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Abstract

A passive autocatalytic hydrogen recombiner (PAR) is a self-starting device, without operator action or external power input, installed in nuclear power plants to remove hydrogen from the containment building of a nuclear reactor. A new mechanistic model of PAR has been presented and validated by experimental data and results of Computational Fluid Dynamics (CFD) simulations. The model allows to quickly and accurately predict gas temperature and composition, catalyst temperature and hydrogen recombination rate. It is assumed in the model that an exothermic recombination reaction of hydrogen and oxygen proceeds at the catalyst surface only, while processes of heat and mass transport occur by assisted natural and forced convection in non-isothermal and laminar gas flow conditions in vertical channels between catalyst plates. The model accounts for heat radiation from a hot catalyst surface and has no adjustable parameters. It can be combined with an equation of chimney draft and become a useful engineering tool for selection and optimisation of catalytic recombiner geometry.

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Authors and Affiliations

Antoni Rożeń
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Abstract

The paper deals with a study of the effect of regulating elements on local values of heat transfer coefficients along shaped heat exchange surfaces with forced air convection. The use of combined methods of heat transfer intensification, i.e. a combination of regulating elements with appropriately shaped heat exchange areas seems to be highly effective. The study focused on the analysis of local values of heat transfer coefficients in indicated cuts, in distances expressed as a ratio x/s for 0; 0.33; 0.66 and 1. As can be seen from our findings, in given conditions the regulating elements can increase the values of local heat transfer coefficients along shaped heat exchange surfaces. An optical method of holographic interferometry was used for the experimental research into temperature fields in the vicinity of heat exchange surfaces. The obtained values correspond very well with those of local heat transfer coefficients αx, recorded in a CFD simulation.

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Authors and Affiliations

Jozef Cernecky
Jan Koniar
Zuzana Brodnianska
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Abstract

The present work comprises a numerical analysis using the Ansys program to solve the problem of combined free-forced convection around a circular cylinder located in a horizontal lid-driven trapezoidal enclosure. The enclosure is filled with water. The upper moving wall and lower fixed wall are cold at a constant temperature, whereas the inclined walls are adiabatically insulated. The uniformly heated cylinder is located at different positions in the cavity. The study covers three values of Richardson number (0.01, 1, and 10). The results show that the streamlines and isotherms in the enclosure, the Nusselt number and friction factor in the moving wall, hot wall and bottom wall are strongly dependent on the position of the inner hot cylinder. The results are validated with previous work, and the comparison gives good agreement.
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Authors and Affiliations

Asmaa Ali Hussein
1

  1. Middle Technical University, Institute of Technology/Baghdad, Baghdad, Iraq
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Abstract

The reason for undertaking this study was to determine the possible involvement of natural convection in the global heat transfer, that occurs in the heated steel rods bed. This problem is related to the setting of the effective thermal conductivity of the bars bed. This value is one of the boundary conditions for heating modeling of steel rods bundles during heat treatment. The aim of this study was to determine for which geometry of the bed bars, there will be no free convection. To analyze the problem the Rayleigh criterion was used. It was assumed that for the value of the number Ra < 1700 convection in the bed bars does not occur. For analysis, the results of measurements of the temperature distribution in the unidirectionally heated beds of bars were used. It has been shown, that for obtained, during the test, differences of temperature between the surfaces of adjacent rods, convection can occur only when the diameter of the rod exceeds 18 mm.

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Authors and Affiliations

Rafał Wyczółkowski
Dorota Musiał
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Abstract

The paper describes tests intended to examine the occurrence of natural convection within the space occupied by 40×20 mm rectangular steel sections. Within these tests the bed of four layers of section was heated by the electric palate heater. Depending on the manner in which the heater was positioned, the tests were divided into two series. In the case of heating from above, the heat flowing through the bed is transferred only by conduction and radiation. When heating the bed from below, in addition to conduction and radiation, also a convective heat transfer will occur. Should this be the case, it will result in the intensification of the heat exchange. The results of measurements carried out have not demonstrated that the occurrence of any possible natural convection would influence the development of a temperature field in this type of charge.
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Authors and Affiliations

