Wyniki wyszukiwania - BazTech

1

Analiza optymalnego ustawienia płomienia gazu spalanego na pionowym wysięgniku palnika gazu platformy morskiej

Magda Waldemar

Inżynieria Morska i Geotechnika

|

2025

|

nr 3

84--91

PL

Analiza optymalizacyjna ustawienia płomienia spalanego gazu dla przypadku wieżowego (pionowego) wysięgnika rurociągu odgazowującego zainstalowanego na platformie morskiej. Wyprowadzenie wzorów na optymalny kąt padania płomienia oraz optymalny kąt widzenia punktu obliczeniowego, charakteryzującego jednoznacznie takie wzajemne ustawienie płomienia gazu i punktu obliczeniowego (tzw. punktu optymalnego) na pokładzie platformy morskiej, dla którego gęstość strumienia promieniowania cieplnego w punkcie optymalnym osiąga wartość maksymalną dla danego kąta odchylenia płomienia od pionu w wyniku działania wiatru w kierunku poziomym o zadanej prędkości.

EN

An optimization analysis of the gas flame orientation in the case of a vertical stack, supporting a vent line (degassing pipeline), installed on an offshore platform. The optimization formulae derived in order to calculate the optimal incident angle and the optimal view angle, characterizing unambiguously such a mutual arrangement of the gas flame and the calculation point (called the optimal point) located on the offshore platform deck, for which the thermal radiation, represented by the radiant heat flux, at the optimal point reaches the maximum for a given value of the flame tilt angle as a result of the wind horizontal operation at a given velocity.

2

The detrimental effect of thermal exposure and thermophoresis on MHD flow with combined mass and heat transmission employing permeability

Mirza Ashik Hussain, Dey Bamdeb, Choudhury Rita

International Journal of Applied Mechanics and Engineering

|

2024

|

Vol. 29, no. 1

90--104

EN

We look at the viscous free-convective transitional magnetohydrodynamic thermal and mass flow over a plate that is always perforated and standing upright through permeable media while thermal radiation, a thermal source, and a chemical reaction are all going on. There is additional consideration for the Soret effect. The plate receives a normal application of a transversely consistent magnetic field. The magnetic Reynolds number is considerably lower considering the axial applied magnetic field instead of the induced magnetic field. The models that control mass, heat, and fluid flow are turned into two-dimensional shapes, and the answers are found by running numerical simulations using the MATLAB algorithm bvp4c. In realistic circumstances, the outcomes have been illustrated graphically. Several fluid properties have been found to have an impact on velocity, temperature, and concentration profiles. There is noticeable increase in velocity along with the growth of the permeability parameter and Soret number. Other dimensionless parameters have a significant impact on the fluid velocity. Likewise, the temperature profile diminishes as the radiation parameter has increased. The concentration distribution falls as the heat source parameter expands. Also, the analysis is encompassed in tabular form for the shearing stress, Nusselt number, and Sherwood number. The combined knowledge of heat and mass moving through viscous flows can be used to make a wide range of mechanisms and processes. These include biological reactors, therapeutic delivery systems, methods of splitting, aerodynamic aircraft design, and modeling for sustainability. It also optimizes automotive radiators and engine efficiency, and it improves cooling systems.

3

Effects of viscous dissipation over an unsteady stretching surface embedded in a porous medium with heat generation and thermal radiation

Falana Ayodeji, Owoeye Samuel Oluyemi, Yussouff Abiodun Abideen, Mumuni Quadri Ademola

International Journal of Applied Mechanics and Engineering

|

2024

|

Vol. 29, no. 3

17--31

EN

This work analyzes the impact of viscous dissipation on an unstable stretching surface in a porous medium with heat generation and thermal radiation—an important factor for numerous engineering applications like cooling baths and plastic sheets. Using MATLAB's Runge-Kutta fourth-order approach, the controlling partial differential equations are converted into highly nonlinear ordinary differential equations that can be solved numerically. The findings show that a decrease in the skin friction coefficient, temperature profiles, velocity, and Nusselt number occurs when the unsteadiness parameter is increased. In contrast to the Prandtl number, which rises with temperature profile and reduced Nusselt number, the Eckert number rises with a dimensionless temperature profile and reduced Nusselt number. Reduced Nusselt number and temperature profile affect the heat generation parameter; a decrease in skin friction coefficient and velocity profile correlate with the porosity parameter. Furthermore, the radiation parameter rises as the temperature distribution and Nusselt number decrease.

