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Active and passive cooling are the two possible methods for removing heat. An active cooling system is the one that involves the use of energy as opposed to passive cooling that uses no energy. Passive cooling methods are cost effective and more reliable than active cooling due to the absence of moving parts. Microchannel heat sink is one of high-tech devices that have widely considered passive cooling methods especially for electronics cooling. In this paper, the use of passive cooling methods in microchannel heat sink is comprehensively discussed. This paper also present the effects of some important parameters such as the type of channel types, surface roughness, fluid additives, and Reynolds number on the rate of heat transfer in microchannel heat sink. Finally, the conclusions and important summaries were presented according to the data collected.

This paper reviews recent progress and applications of CNT nanofluids in energy harvesting system especially solar collectors. In addition to reviewing the efficiency of solar collectors which use CNT nanofluids, the paper also discusses the preparation methods, factors for enhancing thermal conductivity and optical properties of CNT nanofluids. Finally, the challenges and future trends related to the application of CNT nanofluids in thermal solar collector is discussed.

Engine cooling system using nanofluids provides a new foundation for technological integration and innovation. Nanofluids are suitable coolant due to its high thermal diffusivity and can be applied to any system that needs a quick response to thermal changes such as vehicle engine. The presence of nanoparticles in nanofluids contributes better flow of mixing and higher thermal conductivity compared to pure fluid. The current review begins with the overview of preparation methods and thermal conductivity improvement of fluids with nanoparticles. Then, the thermal performance of vehicle engine using nanofluids is highlighted. It has also given emphasis on the major applications of nanofluids in radiator system and as lubricants for improving heat removal efficiency from vehicle engine.

This paper reviews recent progress and applications of nanofluids in machining processes. In addition to reviewing the various conventional and advanced cooling techniques during machining, the paper also discusses the preparation methods, factors for enhancing thermal conductivity and properties of nanofluids. In line with fast development of nanofluid in machining process, the purpose of this paper is to review recent progress on the application of nanoparticles in lubricants especially for MQL technique. The conclusions and important summaries were also presented according to the data collected.

Carbon nanotube (CNT) has the highest thermal conductivity among the nanoparticles that were discovered so far. Attempts to utilize them as heat transfer fluids by dispersing them into any kinds of base fluids called CNT nanofluids have been thoroughly conducted. However, one of the challenges faced by many researchers in applying their prepared CNT nanofluids is to maintain its homogeneous state and long-term stability. This paper presents an inclusive review on the preparation techniques and the reported period of stability of stationary CNT nanofluids. The characteristics of available treatment such as chemical treatment (covalent and non-covalent) and physical treatment methods have been systematically analyzed. Finally, the challenges and future trends of CNT nanofluids are discussed.

Nanofluid, an advanced type of fluid containing small quantity of nanoparticles (usually less than 100 nm), has been proven to provide more efficient heat transfer compared to conventional fluids. The dispersion of a small amount of solid nanoparticles in conventional fluids such as water or ethylene glycol changes their thermal conductivity remarkably. Recently, nanofluid has been used as a heat transfer fluid to enhance the performance of solar collector devices. This paper reviews recent progress and applications of nanofluids in stationary solar collectors. In addition to reviewing the efficiency of solar collectors which use nanofluids, the paper also discusses the impact of nanofluid usage in solar collector based on economic and environmental viewpoints. Finally, the challenges and future trends related to the application of nanofluids in thermal solar collector is discussed.

During the past decades, the technology to make particles in nanometer dimensions has been improved and a new kind of solid–liquid mixture, which is called a nanofluid, has appeared. Nanofluids are an advanced kind of fluid containing a small quantity of nanoparticles (usually less than 100 nm) that are uniformly and stably suspended in the liquid. The dispersion of a small amount of solid nanoparticles in conventional fluids such as water or ethylene glycol changes their thermal conductivity remarkably. Since then, nanofluids have been applied to enhance the thermal performance of many engineering systems. Recently, nanofluids have been used as heat transfer fluids to enhance the performance of solar collector devices. This paper reviews the recent progress and applications of nanofluids in flat-plate and evacuated tube solar collectors. Other than to review the efficiency of solar collectors with nanofluids, the paper also discusses the impact of nanofluids in solar collectors on economic and environmental viewpoints. Finally, the challenges and future trends in the application of nanofluids in thermal solar collectors are discussed.

Nanofluids have gained significant attention in recent years due their great potential for heat transfer enhancement. The heat transfer of nanofluids can be numerically studied using a single-phase or two-phase approaches. The first assumes that the fluid phase and nanoparticles are in thermal equilibrium and move with the same velocity, while the second requires more computational effort but provides the possibility of understanding the behavior of both fluid phase and solid particles in the heat transfer mechanism. This paper reviews various computational approaches to predict fluid flow and heat transfer characteristics of nanofluids. The characteristics of single-phase and two-phase (volume of fluid, mixture, Eulerian–Lagrangian and Eulerian–Eulerian) approaches have been analyzed and discussed systematically. Latest development and recent researches related to the computational nanofluids are also given.

In this article, turbulent flow characteristic of nanofluids is thoroughly reviewed. Turbulent flows have unique characteristics and are preferred in many industrial applications. Therefore, this paper reviews different techniques used to enhance heat transfer using nanofluids within turbulent regime. This paper also presents the effects of some important parameters such as nanoparticle type, nanoparticles concentration, and Reynolds number on heat transfer rate. Studies on numerical techniques are also discussed. Finally, the conclusions and important summaries are presented according to the data collected.

This paper reviewed the application of nanofluids in vehicle engine cooling system. So far, nanoparticles have been used in engine oil, transmission oil, and radiator coolant to enhance heat transfer removal from vehicle engine. The heat transfer performance of nanofluids has been reported to perform better compared to pure fluid. This review focused on the experimental and numerical studies by previous researchers and their suggested amount of nanoparticles for optimum performance in vehicle engine cooling system. Finally, the conclusions and important summaries were presented according to the data collected.

Copper nanoparticles (Cu-NPs) were prepared in virgin coconut oil (VCO) using a laser ablation technique. A copper plate immersed in VCO was irradiated by an Nd:YAG laser at wave lengths of 532 nm for 5, 10, 20, and 30 min. By increasing the ablation time from 5 to 30 min, the particle size inside the nanofluid decreased from 11 to 4 nm and the concentration, refractive index, and the volume fraction of copper nanofluid increased. The Cu-NPs were capped with oxygen from hydroxyl groups of the VCO, as verified by Fourier transform infrared spectroscopy. The refractive indices, obtained by analysis of the surface plasmon resonance signals increased from 1.44371 + 0.0034i to 1.44387 + 0.0142i, and special self-phase modulation due to nonlinearity effect was investigated.

A study of computational fluid dynamics has been conducted to study the characteristics of the heat transfer and friction factor of Al2O3/Ethylene glycol-water nanofluid flowing inside flat tube. The three dimensional realizable k–e turbulent model with an enhanced wall treatment was utilized. The evaluation of the overall performance of the tested tube was predicated on the thermo-hydrodynamic performance index. The obtained results showed that the difference in behaviour depending on the parameter that has been selected to compare the nanofluid with the base fluid. In addition, the friction factor and the heat transfer coefficient increases with an increase of the nanoparticles volume concentration at the same Reynolds number. The penalty of pressure drop is negligible with an increase of the volume concentration of nanoparticles. Conventional correlations that have been used in turbulent flow regime to predict average heat transfer and friction factor are Dittus-Boelter and Blasius correlations, for tubes are also valid for the tested nanofluids which consider that the nanofluids have a homogeneous fluid behaviour.