.075 wt%, 0.05 wt%, and 0.025 wt% the overall effective thermal conductivity was recorded 1.118 W/m-K, 1.091 W/m-K, and 1.079 W/m-K correspondingly, which is greater than that of base fluid (DW), with improved thermo-physical characteristics for novel ZnO + Al2O3+TiO2/DW ternary hybrid composite nanofluids. Also, it shows an improvement in local and average heat transfer with a maximum growth of 0.1 wt %. The maximum heat transfer was observed for ZnO + Al2O3+TiO2/DW based Ternary hybrid composite nanofluids at 0.1 wt % concentrations, up to 900–5700 W/m2K, which is 89% higher than distilled water. While, an enhancement of 900–3870 W/m2K, 900–3350 W/m2K, 900–2750 W/m2K were observed for the other three wt. % 0.075, 0.05 and 0.025, respectively. The study revealed that the metal oxide based ternary hybrid composites nanofluids are suitable for nano coolant applications due to improved thermophysical characteristics and also it is applicable for energy management in industrial applications.

Heat transfer growth of sonochemically synthesized novel mixed metal oxide ZnO+Al2O3+TiO2/DW based ternary hybrid nanofluids in a square flow conduit

A comprehensive experimental investigation is intended to survey consequence of nanofluid on performance of sundry parallel flow heat exchangers with the same heat transfer surface area. An experimental setup including one double-pipe heat exchanger, two shell-and-tube heat exchangers with different tube passes, and one plate heat exchanger is designed and built to carry out the experiments. The experiments are performed under turbulent flow conditions using distilled water and Al2O3/water nanofluid with 0.2, 0.5, and 1% particle volume concentrations. Based on the results from this study, the double-pipe heat exchanger reflected the best outcomes in the heat transfer coefficient with a maximum enhancement of 26%, while only a 7% increment in the heat transfer coefficient is observed for the plate heat exchanger. On the other hand, minimum punishment for pressure drop of the working fluids due to adding the nanoparticles is observed in the plate heat exchanger at 1% volume concentration with a maximum value of 10%.

Sahar Rezaie

Papers

Effect of Al2O3/water nanofluid on performance of parallel flow heat exchangers