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Processes
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Experimental and Numerical Methods in Fluid Mechanics and Energy
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Experimental and Numerical Methods in Fluid Mechanics and Energy

A special issue of Processes (ISSN 2227-9717). This special issue belongs to the section "Energy Systems".

Deadline for manuscript submissions: closed (15 March 2022) | Viewed by 36659

Special Issue Editors

Dr. Richard Lenhard

E-Mail Website
Guest Editor
Associate Professor, Faculty of Mechanical Engineering, Department of Power Engineering, University of Žilina in Žilina, Univerzitná 8215/1, 010 26 Žilina, Slovakia
Interests: natural convection; forced convection; phase change (heat pipes) and the development of their numerical models for simulation in the program Ansys Fluent
Special Issues, Collections and Topics in MDPI journals
Prof. Dr. Milan Malcho

E-Mail Website
Guest Editor
Department of Power Engineering, University of Žilina, 010 26 Žilina, Slovakia
Interests: thermodynamics; experimental methods; applied physics; low-temperature plasma; corona discharge in flowing air; energy machinery and equipment, physics, heat pipes; renewable energy; heat recovery from technological processes; heat transfer; gas flow visualization; numerical methods for solving gas flow
Dr. Peter Durcansky

E-Mail Website
Guest Editor
Department of Energy Technology, University of Žilina, 010 26 Žilina, Slovakia
Interests: heat and mass transfer; thermodynamics; energy system modelling; sustainability
Special Issues, Collections and Topics in MDPI journals
Prof. Dr. Jozef Jandačka

E-Mail Website
Guest Editor
Department of Power Engineering, Faculty of Mechanical Engineering, University of Žilina, Univerzitna 1, 010 26 Žilina, Slovakia
Interests: energy machines and equipment; transport machines and equipment design; experimental determination of bed temperatures during wood pellet combustion; analysis of paper sludge pellets for energy utilization and fuel change possibilities in small heat sources
Special Issues, Collections and Topics in MDPI journals
Dr. Patrik Nemec

E-Mail Website
Guest Editor
Department of Power Engineering, University of Zilina, Univerzitná 8515/1, 010 26 Zilina, Slovakia
Interests: heat and mass transfer; thermomechanics; fluid mechanics; heating and ventilation; experimental measurements of energy machines and equipment

Special Issue Information

Dear Colleagues,

The International Scientific Conference on Application of Experimental and Numerical Methods in Fluid Mechanics and Energy 2020 (XXII. AENMFME-2020) took place at Hotel Magnólia – Piešťany, Slovakia on 07-09 October 2020. 

The aim of the international conference was to bring together researchers, designers, experimenters, modellers, and numerical analysts from laboratories, industry, and academia working in the field of two-phase and multiphase flow and experimental methods used in the field of fluid mechanics, thermodynamics, and energy. 

The international conference covers all topics in the measurement and calculation of state variables in the fluid flow, modelling, and simulation in fluid mechanics and energy, optimization of flow parameters in thermal and hydraulic machines and systems, the application of the latest knowledge in the field of fluid mechanics and energy in technical practice, flow visualization, measurement of the energy systems and systems, special experimental methods in fluid mechanics and energy, renewable energy, current problems in the energy sector. 

The conference should contribute to the establishment closer contacts, presentations on the latest knowledge, exchange of experience in the application of different experimental methods, preparation and implementation experiments, results processing and numerical simulations of experiments. 

The Special Issue “The Application of Experimental and Numerical Methods in Fluid Mechanics and Energy 2020” aims to include extended papers from the conference. Topics include but are not limited to the following:  

  • Measurement and calculation of state variables in the fluid flow
  • Modelling and simulation in fluid mechanics and energy
  • Optimization of flow parameters in the thermal and hydraulic machines and systems
  • Application of latest developments in the field of fluid mechanics and energy in technical practice
  • Visualization of flow
  • Measurement of energy systems and systems
  • Special experimental methods in fluid mechanics and energy
  • Renewable energy
  • Current problems in the energy

Dr. Richard Lenhard
Prof. Dr. Milan Malcho
Dr. Peter Durcansky
Prof. Dr. Jozef Jandačka
Dr. Patrik Nemec
Guest Editors

