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Number of results: 534
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Abstract

The main goal of today’s car designers is to minimize fuel consumption in all possible ways at the same time maintaining the vehicle’s performance as usual. The goal of this work is to study the effect of adding a vortex generator (VG) on the aerodynamics of the vehicle and fuel economy. Both theoretical and experimental works were carried out and the outcomes of the numerical simulations are contrasted with those of the experimental results. A utility vehicle model with a scale ratio of 1:15 was used as a test model. Experimental research has been done on the fluctuation of the coefficient of pressure, dynamic pressure, and coefficients of lift and drag with and without VG on the roof of a utility vehicle. The delta-shaped VG was put to the test both numerically and experimentally. At a velocity of 2.42 m/s, it is observed that the addition of VG can raise the pressure coefficient by about 17%. When compared to the vehicle model without vortex generators, the velocity profile of the ccomputational fluid dynamics analysis shows that at the back end of the vehicle, the wake has been minimized with VG.
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Authors and Affiliations

Ramesh Kumar Chidambaram
1
Rajesh Kanna
2
Poomanandan Gopal
3
Senthil Kumar Arumugam
4

  1. Vellore Institute of Technology, Automotive Research Centre, Vellore – 632014, India
  2. Vellore Institute of Technology, CO2 Research and Green Technologies Center, Vellore – 632014, India
  3. Anna University, Department of Automobile Engineering, BIT Campus, Tiruchirappalli, 620024, India
  4. VIT Bhopal University, Bhopal, 466114, India
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Abstract

The paper presents the first off-grid system designed to supply electricity to the equipment mounted on components of the district heating network in district heating chambers. The proposed off-grid system is equipped, among other things, with a turbine and a generator intended for electricity production. On-grid power supply is a common way of providing electricity with strictly defined, known and verified operating parameters. For off-grid power supply, however, there are no documented testing results showing such parameters. This paper presents selected results of tests and measurements carried out during the operation of an off-grid supply system powering the equipment installed in a district heating chamber. The values of voltage obtained from a turbine-driven generator are analysed in detail. The analysis results can be used as the basis for further works aiming to optimize the off-grid system of electricity supply to devices installed in district heating chambers.
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Authors and Affiliations

Robert Wiśniewski
1
Agata Kania
1
Wiesław Zima
2
Jan Taler
2

  1. Municipal Heat Supply Company, Jana Pawła II 188, 30-969 Kraków, Poland
  2. Cracow University of Technology, Department of Energy, Jana Pawła II 37, 31-864 Kraków, Poland
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Abstract

Inverse boundary problem for cylindrical geometry and unsteady heat conduction equation was solved in this paper. This solution was presented in a convolution form. Integration of the convolution was made assuming the distribution of temperature T on the integration interval (ti, ti+ Δt) in the form T (x, t) = T (x, ti) Θ + T (z, ti+ Δt) (1 - Θ), where Θ ϵ (0,1). The influence of value of the parameter Θ on the sensitivity of the solution to the inverse problem was analysed. The sensitivity of the solution was examined using the SVD decomposition of the matrix A of the inverse problem and by analysing its singular values. An influence of the thermocouple installation error and stochastic error of temperature measurement as well as the parameter Θ on the error of temperature distribution on the edge of the cylinder was examined.
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Authors and Affiliations

M. Joachimiak
M. Ciałkowski
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Abstract

The design of suitable thermophysical properties of reinforced ice as well as employing the novel material in feasible ways represent key aspects towards alternative building sustainability. In this overview research studies dealing with reinforced ice structures have been presented with an emphasis on construction parameters and reinforcement materials of the structures. The main focus of the study is directed to the identification of the main issues related to the construction of reinforced ice structures as well as the environmental and economic impact of such structures. Obtained research data shows that the compressive, tensile, and bending strength of reinforced ice can be increased up to 6 times compared to plain ice. The application of reinforcement materials decreases creep rate, enhances ductility, and reduces brittle behaviour of ice. Assessed reinforced ice structures were mainly found to be environmentally friendly and economically viable. However, in most of the analysed studies construction parameters and physical properties were not defined precisely. The conducted overview indicates the necessity for more comprehensive and more accurate data regarding reinforced ice construction, applied methods, and processes, and preparation of ice composites in general.
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Authors and Affiliations

Jelena Bosnjak
1
Natalia Bodrozic Coko
1
Miso Jurcevic
1
Branko Klarin
1
Sandro Nizetic
1

