Applied sciences

Archives of Thermodynamics

Content

Archives of Thermodynamics | 2023 | vol. 44 | No 2

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Abstract

As the cost of fuel rises, designing efficient solar air heaters (SAH) becomes increasingly important. By artificially roughening the absorber plate, solar air heaters’ performance can be augmented. Turbulators in different forms like ribs, delta winglets, vortex generators, etc. have been introduced to create local wall turbulence or for vortex generation. In the present work, a numerical investigation on a solar air heater has been conducted to examine the effect of three distinct turbulators (namely D-shaped, reverse D- and U-shaped) on the SAH thermo-hydraulic performance. The simulation has been carried out using the computational fluid dynamics, an advanced and modern simulation technique for Reynolds numbers ranging from 4000 to 18000 (turbulent airflow). For the purpose of comparison, constant ratios of turbulator height/hydraulic diameter and pitch/turbulator height, of 0.021 and 14.28, respectively, were adopted for all SAH configurations. Furthermore, the fluid flow has also been analyzed using turbulence kinetic energy and velocity contours. It was observed that the U-shaped turbulator has the highest value of Nusselt number followed by D-shaped and reverse D-shaped turbulators. However, in terms of friction factor, the D-shaped configuration has the highest value followed by reverse D-shaped and U-shaped geometries. It can be concluded that among all SAH configurations considered, the U-shaped has outperformed in terms of thermohydraulic performance factor.
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Authors and Affiliations

Abhishek Ghildyal
1
Vijay Singh Bisht
1
Prabhakar Bhandari
2
Kamal Singh Rawat
3

  1. Veer Madho Singh Bhandari Uttarakhand Technical University, Faculty of Technology, Dehradun 248007, India
  2. K.R. Mangalam University, School of Engineering and Technology, Department of Mechanical Engineering, Gurugram, Haryana 122103, India
  3. Meerut Institute of Engineering and Technology, Mechanical Engineering Department, Meerut 250005, India
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Abstract

Thermophysical properties of frozen soil have a great influence on the quality of cast-in-place concrete piles. In this paper, the embedded concrete temperature monitoring system is used to test the variation law of the concrete temperature during the construction of the bored pile. Thermophysical properties of permafrost around piles are tested. Based on the theory of three-phase unsteady heat conduction of soil, the influence of specific heat capacity, thermal conductivity, thermal diffusivity, and latent heat of phase transformation on the temperature change of a concrete pile is systematically studied. The thermal parameter is obtained which exerts the most significant influence on the temperature field. According to the influence degree of frozen soil on pile temperature, the order from high to low is thermal conductivity, thermal diffusivity, latent heat of phase change, and specific heat capacity. The changes in pile wall temperature caused by the change of these properties range between 2.60–10.97°C, 1.49– 9.39°C, 2.16–2.36°C, and 0.24–3.45°C, respectively. The change percentages of parameters vary between 35.77–47.12%, 12.22–40.20%, 12.46–32.25%, and 3.83–20.31%, respectively. Therefore, when designing and constructing concrete foundation piles, the influence of the thermal conductivity of frozen soil on concrete pile temperature should be considered first. The differences between the simulated and measured temperature along the concrete pile in the frozen soil varying with the respective thermal properties are: –2.99– 7.98°C, –1.89–4.99°C, –1.20–1.99°C, and –1.76–1.27°C. Polyurethane foam and other materials with small thermal conductivity can be added around the pile to achieve pile insulation.
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Authors and Affiliations

Ziying Liu
1
Tianlai Yu
2
Ning Yan
2
Lipeng Gu
2

  1. Northeast Forestry University, College of Home and Art Design, Harbin, 150040, China
  2. Northeast Forestry University, College of Civil Engineering, Harbin, 150040, China
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Abstract

Solar photovoltaic power is widely utilized in the energy industry. The performance of solar panels is influenced by different variables, including solar radiation, temperature, wind speed, relative humidity and the presence of haze or dirt. Outdoor solar panels are particularly susceptible to a decrease in energy efficiency due to the accumulation of dust particles in the air, which occurs as a result of natural weather conditions. The extent of dust deposition is primarily determined by factors such as the tilt angle of the panel, wind direction, cleaning frequency as well as local meteorological and geographical conditions. The dust on the solar cell glazing reduces the optical transmittance of the light beam, causing shadowing and diminishing the energy conversion productivity of the panels. Sand storms, pollution levels and snow accumulations all significantly impact the photovoltaic panel performance. These circumstances reduce the efficiency of solar panels. The experiment was carried out on two identical dust-accumulated and dust-free panels. The evaluation was carried out in two different situations on the offgrid stand-alone system: in a simulated atmosphere and in an open space during the day. The current-voltage curves have been developed for both panels at various tilt degrees. The features provide sufficient information to analyse the performance of the panels under consideration. The measurements demonstrate that as dust collects on the panel’s surface, the average output power and short circuit current decrease dramatically. The installation tilt angle affected the ratio of efficiency and average power outputs of dusty and clean panels.
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Authors and Affiliations

