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Potential applications of deep eutectic solvents in nanotechnology

Nanofluids have been receiving great attention in recent years due to their potential usage, not only as an enhanced thermophysical heat transfer fluid but also because of their great importance in applications such as drug delivery and oil recovery. Nevertheless, there are some challenges that need to be solved before nanofluids can become commercially acceptable. The main challenges of nanofluids are their stability and operational performance. Nanofluids stability is significantly important in order to maintain their thermophysical properties after fabrication for a long period of time. Therefore, enhancing nanofluids stability and understanding nanofluid behaviour are part of the chain needed to commercialise such type of advanced fluids. In this context, the aim of this article is to summarise the current progress on the study of nanofluids, such as the fabrication procedures, stability evaluation mechanism, stability enhancement procedures, nanofluids thermophysical properties, and current commercialisation challenges. Finally, the article identifies some possible opportunities for future research that can bridge the gap between in-lab research and commercialisation of nanofluids.

/pdf/a-review-on-nanofluids-fabrication-stability-and-3srfogqwkp.pdf

A Review on Nanofluids: Fabrication, Stability, and Thermophysical Properties

Recent research contributions concerning use of nanofluids in heat exchangers: A critical review

Plate heat exchangers have been widely applied in numerous industrial applications since their first commercial exploitation in the 1920s. Enhancing the thermal-hydraulic performance of plate heat exchangers is of crucial importance for the energy conversion as well as for the improvement of the system economy, through savings in the capital investment. The efficiency of a plate heat exchanger can be improved either by optimizing its geometry or using heat transfer enhancement techniques. This paper provides a comprehensive review of previous works regarding the effects of chevron corrugation geometrical parameters on the performance of plate heat exchangers, and the application of heat transfer enhancement techniques in plate heat exchangers, focusing on passive surface techniques and the use of nanofluids. The objective of the paper is not only to describe relevant studies, but also to provide an understanding of the heat transfer mechanisms governing the results, and to evaluate and compare the different heat transfer enhancement techniques. In addition, prospective directions for future research are provided. The review indicates that for the chevron-type plate heat exchanger, the chevron angle is the most influential geometrical parameter by changing the flow structures in the single-phase heat transfer; meanwhile the chevron angle has a significant influence on the heat transfer regions characterized by convection in the two-phase heat transfer. An analysis based on the performance evaluation criteria suggests that the thermal-hydraulic performances of the studies with different geometrical parameters and enhancement techniques are generally higher at low Reynold numbers. Furthermore, the review and analysis indicate that the capsule-type embossing surface and the microstructured surface with a nano- and microporous layer are the enhancement techniques that present the highest performance in single-phase and two-phase heat transfer, respectively.

/pdf/a-review-of-heat-transfer-enhancement-techniques-in-plate-3fdqj9gcha.pdf

A review of heat transfer enhancement techniques in plate heat exchangers

In this paper, fully developed turbulent flow and heat transfer behavior in trapezoidal channels using nanofluids are numerically studied. This study evaluates the effects of four different types of nanoparticles, Al2O3, CuO, SiO2 and ZnO, with different volume fractions (0–4%) and diameters (20–80 nm) under constant heat flux (6 kW/m2). The effects of geometrical parameters (wavy amplitudes, longitudinal pitch) of the trapezoidal channel on the thermal and flow fields are also examined. The results indicated that SiO2 has the highest Nusselt number among the nanofluids. Enhancement of heat transfer increases with particle volume concentration, but a slight increase in pressure loss with decreasing nanoparticle diameter is also observed. When nanofluids are used in a forced convection, 10% increase in average Nusselt number is observed for nanoparticles with a diameter of 20 nm and at 4 vol.%. Analysis of the flow and heat transfer in a corrugated trapezoidal channel is made based on the comprehensive evaluation factor J/f. The optimum (J/f) enhancement shows that the CuO nanofluid, lower concentration ratio of nanoparticles, trapezoidal height of 2.5 mm and a longitudinal pitch of 6 mm are the most desirable parameters for saving energy. Using nanofluids with a corrugated channel can improve the thermal performance because it can lead to more compact heat exchangers.

Design characteristics of corrugated trapezoidal plate heat exchangers using nanofluids

Multiple simulations, experiments, and review studies on absorption cooling technology and cycles were conducted over the past few decades. However, the absorption cooling systems are not seen as competitive against more established vapor compression systems. Therefore, further research and development (R&D) are needed to enable absorption cooling technology to compete with vapor compression technology via the development of energy efficient, cost effective, environmentally friendly, and compact size systems. This study reviews the R&D enhancement aspects of single-stage absorption cooling cycles in terms of subcomponents, supported components added to the absorption cycle, internal energy recovery, and working fluids options. The R&D efforts on single-stage absorption cycles are detailed in a rich and simple presentation to provide a base for further modifications in the future, i.e., towards the optimization of the design geometry of distillation column inside within the generator, towards using adjustable ejector to work under actual operating conditions, applying new streamlines re-arrangements as a passive heat recovery technique, combination of internal heat recovery and superior (non-conventional) working fluids, and finally the addition of nanoparticles into the working fluid to optimize the duty of the generator. The outcome(s) of this study are detailed in the lessons-learned section, and future research priorities are highlighted in conclusion section.

Enhancement aspects of single stage absorption cooling cycle: A detailed review

Adsorption of methyl violet dye onto a prepared bio-adsorbent from date seeds: isotherm, kinetics, and thermodynamic studies

Nanomagnetic Salamo-based-Pd(0) Complex: an efficient heterogeneous catalyst for Suzuki–Miyaura and Heck cross-coupling reactions in aqueous medium

The need for sustainable energy sources is now more urgent than ever, and hydrogen is significant in the future of energy. However, several obstacles remain in the way of widespread hydrogen use, most of which are related to transport and storage. Dilute formic acid (FA) is recognized asa a safe fuel for low-temperature fuel cells. This review examines FA as a potential hydrogen storage molecule that can be dehydrogenated to yield highly pure hydrogen (H2) and carbon dioxide (CO2) with very little carbon monoxide (CO) gas produced via nanoheterogeneous catalysts. It also present the use of Au and Pd as nanoheterogeneous catalysts for formic acid liquid phase decomposition, focusing on the influence of noble metals in monometallic, bimetallic, and trimetallic compositions on the catalytic dehydrogenation of FA under mild temperatures (20–50 °C). The review shows that FA production from CO2 without a base by direct catalytic carbon dioxide hydrogenation is far more sustainable than existing techniques. Finally, using FA as an energy carrier to selectively release hydrogen for fuel cell power generation appears to be a potential technique.

/pdf/formic-acid-dehydrogenation-using-noble-metal-srhced64.pdf

Hasan Sh. Majdi

Papers

Design characteristics of corrugated trapezoidal plate heat exchangers using nanofluids

Enhancement aspects of single stage absorption cooling cycle: A detailed review

Adsorption of methyl violet dye onto a prepared bio-adsorbent from date seeds: isotherm, kinetics, and thermodynamic studies

Nanomagnetic Salamo-based-Pd(0) Complex: an efficient heterogeneous catalyst for Suzuki–Miyaura and Heck cross-coupling reactions in aqueous medium

Formic Acid Dehydrogenation Using Noble-Metal Nanoheterogeneous Catalysts: Towards Sustainable Hydrogen-Based Energy