  1. University of Split, Faculty of Electrical Engineering, Mechanical Engineering and Naval Architecture, Rudera Boskovica 32, 21000 Split, Croatia
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Abstract

Improvement in the exegetic efficiency of a solar air heater (SAH) can be done by enhancing the rate of heat transfer. In this work, the exergetic efficiency optimization of an artificially roughened solar air heater having an inverted L-shape rib has been performed. The numerical analysis of the exergetic performance of the solar air heater was carried out at a constant heat flux of 1000 W/m2. The study was conducted to investigate the effect of different relative roughness pitch (7.14–17.86) on the exergy losses, under the Reynolds number range of 3000 to 18 000. The roughness parameter of this geometry has been optimized and found to be among functional operating parameters like average solar intensity and temperature rise across the collector. The optimized value of relative roughness pitch is 17.86 at the isolation of 1000 W/m 2, and the parameter of temperature rise ranges from 0.005 to 0.04.
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Authors and Affiliations

Manmohan Chaudhari
1
Sohan Lal Sharma
2
Ajoy Debbarma
2

  1. Maya Institute of Technology and Management, Selaqui, Dehradun, Uttarakhand-248007, India
  2. National Institute of Technology, Hamirpur, Himachal Pradesh, 177005, India
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Abstract

Conventional fuels are the primary source of pollution. Switching towards clean energy becomes increasingly necessary for sustainable development. Electric vehicles are the most suitable alternative for the future of the automobile industry. The battery, being the power source, is the critical element of electric vehicles. However, its charging and discharging rates have always been a question. The discharge rate depends upon various factors such as vehicle load, temperature gradient, surface inclination, terrain, tyre pressure, and vehicle speed. In this work, a 20 Ah, 13S-8P configured lithium-ion battery, developed specifically for a supermileage custom vehicle, is used for experimentation. The abovementioned factors have been analyzed to check the vehicle’s overall performance in different operating conditions, and their effects have been investigated against the battery’s discharge rate. It has been observed that the discharge rate remains unaffected by the considered temperature difference. However, overheating the battery results in thermal runaway, damaging and reducing its life. Increasing the number of brakes to 15, the impact on the discharge rate is marginal; however, if the number of brakes increases beyond 21, a doubling trend in voltage drops was observed. Thus, a smoother drive at a slow-varying velocity is preferred. Experiments for different load conditions and varying terrains show a rise in discharge with increasing load, low discharge for concrete, and the largest discharge for rocky terrain.
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Authors and Affiliations

Shreya Dhawan
1
Aanchal Sabharwal
2
Rupali Prasad
2
Shreya Shreya
2
Aarushi Gupta
2
Yusuf Parvez
3

  1. Duke University, Durham, USA
  2. Indira Gandhi Delhi Technical University for Women, Mechanical and Automation Engineering, New Delhi, India
  3. Maulana Azad National Urdu University, Mechanical Engineering, Cuttack, Odisha, India
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Abstract

The numerical simulation of the heat transfer in the flow channels of the minichannel heat exchanger was carried out. The applied model was validated on the experimental stand of an air heat pump. The influence of louver heights was investigated in the range from 0 mm (plain fin) to 7 mm (maximum height). The set of simulations was prepared in Ansys CFX. The research was carried out in a range of air inlet velocities from 1 to 5 m/s. The values of the Reynolds number achieved in the experimental tests ranged from 93 to 486. The dimensionless factors, the Colburn factor and friction factor, were calculated to evaluate heat transfer and pressure loss, respectively. The effectiveness of each louver height was evaluated using the parameter that relates to the heat transfer and the pressure drop in the airflow. The highest value of effectiveness (1.53) was achieved by the louver height of 7 mm for the Reynolds number of around 290.
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Authors and Affiliations

Artur Romaniak
1
Michał Jan Kowalczyk
1
Marcin Łęcki
1
Artur Gutkowski
1
Grzegorz Górecki
1

  1. Lodz University of Technology, Zeromskiego 116, 90-924 Łódz, Poland
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Abstract