Rafał Wyczółkowski
Dorota Musiał
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Abstract

The primary objective is to perform a numerical synthesis of a Williamson fluid that has nanoparticles added to it and is directed toward a vertical cone in a uniform transverse magnetic field, under heat and mass transport, suction and injection, and convective boundary conditions. For this particular fluid flow, by utilising similarity transformations, the partial differential equations are transformed into ordinary differential equations. Calculating these kinds of equations with their suitable bounds requires the Runge–Kutta technique in combining a shooting strategy. The functions of a vast number of parameters are graphically represented and assessed on flow field profiles. The results show the local skin friction, local Nusselt number, and local Sherwood number and the changing values of the flow constraints. Finally, the results are compared to those from the previously published works and found to be in good agreement.
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Authors and Affiliations

Manthri Sathyanarayana
1
Tamtam Ramakrishna Goud
2

  1. Osmania University, Department of Mathematics, University College of Science, Hyderabad – 500007, Telangana Sate, India
  2. Osmania University, Department of Mathematics, University College of Science, Saifabad, Hyderabad – 500004, Telangana Sate, India
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Abstract

Laminar mixed convection heat transfer in a vented square cavity separated by a porous layer filled with different nanofluids (Fe3O4, Cu, Ag and Al2O3) has been investigated numerically. The governing equations of mixed convection flow for a Newtonian nanofluid are assumed to be two-dimensional, steady and laminar. These equations are solved numerically by using the finite volume technique. The effects of significant parameters such as the Reynolds number (10 ≤ Re ≤ 1000), Grashof number (103 ≤ Gr ≤ 106), nanoparticle volume fraction (0.1 ≤ ϕ ≤ 0.6), porous layer thickness (0 ≤ γ ≤ 1) and porous layer position (0.1 ≤ δ ≤ 0.9) are studied. Numerical simulation details are visualized in terms of streamline, isotherm contours, and average Nusselt number along the heated source. It has been shown that variations in Reynolds and Darcy numbers have an impact on the flow pattern and heat transfer within a cavity. For higher Reynolds (Re >100), Grashof (Gr > 105) numbers and nanoparticles volume fractions the heat transfer rate is enhanced and it is optimal at lower values of Darcy number (Da = 10-5). In addition, it is noticed that the porous layer thickness and location have a significant effect on the control of the heat transfer rate inside the cavity. Furthermore, it is worth noticing that Ag nanoparticles presented the largest heated transfer rate compared to other nanoparticles.
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Authors and Affiliations

Hamdi Messaoud
1
Sahi Adel
1
Ourrad Ouerdia
2

  1. Université de Bejaia, Laboratoire de Physique Théorique, Faculté de Technologie, Algeria
  2. Université de Bejaia, Laboratoire de Physique Théorique, Faculté des Sciences Exactes, Algeria
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Abstract

The airflow through a two-dimensional horizontal rectangular cross-section channel in the presence of two baffles has been numerically examined and analyzed in the steady turbulent regime. The baffles were of the zig-zag type or plane one. The calculations are based on the finite volume approach and the average Navier–Stokes equations along with the energy equation, have been solved using the SIMPLE algorithm. The nonuniform structured quadrilateral-type element mesh is used in this study. The fluid flow patterns represented for Reynolds numbers based on the hydraulic diameter of the channel ranging from 5000 to 20 000. Effects of various Reynolds number values on flow fields, dimensionless axial velocity profiles, as well as local and average friction coefficients in the test channel is presented. The obtained results show that the flow structure is characterized by strong deformations and large recirculation regions. In general, the fluid velocity and skin friction loss rise with the increase in the flow rate and hence the Reynolds number.

