Applied sciences

Archives of Thermodynamics

Content

Archives of Thermodynamics | 2023 | vol. 44 | No 1

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Abstract

The article presents the results of numerical and analytical investigations of the influence of raw liquid natural gas (LNG) composition on parameters characterizing the combustion process. The high content of higher hydrocarbons influences the thermodynamic combustion process described with parameters like the adiabatic flame temperature, laminar flame speed and ignition delay time. A numerical study of the impact of LNG fuels on emission characteristics using the Cantera code has been performed. Results have shown that the change of grid natural gas to some types of liquid natural gas can result in an incomplete combustion process and an increase of emission of toxic compounds such as carbon monoxide and unburned hydrocarbons. For all investigated fuels the laminar flame speed rises by about 10% compared to natural gas, while the adiabatic flame temperature is nearly the same. The ignition delay time is decreased with an increase of ethane share in the fuel. The analysis of chemical pathways has shown that hydrogen cyanide and hydrogen formation is present, particularly in the high temperature combustion regimes, which results in an increase of nitric oxide molar fraction in flue gases by even 10% compared to natural gas. To summarize, for some applications, liquid natural gases cannot be directly used as interchangeable fuels in an industry sector, even if they meet the legal requirements.
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Authors and Affiliations

Paweł Czyżewski
1
Rafał Ślefarski
1
Joanna Jójka
1

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

In view of the high cost and difficulty of ensuring the accuracy in the measurement of fire smoke velocity, the measurement system developed using platinum resistance temperature detectors and an 8-bit microcontroller, is used to realize the fast measurement of high-temperature fire smoke velocity. The system is based on the thermodynamic method and adopts the Kalman filter algorithm to process the measurement data, so as to eliminate noise and interference, and reduce measurement error. The experimental results show that the Kalman filter algorithm can effectively improve the measurement accuracy of fire smoke velocity. It is also shown that the system has high measurement accuracy, short reaction time, low cost, and is characterized by high performance in the measurement of high-temperature smoke velocity in experiments and practice.
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Authors and Affiliations

Haoyu Wang
1

  1. Department of Fire Engineering, China Fire and Rescue Institute, Nanyan 4, Changping District, 102202, Beijing, China
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Abstract

A numerical model of the high-speed train carriage fire is established in this study. The influence of ceilings, sidewalls, luggage racks, seats, and floors on the heat release rate (HRR) of the high-speed train is studied by numerical methods. The results indicate that the heat release rate per unit area (HRRPUA) of ceiling and seat material dramatically influences the peak HRR and the time to peak HRR of train carriage fire. When the peak HRRPUA of interior ceiling material 1 decreases from 326 to 110 kW/m2, the peak HRR of the high-speed train fire decreases from 36.4 to 16.5 MW, with a reduction ratio of 54.7%. When seat materials with low HRRPUA are used, the peak HRR reduction ratio is 44.8%. The HRRPUA of the sidewall, luggage rack, and floor materials has little effect on the peak HRR of the carriage fire. However, the non-combustible luggage rack can delay the time when the HRR reaches its peak.
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Authors and Affiliations

Yuanlong Zhou
1
Haiquan Bi
2
Honglin Wang
2

  1. University of Science and Technology of China, State Key Laboratory of Fire Science, Hefei, Anhui 230026, China
  2. Southwest Jiaotong University, School of Mechanical Engineering, Chengdu 610031, China
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Abstract

The present paper describes the experimental analysis of heat transfer and friction factor for glass protected three-side artificially roughened rectangular duct solar air heaters (SAHs) having an arrangement of multiple-v and transverse wires (top wall multi-v and two side walls transverse) under the absorber plate, and compares their performance with that of one-side roughened solar air heaters under similar operating conditions. The investigated three-side solar air heaters are characterized by a larger rate of heat transfer and friction factor as compared to one-side artificially roughened SAHs by 24–76% and 4–36%, respectively, for the identical operating parameters. The air temperature below the three-side rugged duct is by 34.6% higher than that of the one-side roughened duct. Three-side solar air heaters are superior as compared to one-side artificially roughened solar air heaters qualitatively and quantitatively both.
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Authors and Affiliations

Dhananjay Kumar
1

  1. B.A. College of Engineering and Technology, Ghutia, P.O. Barakhurshi Jamshedpur, Jharkhand 832304, India
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Abstract

Nowadays, in addition to the thermodynamic properties of refrigerants, their impact on the environment is of high significance. Hence, it is important to use refrigerants with the lowest possible values of ozone depletion potential and global warming potential indices in refrigeration, organic Rankine cycle (ORC), air conditioning, and heat pump systems. Natural refrigerants are the most environmentally friendly; unfortunately, they have less favourable thermodynamic properties. Currently, low-pressure refrigerants from the FC (fluorocarbons, fluorine liquids) and HFE (hydrofluoroether) groups are increasingly used. This paper presents the most important properties and applications of selected refrigerants from these groups and also reviews the literature on their use.
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Authors and Affiliations

Małgorzata Sikora
1
Tadeusz Bohdal
1

  1. Koszalin University of Technology, Śniadeckich 2, 75-453 Koszalin, Poland
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Abstract

This paper is concerned with the rotational motion of the impeller and the thermal buoyancy within a mechanical mixer. The task was investigated numerically using the ANSYS-CFX simulator. The programmer is based on the finite volume method to solve the differential equations of fluid motion and heat transfer. The impeller has hot surfaces while the vessel has cold walls. The rotational movement of the impeller was controlled by the Reynolds number, while the intensity of the thermal buoyancy effect was controlled by the Richardson number. The equations were solved for a steady flow. After analyzing the results of this research, we were able to conclude that there is no effect of the values of Richardson number on the power number. Also, with the presence of the thermal buoyancy effect, the quality of the fluid mixing becomes more important. The increasing Richardson number increases the value of the Nusselt number of the impeller.
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Authors and Affiliations

Souad Hassouni
1
Houssem Laidoudi
2
Oluwole Daniel Makinde
3
Mohamed Bouzit
2
Boumediene Haddou
1

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

This paper presents the results of an experimental study and
mathematical modeling of the effect of dynamic instabilities on the condensation phase transformation of the refrigerants homogeneous R134a and its replacement in the form of isomers R1234yf and R1234ze and R404A or R507 and R448A in pipe mini-channels. In the case of homogeneous chlorofluorocarbons (CFCs), it is the 1234 isomers that are envisioned as substitutes for the withdrawn ones with high ozone depletion potential and global warming potential. For zeotropic and azeotropic mixtures, for example, these are R507 or R448A. The paper presents a dimensional analysis procedure based on the Buckingham Π theorem to develop a regression velocity model of pressure dynamic instabilities. The experimental part of the work was carried out with the use of tubular mini-channels with internal diameter 1.40–3.3 mm.
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Authors and Affiliations

Waldemar Kuczyński
1

  1. Koszalin University of Technology, Faculty of Mechanical Engineering, Department of Power Engineering, Racławicka 15-17, 75-625 Koszalin, Poland

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