In this work, we propose a new method for manufacturing busbars in photovoltaic modules for different solar cell generations, focusing on 1st and 3rd generations. The method is based on high-pressure spray coating using nanometric metallic powder. Our focus is primarily on optimizing conductive paths for applications involving conductive layers used in 3rd generation solar cells, such as quantum dot solar cell, dye-sensitized solar cell, and silicon-based solar cells on glass-glass architecture for buildingintegrated photovoltaic. The advantages of the proposed method include the possibility of reducing the material quantity in the conductive paths and creating various shapes on the surface, including bent substrates.
This paper examines the influence of the proposed high-pressure spraying technique using metallic particles on the morphology of the resulting conductive paths, interface characteristics, and electrical parameters. Conductive paths were created on four different layers commonly used in photovoltaic systems, including transparent conductive oxide, Cu, Ti, and atomic layer deposition processed Al 2O 3. The use of high-pressure technology enables the production of conductive layers with strong adhesion to the substrate and precise control of the spatial parameters of conductive paths. Furthermore, the temperature recorded during the deposition process does not exceed 385 K, making this technique suitable for various types of substrates, including glass and silicon. Additionally, the produced layers exhibit low resistance, measuring less than 0.3Ω . Finally, the mechanical resistance, as determined through tearing tests, as well as environmental and time stability, have been confirmed for the produced paths.

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Authors and Affiliations

Paweł Kwaśnicki
1 2
Anna Gronba-Chyła
1
Agnieszka Generowicz
3
Józef Ciuła
4
Iwona Wiewiórska
5
Krzysztof Gaska
6

  1. John Paul II Catholic University of Lublin, Faculty of Natural and Technical Sciences, Konstantynów 1 H, 20-708 Lublin, Poland
  2. Research & Development Centre for Photovoltaics, ML System S.A., Zaczernie 190G, 36-062 Zaczernie, Poland
  3. Cracow University of Technology, Department of Environmental Technologies, Warszawska 24, 31-155 Cracow, Poland
  4. State University of Applied Sciences in Nowy Sacz, Faculty of Engineering Sciences, Zamenhofa 1A, 33-300 Nowy Sacz, Poland
  5. Sadeckie Wodociagi sp. z o.o., W. Pola 22, 33-300 Nowy Sacz, Poland
  6. Silesian University of Technology, Faculty of Energy and Environmental Engineering, Konarskiego 18, 44-100 Gliwice, Poland
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Abstract

The paper is of practical importance and describes the construction of a test rig and the measurement method for determining the relative emissivity coefficient of thermosensitive thin polymer coatings. Polymers are high-molecular chemical compounds that produce chains of repeating elements called ‘mers’. The polymers can be natural and artificial. The former ones form the building material for living organisms, the latter – for plastics. In this work, the words plastics and polymers are used as synonyms. Some plastics are thermosensitive materials with specific physical and chemical properties. The calorimetric method mentioned in the title consists of two steps. The first stage, described here, involves very accurately measuring the emissivity of black paint with the highest possible relative emissivity coefficient, which covers the surface of the heater and the inner surface of the chamber. In the second step, the thermosensitive polymer will be placed on the inner surface of the chamber, while black paint with a known emissivity coefficient will remain on the heater. Such a way of determining the properties of thermosensitive polymers will increase the error of the method itself, but at the same time will avoid melting of the polymer coating. During the tests, the results of which are presented in this work, the emissivity coefficient of the black paint was obtained in the range of 0.958–0.965.
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Authors and Affiliations

Ewa Pelińska-Olko
1

  1. Wrocław University of Science and Technology, Faculty of Mechanical and Power Engineering, Department of Thermodynamics and Renewable Energy Sources, Wybrzeze Wyspianskiego 27, 50-370 Wrocław, Poland
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Abstract

Thermal analysis of a heat and power plant with a high temperature gas cooled nuclear reactor is presented. The main aim of the considered system is to supply a technological process with the heat at suitably high temperature level. The considered unit is also used to produce electricity. The high temperature helium cooled nuclear reactor is the primary heat source in the system, which consists of: the reactor cooling cycle, the steam cycle and the gas heat pump cycle. Helium used as a carrier in the first cycle (classic Brayton cycle), which includes the reactor, delivers heat in a steam generator to produce superheated steam with required parameters of the intermediate cycle. The intermediate cycle is provided to transport energy from the reactor installation to the process installation requiring a high temperature heat. The distance between reactor and the process installation is assumed short and negligable, or alternatively equal to 1 km in the analysis. The system is also equipped with a high temperature argon heat pump to obtain the temperature level of a heat carrier required by a high temperature process. Thus, the steam of the intermediate cycle supplies a lower heat exchanger of the heat pump, a process heat exchanger at the medium temperature level and a classical steam turbine system (Rankine cycle). The main purpose of the research was to evaluate the effectiveness of the system considered and to assess whether such a three cycle cogeneration system is reasonable. Multivariant calculations have been carried out employing the developed mathematical model. The results have been presented in a form of the energy efficiency and exergy efficiency of the system as a function of the temperature drop in the high temperature process heat exchanger and the reactor pressure.
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Authors and Affiliations