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Authors and Affiliations

Chafika Zidani
Boumédiènne Benyoucef
Faouzi Didi
Nabila Guendouz
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Abstract

The instability characteristics of a dielectric fluid layer heated from below under the influence of a uniform vertical alternating current (AC) electric field is analyzed for different types of electric potential (constant electric potential/ electric current), velocity (rigid/free) and temperature boundary conditions (constant temperature/heat flux or a mixed condition at the upper boundary). The resulting eigenvalue problem is solved numerically using the shooting method for various boundary conditions and the solution is also found in a simple closed form when the perturbation heat flux is zero at the boundaries. The possibility of a more precise control of electrothermal convection (ETC) through various boundary conditions is emphasized. The effect of increasing AC electric Rayleigh number is to hasten while that of Biot number is to delay the onset of ETC. The system is more stable for rigid-rigid boundaries when compared to rigid-free and least stable for free-free boundaries. The change of electric potential boundary condition at the upper boundary from constant electric potential to constant electric current is found to instill more stability on the system. Besides, increase in the AC electric Rayleigh number and the Biot number is to reduce the size of convection cells.

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Authors and Affiliations

M. Ravisha
K.R. Raghunatha
A.L. Mamatha
I.S. Shivakumara
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Abstract

The article presents research data on the amount of salts in the irrigated soils of the Mughan-Salyan massif, their composition, water-salt regime, and their forecast. It was found that the soils on the territory of the massif were saline to varying degrees. In general, the area of non-saline soils in the massif is 125,650 ha, mildly – 272,070 ha, moderately – 210,560 ha, highly – 125,850 ha, very highly – 109,450 ha and saline soils – 27,520 ha. The absorbed bases in the soils of the massif were studied, and it was determined that they change depending on the amount of salts as follows: in mildly saline soils, Ca – 57.82–68.31%, Mg – 25.26–36.28%, Na – 5.49–6.43%; in moderately saline soils – 56.77–65.76%, 27.03–35.58%, 7.12–7.94%, respectively; in highly saline areas – 54.05–64.75%, 24.94–43.67% and 9.19– 14.42%. As you can see, the soils are mildly and moderately saline.
The soils in the surveyed areas are saline to varying degrees (i.e., the average value of salts in the 0–100 cm layer of the soil varies between 0.25 and 1.00%). The biological product used in these soils contains a wide range of macro and microelements, humic acids, fulvic acids, amino acids, vitamins and enzymes that do not contain BioEcoGum mineral fertilisers. This biological product was used for the first time and one of the main goals was to study the improvement of water-physical properties of soils after its use. Therefore, the water-salt regime of the soils of the study area was studied on three experimental sites selected for the area, the number of irrigations for different plants, and their norms were determined taking into account the depth of groundwater in the soils and shown in tabular form. They are widely used in farms and these regions, taking into account the proposed irrigation norms and their quantity.
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Authors and Affiliations

Mustafa Mustafayev
1
ORCID: ORCID
Zulfiya Tukenova
2
ORCID: ORCID
Mereke Alimzhanova
3
ORCID: ORCID
Kazhybek Ashimuly
4
ORCID: ORCID
Farid Mustafayev
1
ORCID: ORCID

  1. Institute of Soil Science and Agrochemistry of Azerbaijan National Academy of Science, M. Rahim St, 5, AZ10073, Baku, Azerbaijan Republic
  2. Al-Farabi Kazakh National University, Faculty of Geography and Environmental Sciences, Department of UNESCO in Sustainable Development, Almaty, Republic of Kazakhstan
  3. Al-Farabi Kazakh National University, Faculty of Thermal Physics and Technical Physics, Department of Physics and Technology, Almaty, Republic of Kazakhstan
  4. Scientific Production Center of Microbiology and Virology, Almaty, Republic of Kazakhstan
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Abstract

The inverse solution to the heat flux identification during the vertical plate cooling in air has been presented. The developed solution allowed to separate the energy absorbed by the chamber due to radiation from the convection heat losses to air. The uncertainty tests were carried out and the accuracy of the solution has been estimated at a level of 1%-5% depending on the boundary condition model. The inverse solution was obtained for the temperature measurements in the vertical plate. The stainless-steel plate was heated to 950°C and then cooled in the chamber in air only to about 30°C. The identified heat transfer coefficient was compared with the Churchill and Chu model. The solution has allowed to separate the radiation heat losses and to determine the Nusselt number values that stay in good agreement with the Churchill and Chu model for a nearly steady-state air flow for the plate temperature below 100°C.
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Authors and Affiliations

