In current research, CuO-H2O nanofluid turbulent flow and second law analysis are investigated in a circular channel equipped with new helical swirl flow device. In order to find the impacts of Reynolds number (Re), height (BR) and pitch (PR) ratios, finite volume method has been used. Good formulas for exergy loss and Bejan number were extracted. Outputs portray that reduction of exergy detracts with enhances of BR but it augments with enhance of PR. Role of height ratio is less effective than other parameters.
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This paper presents a novel approach to boost the productivity of U-pipe solar evacuated-tube system. The integration of a paraffin-nanoparticle mixture enhances the system's heat storage capacity significantly. Additionally, the incorporation of fins expedites the critical melting process. The study utilizes advanced numerical simulations conducted through the finite volume method. This integrated approach represents a notable progression in solar collector technology, offering potential for increased energy efficiency. To expedite the melting process, four fin configurations were taken into account. Six cases, integrating both loading nanoparticles and fin installation, were analyzed numerically using an implicit technique to demonstrate their impact. The required boundary conditions were determined through reference to previous experimental work. The numerical approach was validated using methods outlined in prior publications, resulting in satisfactory agreement. In the absence of fins, the dispersion of nano-powders leads to a 4.5 % increase in the liquid fraction (LF) after approximately 100 s, and a 2.9 % increase after about 400 s. On the other hand, when the optimal configuration of fins is incorporated, the LF experiences significant enhancements of approximately 138.71 % and 54.91 % at time intervals of 100 and 400 s, respectively. At 400 s, the introduction of ZnO nanoparticles and the incorporation of fins lead to temperature increases in the paraffin by approximately 0.5 % and 12.09 %, respectively. Meanwhile, at 250 s, the thermal performance, indicated by the LF value, exhibits a twofold improvement in the finned case compared to the finless case without nanoparticles.
Impact of Coulomb force on Fe3O4-Ethylene glycol nanofluid convective heat transfer is examined. The positive electrode is considered as moving wall. Control Volume based Finite Element Method is selected to obtain the outputs which are the roles of Reynolds number (Re), nanofluid volume fraction and supplied voltage (Δφ). EFD viscosity of nanofluid according to experimental data is taken into account. Results reveal that electric field boosts the convention mode so heat transfer rate augments by augmenting Coulomb force. Isotherms become denser near the lid wall with augment of Re and Δφ. Using electric field is more useful for lower Reynolds number.
In this study, the least square method (LSM) and the Galerkin method (GM) are used to simulate flow and heat transfer of nanofluid flow between two parallel plates. One of the plates is externally heated, and the other plate, in which coolant fluid is injected through it, expands or contracts with time. The fluid in the channel is water containing different nanoparticles (Cu, Ag and Al2O3). The effective thermal conductivity and viscosity of the nanofluid are calculated by the Maxwell–Garnetts (MG) and Brinkman models, respectively. The effects of the nanoparticle volume fraction, Reynolds number, expansion ratio and power law index on flow and heat transfer are investigated. The results show that the Nusselt number increases with an increase of the nanoparticle volume fraction and Reynolds number. Also it can be found that in order to reach the maximum Nusselt number, copper should be used as a nanoparticle.
Thermal storage unit can be utilized to satisfy the balance of energy supply and demand. Copper oxide nanoparticles and V shaped fins are involved in storage unit in current research to expedite the solidification. To show the variation of energy storage efficiency, Finite element method has been employed. Important selected parameters are nanofluid concentration, angle of V shaped fin, copper oxide particle size and length of fins. Contours and profiles in various time steps are depicted. Outputs display that discharging rate augments with rise of angle of V shaped fin. Using copper oxide helps solidification. Length of fin has inverse relationship with discharging rate.
The influence of non-uniform electric filed on Fe3O4-Ethylene glycol nanofluid hydrothermal treatment in an enclosure with sinusoidal upper and moving lower walls is investigated in this study. Control Volume based Finite Element Method (CVFEM) is utilized to simulate in the presented model. Numerical investigation are conducted for the sundry parameters such as Reynolds number; nanoparticle volume fraction and supplied. Results show that supplied voltage can change the flow shape. Coulomb force causes isotherms denser near the moving wall. Heat transfer rises with augment of supplied voltage and Reynolds number. Effect of electric filed on heat transfer is more pronounced at low Reynolds number. Finally, a comparison with the existing literature is also made.
No abstract is provided for this article.
The usage of carbon nanotubes (CNTs) in evacuated tube solar collectors (ETSCs) is this chapter's major subject. An overview of the subject is given in the introduction, which highlights the importance of solar energy and the possibility of using CNTs to enhance solar energy systems. The properties of CNTs are next examined, with an emphasis on their thermal conductivity and how temperature, concentration, and CNT geometries impact them. On CNT properties, the impacts of chemical and physical treatment techniques are also covered. The study of CNTs in nanofluids is then studied. This section discusses CNT nanofluid production techniques, including those for hybrid CNT nanofluids, and it emphasizes the benefits of employing CNT nanofluids. Next, it looks at how CNTs are used in different kinds of ETSCs. This comprises ETSCs made of U-tubes, thermosyphons, and heat pipes. Also presented are the ETSCs' economic, environmental, and life cycle analyses. This chapter concludes by giving a thorough review of solar energy systems utilizing CNTs. It draws attention to the potential advantages of employing CNTs to improve thermal conductivity and effectiveness in various solar energy systems.
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Forced convection is a mechanism or a type of transport in which fluid motion is generated by an external source (such as a pump, fan, suction device, etc.). It should be considered as one of the main methods of useful heat transfer, as significant amounts of heat energy can be transported very efficiently. Nanofluid can be used as a working fluid to the improve rate of heat transfer. In this chapter, some applications of nanofluid forced convective heat transfer are presented.
