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The purpose of this paper is to first present the key features of hybrid numerical methods that enable cost-effective simulations of complex thermofluid systems, and then demonstrate the formulation and application of such a method.

A hybrid numerical method is formulated for simulations of a closed-loop thermosyphon operating with slurries of a micro-encapsulated phase-change material suspended in distilled water. The slurries are modeled as homogeneous mixtures, with inputs of effective properties and overall heat-loss coefficients. Combinations of an axisymmetric two-dimensional (2D) control-volume finite-element method and a segmented-quasi-one-dimensional (1D) model are used to achieve cost-effective simulations. Proper matching of the solutions at the interfaces between adjacent axisymmetric 2D and quasi-1D zones is ensured by incorporating and heuristically determining suitable lengths of pre- and post-heating (and also pre- and post-cooling) sections.

In the demonstration problem, which would strictly require full three-dimensional simulations of the fluid flow and heat transfer phenomena, the proposed hybrid 1D/2D numerical method produces results that are in very good agreement with those obtained in a complementary experimental investigation.

The hybrid numerical methods discussed in this paper allow cost-effective computer simulations of complex thermofluid systems. These methods can therefore serve as very useful tools for the design, parametric studies, and optimization of such systems.

The hydrodynamic characteristic of a buoyancy‐driven convection loop containing an electrically‐conducting fluid in a transverse magnetic field is numerically investigated using a two‐dimensional spectral element numerical model. One side of the loop is heated isothermally, the other side is cooled isothermally and the top and bottom sections are insulated. The study covers ranges of Grashof number, Gr, from 10³ to 10⁵, the Hartmann number, Ha, from 0 to 20, loop height to thickness ratio, L/d, from 10 to 20 and at Prandtl numbers of Pr = 0.02 and Pr = 1. Results are presented for the velocity, temperature profiles and heat transfer in terms of Hartmann number. At high Hartmann numbers the velocity gradient in the core of the flow decreases outside the Hartmann layer in the vicinity of the walls normal to the magnetic field. Comparison is made with the analytical solution of Ghaddar (1997), based on a parallel flow approximation and its range of validity is delineated. The numerical analysis compares well with the closed form analytical solution of the magnetohydrodynamic generator for the flow velocity and the induced current. This study reveals the existence of an optimal Hartmann number at which the induced electric current is maximised for all ranges of Prandtl numbers. The optimal Hartmann number found numerically for Pr = 0.02 is similar to the one predicted by the analytical 1‐D model.

Extra protection at Esso. At Esso Petroleum's Avonmouth terminal, Denso Protal modified wax coating has been used for anti‐corrosion protection of 5km of foreshore pipework, replacing a four coat alkyd paint system.

The purpose of this paper is to present outcomes of efforts made over the last 20 years to extend the applicability of the Richardson extrapolation procedure to numerical predictions of multidimensional, steady and unsteady, fluid flow and heat transfer phenomena in regular and irregular calculation domains.

Pattern-preserving grid-refinement strategies are proposed for mathematically rigorous generalizations of the Richardson extrapolation procedure for numerical predictions of steady fluid flow and heat transfer, using finite volume methods and structured multidimensional Cartesian grids; and control-volume finite element methods and unstructured two-dimensional planar grids, consisting of three-node triangular elements. Mathematically sound extrapolation procedures are also proposed for numerical solutions of unsteady and boundary-layer-type problems. The applicability of such procedures to numerical solutions of problems with curved boundaries and internal interfaces, and also those based on unstructured grids of general quadrilateral, tetrahedral, or hexahedral elements, is discussed.

Applications to three demonstration problems, with discretizations in the asymptotic regime, showed the following: the apparent orders of accuracy were the same as those of the numerical methods used; and the extrapolated results, measures of error, and a grid convergence index, could be obtained in a smooth and non-oscillatory manner.

Strict or approximate pattern-preserving grid-refinement strategies are used to propose generalized Richardson extrapolation procedures for estimating grid-independent numerical solutions. Such extrapolation procedures play an indispensable role in the verification and validation techniques that are employed to assess the accuracy of numerical predictions which are used for designing, optimizing, virtual prototyping, and certification of thermofluid systems.

The purpose of this paper was to study the parameters affecting corrosion of the closed-loop oscillating heat-pipe with check valves (CLOHP/CV) in a system in clear that will be basic data to be used in future research. The majority of research focuses on the inner surface corrosion heat-pipe systems. The CLOHP/CV is commonly favored in cooling electronic devices, etc. Despite these common applications, limited reliable experimental research findings are available on the operation of the CLOHP/CV. Because of these reasons, the lack of detailed data, working fluids effect, working temperatures and duration of testing of the CLOHP/CV, this study focuses on determining the actual inner surface corrosion.

