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1

Exact solution for heat conduction inside a sphere with heat absorption using the regularized Hilfer-Prabhakar derivative

Elhadedy Hager, Latif Mohamed S. Abdel, Nour Hamed M., Kader Abbas H. Abdel

Journal of Applied Mathematics and Computational Mechanics

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2022

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Vol. 21, nr 2

27--37

EN

In this article, we utilize the finite Sine-Fourier transform and the Laplace transform for solving fractional partial differential equations with regularized Hilfer-Prabhakar derivative. These transforms are used to get analytical solutions for the time fractional heat conduction equation (TFHCE) with the regularized Hilfer-Prabhakar derivative associated with heat absorption in spherical coordinates. Two cases of Dirichlet boundary conditions are considered by obtaining an analytical solution in each case. The effect of the parameters of the regularized Hilfer-Prabhakar derivative on the heat transfer inside the sphere is discussed using some figures.

2

Wpływ struktury przepływu na wymianę ciepła w procesie skraplania proekologicznych czynników chłodniczych w minikanałach

Sikora Małgorzata, Bohdal Tadeusz

Instal

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2022

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nr 5

20--26

PL

Podczas procesu skraplania w minikanałach następuje zmiana mechanizmów przenoszenia ciepła i masy wynikająca ze zmiany stopnia suchości x i stopnia zapełnienia φ, które wpływają na proces formowania się różnych struktur przepływu. Miarą efektywności energetycznej procesu jest współczynnik przejmowania ciepła α, który zależy od charakteru przepływu dwufazowego. W niniejszym artykule zaprezentowano wpływ formujących się struktur przepływu dwufazowego na proces wymiany ciepła podczas procesu skraplania czynników chłodniczych w poziomych minikanałach rurowych. Badania przeprowadzono dla trzech proekologicznych czynników niskociśnieniowych HFE7000, HFE7100, Novec649, o niskich wskaźnikach ODP i GWP. Proces skraplania zachodził w minikanałach rurowych o średnicy wewnętrznej dh = 2,0; 1,2; 0,8; 0,5 mm.

EN

During the condensation process in the mini-channels, the heat and mass transfer mechanisms change, resulting from the change in the vapor quality x and the void fraction φ, which in turn affect the process of formation of various flow structures. The measure of the energy efficiency of the process is the heat transfer coefficient α, which depends on the kind of the two-phase flow. This article presents the influence of the two-phase flow structures formed during the condensation process in horizontal pipe mini-channels on the heat transfer process. The research was carried out on three pro-ecological low-pressure refrigerants with low ODP and GWP coefficients, HFE7000, HFE7100, and Novec649. The condensation process took place in pipe mini-channels with an internal diameter of dh = 2.0; 1.2; 0.8; 0.5 mm

3

Economic analysis of artificially roughened solar air heater with v-shaped ribs

Bahuguna Rahul, Chamoli Sunil, Barthwal Yogesh, Rana Sumit, Gupta Ashutosh, Bisht Vijay Singh

Acta Innovations

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2022

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no. 44

18--33

EN

Due to the minimal transfer of heat from absorber plate to moving air in the duct, solar air heaters have low performance. One of the procedures to augment the heat transfer by substantial amount is by utilizing artificial roughness, by which the performance can be improved considerably. In this study, an economic investigation of solar air heater embedded with artificial roughness is accomplished numerically employing v-shaped roughness, with the objective of optimising life cycle solar savings. The non-dimensional parameters of roughness, namely, angle of attack (α), roughness pitch (p/e) and roughness height (e/Dh) are examined by varying temperature rise over the solar air heater (∆T) and solar radiations (I) for different economic parameters values i.e., cost of collector, cost of roughness elements, and cost of conventional fuel.