Adam Fic
Jan Składzień
Michał Gabriel
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Abstract

Detailed studies have suggested that the critical heat flux in the form of dryout in minichannels occurs when the combined effects of entrainment, deposition, and evaporation of the film make the film flow rate go gradually and smoothly to zero. Most approaches so far used the mass balance equation for the liquid film with appropriate formulations for the rate of deposition and entrainment respectively. It must be acknowledged that any discrepancy in determination of deposition and entrainment rates, together with cross-correlations between them, leads to the loss of accuracy of model predictions. Conservation equations relating the primary parameters are established for the liquid film and vapor core. The model consists of three mass balance equations, for liquid in the film as well as two-phase core and the gas phase itself. These equations are supplemented by the corresponding momentum equations for liquid in the film and the two-phase core. Applicability of the model has been tested on some experimental data.

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Authors and Affiliations

Dariusz Mikielewicz
Jan Wajs
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Abstract

In the paper the influence of moisture content of wood on the heat losses and thermal efficiency of a boiler is analysed. The moisture content of wood has a negative effect, especially on flue gas loss. The mathematical dependence of the thermal efficiency of a boiler is presented for the following boundary conditions: the moisture content of wood 10–60%, range of temperatures of emitted flue gases from the boiler into the atmosphere 120–200 C, the emissions meeting the emission standards: carbon monoxide 250 mgm-3, fly ash 50 mgm-3and the heat power range 30–100%.

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Authors and Affiliations

Ladislav Dzurenda
Adrián Banski
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Abstract

In this work, a new dual-evaporator CO2transcritical refrigeration cycle with two ejectors is proposed. In this new system, we proposed to recover the lost energy of condensation coming off the gas cooler and operate the refrigeration cycle ejector free and enhance the system performance and obtain dual-temperature refrigeration simultaneously. The effects of some key parameters on the thermodynamic performance of the modified cycle are theoretically investigated based on energetic and exergetic analysis. The simulation results for the modified cycle indicate more effective system performance improvement than the single ejector in the CO2vapor compression cycle using ejector as an expander ranging up to 46%. The exergetic analysis for this system is made. The performance characteristics of the proposed cycle show its promise in dual-evaporator refrigeration system.

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Authors and Affiliations

Ezzaalouni Yathreb Abdellaoui
Lakdar Kairouani Kairouani
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Abstract

The interrelation between fuzzy logic and cluster renewal approaches for heat transfer modeling in a circulating fluidized bed (CFB) has been established based on a local furnace data. The furnace data have been measured in a 1296 t/h CFB boiler with low level of flue gas recirculation. In the present study, the bed temperature and suspension density were treated as experimental variables along the furnace height. The measured bed temperature and suspension density were varied in the range of 1131–1156 K and 1.93–6.32 kg/m3, respectively. Using the heat transfer coefficient for commercial CFB combustor, two empirical heat transfer correlation were developed in terms of important operating parameters including bed temperature and also suspension density. The fuzzy logic results were found to be in good agreement with the corresponding experimental heat transfer data obtained based on cluster renewal approach. The predicted bed-to-wall heat transfer coefficient covered a range of 109–241 W/(m2K) and 111–240 W/(m2), for fuzzy logic and cluster renewal approach respectively. The divergence in calculated heat flux recovery along the furnace height between fuzzy logic and cluster renewal approach did not exceeded ±2%.

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Authors and Affiliations

Artur Błaszczuk
Jarosław Krzywański
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Abstract

Calculations were performed of the thermal system of a power plant with installed water pressure tanks. The maximum rise in the block electric power resulting from the shut-off of low-pressure regenerative heaters is determined. At that time, the boiler is fed with hot water from water pressure tanks acting as heat accumulators. Accumulation of hot water in water tanks is also proposed in the periods of the power unit small load. In order to lower the plant electric power in the off-peak night hours, water heated in low-pressure regenerative heaters and feed water tank to the nominal temperature is directed to water pressure tanks. The water accumulated during the night is used to feed the boiler during the period of peak demand for electricity. Drops in the power block electric power were determined for different capacities of the tanks and periods when they are charged. A financial and economic profitability analysis (of costs and benefits) is made of the use of tanks for a 200 MW power unit. Operating in the automatic system of frequency and power control, the tanks may also be used to ensure a sudden increase in the electric power of the unit. The results of the performed calculations and analyses indicate that installation of water pressure tanks is well justified. The investment is profitable. Water pressure tanks may not only be used to reduce the power unit power during the off-peak night hours and raise it in the periods of peak demand, but also to increase the power capacity fast at any time. They may also be used to fill the boiler evaporator with hot water during the power unit start-up from the cold state.

