Applied sciences

Archives of Thermodynamics

Content

Archives of Thermodynamics | 2021 | vol. 42 | No 2 |

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Abstract

The most power consuming part in the vapor compression cycle (VCC) is the gas compressor. Heating the refrigerant under constant volume after the compressor increases the condenser pressure, which consequently increases the cooling rate of the VCC. This study examined the influence of heating different refrigerants, i.e. R143a, R22, and R600a on the cooling rate of the VCC. Four experiments have been performed: the first experiment is a normal VCC, i.e. without heating, while in the second, third, and fourth experiments were carried out to raise the temperature of the refrigerant to 50°C, 100°C, and 150°C. It has been found that heating raises the refrigerant pressure in VCC and thereby improves the refrigerant’s mass flow rate resulting in an improvement in the cooling power for the same compressor power. Heating the refrigerant after the mechanical compressor increases the temperature of the condenser as well as the temperature of the evaporator when using refrigerant R134a, which prevents the refrigeration cycle to be used in freezing applications, however using refrigerant R22 or refrigerant R600a promotes the heated VCC to be used in freezing applications. Refrigerant R600a has the lowest operating pressure compared to R134a and R22, which promotes R600a to be used rather than R134a and R22 from a leakage point of view.
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Authors and Affiliations

Mohamed Salama Abd-Elhady
1
Emmanoueil Bishara Melad
2
Mohamed Abd-Elhalim
3
Seif Alnasr Ahmed
1

  1. Mechanical Engineering Department, Faculty of Engineering, Beni-Suef University, Sharq El-Nile, New Beni-Suef, 62521 Beni-Suef, Egypt
  2. Faculty of Technology and Education, Beni-Suef University, Sharq El-Nile, New Beni-Suef, 62521 Beni-Suef, Egypt
  3. Faculty of Technology and Education, Suez University, 43527 Suez, Egypt
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Abstract

The paper is devoted to the control of operability of Peltier modules based on the analysis of transient modes of their operation. Advantages of using low-power thermoelectric modules for the development of thermoelectric plants with adaptive control systems for the needs of the agricultural complex, which significantly reduce their cost characteristics, are shown. The problem of using the stationary mode of their operation, associated with the low efficiency of the modules, as well as the dynamic mode, associated with the presence of transient processes, is indicated. It is noted that overcoming this problem requires solution of the task of automation of reliability providing the well-known approaches to its solution are shown, for which the key advantages and disadvantages are given. An approach is proposed to complex control of the operability and quality of thermoelectric modules during their expluatation in three components of the physical process of thermoelectric conversion (Peltier thermoelectric effect, electrical and thermal transfer phenomena) by analyzing transients in the system based on identification algorithms. To justify it, the necessary equations and mathematical relations are given. Aprobating of the proposed approach was carried out experimentally by determining the time constants for operable and defective commercially available modules and showed its significant advantages over the standard verification procedure.
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Authors and Affiliations

Oleg Rudolfovich Kuzichkin
1
Igor Sergeevich Konstantinov
2
Gleb Sergeevich Vasilyev
1
Dmitry Igorevich Surzhik
1

  1. Belgorod State University, Pobedy 85, 308015 Belgorod, Russia
  2. Russian State Agrarian University – Moscow Timiryazev Agricultural Academy, Listvennichnaya 5, 127550 Moscow, Russia
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Abstract

The paper is a thermodynamics analysis of the removal of any inert gas from the tank using the vapors of any liquefied petroleum gas cargo (called cargo tank gassing-up operation). For this purpose, a thermodynamic model was created which considers two boundary cases of this process. The first is a ‘piston pushing’ of inert gas using liquefied petroleum gas vapour. The second case is complete mixing of both gases and removal the mixture from the tank to the atmosphere until desired concentration or amount of liquefied petroleum gas cargo in the tank is reached. Calculations make it possible to determine the amount of a gas used to complete the operation and its loss incurred as a result of total mixing of both gases.
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Authors and Affiliations

Agnieszka Wieczorek
1

  1. Gdynia Maritime University, Morska 81–87, 81-225 Gdynia, Poland
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Abstract