4

A review on active techniques in microchannel heat sink for miniaturization problem in electronic industry

Bhandari Prabhakar, Singh Jarnail, Kumar Kaushal, Ranakoti Lalit

Acta Innovations

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2022

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no. 45

45--54

EN

With continuous miniaturization of modern electronic components, the need of better cooling devices also keeps on increasing. The improper thermal management of these devices not only hampers the efficiency but can also cause permanent damage. Among various techniques, microchannel heat sink has shown most favourable performance. To further enhance the performance, two techniques i.e., active and passive are used. In passive technique, no external power source is required like heat sink design alteration and working fluid modification. External power source is necessary for heat transfer augmentation in the microchannel heat sink when using the active approach. Due to compact size of microchannel, active techniques are not used more often. However, the present work highlights the different active technique used in microchannel i.e., Electrostatic forces, flow pulsation, magnetic field, acoustic effects, and vibration active techniques. Above mentioned techniques have been analysed in detail.

5

Thermal Properties of Solids : Theoretical Basis, Research Methods and Selected Results of Proprietary Research

Zmywaczyk Janusz

Problemy Mechatroniki : uzbrojenie, lotnictwo, inżynieria bezpieczeństwa

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2021

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Vol. 12, Nr 2 (44)

9--38

EN

This paper refers to an inaugural lecture prepared by the author for the inauguration of the New Academic Year 2020/2021 at the Faculty of Mechatronics, Armament and Aerospace of Military University of Technology (MUT) in Warsaw (Poland) on 2 October 2020. It presents the origins of research into thermal properties of solids since the mid-1970s by the employees of the thermodynamic research unit at the Department of Aerodynamics and Thermodynamics, followed by the basic modalities of heat transfer, theoretical foundations of thermal expansion, specific heat, thermal conductivity and thermal diffusivity of solids. The measuring apparatus created as a result of proprietary research studies and purchased from market-leading manufacturers is shown with a selection of results from the research into the thermal properties of solids, which are largely the outcome of the application our own research procedures.

PL

Artykuł nawiązuje do wykładu inauguracyjnego opracowanego przez autora w związku z inauguracją Nowego Roku Akademickiego 2020/2021 na Wydziale Mechatroniki, Uzbrojenia i Lotnictwa WAT w dniu 2 października 2020 r. Przedstawiono genezę badań właściwości cieplnych ciał stałych prowadzonych od połowy lat siedemdziesiątych XX w. przez pracowników części termodynamicznej Zakładu Aerodynamiki i Termodynamiki, a w dalszej kolejności podstawowe mody wymiany ciepła, podstawy teoretyczne rozszerzalności cieplnej, ciepła właściwego, przewodności cieplnej i dyfuzyjności cieplnej ciał stałych. Pokazano aparaturę pomiarową powstałą w wyniku realizacji własnych opracowań naukowych oraz zakupioną od wiodących na rynku producentów jak również przedstawiono wybrane wyniki badań właściwości cieplnych ciał stałych, które w dużej mierze są efektem zastosowania własnych procedur badawczych.

6

Enhancement of turbulent airflow and heat transfer through a rectangular microchannel with different types of baffles

Saha Sandip, Raut Santanu, Das Apurba Narayan

Journal of Applied Mathematics and Computational Mechanics

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2021

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Vol. 20, nr 3

41--52

EN

The objective of this work is to discuss the turbulent air hydro-thermal phenomena over a rectangular microchannel with different types of baffle (rectangular, triangular, and trapezoidal) mounted on both the walls of the microchannel. The finite volume method with the second order upwind scheme has been utilized to discretize the governing equations and to study the turbulent airflow characteristics; the SST k-ꞷ turbulence model has been adopted. For nine different cases, the different characteristics of fluid flow phenomena and thermal behaviour with the variations in the Reynolds number ranging from [5,000-25,000] and for three different values of inter baffle spacing have been studied in this manuscript. Due to the presence of baffle, it is revealed that the vortex arises on the upper wall and the thermal phenomena enhances with the decrease in inter baffle spacing.