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Authors and Affiliations

Jan Taler
Marcin Trojan
Dawid Taler
Piotr Dzierwa
Karol Kaczmarski
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Abstract

The main purpose of this article is to verify and validate the mathematical description of the airflow around a wind turbine with vertical axis of rotation, which could be considered as representative for this type of devices. Mathematical modeling of the airflow around wind turbines in particular those with the vertical axis is a problematic matter due to the complex nature of this highly swirled flow. Moreover, it is turbulent flow accompanied by a rotation of the rotor and the dynamic boundary layer separation. In such conditions, the key aspects of the mathematical model are accurate turbulence description, definition of circular motion as well as accompanying effects like centrifugal force or the Coriolis force and parameters of spatial and temporal discretization. The paper presents the impact of the different simulation parameters on the obtained results of the wind turbine simulation. Analysed models have been validated against experimental data published in the literature.
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Authors and Affiliations

Andrzej J. Nowak
Tomasz Krysiński
Zbigniew Buliński
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Abstract

The article presents the results of thermodynamic analysis of the supercritical coal-fired power plant with gross electrical output of 900 MW and a pulverized coal boiler. This unit is integrated with the absorption-based CO2separation installation. The heat required for carrying out the desorption process, is supplied by the system with the gas turbine. Analyses were performed for two variants of the system. In the first case, in addition to the gas turbine there is an evaporator powered by exhaust gases from the gas turbine expander. The second expanded variant assumes the application of gas turbine combined cycle with heat recovery steam generator and backpressure steam turbine. The way of determining the efficiency of electricity generation and other defined indicators to assess the energy performance of the test block was showed. The size of the gas turbine system was chosen because of the need for heat for the desorption unit, taking the value of the heat demand 4 MJ/kg CO2. The analysis results obtained for the both variants of the installation with integrated CO2separation plant were compared with the results of the analysis of the block where the separation is not conducted.
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Authors and Affiliations

Janusz Kotowicz
Łukasz Bartela
Mikosz Dorota
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Abstract

This paper describes the simulation, exergy analysis and comparison of two commonly applied liquefaction of technologies natural gas, namely: propane precooled mixed refrigerant process (C3MR) and dual mixed refrigerant process (DMR) alongside two modifications of each employing end flash systems. The C3MR and DMR process schemes were simulated using the commercial software to mathematically model chemical processes. These schemes were then analysed using energy and exergy calculations to determine their performances. The exergy efficiency for the C3MR processes without end flash system, with simple end flash system and extended end flash system were evaluated as 29%, 31%, and 33%, respectively, while the exergy efficiency for the DMR processes without end flash system, with simple end flash system, and extended end flash system were evaluated as 26%, 25.5%, and 30%, respectively. The results achieved show that the extended end flash system versions of the schemes are most efficient. Furthermore, the exergy analysis depicted that the major equipment that must be enhanced in order to improve the cycle exergy efficiencies are the compressors, heat exchangers, and coolers.

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Authors and Affiliations

Oluwagbemisola Akinsipe
Ambrose Anozie
Damilola Babatunde
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Abstract

The dynamic process of the interaction between a turbulent jet diffusion methane flame and a lateral wall was experimentally studied. The evolution of the flame temperature field with the Nitrogen dilution of the methane jet flame was examined. The interaction between the diffusion flame and the lateral wall was investigated for different distance between the wall and the central axes of the jet flame. The dilution is found to play the central role in the flame extinction process. The flame response as the lateral wall approaches from infinity and the increasing of the dilution rate make the flame extinction more rapid than the flame without dilution, when the nitrogen dilution rate increase the flame temperature decrease.
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Authors and Affiliations

Nadjib Ghiti
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Abstract

The theory of generalized two-temperature thermoelasticity is used to solve the boundary value problems between two elastic media with two different types of temprature under the influence of gravity.The classical dynamical coupled theory and Lord-Şhulman theory are used to obtain the general solution of the governing equations and investigate the effect of surface waves in an isotropic elastic medium subjected to gravity field. The harmonic vibrations method is used to obtain the displacement components, stress tensor and temperature distribution in the considerd physical domain with comparison with the two theories. The obtained analytic solution of the problem is applied for special cases for which the effect of two temperatures is studied. The conductive and dynamical temperatures as well as stress and strain components are shown graphically for a suitable material. Some comparisons are also introduced in the absence and in the presence of gravity, and two-temperature parameter. The differences in the obtained results between the two theories are considered.

