A wide range of heat transfer systems require efficient heat transfer management from source to sink and vice versa. Over the last decade, graphene nanoparticles, matrix nanofluids have been one of the most investigated nanoparticles for a wide range of engineering applications. Graphene-based nanoparticles have several advantages over other nanoparticles: high stability, high thermal conductivity, low erosion and corrosion, and higher carrier mobility. Graphene-based nanofluids have found applications such as heat transfer, defect sensor, anti-infection therapy, energy harvesting systems, biomedical and cosmetics. With advancement of technology, more compact and efficient cooling media are needed to ensure efficiency and reliability of engineering systems and devices. This research study reports an overview of experimental and numerical investigations of graphene nanometer-sized particles with different base host fluids for major engineering applications of energy transfer systems and further thermophysical properties of graphene nanofluids.

Due to their low cost, light weight and corrosive resistant features, polymer heat exchangers have been intensively studied by researchers with the aim to replace metallic heat exchangers in a wide range of applications. This paper reviews the development of polymer heat exchangers in the last decade, including cutting edge materials characteristics, heat transfer enhancement methods of polymer materials and a wide range of polymer heat exchanger applications. Theoretical modelling and experimental testing results have been reviewed and compared with literature. A recent development, the polymer micro-hollow fibre heat exchanger, is introduced and described. It is shown that polymer materials do hold promise for use in the construction of heat exchangers in many applications, but that a considerable amount of research is still required into material properties, thermal performance and life-time behaviour.

A theoretical treatment is prcsented which attempts to quantify the benefits obtained by using smaller bubbles or larger particles in dispersed air flotation. The limited experimental data obtained so far suggest that the theory is sound, particularly in its prediction of the effect of bubble size.any liquid effluents contain particles which are M too small to be removed economically in sedimentation tanks or by conventional filters. The diameters of such particles are normally less than 20 microns. Dispersed air flotation removes them by adsorbing them on small rising air bubbles, typically of diameters up to 0.1 mm. The bubbles may be generated either by electrolysis, or by forcing air through a porous plate or through spargers. As they rise through the liquid they contact particles either by collision or by Brownian diffusion, depending on particle size. An example of an industrial application is Saint Gobain's Electro-flotation process"', designed initially for removing oil-covered iron dust particles from rolling mill effluents.In dissolved-air flotation, a technique long established in industry, the bubbles are formed by nucleation on the particles'e', For this to happen a substantial portion of the clarified effluent must be recycled, compressed to 4 to 6 atmospheres and saturated with air. Dispersed air flotation has the advantage of eliminating the need for recycling and compression. However, bubble-particle contacting is necessarily less efficient and contacting efficiency becomes an important design parameter. This paper explores the effect of bubble size and particle size on contacting efficiency. Previous workThe removal of suspended solids from effluents by dispersed air flotation is obviously similar in many ways to the froth flotation process used in mineral dressing. The mineral flotation literature records little or no quantitative work on the effect of bubble size, although it is known qualitatively that smaller bubbles tend to increase the flotation rate and a subsidiary function of frothers (long-chain alcohols) is t o reduce bubble size"). Many empirical studies have been made on the effect of particle size in mineral flotation without any clear-cut relation emerging. If the first order flotation rate constant is k, and the particle diameter is d, then Morris") found k, a In dp; Bushell"' found ?c, independent of d, ; Tomlinson and On prksente un traitcment thhriqne par lequel on cherche A dkterniiner quantitativement les avantages qu'on obtient en employant des bulles plus petites ou des particules plus grosses flottant disperdxs dam l'air. Les rksultats maigres qu'on a obtenus expkrimentaleriient jusqn'ici tendent 8 indiquer que la thCorie est bien fondke, surtout en ce qui a trait i sa prkdiction de I'effet des dimensions des bulles.Fleming'" found kl a d,? for easily floated minerals and kl a d, for poorly floated minerals; Gaudin et a P found k1 to be independent of d, for d, = 1 to 4 microns and kl a d , for d , = 4 to 20 microns. Only Tomlinson and Fleming reported the bubble size us...

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