7

Analysis of solutions of the 1D fractional Cattaneo heat transfer equation

Siedlecka Urszula, Ciesielski Mariusz

Journal of Applied Mathematics and Computational Mechanics

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2021

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Vol. 20, nr 4

87--98

EN

In this paper, a solution of the single-phase lag heat conduction problem is presented. The research concerns the generalized 1D Cattaneo equation in a whole-space domain, where a second order time derivative is replaced by the fractional Caputo derivative. The Fourier-Laplace transform technique is used to determine a solution of the considered problem. The numerical inversion of the Laplace transforms is applied. The effect of the order of the fractional derivative on the temperature distribution is investigated.

8

Electro-magnetohydrodynamic two fluid flow of ionized-gases with hall and rotation effects

Linga Raju T.

International Journal of Applied Mechanics and Engineering

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2021

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Vol. 26, no. 4

128--144

EN

An electro-magnetohydrodynamic (EMHD) two fluid flow and heat transfer of ionized gases through a horizontal channel surrounded by non-conducting plates in a rotating framework with Hall currents is investigated. The Hall effect is considered with an assumption that the gases are completely ionized and the strength of the applied transverse magnetic field is strong. The governing equations are solved analytically for the temperature and velocity distributions in two fluid flow regions. The numerical solutions are demonstrated graphically for various physical parameters such the Hartmann number, Hall parameter, rotation parameter, and so on. It was noticed that an increment is either due to the Hall parameter or the rotation parameter reduces the temperature in the two regions.

9

Effect of Hall currents on unsteady magnetohydrodynamic two-ionized fluid flow and heat transfer in a channel

Raju T. Linga, Rao V. Gowrisankara

International Journal of Applied Mechanics and Engineering

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2021

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Vol. 26, no. 2

84--106

EN

An unsteady magnetohydrodynamic (MHD) heat transfer two-fluid flow of ionized gases through a horizontal channel between parallel non-conducting plates, by taking Hall currents into account is studied. The governing partial differential equations that describe the flow and heat transfer under the adopted conditions are solved for the velocity and temperature distributions by a regular perturbation technique. Profiles for the velocity and temperature distributions as well the rates of heat transfer coefficient are presented graphically, and a parametric study is performed. The results reveal that the combined effects of the Hartmann number, Hall parameter, and the ratios of viscosities, heights, electrical and thermal conductivities have a significant impact on an unsteady MHD heat transfer two-ionized fluid flow characteristics.

10

Convective flow of hydromagnetic couple stress fluid with varying heating through vertical channel

Makhalemele C. R., Rundora L., Adesanya S. O.

International Journal of Applied Mechanics and Engineering

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2021

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Vol. 26, no. 2

107--127

EN

This article addresses the impact of magnetic field induction on the buoyancy-induced oscillatory flow of couple stress fluid with varying heating. Modelled equations for the incompressible fluid are coupled and nonlinear due to the inclusion of viscous heating and thermal effect on the fluid density. Approximate solutions are constructed and coded on a symbolic package to ease the computational complexity. Graphical representations of the symbolic solutions are presented with detailed explanations. Results of the present computation show that the effect of induced magnetic field on the oscillatory flow and heat transfer is significant and cannot be neglected.

11

Analysis of transient natural convective flow of a nanofluid in a vertical tube

Jha Basant K., Chitumu Ali J., Oni Michael O.

International Journal of Applied Mechanics and Engineering

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2021

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Vol. 26, no. 2

31--46

EN

An analysis into the transient natural convective flow of a nanofluid in a vertical tube is made. The governing equations of momentum, heat transfer and nanoparticle volume fraction are deduced, and the influence of the thermophoresis parameter and Brownian motion is incorporated. By direct integration and variation of the parameter, analytical solutions are obtained for flow formation and heat/mass transfer at steady-state. On the other hand, due to the complexity of same problem at transient state, a numerical solution is used to solve the discretized equations of motion using the implicit finite difference technique. The influence of the thermophoresis parameter and Brownian motion is noted and well discussed. For accuracy check, a numerical comparison is made between the steady state and transient state solution at large time; this comparison gives an excellent agreement. The role of various principal parameters on velocity profile, temperature, concentration of nanoparticles, Sherwood and Nusselt numbers are presented graphically and well discussed. It is noted that the buoyancy ratio decreases the fluid velocity significantly.