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Processes is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2400 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • Modelling and simulation
  • energy
  • visualization of flow
  • PIV method
  • heat exchanger
  • combustion
  • cavitation

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Published Papers (15 papers)

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Research

22 pages, 6469 KiB  
Article
Hot-Wire Investigation of Turbulence Topology behind Blades at Different Shape Qualities
by Vitalii Yanovych, Daniel Duda, Václav Uruba and Tetjana Tomášková
Processes 2022, 10(3), 522; https://doi.org/10.3390/pr10030522 - 5 Mar 2022
Cited by 10 | Viewed by 2739
Abstract
The scope of this paper is to perform a detailed experimental investigation of the shape error effect on the turbulence evolution behind NACA 64-618 airfoil. This airfoil is 3D-printed with predefined typical shape inaccuracies. A high-precision optical 3D scanner was used to assess [...] Read more.
The scope of this paper is to perform a detailed experimental investigation of the shape error effect on the turbulence evolution behind NACA 64-618 airfoil. This airfoil is 3D-printed with predefined typical shape inaccuracies. A high-precision optical 3D scanner was used to assess the shape and surface quality of the manufactured models. The turbulent flow was studied using hot-wire anemometry. The developed force balance device was provided to measure the aerodynamic characteristics of the airfoil. Experimental studies were carried out for three angles of attack, +10∘, 0∘, −10∘, and different chord-based Reynolds numbers from 5.3×104 to 2.1×105. The obtained results show that the blunt trailing edge and rough surface decline the aerodynamic performance of the blades. In addition, the experimental results revealed a strong sensitivity of the Taylor microscale Reynolds number to the type of shape inaccuracy, especially at Re≈1.7×105. We also discuss the evolution of the Reynolds stress components, the degree of flow anisotropy, and the power spectrum distributions depending on the airfoil inaccuracies. Full article
(This article belongs to the Special Issue Experimental and Numerical Methods in Fluid Mechanics and Energy)
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14 pages, 2446 KiB  
Article
Effects of a Single Blade Incidence Angle Offset on Adjacent Blades in a Linear Cascade
by Jiří Fürst, Martin Lasota, Jan Lepicovsky, Josef Musil, Jan Pech, Petr Šidlof and David Šimurda
Processes 2021, 9(11), 1974; https://doi.org/10.3390/pr9111974 - 4 Nov 2021
Cited by 7 | Viewed by 2337
Abstract
The paper presents a numerical and experimental investigation of the effect of incindence angle offset in a two-dimensional section of a flat blade cascade in a high-speed wind tunnel. The aim of the current work is tp determine the aerodynamic excitation forces and [...] Read more.
The paper presents a numerical and experimental investigation of the effect of incindence angle offset in a two-dimensional section of a flat blade cascade in a high-speed wind tunnel. The aim of the current work is tp determine the aerodynamic excitation forces and approximation of the unsteady blade-loading function using a quasi-stationary approach. The numerical simulations were performed with an in-house finite-volume code built on the top of the OpenFOAM framework. The experimental data were acquired for regimes corresponding to the numerical setup. The comparison of the computational and experimental results is shown for the static pressure distributions on three blades and upstream and downstream of the cascade. The plot of the aerodynamic moments acting on all five blades shows that the adjacent blades are significantly influenced by the angular offset of the middle blade. Full article
(This article belongs to the Special Issue Experimental and Numerical Methods in Fluid Mechanics and Energy)
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14 pages, 4171 KiB  
Article
Flow of Oil and Water through the Nozzle and Cavitation
by Jana Jablonská, Milada Kozubková and Marian Bojko
Processes 2021, 9(11), 1936; https://doi.org/10.3390/pr9111936 - 28 Oct 2021
Cited by 4 | Viewed by 2732
Abstract
Today, the correct understanding of the issue of oil and water cavitation is important due to the growing demands on working conditions in hydraulic systems (pressure and flow rate). This article deals with the measurement and subsequent mathematical modeling of cavitation in a [...] Read more.