B. Hadała
1
ORCID: ORCID
Z. Malinowski
1
ORCID: ORCID
A. Gołdasz
2
ORCID: ORCID
A. Cebo-Rudnicka
1
ORCID: ORCID

  1. AGH University of Science and Technology, Faculty of Metals Engineering and Industrial Computer Science, Department of Heat Engineering and Environment Protection, al. Mickiewicza 30, 30-059 Kraków, Poland
  2. AGH University of Science and Technology, Faculty of Energy and Fuels, al. Mickiewicza 30, 30-059 Kraków, Poland
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Abstract

Experimental investigation of natural convection heat transfer in heated vertical tubes dissipating heat from the internal surface is presented. The test section is electrically heated and constant wall heat flux is maintained both circumferentially and axially. Four different test sections are taken having 45 mm internal diameter and 3.8 mm thickness. The length of the test sections are 450 mm, 550 mm, 700 mm and 850 mm. Ratios of length to diameter of the test sections are taken as 10, 12.22, 15.56, and 18.89. Wall heat fluxes are maintained at 250–3341 W/m2. Experiments are also conducted on channels with internal rings of rectangular section placed at various distances. Thickness of the rings are taken as 4 mm, 6 mm, and 8 mm. The step size of the rings varies from 75 mm to 283.3 mm. The nondimensional ring spacing, expressed as the ratios of step size to diameter, are taken from 1.67 to 6.29 and the non-dimensional ring thickness, expressed as the ratios of ring thickness to diameter are taken from 0.089 to 0.178. The ratios of ring spacing to its thickness are taken as 9.375 to 70.82. The effects of various parameters such as length to diameter ratio, wall heat flux, ring thickness and ring spacing on local steady-state heat transfer behavior are observed. From the experimental data a correlation is developed for average Nusselt number and modified Rayleigh number. Another correlation is also developed for modified Rayleigh number and modified Reynolds number. These correlations can predict the data accurately within ±10% error.

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Authors and Affiliations

Ramesh Chandra Nayak
Manmatha Kumar Roul
Saroj Kumar Sarangi
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Abstract

The production of thermal energy from solar energy by flat collectors finds nowadays many applications due to their innumerable economic and environmental interests. Currently, conservation of energy resources has become a global priority. On the other hand, given the dizzying demand for energy, has led specialists to find new techniques, such as renewable energies (solar, wind and geothermal). The present work is a contribution, by numerical simulation, to the study of heat transfer in flat solar collectors. On the basis of some experimental data, several simulation calculations have been carried out in order to determine the influencing parameters allowing better performance of the sensors and ensuring a good homogeneity of the temperature distributions. Based on the observation that, due to the low thermophysical properties of the air used as heat transfer fluid, solar air collectors rather give poor yields. It has been found very useful to have ‘baffling’ obstacles of various shapes and forms in the solar collector duct. This increases the thermal transfer of a coolant, which clearly improves the thermal efficiency of the solar air collector. This article consists mainly of studying the effects on heat transfer of turbulent forced convection by baffles of zigzag shapes, placed in a rectangular channel, using the finite volume method. The pressure-velocity coupling has been processed by the SIMPLEC algorithm. The results are presented in terms of the average Nusselt number and temperature field for different positions.

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Authors and Affiliations

Nabila Guendouz
Nacereddine Bibi-Triki
Faouzi Didi
Chhafika Zidani
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Abstract

In this work, steady flow-field and heat transfer through a copper-water nanofluid around a rotating circular cylinder with a constant nondimensional rotation rate α varying from 0 to 5 was investigated for Reynolds numbers of 5–40. Furthermore, the range of nanoparticle volume fractions considered is 0–5%. The effect of volume fraction of nanoparticles on the fluid flow and heat transfer characteristics are carried out by using a finite-volume method based commercial computational fluid dynamics solver. The variation of the local and the average Nusselt numbers with Reynolds number, volume fractions, and rotation rate are presented for the range of conditions. The average Nusselt number is found to decrease with increasing value of the rotation rate for the fixed value of the Reynolds number and volume fraction of nanoparticles. In addition, rotation can be used as a drag reduction technique.