Minakshi Katoch
1
Vineet Dahiya
1
Surendra Kumar Yadav
1

  1. K.R. Mangalam University, Gurugram – 122103, India
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Abstract

This work is an attempt to study the behaviour of fluid in the mixing vessel with a two-bladed or four-bladed impeller. The working fluid is complex, of a shear-thinning type and the Oswald model is used to describe the fluid viscosity. The study was accomplishedby numerically solving the governing equations of momentum and continuity. These equations were solved for the following range of conditions: 50–1000 for the Reynolds number, 0–0.15 for the baffle length ratio, and the number of impeller blades 2 and 4. The simulations were done for the steady state and laminar regime. The results show that the increase in baffle length (by increasing the ratio baffle length ratio) decreases the fluid velocity in the vessel. Increasing the speed of rotation of the impeller and/or increasing the number of blades improves the mixing process. Also, the length of the baffles does not affect the consumed power.
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Authors and Affiliations

Malika Seddik Bouchouicha
1
Houssem Laidoudi
1
Souad Hassouni
1
Oluwole Daniel Makinde
2

  1. University of Science and Technology of Oran Mohamed-Boudiaf, Faculty of Mechanical Engineering, BP 1505, El-Menaouer, Oran, 31000, Algeria
  2. Stellenbosch University, Faculty of Military Science, Private Bag X2, Saldanha 7395, South Africa
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Abstract

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

Hamdi Messaoud
1
Sahi Adel
1
Ourrad Ouerdia
2

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

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

Manthri Sathyanarayana
1
Tamtam Ramakrishna Goud
2

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

This paper presents new results for the dynamic behaviour of fluid around a rotating turbulator in a channel. The turbulator has a propeller form which is placed inside a flat channel. The research was carried out using 3D numerical simulation. The rationale of the experiment was as follows: we put a propeller-turbulator inside a flat channel, and then we insert a water flow inside the channel. The turbulator rotates at a constant and uniform speed. The main points studied here are the effect of the presence of turbulator and its rotational direction on the flow behaviour behind the turbulator. The results showed that the behaviour of flow behind the turbulator is mainly related to the direction of turbulator rotating. Also, the studied parameters affect coefficients of drag force and power number. For example, when the turbulator rotates in the positive direction, the drag coefficient decreases in terms of rotational speed of the turbulator, while the drag coefficient increases in terms of rotational speed when the turbulator rotates in the negative direction.
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Authors and Affiliations

Elhadi Zoubai
1
Houssem Laidoudi
1
Ismail Tlanbout
1
Oluwole Daniel Makinde
2

  1. University of Science and Technology of Oran Mohamed-Boudiaf, Faculty of Mechanical Engineering, Laboratory of Sciences and Marine Engineering, BP 1505, El-Menaouer, Oran, 31000, Algeria
  2. Stellenbosch University, Faculty of Military Science, Private Bag X2, Saldanha 7395, South Africa
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Abstract

Thermochemical treatment processes are used to produce a surface layer of the workpiece with improved mechanical properties. One of the important parameters during the gas nitriding processes is the temperature of the surface. In thermochemical treatment processes, there is a problem in precisely determining the surface temperature of heat-treated massive components with complex geometries. This paper presents a simulation of the heating process of a die used to extrude aluminium profiles. The maximum temperature differences calculated in the die volume, on the surface and at the most mechanically stressed edge during the extrusion of the aluminum profiles were analysed. The heating of the die was simulated using commercial transient thermal analysis software. The numerical calculations of the die assumed a boundary condition in the form of the heat transfer coefficient obtained from experimental studies in a thermochemical treatment furnace and the solution of the nonstationary and non-linear inverse problem for the heat conduction equation in the cylinder. The die heating analysis was performed for various heating rates and fan settings. Major differences in the surface temperature and in the volume of the heated die were obtained. Possible ways to improve the productivity and control of thermochemical treatment processes were identified. The paper investigates the heating of a die, which is a massive component with complex geometry. This paper indicates a new way to develop methods for the control of thermochemical processing of massive components with complex geometries.
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Authors and Affiliations

Damian Joachimiak
1
Wojciech Judt
1
Magda Joachmiak
1

  1. Poznan University of Technology, Institute of Thermal Engineering, Piotrowo 3a, 60-965, Poznan, Poland
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Abstract

The trend of reducing electricity consumption and environmental protection has contributed to the development of refrigeration technologies based on the thermal effect of adsorption. This article proposes a methodology for conducting numerical simulations of the adsorption and desorption processes. Experimental data available in the literature were used as guidelines for building and verifying the model, and the calculations were carried out using commercial computational fluid dynamics software. The simulation results determined the amount of water vapor absorbed by the adsorbent bed and the heat generated during the adsorption process. Throughout the adsorption process, the inlet water vapor velocity, temperature, and pressure in the adsorbent bed were monitored and recorded. The results obtained were consistent with the theory in the literature and will serve as the basis for further, independent experimental studies. The validated model allowed for the analysis of the effect of cooling water temperature on the sorption capacity of the material and the effect of heating water temperature on bed regeneration. The proposed approach can be useful in analyzing adsorption processes in refrigeration applications and designing heat and mass exchangers used in adsorption systems.
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Authors and Affiliations

Szymon Janusz
1 2
Maciej Szudarek
3
Leszek Rudniak
4
Marcin Borcuch
2

  1. Cracow University of Technology, Jana Pawla II 37, 31-864 Kraków, Poland
  2. M.A.S. Sp z o.o., Research and Development Department, Składowa 34, 27-200 Starachowice, Poland
  3. Warsaw University of Technology, Institute of Metrology and Biomedical Engineering, sw. Andrzeja Boboli 8, 02-525 Warszawa, Poland
  4. Warsaw University of Technology, Faculty of Chemical and Process Engineering, Warynskiego 1, 00-645 Warszawa, Poland

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