Today, the correct understanding of the issue of oil and water cavitation is important due to the growing demands on working conditions in hydraulic systems (pressure and flow rate). This article deals with the measurement and subsequent mathematical modeling of cavitation in a convergent-divergent nozzle of circular cross-section. Cavitation depends on the physical properties of the flowing medium as a function of temperature. Usually, cavitation in water is defined by a two-phase flow of water and vapor, but the air contained in the water significantly affects cavitation. There is usually no vapor cavitation in the oil. Far more often, cavitation in oil is caused by the air it contains. For comparison, cavitation in water and oil was generated in experiments with an identical nozzle. The measurement was used to define boundary conditions in mathematical models and to verify simulations. The problem of cavitation was solved by three variants of multiphase flow, single-phase flow (water, oil), two-phase flow (water–vapor, oil–air) and three-phase flow (water–vapor–air, oil–vapor–air). A turbulent model with cavitation was used for all variants. The verification of simulations shows that for water cavitation it is necessary to use a three-phase model (water, vapor, air) and for oil cavitation a two-phase model (oil, air) is sufficient. The measurement results confirm the importance of the air phase in modeling cavitation in both water and oil. Full article
(This article belongs to the Special Issue Experimental and Numerical Methods in Fluid Mechanics and Energy)
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14 pages, 2559 KiB  
Article
Numerical Simulation and Experimental Validation of Melt Flow in the Naturally Pressurized Gating System
by Marek Brůna, Iveta Vasková and Marek Galčík
Processes 2021, 9(11), 1931; https://doi.org/10.3390/pr9111931 - 28 Oct 2021
Cited by 3 | Viewed by 2043
Abstract
The main problem during the production of castings from aluminium alloys is the presence of the reoxidation, which negatively affects the final casting quality. Liquid metal surface reacts with the surrounding atmosphere and oxide layer of Al2O3 is formed on [...] Read more.
The main problem during the production of castings from aluminium alloys is the presence of the reoxidation, which negatively affects the final casting quality. Liquid metal surface reacts with the surrounding atmosphere and oxide layer of Al2O3 is formed on its surface. The problem occurs when the oxide layer is entrained to the internal volume of the melt by turbulence and double oxide layers are formed, also known as “bifilms”. Its formation is related to the melt velocity and gating system design. In paper, naturally pressurized gating system was calculated and designed. Effect of the filter media and vortex element on the melt velocity, amount of oxides, mechanical properties, and porosity were observed. Designs with 10 ppi and 20 ppi foam filters and vortex element were compared with design without filters to prove the positive (or negative) effect of filter media on melt velocity and thus on final casting quality. The melt velocity and amount of oxides were observed with the aid of simulation software. Mechanical properties, quantity of pores, bifilm index and EDX analysis were evaluated after experimental casts. It was proven that by using 20 ppi foam filter in combination with vortex element, the best results were achieved. Full article
(This article belongs to the Special Issue Experimental and Numerical Methods in Fluid Mechanics and Energy)
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16 pages, 75073 KiB  
Article
Research of Flow Stability of Non-Newtonian Magnetorheological Fluid Flow in the Gap between Two Cylinders
by Milada Kozubková, Jana Jablonská, Marian Bojko, František Pochylý and Simona Fialová
Processes 2021, 9(10), 1832; https://doi.org/10.3390/pr9101832 - 15 Oct 2021
Viewed by 2170
Abstract
This paper deals with a mathematical modeling of flow stability of Newtonian and non-Newtonian fluids in the gap between two concentric cylinders, one of which rotates. A typical feature of the flow is the formation of a vortex flow, so-called Taylor vortices. Vortex [...] Read more.
This paper deals with a mathematical modeling of flow stability of Newtonian and non-Newtonian fluids in the gap between two concentric cylinders, one of which rotates. A typical feature of the flow is the formation of a vortex flow, so-called Taylor vortices. Vortex structures are affected by the speed of the rotating cylinder and the physical properties of the fluids, i.e., viscosity and density. Analogy in terms of viscosity is assumed for non-Newtonian and magnetorheological fluids. Mathematical models of laminar, transient and turbulent flow with constant viscosity and viscosity as a function of the deformation gradient were formulated and numerically solved to analyze the stability of single-phase flow. To verify them, a physical experiment was performed for Newtonian fluids using visualizations of vortex structures—Taylor vortices. Based on the agreement of selected numerical and physical results, the experience was used for numerical simulations of non-Newtonian magnetorheological fluid flow. Full article
(This article belongs to the Special Issue Experimental and Numerical Methods in Fluid Mechanics and Energy)