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Authors and Affiliations

Khaled Lotfy
Mahmoud Gabr
Alaa Abd El-bary
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Abstract

In the present research, an experimental investigation was conducted to assess the heat transfer coefficient of aqueous citric acid mixtures. The experimental facility provides conditions to assess the influence of various operating conditions such as the heat flux (0–190 kW/m2), mass flux (353–1059 kg/m2s) and the concentration of citric acid in water (10%– 50% by volume) with a view to measure the subcooled flow boiling heat transfer coefficient of the mixture. The results showed that two main heat transfer mechanisms can be identified including the forced convective and nucleate boiling heat transfer. The onset point of nucleate boiling was also identified, which separates the forced convective heat transfer domain from the nucleate boiling region. The heat transfer coefficient was found to be higher in the nucleate boiling regime due to the presence of bubbles and their interaction. Also, the influence of heat flux on the heat transfer coefficient was more pronounced in the nucleate boiling heat transfer domain, which was also attributed to the increase in bubble size and rate of bubble formation. The obtained results were also compared with those theoretically obtained using the Chen type model and with some experimental data reported in the literature. Results were within a fair agreement of 22% against the Chen model and within 15% against the experimental data.

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Authors and Affiliations

Mohammad Amin Abdolhossein Zadeh
Shima Nakhjavani

Abstract

The Bulletin of the Polish Academy of Sciences: Technical Sciences (Bull.Pol. Ac.: Tech.) is published bimonthly by the Division IV Engineering Sciences of the Polish Academy of Sciences, since the beginning of the existence of the PAS in 1952. The journal is peer‐reviewed and is published both in printed and electronic form. It is established for the publication of original high quality papers from multidisciplinary Engineering sciences with the following topics preferred: Artificial and Computational Intelligence, Biomedical Engineering and Biotechnology, Civil Engineering, Control, Informatics and Robotics, Electronics, Telecommunication and Optoelectronics, Mechanical and Aeronautical Engineering, Thermodynamics, Material Science and Nanotechnology, Power Systems and Power Electronics.

Journal Metrics: JCR Impact Factor 2018: 1.361, 5 Year Impact Factor: 1.323, SCImago Journal Rank (SJR) 2017: 0.319, Source Normalized Impact per Paper (SNIP) 2017: 1.005, CiteScore 2017: 1.27, The Polish Ministry of Science and Higher Education 2017: 25 points.

Abbreviations/Acronym: Journal citation: Bull. Pol. Ac.: Tech., ISO: Bull. Pol. Acad. Sci.-Tech. Sci., JCR Abbrev: B POL ACAD SCI-TECH Acronym in the Editorial System: BPASTS.

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Abstract

Flow mechanism under roughened solar air heater is quite complex. This paper is an effort towards determining the governing equations for heat transfer and friction factor for inclined spherical balls roughened ducts. With the availability of these equations, it is easier to predict the thermal and thermohydraulic performance of such roughened solar air heaters. The governing equations are derived based on the experimental data generated under actual outdoor condition at the test rig designed and fabricated at the terrace of the Mechanical Engineering Department, the National Institute of Technology Jamshedpur in India, in terms of roughness and flow parameters. Maximum augmentation in Nusselt number and friction factor for varying relative roughness pitch, relative roughness height, spherical ball height to diameter ratio, and angle of attack was respectively found to be of the order of 2.1 to 3.54 times, 1.87 to 3.21 times, 2.89 to 3.27 times and 1.74 to 3.56 times for Nusselt number and 0.84 to 1.79 times, 1.46 to 1.91 times, 1.67 to 2.34 times and 1.21 to 2.67 times for friction factor in comparison to non-roughened duct. The optimum roughness parameters under present investigation have been found.

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Authors and Affiliations

Ramesh Murmu
Parmanand Kumar
Hari N. Singh

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