12

Wpływ składowych współczynnika przenikania ciepła na wydajność wymiennika rurowego małej mocy

Pelińska-Olko Ewa, Barnaś Yessica

Instal

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2021

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nr 1

25--30

PL

Przebadano wymienniki współprądowe i przeciwprądowe (odpowiednio WW, WP) typu rura w rurze o małej mocy w konfiguracji 1, 2. Konfiguracja 1 oznacza przepływ cieplejszego czynnika w rurze wewnętrznej oraz zimniejszego w rurze zewnętrznej, natomiast konfiguracja 2 - chłodniejszego w rurze wewnętrznej oraz cieplejszego w rurze zewnętrznej. Wyższe wartości doświadczalnego współczynnika przenikania ciepła k| zarówno dla WW i WP zaobserwowano w konfiguracji 2. W tej pracy, porównano doświadczalne wartości k| z wartościami obliczonymi przy pomocy wybranych metod z teorii podobieństwa. Największą liczbę zgodnych z eksperymentem wartości teoretycznych k|, w zakresie wszystkich przebadanych rodzajów wymienników i ich konfiguracji, uzyskano dla formuły Hausena. Współczynnik k| zawiera trzy składowe: człon opisujący wnikanie ciepła od cieplejszego czynnika roboczego do przepony, przewodzenie przez przeponę rozdzielającą oba czynniki oraz przejmowanie ciepła od przepony do czynnika chłodniejszego. Wielkość tego współczynnika decyduje o wydajności z 1 mb wymiennika rurowego i w ten sposób wraz z średnią różnicą temperatury czynników roboczych wpływa ona na wielkość powierzchni wymiany ciepła a tym samym na gabaryty całego wymiennika.

EN

Co-flow and counter-flow (WW, WP) heat exchangers of low-power tube-in-tube in configuration 1, 2 were tested. Configuration 1 meant the flow of the warmer medium in the inner pipe and colder in the outer pipe, while configuration 2 - the cooler medium in the inner pipe, warmer in the outer pipe. Higher values of the experimental heat transfer coefficient k|, both for WW and WP were observed in configuration 2. In this work, the experimental values of k| were compared with the values calculated with the use of selected theoretical methods. The largest number of theoretical values of k|, consistent with the experiment, for all rested types of exchangers and their configurations, were obtained for the Hausen formula. The coefficient k| includes three components: the element describing the heat transfer from the warmer working medium to the diaphragm, conduction through the diaphragm separating both factors and the transfer of heat from the diaphragm to the cooler medium. The size of this coefficient determines the capacity per 1 running meter of the tube exchanger and thus, together with the average temperature difference of the working media, it affects the heat exchange surface and thus the dimensions of the entire exchanger.

13

Numerical Simulation of Solar Radiation and Conjugate Heat Transfer through Cabin Seat Textile

Zhang Yijie, Jia Juhong

Autex Research Journal

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2021

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Vol. 21, no. 4

501--507

EN

The solar radiation and the conjugate heat transfer through the cabin seat fabric were investigated numerically with a focus on a comparative analysis of various fabric solar reflectance or reflectivity (SR) and inlet cooling air velocity. For this purpose, 3D compressible Reynolds-averaged Navier–Stokes equations with the low Reynolds number turbulence model were utilized to simulate the airflow in the cabin. The discrete ordinate radiation model was adopted to describe the solar radiation. The conjugate heat transfer between the airflow and the fabric seats was included. The airflow temperature, radiative heat flux, and radiative heat transfer through the fabrics in a fixed cross section were studied. The results demonstrate that the increase in fabric SR leads to the increase in energy reflected to the atmosphere, which will bring about a lower temperature on the seat fabric. The decrease in emissivity and the energy absorbed results in the lower heat transfer and heat radiation and leads to the improvement of the cabin thermal environment. The high-temperature gradient near the seat causes the forced air circulation and is beneficial for the improvement of the thermal comfort. However, the cooling effect is not so obvious near the cabin seats when the inflow speed is increased.