4

Temporal evolution of an optically dense fluid adjacent to an oscillated vertical plate with slip condition

Das Sanatan, Karmakar Poly, Sarkar Soumitra, Ali Asgar, Jana Rabindra Nath

Archives of Civil and Mechanical Engineering

|

2024

|

Vol. 24, no. 2

art. no. e122, 2024

EN

This paper explores the time-evolving behaviour of an optically dense fluid in proximity to a vertically oscillating plate with a slip condition. By utilizing the Laplace transform (LT) method, the non-dimensional governing equations are resolved. The study delves into the influence of various parameters on the velocity and temperature distributions and the shear stress and heat transfer rate, presenting these effects through detailed graphical visualizations and thorough analysis. The dynamics of the fluid flow are extensively discussed, particularly contrasting the behaviours in scenarios involving an oscillated plate (OP) and a stationary plate (SP). It is observed that the fluid velocity is consistently higher in the presence of an oscillated plate. The shear stress on the plate upsurges with more intense cooling or heating, while an upswing in the slip parameter tends to reduce the shear stress. Furthermore, the heat transfer rate across the plate is raised with an amplified radiation parameter. The insights from this study have significant implications for various engineering fields, including aerospace and environmental engineering, with practical applications in the design and optimization of heat exchangers, cooling systems, chemical reactors, and in understanding ocean currents near dynamically changing coastal structures.

5

Numerical study of a transient MHD flow across an oscillating vertical plate with thermal radiation and viscous dissipation

Rajaraman R., Muthucumaraswamy R.

International Journal of Applied Mechanics and Engineering

|

2023

|

Vol. 28, no. 2

77--89

EN

The flow of an electrically conducting fluid across a vertically positioned oscillating semi-boundless plate with uniform mass diffusion and temperature is examined in this study in terms of the effects of thermal radiation and viscous dissipation. The dimensionless governing equations were solved using an effective and unconditionally stable implicit finite-difference approach known as the Crank-Nicolson method. Based on the numerical results, the impacts of various physical parameter values on concentration, temperature; velocity; Sherwood numbers, Nusselt numbers and skin-friction profiles are displayed graphically and their consequences thoroughly analyzed. We observed that when the magnetic field, radiation and phase angle parameters are increased, the velocity is reduced. This shows that plate oscillation, radiation and magnetic fields affect the flow pattern significantly.

6

Impacts of chemical reaction, thermal radiation, and heat source/sink on unsteady MHD natural convective flow through an oscillatory infinite vertical plate in porous medium

Saikia Dibya Jyoti, Ahmed Nazibuddin

International Journal of Applied Mechanics and Engineering

|

2023

|

Vol. 28, no. 4

114--136

EN

The main objective of this exploration is to analyze the effects of heat source/sink, chemical reactions, and radiation on the unsteady free convective flow through a porous medium using an infinitely oscillating vertical plate. The Laplace transformation tactics is utilized to solve the governing equations for concentration, energy, and momentum. The simulation results demonstrate that the chemical reaction parameter dwindles both primary and secondary velocities. It has been noted that an upsurge in heat generation (heat source) enhances the temperature field, while a decrease in heat absorption (heat sink) leads to a reduction in the temperature field. Furthermore, the radiation parameter causes a drop in both temperature and velocity patterns. The equation for skin friction is derived and presented graphically, and 3-dimensional surface plots are provided to depict the Nusselt number and Sherwood number. Additionally, graphical illustrations are employed to showcase the influence of various non-dimensional variables on concentration, temperature, and velocity patterns.