Seven types of copper tubes used in the CLOHP/CV set were sectioned to observe their inner surfaces. Seven different specimens with tube corrosion were examined by a visual inspection, scanning electron microscopy (SEM) and energy dispersive X-ray spectrometry (EDX). The technique for detecting metals solution in samples is based on the fact that ground state metals absorb light at specific wavelengths. Metal ions in a solution are converted to atomic state by means of a flame. In this study, concentration of copper particle in the working fluid was found by flame atomic absorption spectroscopy (Flame-AAS) and elements that occurred on inner surface tube were analyzed by EDX.

The analyses with SEM and EDX testing found that the character corrosion of inner surface of CLOHP/CV was pitting clearly. The analysis with Flame-AAS found that the concentration of copper particles in the distilled water and ethanol as working fluid is more than after 1,000 hours until 3,000 hours because of excess volume of oxygen in working fluid which causes many reactions at the beginning. When the oxygen decreases after 1,000 hours, it causes the reaction to decrease too and get the most concentration of copper particles, i.e. 18.57228 ppm or 0.40859 mg.

Corrosion-dependant maintenance must also be factored into the design. Producing reliable equipment that will become standardized and fixing the time for proper maintenance will require individuals that are knowledgeable about the materials that are going to be used in the design of such equipment. Nowadays, the lack of detailed data of working fluids effect, working temperatures and duration of testing of the CLOHP/CV focuses on determining the actual inner surface corrosion. Therefore, this research aimed to study the parameters affecting corrosion of the CLOHP/CV in a system in clear that will be basic data to be used in future research.

The purpose of this paper is to use numerical simulations to investigate the energy conversion performance and the flow and temperature structures inside horizontal tubes connected to a vertical manifold channel.

The simulations are performed for different flow rates and inlet temperatures using CFD.

In both the “flowing wind mode” and “upwind mode,” the inlet velocity is not infinitely small under the influence of natural convection; however, such small inlet velocities cannot be achieved in practice and are of no practical significance. In the “flowing wind mode,” the appropriate velocity for achieving high efficiency is 0.01-0.02 m/s. In the “upwind mode,” the appropriate velocity for obtaining high efficiency is 0.1-0.2 m/s. A high inlet temperature can lead to high efficiency; therefore, a large temperature difference and a small flow can be used in actual designs.

The energy conversion performance and flow structures inside evacuated tubular collectors were investigated using CFD for different operating conditions, notably in the “following wind mode” and the “upwind mode.”

The purpose of this paper is to present a numerical investigation on pulsating heat pipe (PHP) to study the slug velocities as a function of various parameters.

The governing equation of PHP is solved using explicit embedded Runge‐Kutta method, the Dormand–Prince pair in conjunction with MATLAB with the nomenclature 45 for the determination of displacement and the velocity of the slug.

The results show that lower fill ratio, higher diameter, higher operating temperature and higher temperature difference between evaporator and condenser for a given working fluid results in higher slug velocities, indicating higher momentum transfer and hence better heat transport.

Under steady state conditions, the design of a PHP is facilitated through the introduction of non‐dimensional numbers.

The displacement and slug velocities for additional working fluids, namely ethanol and methanol, are determined for the first time. The behaviour of non‐dimensional numbers, i.e. Poiseuille number, capillary number and Eckert number in a PHP as a function of various parameters have been studied for the first time.

The purpose of this study is to investigate the pulsating flow in a three-dimensional channel. Channel flow is laminar and turbulent. After validation, the effect of different channel cross-sectional geometries (circular, hexagonal and triangular) with the pulsating flow are investigated. For this purpose, the alumina nanofluid was considered as a working fluid with different volume percentages (0 per cent [pure water], 3 per cent and 5 per cent).

In this study, the pulsatile flow was investigated in a three-dimensional channel. Channel flow is laminar and turbulent.

The results show that the fluid temperature decreases by increasing the volume percentage of particles of Al₂O₃; this is because of the fact that the input energy through the wall boundary is a constant value and indicates that with increasing the volume percentage, the fluid can save more energy at a constant temperature. And by adding Al₂O₃ nanofluid, thermal performance improves in channels, but it should be considered that the use of nanofluid causes a pressure drop in the channel.

Alumina/water nanofluid with the pulsating flow was investigated and compared in three different cross-sectional channel geometries (circular, hexagonal and triangular). The effect of different volume percentages (0 per cent [pure water], 3 per cent and 5 per cent) of Al₂O₃ nanofluid on temperature, velocity and pressure are studied.