14

Evolutionary identification method for determining thermophysical parameters of hardening concrete

Długosz Adam, Pokorska Iwona, Jaskulski Roman, Glinicki Michał A.

Archives of Civil and Mechanical Engineering

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2021

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Vol. 21, no. 1

585--598

EN

The kinetics of heat transfer in hardening concrete is a key issue in engineering practice for erecting massive concrete structures. Prediction of the temperature fields in early age concrete should allow for proper control of the construction process to minimize temperature gradients and the peak temperatures, which is of particular importance for concrete durability. The paper presents a method of identification of the thermophysical parameters of early age concrete such as the thermal conductivity, the specific heat, and the heat generated by cement hydration in time. Proper numerical models of transient heat conduction problems were formulated by means of finite-element method, including two types of heat losses. The developed experimental–numerical approach included the transient temperature measurements in an isolated tube device and an in-house implementation of an evolutionary algorithm to solve the parameter identification task. Parametric Bezier curves were proposed to model heat source function, which allowed for identifying such function as a smooth curve utilizing a small number of parameters. Numerical identification tasks were solved for experimental data acquired on hardening concrete mixes differing in the type of cement and type of mineral aggregate, demonstrating the effectiveness of the proposed method (the mean-squared error less than 1 °C). The proposed approach allows for the identification of thermophysical parameters of early age concrete even for mixtures containing non-standard components while omitting drawbacks typical for classical optimization methods.

15

Sustainability assessment of different nanoparticle for heat exchanger applications: an intuitionistic fuzzy combinative distance-based assessment method

Kumar Sunil, Gautam Sandeep Kumar, Kumar Ankush, Maithan Rajesh, Kumar Anil

Acta Innovations

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2021

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no. 40

44--63

EN

The rate at which the conventional energy sources are depleting is a matter of concern, and there have been major attention on this to make the thermal systems environment friendly, efficient, economic, sustainable, technically reliable. Sustainability of five different types of nanoparticles (Ceramic, carbon based, metal based, polymeric, and lipid based) from the perspective of four aspects involving cost, efficiency, technicality and environmental effect, in heat exchangers has been assessed. The analysis is carried out using the intuitionistic fuzzy combative distance based assessment (IFCODAS) method. In order to measure the sustainability of nanoparticles, a set of eleven evaluating criteria have been accredited on the basis of expert opinions and focus group meetings. By amalgamating the intuitionistic fuzzy set (IFS) theory as well as the use of distance-based assessment (CODAS) method, the IFCODASIFCODAS method has permitted the decision-makers to rate the alternative five nanoparticles pertaining to each criterion. On the basis of the results obtained from IFCODAS method, it is observed that the carbon based nanoparticles have an immense potential to provide significantly reliable and sustainable thermal system than other nanoparticles.

16

Numeryczne modelowanie parametrów współczynnika przenikania ciepła okien i ścian osłonowych. Cz.1

Brouard Olivier C.

Świat Szkła

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2020

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R. 25, nr 11

50--56

17

Technologia hartowania indukcyjnego hutniczych walców kutych do przeróbki plastycznej na zimno

Pawlak Stanisław Jerzy

Stal, Metale & Nowe Technologie

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2020

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nr 7-8

42--47

PL

W artykule przedstawiono technologię hartowania indukcyjnego kutych walców roboczych do przeróbki na zimno, wykonanych ze stali chromowych. W oparciu o pomiary eksperymentalne rozkładu temperatury na przekroju walca oraz koncepcję równoważnego parametru austenityzowania analizowano poprawność procesu nagrzewania indukcyjnego. Pozwoliło to na zniwelowanie negatywnych skutków niejednorodnych warunków austenityzowania na wymaganej grubości od powierzchni beczki walca.