7

Unsteady hydromagnetic mixed convection of a radiating and reacting nanofluid in a microchannel with variable properties

Kefene Mesfin Zewde, Makinde Oluwole Daniel, Enyadene Lemi Guta

Engineering Transactions

|

2023

|

Vol. 71, iss. 1

53--79

EN

Unsteady MHD mixed convection of nanofluid heat transfer in a permeable microchannel with temperature-dependent fluid properties is studied under the influence of a first-order chemical reaction and thermal radiation. The viscosity and thermal conductivity are assumed to be related to temperature exponentially. Using suitable dimensionless variables and parameters, the governing partial differential equations (PDEs) are transformed to their corresponding dimensionless forms solved numerically by a semi-discretization finite difference scheme along with the Runge-Kutta-Fehlberg integration technique. The effects of model parameters on the profiles of velocity, temperature, concentration, skin friction, the Nusselt number, and the Sherwood number are discussed qualitatively with the aid of graph.

8

Thermodynamic analysis of radiating nanofluids mixed convection within concentric pipes filled with a porous medium

Makinde Oluwole Daniel, Mabood Fazle, Khan Waqar Ahmed, Makinde Anuoluwa Esther

Engineering Transactions

|

2023

|

Vol. 71, iss. 3

419--438

EN

In this study, the entropy generation resulting from heat and mass transfer of waterbased nanofluid through an annulus within two concentric vertical pipes filled with a porous medium is investigated. This study considers the effects of thermal radiation, viscous dissipation, thermal buoyancy, and axial pressure gradient in addition to heat and mass transfer. Brownian motion and thermophoresis have been introduced through the Buongiorno model. The similarity solution was used to solve nonlinear ordinary differential equations. The RungeKutta-Fehlberg method is used to solve these equations with the related boundary conditions. The effects of pertinent parameters such as pressure gradient, thermal radiation, viscosity parameter, thermophoretic parameter, Brownian motion parameter, and Eckert number are investigated numerically. This study found that the Bejan number increases as the viscosity parameter increases and decreases as the other active parameters increase. As the radiation parameter, thermophoretic parameter, Brownian parameter, and Eckert number increase, the Nusselt number decreases. The total entropy generation rate is found to increase with the fluid viscosity rate, Grashof number, thermal Biot number, and variable pressure gradient. However, the Bejan number is found to decrease with these parameters, as well as the Prandtl number.

9

Study of temperature field in large-span steel structure under radiation-thermal-fluid coupling

Jiang Pengcheng

Archives of Civil Engineering

|

2023

|

Vol. 69, nr 1

661--674

EN

The non-uniformity of temperature field distribution of long-span steel structure is proportional to the intensity of solar radiation. Based on the background of Guangzhou Baiyun Station large-span complex steel roof structure, this paper studies the non-uniform temperature field distribution of large-span steel structure under the Summer Solstice daily radiation-thermal-fluid coupling action based on Star-ccm+ finite element software, and uses Spa2000 software to analyze the stress and deformation of steel roof under temperature action. Combined with the on-site temperature monitoring, the maximum difference with the measured value is 2.5°C compared with the numerical simulation results, which verifies the validity of the finite element simulation. The results show that: from 8:00, with the increase of solar altitude angle, the intensity of solar radiation increases, the temperature rises, and the temperature distribution of large-span steel structure becomes more and more non-uniform. From14:00 to18:00, the solar radiation weakens, and the temperature distribution tends to be uniform. Finally, reasonable construction suggestions and measures are proposed to reduce the adverse effects of temperature effects, which can provide theoretical references for the safe construction and normal operation of large-span steel structures located in the subtropics.