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16 pages, 6561 KiB  
Article
Experimental Evaluation of Axial Reaction Turbine Stage Bucket Losses
by Marek Klimko, Richard Lenhard, Pavel Žitek and Katarína Kaduchová
Processes 2021, 9(10), 1816; https://doi.org/10.3390/pr9101816 - 13 Oct 2021
Cited by 7 | Viewed by 1582
Abstract
The article describes the measurement methods and data evaluation from a single-stage axial turbine with high reaction (50%). Four operating modes of the turbine were selected, in which the wake traversing behind nozzle and bucket with five-hole pneumatic probes took place. The article [...] Read more.
The article describes the measurement methods and data evaluation from a single-stage axial turbine with high reaction (50%). Four operating modes of the turbine were selected, in which the wake traversing behind nozzle and bucket with five-hole pneumatic probes took place. The article further focuses on the evaluation of bucket losses for all four measured operating modes, including the analysis of measurement uncertainties. Full article
(This article belongs to the Special Issue Experimental and Numerical Methods in Fluid Mechanics and Energy)
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8 pages, 2888 KiB  
Article
Possible Limitations of the Particle Image Velocimetry Method in the Presence of Strong Electric Fields
by Michal Malík, Jiří Primas, Petr Schovanec, Josef Novák, Pavel Pokorný and Filip Sanetrník
Processes 2021, 9(10), 1790; https://doi.org/10.3390/pr9101790 - 9 Oct 2021
Cited by 1 | Viewed by 1745
Abstract
While examining the airflow generated between the asymmetrical electrodes connected to high voltage, the authors investigated the possible limitations of the particle image velocimetry (PIV) method in the presence of strong electric fields. The tracer particles used in the PIV method in these [...] Read more.
While examining the airflow generated between the asymmetrical electrodes connected to high voltage, the authors investigated the possible limitations of the particle image velocimetry (PIV) method in the presence of strong electric fields. The tracer particles used in the PIV method in these conditions are affected by electromagnetic forces; therefore, it is necessary to determine whether these forces have any non-negligible negative influence on the measurement results. For this purpose, the authors theoretically analyzed all the possible forces and measured the generated airflow using PIV and constant temperature anemometry methods. The experimental and theoretical results clearly show the viability of the PIV measurement method even in these very specific conditions. Full article
(This article belongs to the Special Issue Experimental and Numerical Methods in Fluid Mechanics and Energy)
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13 pages, 4063 KiB  
Article
Photolithographically Home-Made PVDF Sensor for Cavitation Impact Load Measurement
by Jan Hujer, Petra Dančová, Tomáš Kořínek and Miloš Müller
Processes 2021, 9(10), 1761; https://doi.org/10.3390/pr9101761 - 30 Sep 2021
Cited by 3 | Viewed by 2085
Abstract
Piezoelectric PVDF sensors offer a unique option for the measurement of cavitation aggressiveness represented by the magnitude of impacts due to cavitation bubble collapses near walls. The aggressiveness measurement requires specific sensor shape and area, whereas commercial PVDF sensors are fabricated in limited [...] Read more.
Piezoelectric PVDF sensors offer a unique option for the measurement of cavitation aggressiveness represented by the magnitude of impacts due to cavitation bubble collapses near walls. The aggressiveness measurement requires specific sensor shape and area, whereas commercial PVDF sensors are fabricated in limited geometry and size ranges. The photolithography method offers a possibility of production of home-made PVDF sensors of arbitrary shape and size. The methodology of a unique application of the standard photolithography method, which is commonly used for the production of printed circuit boards, is described in this paper. It enables mass production of high quality sensors contrary to laboratory techniques. This paper deals with the fabrication and the calibration of a photolithographically home-made PVDF sensor for the cavitation impact load measurement. The calibration of sensors was carried out by the ball drop method. Sensors of different sizes were fabricated by the photolithography method from a multi-purpose, both side metallized PVDF sheet. Commercial PVDF sensors of the same size were calibrated, and the calibration results were compared with the home-made sensors. The effect of size and the effect of one added protective layer of Kapton tape on a sensor sensitivity were investigated. The theoretical and numerical analysis was conducted to explain some issues during the ball impact. Full article