The paper presents a thermodynamic analysis of the removal of an inert gas from the tank using the vapor of liquefied petroleum gas cargo (called cargo tank gassing-up operation). For this purpose a thermodynamic model was created which considers two extreme cases of this process. The first is ‘piston pushing’ of inert gas using liquefied petroleum gas vapour. The second case is the complete mixing of both gases and removal the mixture from the tank to the atmosphere until desired concentration or amount of liquefied petroleum gas cargo in the tank is reached. On the example of nitrogen as inert gas and ethylene as a cargo, by thermodynamic analysis an attempt was made to determine the technical parameters of the process, i.e., pressure in the tank, temperature, time at which the operation would be carried out in an optimal way, minimizing the loss of cargo used for gassingup. Calculations made it possible to determine the amount of ethylene used to complete the operation and its loss incurred as a result of total mixing of both gases.
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Authors and Affiliations

Agnieszka Wieczorek
1

  1. Gdynia Maritime University, Morska 81–87, 81-225 Gdynia, Poland
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Abstract

The paper presents results of a parametric analysis of a hightemperature nuclear-reactor cogeneration system. The aim was to investigate the power efficiency of the system generating heat for a high-temperature technological process and electricity in a Brayton cycle and additionally in organic Rankine cycles using R236ea and R1234ze as working fluids. The results of the analyses indicate that it is possible to combine a 100 MW high-temperature gas-cooled nuclear reactor with a technological process with the demand for heat ranging from 5 to 25 MW, where the required temperature of the process heat carrier is at the level of 650°C. Calculations were performed for various pressures of R236ea at the turbine inlet. The cogeneration system maximum power efficiency in the analysed cases ranges from ~35.5% to ~45.7% and the maximum share of the organic Rankine cycle systems in electric power totals from ~26.9% to ~30.8%. If such a system is used to produce electricity instead of conventional plants, carbon dioxide emissions can be reduced by about 216.03–147.42 kt/year depending on the demand for process heat, including the reduction achieved in the organic Rankine cycle systems by about 58.01–45.39 kt/year (in Poland).
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Authors and Affiliations

Julian Jędrzejewski
1
Małgorzata Hanuszkiewicz-Drapała
2

  1. Antea Polska S.A., Duleby 5, 40-833 Katowice, Poland
  2. Silesian University of Technology, Faculty of Energy and Environmental Engineering, Konarskiego 18, 44-100 Gliwice, Poland
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Abstract

By the emergence of distributed energy resources, with their associated communication and control complexities, there is a need for an efficient platform that can digest all the incoming data and ensure the reliable operation of the power system, which can be achieved by using digital twins. The paper discusses the advantages of using digital twins in the development of control systems and operation of distributed heat and electric power generation facilities. The possibilities of using the digital doubles for increasing the efficiency of the considered objects is presented as the example of optimizing the configuration of a control system of solar collectors in the presence of heat losses in pipelines of the external circuit. Further, the total balance consumed and generated electric and heat energy are presented. Examples of algorithms for protecting equipment to improve security are given, and the possibilities of improving the reliability of distributed power systems are considered. The system use of the digital twins provides the possibility of developing and debugging control algorithms, which increase the efficiency, reliability and safety of control objects, including distributed thermal and electrical power generation complexes.
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Authors and Affiliations

Makhsud Mansurovich Sultanov
1
Edik Koirunovich Arakelyan
1
Ilia Anatolevich Boldyrev
1
Valentina Sergeevna Lunenko
1
Pavel Dmitrievich Menshikov
1

  1. National Research University MPEI, Krasnokazarmennaya 17, Moscow, 111250 Russia
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Abstract

This study presents the behavior of a single wall carbon nanotube (SWCNT)/water nanofluid for convective laminar flow inside a straight circular pipe heated by a constant heat flux. Five volume fractions of SWCNT were used to investigate their effect on the heat transfer coefficient, Nusselt number, temperature distribution and velocity field in comparison with pure water flow. One model for each property was tested to calculate the effective thermal conductivity, effective dynamic viscosity, and effective specific heat of the SWCNT/water mixture. The models were extracted from experimental data of a previous work. The outcomes indicate that the rheological behavior of SWCNT introduces a special effect on the SWCNT/water properties, which vary with SWCNT volume fraction. The results show an improvement in the heat transfer coefficient with increasing volume fraction of nanoparticles. The velocity of SWCNT/water nanofluid increased by adding SWCNT nanoparticles, and the maximum increase was registered at 0.05% SWCNT volume fraction. The mixture temperature is increased with the axial distance of the pipe but a reduction in temperature distribution is observed with the increasing SWCNT volume fraction, which reflects the effect of thermophysical properties of the mixture.
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Authors and Affiliations