10

Testing of Large Scale Pool Fire of Technical Ethanol

Tępiński Jarosław, Klapsa Wojciech, Cygańczuk Krzysztof, Lesiak Piotr, Lewak Michał Wojciech

Safety & Fire Technology

|

2022

|

Vol. 59, iss. 1

96--109

EN

Aim: The aim of this article is to determine the characteristics of a pool fire, including the temperatures and thermal radiation densities caused by it. Mappings of pool fires occurring in actual emergency events were conducted by performing large-scale polygon tests. Project and methods: Experimental study of pool fire of technical ethanol was carried out on a specially built test stand in the training area of the Training Centre in Pionki of the Regional Headquarters of the State Fire Service in Warsaw. The pool fire test stand consisted of a test tray, with a test chamber with the diameter of 300 cm, founded on a reinforced concrete slab. Using a developed measurement system with data acquisition that included measurement sensors mounted at defined locations relative to the fire, temperatures and thermal radiation densities were measured at various distances/locations relative to the fire. Metrological data such as air temperature, atmospheric pressure, humidity, wind direction and speed were monitored and recorded using the weather station. The height of the fire flame was measured by comparing it to racks set up nearby with marked scales of specific lengths. Results: A polygon stand that was built to study pool fires, equipped with a temperature and thermal radiation density measuring system with measuring sensors distributed in defined locations, is discussed. A study of a pool fire resulting from the combustion of dehydrated, fully contaminated ethanol was conducted. The study measured temperatures, thermal radiation densities, and flame heights. The average and maximum values of temperatures and thermal radiation densities during the steady-state combustion stage (i.e., phase II of the fire) were determined. Conclusions: Based on the presented results of temperature and thermal radiation density measurements at various distances/locations relative to the pool fire site, there was a significant effect of wind direction and speed on these values. Higher temperature and heat radiation density were recorded at the sensors on the leeward side than on the windward side. As the wind speed decreased, there was an increase in the temperature values recorded on the thermocouples located above the centre of the bottom of the tray test chamber due to the flame, which, when not blown away, was allowed to rise vertically upward and fully sweep the temperature sensors.

PL

Cel: Celem artykułu jest określenie charakterystyki pożaru powierzchniowego, w tym temperatur i gęstości promieniowań cieplnych przez niego wywoływanych. Odwzorowania pożarów powierzchniowych mających miejsce w rzeczywistych zdarzeniach awaryjnych przeprowadzono poprzez wykonanie poligonowych badań w dużej skali. Projekt i metody: Badanie doświadczalne pożaru powierzchniowego etanolu technicznego zrealizowano na specjalnie do tego celu zbudowanym stanowisku badawczym na terenie poligonu Ośrodka Szkolenia w Pionkach Komendy Wojewódzkiej Państwowej Straży Pożarnej w Warszawie. W skład stanowiska do badania pożarów powierzchniowych wchodziła taca badawcza, o średnicy komory badawczej wynoszącej 300 cm, posadowiona na płycie żelbetowej. Przy pomocy opracowanego układu pomiarowego z akwizycją danych, w skład którego wchodziły czujniki pomiarowe zamontowane w zdefiniowanych lokalizacjach względem pożaru, dokonano pomiarów temperatur i gęstości promieniowań cieplnych w różnych odległościach/lokalizacjach względem miejsca pożaru. Za pomocą stacji pogodowej monitorowano i rejestrowano dane metrologiczne, takie jak temperatura powietrza, ciśnienie atmosferyczne, wilgotność, kierunek i prędkość wiatru. Pomiaru wysokości płomienia pożaru dokonano przez jego porównanie z ustawionymi w pobliżu stojakami z zaznaczonymi podziałkami o określonych długościach. Wyniki: Omówiono poligonowe stanowisko, które zostało zbudowane do badania pożarów powierzchniowych, wyposażone w układ pomiarowy temperatur i gęstości promieniowań cieplnych z czujnikami pomiarowymi rozmieszczonymi w zdefiniowanych lokalizacjach. Przeprowadzono badania pożaru powierzchniowego powstałego w wyniku spalania etanolu odwodnionego, całkowicie skażonego. W ramach badań dokonano pomiarów temperatur, gęstości promieniowań cieplnych oraz wysokości płomienia. Wyznaczono średnie i maksymalne wartości temperatur i gęstości promieniowań cieplnych w etapie ustalonego spalania (tzn. II faza pożaru). Wnioski: Na podstawie przedstawionych wyników pomiarów temperatur i gęstości promieniowań cieplnych w różnych odległościach/lokalizacjach względem miejsca pożaru powierzchniowego, odnotowano znaczący wpływ kierunku i prędkości wiatru na te wartości. Wyższą temperaturę i gęstość promieniowań cieplnych rejestrowano na czujnikach po stronie zawietrznej niż po stronie nawietrznej. Na skutek spadku prędkości wiatru następował wzrost wartości temperatur rejestrowanych na termoparach umieszczonych nad środkiem dna komory badawczej tacy, co było spowodowane przez płomień, który niezdmuchiwany, mógł unosić się pionowo do góry i w pełni omiatać czujniki temperatury.