(This article belongs to the Special Issue Experimental and Numerical Methods in Fluid Mechanics and Energy)
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13 pages, 4975 KiB  
Article
Numerical Simulation of the Effect of Different Numbers of Inlet Nozzles on Vortex Tubes
by Qijun Xu and Jing Xie
Processes 2021, 9(9), 1531; https://doi.org/10.3390/pr9091531 - 28 Aug 2021
Cited by 4 | Viewed by 2325
Abstract
In order to broaden the application of vortex tubes (VOTU) in industry and to improve the efficiency of cooling and heating, numerical simulations of vortex tubes were carried out. In this study, the temperature, velocity, and pressure fields of three VOTUs with inlet [...] Read more.
In order to broaden the application of vortex tubes (VOTU) in industry and to improve the efficiency of cooling and heating, numerical simulations of vortex tubes were carried out. In this study, the temperature, velocity, and pressure fields of three VOTUs with inlet nozzles of 2, 3, and 6 were investigated at different inlet pressures based on previous experimental data and by three-dimensional numerical simulation. It was found that the increase of inlet pressure leads to the increase of energy separation between the hot and cold ends of the three VOTUs. As the number of inlets increases, the pressure difference between the tube wall and the core region gradually strengthens. In contrast, the pressure in the tube center is not affected by the inlet pressure. The number of nozzles affects the inlet and outlet temperatures of the VOTU. When the number of nozzles is 3, and the inlet pressure is 0.6 MPa, the VOTU shows the maximum hot and cold outlet temperature difference of 66 K. The maximum velocity of VOTU appears at the connection of the inlet and vortex chamber, so the inlet is tangential to VOTU, which is beneficial to reduce the loss of gas energy. The wall thickness of the inlet increases gradually to avoid the high-speed gas flow on the erosion of the wall surface. This study has profound guidance for the one-dimensional design of VOTUs. Full article
(This article belongs to the Special Issue Experimental and Numerical Methods in Fluid Mechanics and Energy)
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14 pages, 3012 KiB  
Article
Experimental Simulation of Hydrate Formation Process in a Circulating Device
by Dávid Hečko, Pavol Mičko, Michal Holubčík and Andrej Kapjor
Processes 2021, 9(9), 1529; https://doi.org/10.3390/pr9091529 - 28 Aug 2021
Cited by 2 | Viewed by 2174
Abstract
This paper focuses on the model of gas hydrate formation in an experimental device, which allows the circulation of the resulting mixture (water and gas) and significantly accelerates the process of hydrate formation in the laboratory. A 3D model was developed to better [...] Read more.
This paper focuses on the model of gas hydrate formation in an experimental device, which allows the circulation of the resulting mixture (water and gas) and significantly accelerates the process of hydrate formation in the laboratory. A 3D model was developed to better imagine the placement of individual parts of the device. The kinetics of hydrate formation were predicted from equilibrium values of chemical potentials. The aim of solving the equations of state gases in the mathematical model was to optimize the parameters involved in the formation of hydrates. The prediction of the mathematical model was verified by numerical simulation. The mathematical model and numerical simulation predict the chemical reaction evolving over time and determine the amount of crystallized water in the reactor. A remarkable finding is that the deviation of the model and simulation at the initiation the calculation of crystallized water starts at 76% and decreases over time to 2%. Subsequently, the number of moles of bound gas in the hydrate acquires the same percentage deviations. The amount of water supplied to the reactor is expressed by both methods identically with a maximum deviation of 0.10%. The different character is shown by the number of moles of gas remaining in the reactor. At the beginning of the calculation, the deviation of both methods is 0%, but over time the deviation slowly increases, and at the end it expresses the number of moles in the reactor with a deviation of 0.14%. By previous detection, we can confirm that the model successfully determines the amount of methane hydrate formed in the reactor of the experimental equipment. With the attached pictures from the realized experiment, we confirmed that the proposed method of hydrate production is tested and takes minutes. The article calculates the energy efficiency of natural gas hydrate in the proposed experimental device. Full article
(This article belongs to the Special Issue Experimental and Numerical Methods in Fluid Mechanics and Energy)
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22 pages, 9847 KiB  
Article
Numerical Simulation of Passive Cooling Beam and Its Optimization to Increase the Cooling Power