Farqad Rasheed Saeed
1
Marwah A. Jasim
2
Natheer B. Mahmood
3
Zahraa M. Jaffar
4

  1. Ministry of Science Technology, Directorate of Materials Research, 55509 Al-Jadriya, Iraq
  2. University of Baghdad, College of Engineering, Al-Jadriya,10074 Al-Jadriya, Iraq
  3. Ministry of Education, General Directorate of Baghdad Education, Karkh 2, 10072 Al-Jadriya, Iraq
  4. Al Nahrain University, College of Science, 10072 Al-Jadriya, Iraq
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Abstract

This paper studies hydrodynamic and heat transfer performance of Al2O3/H2O nanofluid flowing through a Bessel-like converging pipe in laminar flow regime using the computational fluid dynamic approach. A parametric study was carried out on the effect of Reynolds number (300– 1200), convergence index (0-3) and nanoparticle concentration (0–3%) on the both hydrodynamic and thermal fields. The results showed the pressure drop profile along the axial length of the converging pipes is parabolic compared to the downward straight profile obtained in a straight pipe. Furthermore, an increase in convergence index, Reynolds number and nanoparticle concentration were found to enhance convective heat transfer performance. Also, a new empirical model was developed to estimates the average Nusselt number as a function of aforementioned variables. Finally, the result of the thermohydraulic performance evaluation criterion showed that the usage of Bessel-like converging pipes is advantageous at a low Reynolds number.
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Authors and Affiliations

Chukwuka S. Iweka
1
Olatomide G. Fadodun
2

  1. Department of Mechanical Engineering, Delta State Polytechnic, Ozoro, P.M.B 5, Ozoro 334111, Delta State, Nigeria
  2. Centre for Energy Research and Development, Obafemi Awolowo University, Ile-Ife 220282, Osun State, Nigeria
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Abstract

This paper presents the results of experimental research on heat transfer distribution under the impinging jets at high jet velocity on curved surfaces. The air jets flow out from the common pipe and impinge on a surface which is cooled by them, in this way all together create a model of external cooling system of low pressure gas turbine casing. Preliminary measurement results from the flat plate case were compared with the results from the curved surface case. Surface modification presented in this paper relied on geometry change of flat surface to the form of a ‘bump’. The special system of pivoted mirrors was implemented during the measurements to capture the heat exchange on curved surfaces of the bump. The higher values of mean heat transfer coefficient were observed for all flow cases with a bump in relation to the reference flow case with a flat plate.
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Authors and Affiliations

Marcin Kurowski
1

  1. Institute of Fluid Flow Machinery, Polish Academy of Sciences, Fiszera 14, 80-231 Gdansk, Poland
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Abstract

Power generation units, suitable for individual users and small scale applications, are mainly based on spark ignition engines. In recently performed research, reductions of emissions coming from such units, especially considering carbon dioxide emissions, are deemed as the issue of particular importance. One of solutions, postponed to reduce impact of spark ignition engine-based units on the natural environment, is transition from fossil fuels into renewable gaseous fuels, as products of organic digestion. Nonetheless, development of new solutions is required to prevent further carbon dioxide emissions. The paper presents a novel dual approach developed to reduce carbon dioxide emissions from stationary power units, basing on spark ignition engine. The discussed approach includes both reduction in carbon content in the fuel, which is realized by its enrichment with hydrogen produced using the solar energy-supported electrolysis process, as well as application of post-combustion carbon dioxide separation. Results of the performed analysis suggest profitability of transition from fossil into the hydrogen-enriched fuel mixture, with significant rise in operational parameters of the system following increase in the hydrogen content. Nevertheless, utilization of the carbon dioxide separation leads to vital soar in internal energy demand, causing vital loss in operational and economical parameters of the analyzed system.
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Authors and Affiliations

Katarzyna Janusz-Szymańska
1
Krzysztof Grzywnowicz
1
Grzegorz Wiciak
1
Leszek Remiorz
1

  1. Silesian University of Technology, Faculty of Energy and Environmental Engineering, Akademicka 2A, 44-100 Gliwice, Poland

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