11

Badania pożarów strumieniowych propanu przeprowadzone w dużej skali

Tępiński Jarosław, Lewak Michał, Lesiak Piotr

Przemysł Chemiczny

|

2022

|

T. 101, nr 11

950--956

PL

Przedstawiono i omówiono wyniki pomiarów temperatury i promieniowania cieplnego w czasie pożaru strumieniowego propanu wydobywającego się pod ciśnieniem z instalacji gazowej. Badania pożaru strumieniowego w dużej skali przeprowadzono na poligonowym stanowisku badawczym zbudowanym na terenie Ośrodka Szkolenia w Pionkach Komendy Wojewódzkiej Państwowej Straży Pożarnej w Warszawie.

EN

A test of propane jet fire was performed in an outdoor test stand built in the fire brigade training center. A propane jet with a flow rate of about 196.1 m3/h for 110 s was continuously released from pressurized liquid propane tank. The values of temp. and thermal radiation were recorded at 20 and 4 measuring points, resp. A significant effect of even low wind speeds on the values of the recorded parameters was obsd. The results of measurements of temp., thermal radiation and flame dimensions allowed to estimate the effects of jet fire.

12

Chemical reaction and MHD flow for magnetic field effect on heat and mass transfer of fluid flow through a porous medium onto a moving vertical plate

Goud B. Shankar, Nandeppanavar Mahantesh M.

International Journal of Applied Mechanics and Engineering

|

2022

|

Vol. 27, no. 2

226--244

EN

This article discusses the effect of heat and mass transfer in a boundary layer flow in the presence of a magnetic field of an electrically conducting and viscous fluid as it passes through a porous medium containing a heat source and a chemical reaction. By employing similarity variables, the governing equations are changed into nonlinear ordinary differential equations(ODEs). To solve the obtained equations numerically the Keller box method is used. Numerical and graphical representations of the results of different parameter values governing the flow system are given. The non-dimensional distributions of velocity, heat, and concentration are depicted graphically, while the Nusselt number, Sherwood number, and skin friction are determined numerically.

13

Absorption characteristics of thermal radiation for carbon dioxide

Kubicki Jan, Kopczyński Krzysztof, Młyńczak Jarosław

Informatyka, Automatyka, Pomiary w Gospodarce i Ochronie Środowiska

|

2022

|

T. 12, nr 3

4--7

EN

The article presents graphs of absorption of thermal radiation as a function of the mass of absorbing carbon dioxide per unit of illuminated area. Experimental research was preceded by an analysis of a simplified model of radiation absorption, paying attention to the phenomenon of saturation. The results of the experimental research were compared with the theoretical ones and the discrepancies were interpreted. Based on the conclusions, suggestions were made regarding the impact of further CO2 emissions on climate change.

PL

W artykule przedstawiono wykresy absorpcji promieniowania cieplnego w funkcji masy absorbującego dwutlenku węgla na jednostkę oświetlanej powierzchni. Badania eksperymentalne poprzedzono analizą uproszczonego modelu absorpcji promieniowania, zwracając uwagę na zjawisko nasycenia. Wyniki badań eksperymentalnych porównano z teoretycznymi, a rozbieżności zinterpretowano. Na podstawie wniosków sformułowano sugestie dotyczące wpływu dalszej emisji CO2 na zmiany klimatyczne.