by Katarína Kaduchová and Richard Lenhard
Processes 2021, 9(8), 1478; https://doi.org/10.3390/pr9081478 - 23 Aug 2021
Cited by 4 | Viewed by 2497
Abstract
This article is focused on the research of passive cooling beams and increasing their cooling capacity. A passive cooling beam with four tubes was chosen as a model. A mathematical model was built using the corresponding criterion equations to capture the behavior of [...] Read more.
This article is focused on the research of passive cooling beams and increasing their cooling capacity. A passive cooling beam with four tubes was chosen as a model. A mathematical model was built using the corresponding criterion equations to capture the behavior of a passive cooling beam. This mathematical model can be used to optimize geometrical parameters (the distance between the ribs, rib height and thickness, and diameter and number of tubes), by changing these geometric parameters we can increase the cooling performance. The work includes a mathematical model for calculating the boundary layer, which has a significant influence on the cooling performance. The results obtained from the created mathematical model show that the model works correctly and can be used to optimize the cooling performance of passive cooling beams. To better understand the behavior of a passive cooling beam in a confined space, the entire device was numerically simulated, as was the flow in the intercostal space. Full article
(This article belongs to the Special Issue Experimental and Numerical Methods in Fluid Mechanics and Energy)
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21 pages, 9843 KiB  
Article
The Effect of Load Control on the Performance of Contra-Rotating Fans
by Xi Zhang, Xingyu Jia and Xuan Jiang
Processes 2021, 9(7), 1227; https://doi.org/10.3390/pr9071227 - 16 Jul 2021
Cited by 2 | Viewed by 2309
Abstract
In recent years, few studies focused on adjusting the load distribution of contra-rotating fan (CRF) blades. To improve the overall performance of CRFs, we used a design code to build 32 sets of CRFs to determine the effects of three factors—the front and [...] Read more.
In recent years, few studies focused on adjusting the load distribution of contra-rotating fan (CRF) blades. To improve the overall performance of CRFs, we used a design code to build 32 sets of CRFs to determine the effects of three factors—the front and rear rotor load matching, the load distribution of each rotor and the axial distance between the rotors—on the total pressure rise and efficiency of CRFs using numerical calculations. The relationship between the CRF blades load and velocity components was theoretically analyzed using blade element analysis and the forward problem method. According to the performance curve, it can be concluded that the rear rotor (RR) is the key factor that determines the performance of CRFs. Through analyzing Mach number contours from different perspectives, the relationship between velocity and adjustment load was verified. Furthermore, the flow field characteristics for three specific CRFs were explored at the stall points, design points and choke points to reveal their flow mechanisms. This study provides a reference for the CRF blade design method. Full article
(This article belongs to the Special Issue Experimental and Numerical Methods in Fluid Mechanics and Energy)
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11 pages, 2613 KiB  
Article
Experimental Verification of CFD Simulation When Evaluating the Operative Temperature and Mean Radiation Temperature for Radiator Heating and Floor Heating
by Pavol Mičko, Andrej Kapjor, Michal Holubčík and Dávid Hečko
Processes 2021, 9(6), 1041; https://doi.org/10.3390/pr9061041 - 15 Jun 2021
Cited by 9 | Viewed by 3145
Abstract
The assessment of heating systems is not only interested in the efficiency of the heating system itself, but also in the quality of the environment that the heating system creates. The quality of the environment and the heat-humidity microclimate is closely related to [...] Read more.
The assessment of heating systems is not only interested in the efficiency of the heating system itself, but also in the quality of the environment that the heating system creates. The quality of the environment and the heat-humidity microclimate is closely related to thermal comfort. A suitable environment has a positive effect, for example, on the efficiency of work at the workplace. The range of temperatures, humidity and operating temperatures in workplaces is often also legally prescribed in such a way that there is no thermal discomfort for users in the heated space. In terms of savings, it is therefore best to use heating systems that can create a comfortable environment with the lowest possible energy costs. During their development, variations are possible with temperature gradients, the size of the heat exchange area, or the ratio of the radiant and convective components of heat transfer. When developing such systems, it is appropriate to consider CFD simulations. The comparison of the results of CFD simulation and experimental measurement is also in the following article, where the comparison of the operating temperature and the mean radiation temperature of two different heating systems in the model office is monitored. Full article