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Authors and Affiliations

Rafik Bouakkaz
Fouzi Salhi
Yacine Khelili
Mohamed Quazzazi
Kamel Talbi
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Abstract

The aim of this paper is to investigate the effect of thermal stratification together with variable viscosity on free convection flow of non- Newtonian fluids along a nonisothermal semi infinite vertical plate embedded in a saturated porous medium. The governing equations of continuity, momentum and energy are transformed into nonlinear ordinary differential equations using similarity transformations and then solved by using the Runge-Kutta-Gill method along with shooting technique. Governing parameters for the problem under study are the variable viscosity, thermal stratification parameter, non-Newtonian parameter and the power-law index parameter.The velocity and temperature distributions are presented and discussed. The Nusselt number is also derived and discussed numerically.
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Authors and Affiliations

M.B.K. Moorthy
K. Senthilvadivu
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Abstract

The effect of rotating magnetic field on the heat transfer process in a magnetically assisted bioreactor was studied experimentally. Experimental investigations are provided for the explanation of the influence of the rotating magnetic field on natural convection. The heat transfer coefficients and the Nusselt numbers were determined as a function of the product of Grashof and Prandtl dimensionless numbers. Moreover, the comparison of the thermal performance between the tested set-up and a vertical cylinder was carried out. The relative enhancement of heat transfer was characterized by the rate of the relative heat transfer intensification. The study showed that along with the intensity of the magnetic field the heat transfer increased.

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Authors and Affiliations

Maciej Konopacki
Marian Kordas
Rafał Rakoczy
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Abstract

The present work aims at studying the effects of orientation, size, position, and the combination of multiple internal diathermal obstructions in a fluid-saturated square porous enclosure, generally encountered in thermal insulations. The overall objective is to suppress the natural convection fluid flow and heat transfer across a differentially heated porous enclosure. To serve this purpose, multiple diathermal obstructions are employed to mechanically protrude into a porous medium. It is sought to estimate the effect of various types of orientation, clustering and alternate positioning of obstructions by considering number of obstructions (Np), length of obstructions (λ), modified Rayleigh number (Ra*) on local and average Nusselt number (Nu). The Darcy model for porous media is solved using Finite difference method along with Successive Accelerated Replacement scheme. One of the findings is that the value of the Nusselt number decreases by increasing both, the number of obstructions as well as the length of obstructions irrespective of its orientation and positioning. The reduction in Nusselt number is significant with obstructions attached on lower half of the hot wall and/or on upper half of cold wall. In addition, the overall reduction in Nusselt number is slightly greater with obstructions attached explicitly to the cold wall.

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Authors and Affiliations

Jayesh Subhash Chordiya
Ram Vinoy Sharma
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Abstract

This study presents the behavior of a single wall carbon nanotube (SWCNT)/water nanofluid for convective laminar flow inside a straight circular pipe heated by a constant heat flux. Five volume fractions of SWCNT were used to investigate their effect on the heat transfer coefficient, Nusselt number, temperature distribution and velocity field in comparison with pure water flow. One model for each property was tested to calculate the effective thermal conductivity, effective dynamic viscosity, and effective specific heat of the SWCNT/water mixture. The models were extracted from experimental data of a previous work. The outcomes indicate that the rheological behavior of SWCNT introduces a special effect on the SWCNT/water properties, which vary with SWCNT volume fraction. The results show an improvement in the heat transfer coefficient with increasing volume fraction of nanoparticles. The velocity of SWCNT/water nanofluid increased by adding SWCNT nanoparticles, and the maximum increase was registered at 0.05% SWCNT volume fraction. The mixture temperature is increased with the axial distance of the pipe but a reduction in temperature distribution is observed with the increasing SWCNT volume fraction, which reflects the effect of thermophysical properties of the mixture.
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Authors and Affiliations