14

High Temperature Effects in Fused Silica Optical Fibers

Borzycki Krzysztof, Jaworski Marek, Kossek Tomasz

Journal of Telecommunications and Information Technology

|

2021

|

nr 3

56--71

EN

Fire-resistant fiber optic cables used in safety and monitoring systems playing an essential role in fire fighting and building evacuation procedures are required to temporarily maintain optical continuity when exposed to fire. However, the use of fused silica fiber at temperatures between 800◦C and 1000◦C is associated with two highly undesirable phenomena. Thermal radiation (incandescence) of optical fibers, with its intensity and spectral distribution being proportional to additional attenuation observed in the fiber’s hydroxyl absorption bands (“water peaks”) is one of them. The other consists in penetration of thermal radiation from the surroundings into the fiber, due to defects in glass, causing light scattering and resulting in fiber brittleness. Thermal radiation is a source of interference in fiber attenuation measurements performed during fire tests and affects normal operation of fiber optic data links in the event of a fire. In this article, results of laboratory tests performed on a telecom single mode and multimode fibers subjected to temperatures of up to 1000◦C are presented.

15

Unsteady MHD plane Couette-Poiseuille flow of fourthgrade fluid with thermal radiation, chemical reaction and suction effects

Joseph K. M., Ayankop-Andi E., Mohammed S. U.

International Journal of Applied Mechanics and Engineering

|

2021

|

Vol. 26, no. 4

77--98

EN

This study investigates the unsteady MHD flow of a fourth-grade fluid in a horizontal parallel plates channel. The upper plate is oscillating and moving while the bottom plate is stationary. Solutions for momentum, energy and concentration equations are obtained by the He-Laplace scheme. This method was also used by Idowu and Sani [12] and there is agreement with our results. The effect of various flow parameters controlling the physical situation is discussed with the aid of graphs. Significant results from this study show that velocity and temperature fields increase with the increase in the thermal radiation parameter, while velocity and concentric fields decrease with an increase in the chemical reaction parameter. Furthermore, velocity, temperature and concentric fields decrease with an increase in the suction parameter. It is also interesting to note that when 4S0=, our results will be in complete agreement with Idowu and Sani [12] results. The results of this work are applicable to industrial processes such as polymer extrusion of dye, draining of plastic films etc.

16

Micropolar flow over a black isothermal plate in the presence thermal radiation

Raptis A.

International Journal of Applied Mechanics and Engineering

|

2021

|

Vol. 26, no. 2

235--241

EN

This study numerically investigates the effects of thermal radiation on the flow over a black isothermal plate for an optically thin gray micropolar fluid. The flowing medium absorbs and emits radiation, but scattering is not included. The computational results are discussed graphically for several selected flow parameters.

17

Heat transfer effects on free convection of viscous dissipative fluid flow over an inclined plate with thermal radiation in the presence of induced magnetic field

Kumar P. Pramod, Malga Bala Siddulu, Appidi Lakshmi, Matta Sweta

International Journal of Applied Mechanics and Engineering

|

2021

|

Vol. 26, no. 1

122--134

EN

The principal objective of the present paper is to know the reaction of thermal radiation and the effects of magnetic fields on a viscous dissipative free convection fluid flow past an inclined infinite plate in the presence of an induced magnetic field. The Galerkin finite element technique is applied to solve the nonlinear coupled partial differential equations and effects of thermal radiation and other physical and flow parameters on velocity, induced magnetic field, along with temperature profiles are explained through graphs. It is noticed that as the thermal radiation increases velocity and temperature profiles decrease and the induced magnetic field profiles increases.

18

A numerical examination of an unsteady nonlinear MHD flow in the presence of thermal radiation and heat generation

Agbaje T. M., Leach P. G. L.