EN

The paper presents a technology of the induction hardening of cold rolling mill rolls made of chromium steels. On the basis of experimental measurements of temperature distribution across the roll barrel and the concept of equivalent austenitizing parameter, the optimal condition for roll heating has been established. The heat exchange during roll quenching has been also analysed.

18

Wpływ cenosferowego i piaskowego złoża fluidalnego na emisję produktów gazowych w procesie spalania ziaren węgla

Migas Przemysław, Baron Jerzy

Przemysł Chemiczny

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2020

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T. 99, nr 10

1477--1481

PL

Określono wpływ rodzaju złoża na zawartość wybranych składników spalin podczas spalania pojedynczych ziaren węgla w reaktorze fluidyzacyjnym. Proces prowadzono w złożu piaskowym i cenosferowym w temp. 600, 700 i 800°C. Porównano zawartość NO, CO i LZO w spalinach. Stwierdzono, że emisja NO i LZO w wyniku spalania ziaren węgla w złożu cenosferowym była zdecydowanie mniejsza niż przy spalaniu w złożu piaskowym.

EN

Granulated coal (grain size 10–11 mm) was combusted in sand or cenosphere-fluidized beds at 600, 700 and 800°C. The contents of NO, CO and volatile org. compds. (VOC) in the flue gases generated in each bed were compared. Emission of NO and VOC during combustion in cenosphere bed was much lower than during combustion in the sand bed.

19

Enhancement of convective heat transfer in a parabolic trough collector using vibrations - an introductory numerical analysis

Grzywnowicz Krzysztof, Bartela Łukasz, Remiorz Leszek, Stanek Bartosz

Journal of Power Technologies

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2020

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Vol. 100, nr 4

291--300

EN

Energy generation systems based on renewable energy sources (RES) are rapidly gaining ground in the global power and heatmarket. Most of these systems are well-suited to distributed energy solutions, including distributed heat production. Individual users and local low-power plants can use solar thermal devices for the purpose of providing domestic hot water, heating and cooling. Nevertheless, the variability of solar irradiance can make it difficult to harvest energy efficiently all year round. Therefore, from the point of view of improving the overall, year-averaged operational parameters of a solar thermal device it isparamount to maximize the heat acquired from it at times ofhigh radiation flux. This paper discusses computational research on enhancing convective heat transfer in the absorber of a parabolic trough collector (PTC), through inducing vibrations of an immersed flat plate. The investigation identifies the influence of different amplitudes and frequencies of oscillatory motion on the absorber’s parameters, compares them with the construction of a classical absorber and considers flow turbulization. The results indicate there is only a limited application of vibrations to enhance operational parameters of solar thermal absorbers, with the best results obtained for thermal fluidflows of below 0.1 dms.

20

Unsteady MHD natural convective boundary layer flow and heat transfer over a truncated cone in the presence of pressure work

Ajay C. K., Srinivasa A. H.

Journal of Applied Mathematics and Computational Mechanics

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2020

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Vol. 19, nr 1

5--16

EN

The aim of the present paper is to analyse the effect of MHD on unsteady natural convection boundary layer flow and heat transfer over a truncated cone in the presence of pressure work. Suitable transformation is utilized to form a system of coupled non-linear partial differential equations for governing both the flow and heat transfer. These equations have been solved numerically by utilizing an implicit finite difference scheme along with quasilinearization method. Here, the computed numerical results are displayed graphically in terms of the local Nusselt number, skin friction, temperature distribution, and velocity distribution for various values of the magnetic and pressure work parameters along with the fixed Prandtl number