Farqad Rasheed Saeed
1
Marwah A. Jasim
2
Natheer B. Mahmood
3
Zahraa M. Jaffar
4

  1. Ministry of Science Technology, Directorate of Materials Research, 55509 Al-Jadriya, Iraq
  2. University of Baghdad, College of Engineering, Al-Jadriya,10074 Al-Jadriya, Iraq
  3. Ministry of Education, General Directorate of Baghdad Education, Karkh 2, 10072 Al-Jadriya, Iraq
  4. Al Nahrain University, College of Science, 10072 Al-Jadriya, Iraq
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Abstract

The paper is a thermodynamics analysis of the removal of any inert gas from the tank using the vapors of any liquefied petroleum gas cargo (called cargo tank gassing-up operation). For this purpose, a thermodynamic model was created which considers two boundary cases of this process. The first is a ‘piston pushing’ of inert gas using liquefied petroleum gas vapour. The second case is complete mixing of both gases and removal the mixture from the tank to the atmosphere until desired concentration or amount of liquefied petroleum gas cargo in the tank is reached. Calculations make it possible to determine the amount of a gas used to complete the operation and its loss incurred as a result of total mixing of both gases.
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Authors and Affiliations

Agnieszka Wieczorek
1

  1. Gdynia Maritime University, Morska 81–87, 81-225 Gdynia, Poland
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Abstract

The work presents a numerical investigation for the convective heat transfer of nanofluids under a laminar flow inside a straight tube. Different models applied to investigate the improvement in convective heat transfer, and Nusselt number in comparison with the experimental data. The impact of temperature dependence, temperature independence, and Brownian motion, was studied through the used models. In addition, temperature distribution and velocity field discussed through the presented models. Various concentrations of nanoparticles are used to explore the results of each equation with more precision. It was shown that achieving the solution through specific models could provide better consistency between obtained results and experimental data than the others.
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Bibliography

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[4] Choi S.U.S., Eastman J.A.: Enhancing thermal conductivity of fluids with nanoparticles. Argonne National Lab., ANL/MSD/CP-84938, CONF-951135-29, 1995.
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Authors and Affiliations

Farqad Rasheed Saeed
1
Marwah Abdulkareem Al-Dulaimi

  1. Ministry of Science and Technology, Directorate of Materials Research, 55509 Al-Jadriya, Iraq
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Abstract

Nitrous oxide is often used in the space industry, as an oxidiser or monopropellant, mostly in self-pressurised configurations. It has potential for growth in use due to the recent rising interest in green propellants. At the same time, modelling the behaviour of a self-pressurising nitrous oxide tank is a challenging task, and few accurate numerical models are currently available. Two-phase flow, heat transfer and rapid changes of mass and temperature in the investigated system all increase the difficulty of accurately predicting this process. To get a get better understanding of the emptying of a self-pressurised nitrous oxide tank, two models were developed: a phase equilibrium model (single node equilibrium), treating the control volume as a single node in equilibrium state, and a phase interface model, featuring a moving interface between parts of the investigated medium. The single node equilibrium model is a variation of equilibrium model previously described in the literature, while the phase interface model involves a novel approach. The results show that the models are able to capture general trends in the main parameters, such as pressure or temperature. The phase interface model predicts nitrous oxide as a liquid, a two-phase mixture, and vapour in the lower part of the tank, which is reflected in the dynamics of changes in pressure and mass flow rate. The models developed for self-pressurisation, while created for predicting nitrous oxide behaviour, could be adapted for other media in conditions near vapour– liquid equilibrium by adding appropriate state equations.
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Authors and Affiliations

Jakub Szymborski
1
Dariusz Kardaś
1

  1. The Szewalski Institute of Fluid Flow Machinery, Polish Academy of Sciences, Fiszera 14, 80-231 Gdansk, Poland
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Abstract