(This article belongs to the Special Issue Experimental and Numerical Methods in Fluid Mechanics and Energy)
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10 pages, 1173 KiB  
Article
A Similarity Model of the Cooling Process of Fluids during Transportation
by Tomáš Brestovič, Mária Čarnogurská, Miroslav Příhoda, Marián Lázár, René Pyszko and Natália Jasminská
Processes 2021, 9(5), 802; https://doi.org/10.3390/pr9050802 - 3 May 2021
Cited by 2 | Viewed by 1569
Abstract
This article presents a description of a novel method for the identification of a decrease in the temperature of a liquid medium transported by railroad tank cars. No exact analytical solution exists for this phenomenon; therefore, the authors of this article have prepared [...] Read more.
This article presents a description of a novel method for the identification of a decrease in the temperature of a liquid medium transported by railroad tank cars. No exact analytical solution exists for this phenomenon; therefore, the authors of this article have prepared a mathematical expression for the cooling process of the transported fluid by applying a dimensional analysis, which facilitated the identification of the dimensionless criteria using the relevant dimensional parameters. A functional dependence between the criteria can be identified through a physical or numerical experiment. In this case, a database of the results from a detailed numerical model was used; however, its disadvantage is that the calculation takes much longer than in a simpler similarity model. The output of the similarity model was a function of the average temperature of the fluid at a time applicable to various alternatives in the geometrical, physical, and boundary conditions. The standard deviation of the difference between the temperatures predicted by the similarity model and those calculated by the numerical simulation Tmod − Tsim represented 4.8% relative to the simulated fluid temperature. Full article
(This article belongs to the Special Issue Experimental and Numerical Methods in Fluid Mechanics and Energy)
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17 pages, 5592 KiB  
Article
Analysis of the Heat Balance of a Metal Hydride Separator Used for the Separation of Hydrogen from Syngas
by Tomáš Brestovič, Marián Lázár, Natália Jasminská, Jozef Živčák, Lukáš Tóth, Romana Dobáková, Filip Duda, Ľubomíra Kmeťová and Ľubomíra Bednárová
Processes 2021, 9(2), 251; https://doi.org/10.3390/pr9020251 - 29 Jan 2021
Cited by 4 | Viewed by 2259
Abstract
The present article discusses the potential for hydrogen separation using a metal hydride separator, which facilitates the generation of hydrogen contained in syngas following the thermal recovery of wastes. The article provides a detailed description of the separator heat balance using analytical calculations [...] Read more.
The present article discusses the potential for hydrogen separation using a metal hydride separator, which facilitates the generation of hydrogen contained in syngas following the thermal recovery of wastes. The article provides a detailed description of the separator heat balance using analytical calculations and optimised calculations, and by applying numerical methods. The proposed concept of a separator intended for hydrogen separation from syngas offers a solution to a problem associated with the use of metal hydride alloy powders; in particular, their low thermal conductivity. In order to eliminate big temperature differences in the alloy, a heat transfer intensifier was implemented in the metal hydride alloy volume; the intensifier was made of metal and exhibited high thermal conductivity. For the purpose of comparing the thermal fields, the first stage comprised the creation of a numerical simulation of hydrogen absorption without the use of an intensifier. Subsequently, three different geometries were created for an intensifier intended to remove heat from the metal hydride alloy powder towards the separator cover, and the effects of these three geometries were analysed. The implementation of heat transfer intensifiers into the metal hydride alloy powder improved the heat removal by as much as 43.9% and increased the thermal field homogeneity by 77%. A result of the heat removal optimisation was an increase in the hydrogen absorption kinetics and the efficiency of the separator operation. Full article
(This article belongs to the Special Issue Experimental and Numerical Methods in Fluid Mechanics and Energy)
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