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The fully developed laminar mixed convection flow in inclined tubes subject to axially and circumferentially uniform heat flux has been studied numerically for a Boussinesq fluid. Dual solutions characterized by a two‐ and a four‐vortex secondary flow structure in a cross‐section normal to the tube’s longitudinal axis have been found for different combinations of the Grashof number Gr and of the tube inclination α for all Prandtl numbers between 0.7 and 7. In the two‐parameter space defined by Gr and α dual solutions occur: at a given α, if the Grashof number exceeds a critical value Gr_ℓ (for horizontal tubes Gr_ℓ is approximately 5.5 × 10⁵, 1.7 × 10⁵ and 1.7 × 10⁴ respectively for Pr = 0.7, 7 and 70); at a given Gr, if the tube inclination is below a critical value α_c (for Gr = 10⁶ this critical angle is approximately 62.5° and 83.5° respectively for Pr = 0.7 and 7). Numerical experiments carried out for developing flows indicate that the two‐vortex solution is the only stable flow structure.

The effects of tube inclination and Grashof number on the fully developed hydrodynamic and thermal fields are investigated numerically for laminar ascending flow of air and water in uniformly heated circular tubes. The effects of the buoyancy induced secondary flow on the hydrodynamic and thermal fields are complex and strongly dependent on the Grashof number, the Prandtl number and the tube inclination. The influence of these parameters on the intensity of the secondary flow, on the distortion of the axial velocity profile and of the temperature field from the corresponding distributions for pure forced flow, as well as on the circumferential variation of the local shear stress and of the local Nusselt number are analysed. The average shear stress is higher than for pure forced flow and it increases with both the tube inclination and with the Grashof number. The average Nusselt number is higher than for pure forced flow and increases with the Grashof number. For a given fluid and Grashof number there exists an optimum tube inclination which maximizes the average Nusselt number. Correlations for the average Nusselt number in terms of Gr and Pr are presented for four different tube inclinations.

The aim is to study the conjugate problem of developing laminar mixed convection flow and heat transfer of water‐Al₂O₃ nanofluid inside an inclined tube submitted to a uniform wall heat flux.

The set of non‐linear, coupled and fully elliptic governing equations has been solved using a “finite‐control‐volume” numerical method, the classical power‐law scheme for computing heat and momentum fluxes staggered and non uniform grids for spatial discretization of various regions of the tube.

Numerical results have shown that the presence of nanoparticles slightly intensifies the secondary flow due to buoyancy, in particular in the developing region. It also increases the average Nusselt number and decreases slightly the product ReC_f with respect to those of water. For the horizontal inclination, two new correlations have been proposed to calculate these two variables in the fully developed region, for Grashof number ranging from 10³ to 10⁵ and particle volume concentrations up to 7 per cent.

The results of this study can be employed for various practical heat transfer and thermal applications using nanofluids.

The present study constitutes an original contribution to the knowledge of nanofluid thermal behaviour.

Upward mixed convection flow of air in a uniformly heated vertical tube was studied numerically using the three‐dimensional elliptic conservation equations and the Launder and Sharma low Reynolds number k–ε turbulence model. For Re=1,000 the fully developed flow field undergoes two transitions as the Grashof number increases: thus, this flow field is laminar for Gr<8×10⁶, turbulent for 8×10⁶<Gr<5×10⁷ and again laminar for Gr>5×10⁷. In the entry region, turbulent kinetic energy decays monotonically for Gr≤3×10⁶ and Gr≥7.1×10⁷. For Gr between these two values it initially increases from the imposed inlet condition and then decreases towards its calculated fully developed value. The mean velocity profiles as well as the axial evolution of the skin friction coefficient are presented for representative values of Gr.

To determine the axial evolution of the hydrodynamic and the thermal fields for mixed convection in inclined tubes and to investigate the presence of flow reversal.

The elliptical, coupled, steady state, three‐dimensional governing partial differential equations for heated ascending laminar mixed convection in an inclined isothermal tube were solved numerically using a finite volume staggered grid approach.

The axial evolution of the velocity profiles and fluid temperatures show that upstream diffusion has an important effect near the inlet of the heating region. As a result, both the wall shear stress and the Nusselt number are affected upstream of the heating zone. Flow reversal occurs of GF≥9 × 10⁵. The shape and size of the region with negative velocities depends strongly on the value of the Grashof number. The effect of the Grashof number on the axial evolution of the wall shear stress and the Nusselt number is shown to be very important in the region of developing flow.

The results have been calculated for one Reynolds number (Re=100), a single fluid (air) and one tube inclination (45°).

Further results of this type can be mapped and would be useful for heat exchanger design.

This is the first time that flow reversal has been calculated numerically for inclined tubes. Most previous studies concern horizontal or vertical tubes and use axially parabolic equations which are easier to solve but can not calculate the flow field in the region with backflow.

The purpose of this paper is to evaluate the capacity of two equation turbulence models to reproduce mean and fluctuating quantities in the case of both natural convection and isothermal flows.

Numerical predictions of mean velocity profiles, air and wall temperatures as well as turbulent kinetic energy by three different two equation models (standard k‐ε, renormalisation group k‐ε and shear‐stress transport‐k‐ω) are compared with corresponding experimental values.

The prediction of mean velocities and temperatures is in all cases satisfactory. On the other hand, the prediction of turbulent quantities is less precise.

The three models under consideration in this paper can be used for engineering applications such as HVAC calculations.

This paper's aim is to examine flow and heat transfer through vertical channels between parallel plates, which is of prime importance in the design of cooling systems for electronic equipment such as that of finned cold plates in general, plate‐and‐frame heat exchangers, etc.