International Journal of Applied Mechanics and Engineering

|

2021

|

Vol. 26, no. 1

1--17

EN

In this study, the spectral perturbation method and the spectral relaxation method are used to solve the nonlinear differential equations of an unsteady nonlinear MHD flow in the presence of thermal radiation and heat generation. The SPM is mainly based on series expansion, generating series approximation coupled with the Chebyshev spectral method. The numerical results generated using the spectral perturbation method were compared with those found in the literature, and the two results were in good agreement.

19

Effect of thermal radiation on biomagnetic fluid flow and heat transfer over an unsteady stretching sheet

Alam Jahangir Md., Murtaza Ghulam Md., Tzirtzilakis Efstratios E., Ferdows Mohammad

Computer Assisted Methods in Engineering and Science

|

2021

|

Vol. 28, no. 2

81--104

EN

This study examines the influence of thermal radiation on biomagnetic fluid, namelyblood that passes through a two-dimensional stretching sheet in the presence of magneticdipole. This analysis is conducted to observe the behavior of blood flow for an unsteadycase, which will help in developing new solutions to treat diseases and disorders related tohuman body. Our model is namely biomagnetic fluid dynamics (BFD), which is consistentwith two principles: ferrohydrodynamic (FHD) and magnetohydrodynamic (MHD), whereblood is treated as electrically conductive. It is assumed that the implemented magneticfield is sufficiently strong to saturate the ferrofluid, and the variation of magnetization withtemperature may be approximated with the aid of a function of temperature distinction.The governing partial differential equations (PDEs) converted into ordinary differentialequations (ODEs) using similarity transformation and numerical results are thus obtainedby using the bvp4c function technique in MATLAB software with considering applicableboundary conditions. With the help of graphs, we discuss the impact of various param-eters, namely radiation parameter, unsteady parameter, permeability parameter, suctionparameter, magnetic field parameter, ferromagnetic parameter, Prandtl number, velocityand thermal slip parameter on fluid (blood) flow and heat transfer in the boundary layer.The rate of heat transfer and skin friction coefficient is also computationally obtained forthe requirement of this study. The fluid velocity decreases with increasing values of themagnetic parameter, ferromagnetic interaction parameter, radiation parameter whereastemperature profile increases for the unsteady parameter, Prandtl number, and permeability parameter. From the analysis, it is also observed that the skin friction coefficientdecreases and the rate of heat transfer increases respectively with increasing values ofthe ferromagnetic interaction parameter. The most important part of the present analy-sis is that we neither neglect the magnetization nor electrical conductivity of the bloodthroughout this study. To make the results more feasible, they are compared with thedata previously published in the literature and found to be in good accuracy.

20

Passive cooling through the atmospheric window for vehicle temperature control

Khan Umara, Zevenhoven Ron

Archives of Thermodynamics

|

2021

|

Vol. 42, no. 3

25--44

EN

One of the most energy-intensive activities for a vehicle is space air conditioning, for either cooling or heating. Considerable energy savings can be achieved if this can be decoupled from the use of fuel or electricity. This study analyzes the opportunities and effectiveness of deploying the concept of passive cooling through the atmospheric window (i.e. the 8– 14 nm wavelength range where the atmosphere is transparent for thermal radiation) for vehicle temperature control. Recent work at our institute has resulted in a skylight (roof window) design for passive cooling of building space. This should be applicable to vehicles as well, using the same materials and design concept. An overall cooling effect is obtained if outgoing (long wavelength greater than 4 nm) thermal radiation is stronger than the incoming (short wavelength less than 4 nm) thermal radiation. Of particular interest is to quantify the passive cooling of a vehicle parked under direct/indirect sunlight equipped with a small skylight, designed based on earlier designs for buildings. The work involved simulations using commercial computational fluid dynamics software implementing (where possible) wavelength-dependency of thermal radiation properties of materials involved. The findings show that by the use of passive cooling, a temperature difference of up to 7–8 K is obtained with an internal gas flow rate of 0.7 cm/s inside the skylight. A passive cooling effect of almost 27 W/m2 is attainable for summer season in Finland. Comparison of results from Ansys Fluent and COMSOL models shows differences up to about 10 W/m2 in the estimations.