The aim of present work is to investigate the mass transfer of steady incompressible hydromagnetic fluid near the stagnation point with deferment of dust particles over a stretching surface. Most researchers tried to improve the mass transfer by inclusion of cross-diffusion or dust particles due to their vast applications in industrial processes, extrusion process, chemical processing, manufacturing of various types of liquid drinks and in various engineering treatments. To encourage the mass transport phenomena in this study we incorporated dust with microorganisms. Conservation of mass, momentum, concentration and density of microorganisms are used in relevant flow equations. The arising system of nonlinear partial differential equations is transformed into nonlinear ordinary differential equations. The numerical solutions are obtained by the Runge-Kutta based shooting technique and the local Sherwood number is computed for various values of the physical governing parameters (Lewis number, Peclet number, Eckert number). An important finding of present work is that larger values of these parameters encourage the mass transfer rate, and the motile organisms density profiles are augmented with the larger values of fluid particle interaction parameter with reference to bioconvection, bioconvection Lewis number, and dust particle concentration parameter.

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Authors and Affiliations

S.U. Mamatha
K. Ramesh Babu
P. Durga Prasad
C.S.K. Raju
S.V.K. Varma
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Abstract

Heat transfer in steady free convection from differentially heated cylinders enclosed in a rectangular duct filled with Bingham plastic fluids has been solved numerically for the ranges of the dimensionless groups as, Rayleigh number, 10 2 ≤ Ra ≤ 10 6; Prandtl number, 10 ≤ Pr ≤ 100 and, Bingham number, 0 ≤ Bn ≤ 50 for aspect ratios AR = 0.5, 0.6, 0.7, 0.8, 0.9 and 2. The streamlines, isotherm contours, yield surfaces, local and average Nusselt numbers were analysed and discussed. It is found that as the aspect ratio of the enclosure increases from 0.5 to 0.9, the average Nusselt number on the surface of the hot cylinder increases as a larger amount of fluid takes part in convection. Moreover, at sufficiently large Bingham numbers, yield stress forces dominate over buoyancy causing the flow to cease and thus the Nusselt number approaches its conduction limit. Finally, the Nusselt number approaches its conduction limit once the maximum Bingham number is reached.
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Authors and Affiliations

Ashok Kumar Baranwal
1
Anoop Kumar Gupta
2
Anurag Kumar Tiwari
3
Roderick Melnik
4 5

  1. Department of Chemical Engineering, BIT Sindri, Dhanbad 828123, India
  2. Department of Chemical and Biochemical Engineering, IIT Patna 801106, India
  3. Department of Chemical Engineering, NIT Jalandhar 144011, India
  4. Wilfrid Laurier University, 75 University Avenue West, Waterloo, Ontario, Canada
  5. BCAM Basque Center for Applied Mathematics, Bizkaia, Spain
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Abstract

The aim of the present study was to explore the influence of aiding buoyancy on mixed convection heat transfer in power-law fluids from an isothermally heated unconfined square cylinder. Extensive numerical results on drag coefficient and surface averaged values of the Nusselt number are reported over a wide range of parameters i.e. Richardson number, 0.1 ≤ Ri ≤ 5, power-law index, 0.4 ≤ n ≤ 1.8, Reynolds number, 0.1 ≤ Re ≤ 40, and Prandtl number, 1 ≤ Pr ≤ 100. Further, streamline profiles and isotherm contours are presented herein to provide an insight view of the detailed flow kinematics.
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Authors and Affiliations

Pragya Mishra
1
Lubhani Mishra
2
Anurag Kumar Tiwari
3

  1. Chaitanya Bharathi Institute of Technology, Department of Chemical Engineering, Hyderabad, Telangana 500075, India
  2. The University of Texas at Austin, Walker Department of Mechanical & Material Science Engineering, Texas Materials Institute, Austin, TX 78705, USA
  3. National Institute of Technology Jalandhar, Department of Chemical Engineering, Jalandhar, Punjab 144011, India

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