Numerical and analytical solutions are presented to investigate the heat transfer enhancement and the pressure drop reduction due to buoyancy effects (for buoyancy‐aided flow) for the developing laminar mixed convection in vertical channel between parallel plates in the vicinity of the critical values of the buoyancy parameter (Gr/Re)crt that are obtained analytically. The numerical solutions are presented for a wide range of the buoyancy parameters Gr/Re that cover both of buoyancy‐opposed and buoyancy‐aided flow situations under each of the isothermal boundary conditions under investigation.

Buoyancy parameters greater than the critical values result in building‐up the pressure downstream of the entrance such that the vertical channel might act as a thermal diffuser with possible incipient flow reversal. Locations at which the pressure gradient vanishes and the locations at which the pressure‐buildup starts have been numerically obtained and presented for all the investigated cases.

The study is limited to the laminar flow situation.

The results clearly show that for buoyancy‐aided flow, the increase of the buoyancy parameter enhances the heat transfer and reduces the pressure drop across the vertical channel. These findings are very useful for cooling channel or chimney designs.

The study is original and presents new findings, since none of the previous studies reported the conditions for which pressure buildup might take place due to mixed convection in vertical channels between parallel plates.

The aim of this article is to present the results of a parametric analysis of the entropy generation due to mixed convection in the entry‐developing region between two differentially heated isothermal vertical plates.

The entropy generation was estimated via a numerical solution of the mass, momentum and energy conservation equations governing the flow and heat transfer in the vertical channel between the two parallel plates. The resultant temperature and velocity profiles were used to estimate the entropy generation and other heat transfer parameters over a wide range of the operating parameters. The investigated parameters include the buoyancy parameter (Gr/Re), Eckert number (Ec), Reynolds number (Re), Prandtl number (Pr) and the ratio of the dimensionless temperature of the two plates (θ_T).

The optimum values of the buoyancy parameter (Gr/Re) optimum at which the entropy generation assumes its minimum for the problem under consideration have been obtained numerically and presented over a wide range of the other operating parameters. The effect of the other operating parameters on the entropy generation is presented and discussed as well.

The results of this investigation are limited to the geometry of vertical channel parallel plates under isothermal boundary conditions. However, the concept of minimization of entropy generation via controlling the buoyancy parameter is applicable for any other geometry under any other thermal boundary conditions.

The results presented in this paper can be used for optimum designs of heat transfer equipment based on the principle of entropy generation minimization with particular focus on the optimum design of plate and frame heat exchanger and the optimization of electronic packages and stacked packaging of laminar‐convection‐cooled printed circuits.

This paper introduces the entropy generation minimization via controlling the operating parameters and clearly identifies the optimum buoyancy parameter (Gr/Re) at which entropy generation assumes its minimum under different operating conditions.

Presents a physical model for determining the effective thermal conductivity of a two‐phase composite medium with fixed or moving interfaces. A rigorous numerical method for removing oscillations in the thermal field is proposed. The methodology is based on the volume averaging technique with the assumption that the phases may coexist at a temperature different from that of fusion. The analysis reveals that the effective conductivity of a two‐phase medium is dependent on the phase volume fractions, on their thermal conductivities and on a constitutive constant which determines the geometric structure of the medium and the nature of the interface (fixed or moving). The results for the one and two dimensional conduction‐dominated phase change problem show that the oscillations produced by previous fixed‐grid methods are eliminated.

The purpose of this paper is to describe a support system to the selection of enrichment activities in educational environment called RunayaySoft, where Runayay comes from the word Quechua that means develop and Soft as it is an informatics tool that supports the educational institutions and their students, in the selection of activities that allow foster some of their skills based on their interests, learning styles, aptitudes, multiple intelligences, preferences and so on. Moreover, it suggests institutions about the activities that they should make in their building considering student´s characteristics and the agreements that they have.

It does a diagnostic for identifying which characteristics are going to be considered to students and institutions. Then, it generates adaptive profiles with the aim of generating suggestions of enrichment activities that allow to boost some of their skills. For the students were considered their preferences, learning style, aptitude, multiple intelligences and interests. In the case of institutions were the agreements, resources and activities that they develop. Based on this information, it defines the relations for the generation of suggestions of activities toward students, where it does the prioritization of which activities should be considered.

For validating the system, it was done as a functional prototype that generates suggestions to students, as well as educative institutions, through a satisfaction test student assess if they agree or disagree with the suggestions given. With that assessment, it is validated the relationship between student’s characteristics, activity and institution are related for generating activities suggestions.

RunayaySoft generates adaptive profiles for the students, activity and institution. Each profile has information that allows adapt an advice toward students and institutions.

RunayaySoft considers student’s characteristics, activities and educational institutions for generating suggestions for enrichment activities that allow to boost some of their skills. Many times, when activities are generated in educative institutions, they are not considered a learner’s needs and characteristics. For that reason, the system helps institutions to identify activities that should be done in their facilities or with those institutions which they have agreements when the institutions that students come from do not have the required resources.

RunayaySoft suggests enrichment activities to students as well as educative institutions. For students, it suggests disciplinary areas where they can boost their skills; for each disciplinary area are recommended activities based on their preferences. Once students select the disciplinary area and activities, the system suggests educative institutions activities that they can do. If the institutions do not have the necessary facilities, the system shows with which other institutions they can set agreements. Moreover, it supports educative institutions to identify enrichment clusters, where it clusters students based on similar interest, allowing institutions to identify the activities that they should focus on.