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Enhancement of heat transfer in helical coil heat exchangers using nano-fluids

Malik Parveez Mohammad Hanief
Chemical and Process Engineering | 2022 | vol. 43 | No 2 (The International Chemical Engineering Conference 2021 (ICHEEC): 100 Glorious Years of Chemical Engineering and Technology, held from September 16–19, 2021 at Dr B. R. Ambedkar National Institute of Technology, Jalandhar, Punjab, India. Guest editor: Dr Raj Kumar Arya, Dr Anurag Kumar Tiwari) | 279-283 | DOI: 10.24425/cpe.2022.140832
Keywords nano-fluids heat transfer Nusselt number Prandtl number volume fraction
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Abstract

Investigation for heat transfer behaviour of Al 2O 3 and CuO nano-fluid in helical coil heat exchangers was carried out in this study. The thermo-physical properties of the fluids have temperature dependent nature. The main emphasis was to depict the influence of nano-particle concentration by volume on the characteristics of temperature, rate of heat transfer and heat transfer coefficients (convective). In order to enhance efficiency, density and thermal conductivity are considered to be the most important variables. In comparison towater and for equal flowrate, the rate of heat transfer of nano-fluid increases conspicuously. Efficiency of the helical coil heat exchanger increased by 38.80%.
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Authors and Affiliations

Malik Parveez
1
Mohammad Hanief
2
  1. National Institute of Technology, Chemical Engineering Department, Srinagar, Jammu and Kashmir,190006, India
  2. National Institute of Technology, Mechacahnical Engineering Department, Srinagar, Jammu and Kashmir, 190006, India

Influence of Particle Sizes and Volume Fractions on Fatigue Crack Growth Rates of Aerospace Al-Alloys Composites

I. Uygur
Archives of Metallurgy and Materials | 2024 | vol. 69 | No 1 | 337-341 | DOI: 10.24425/amm.2024.149098
Keywords fatigue crack propagation particle size volume fraction Al-alloy composites
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Abstract

Recently, the need to develop fuel efficient transport systems has led to the development of a range of materials of low density, high stiffness and high strength each can be made at a reasonable cost. The aluminium based alloys are particularly important because of their improved mechanical, physical and technical properties. Fatigue failures have been recognised since the early days of the industrial revolution. Fatigue response of most of materials is related with the microstructural variations in the structure. Hence, in this study, influence of particle size and volume fractions on fatigue properties of Al-alloy composites was investigated. It was found that particle size and volume fraction of reinforcement particles play significant role on fatigue propagation rates, stress intensity threshold values, crack tip opening distance and crack tip plastic zone sizes.
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Authors and Affiliations

I. Uygur
1
ORCID: ORCID
  1. Duzce University, Faculty of Engineering, Department of Mechanical Eng. 81620, Duzce

Simulation Studies on the Influence of Other Combustible Gases on the Characteristics of Methane Explosions at Constant Volume and High Temperature

Zhenmin Luo Litao Liu Shuaishuai Gao Tao Wang Bin Su Lei Wang Yong Yang Xiufang Li
Archives of Mining Sciences | 2021 | vol. 66 | No 2 | 279-295 | DOI: 10.24425/ams.2021.137462
Keywords Constant volume Volume fraction of combustible gas Initial temperature adiabatic flame temperature Maximum explosion pressure
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Abstract

Gas explosions are major disasters in coal mining, and they typically cause a large number of deaths, injuries and property losses. An appropriate understanding of the effects of combustible gases on the characteristics of methane explosions is essential to prevent and control methane explosions. FLACS software was used to simulate an explosion of a mixture of CH4 and combustible gases (C2H4, C2H6, H2, and CO) at various mixing concentrations and different temperatures (25, 60, 100, 140 and 180℃). After adding combustible gases to methane at a constant volume and atmospheric pressure, the adiabatic flame temperature linearly increases as the initial temperature increases. Under stoichiometric conditions (9.5% CH4-air mixture), the addition of C2H4 and C2H6 has a greater effect on the adiabatic flame temperature of methane than H2 and CO at different initial temperatures. Under the fuel-lean CH4-air mixture (7% CH4-air mixture) and fuel-rich mixture (11% CH4-air mixture), the addition of H2 and CO has a greater effect on the adiabatic flame temperature of methane. In contrast, the addition of combustible gases negatively affected the maximum explosion pressure of the CH4-air mixture, exhibiting a linearly decreasing trend with increasing initial temperature. As the volume fraction of the mixed gas increases, the adiabatic flame temperature and maximum explosion pressure of the stoichiometric conditions increase. In contrast, under the fuel-rich mixture, the combustible gas slightly lowered the adiabatic flame temperature and the maximum explosion pressure. When the initial temperature was 140℃, the fuel consumption time was approximately 8-10 ms earlier than that at the initial temperature of 25℃. When the volume fraction of the combustible gas was 2.0%, the consumption time of fuel reduced by approximately 10 ms compared with that observed when the volume fraction of flammable gas was 0.4%.
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Authors and Affiliations

Zhenmin Luo
1 2
ORCID: ORCID
Litao Liu
1 2
ORCID: ORCID
Shuaishuai Gao
1 2
ORCID: ORCID
Tao Wang
1 2 3
ORCID: ORCID
Bin Su
1 2
ORCID: ORCID
Lei Wang
1 2
ORCID: ORCID
Yong Yang
4 2
ORCID: ORCID
Xiufang Li
4
ORCID: ORCID
  1. Xi’an University of Science and Technology, School of Safety Science & Engineering, 58, Yanta Mid. Rd., Xi’an, 710054, Shaanxi, PR China
  2. Shaanxi Key Laboratory of Prevention and Control of Coal Fire, 58, Yanta Mid. Rd, Xi’an, 710054, Shaanxi, PR China
  3. Xi’an University of Science and Technology, Postdoctoral Program, 58, Yanta Mid. Rd., Xi’an 710054, Shaanxi, PR China
  4. Xi’an University of Science and Technology, School of Safety Science & Engineering, 58, Yanta Mid. Rd., Xi’an, 710054, Shaanxi, PR

Study on Dynamic Recrystallization Models of 21-4N Heat Resistant Steel

Yiming Li Xiaomin Huang Hongchao Ji Yaogang Li Baoyu Wang Xuefeng Tang
Archives of Metallurgy and Materials | 2021 | vol. 66 | No 1 | 145-152 | DOI: 10.24425/amm.2021.134770
Keywords 21-4N hot deformation dynamic recrystallization critical strain volume fraction
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Abstract

The high-temperature deformation process and dynamic recrystallization (DRX) process of 21-4N were investigated under the conditions of the deformation temperature range of 1273~1453K, the strain rate range of 0.01~10s–1 and the deformation degree of 60% (the total deformation is 0.916) by using Gleeble-1500D thermal simulated test machine. The curves of stress-strain (σ – ε) were obtained, and the curves of work hardening rate (θ) and strain (ε) were obtained by taking derivative of σ – ε. The DRX critical strains under different conditions were determined by the curves of work hardening rate (θ – ε), and the DRX critical strain model was established. The peak strains of 21-4N were obtained by the curves of σ – ε, the relationship between peak stress (σp) and critical strain (εc) was determined, and the peak strain model was established. The DRX volume fraction models of 21-4N were established by using Avrami equation. The DRX grain size of 21-4N was calculated by Image Pro Plus 6.0, and its DRX grain size models were established.

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Authors and Affiliations

Yiming Li
Xiaomin Huang
Hongchao Ji
Yaogang Li
Baoyu Wang
Xuefeng Tang

Analysis of the void volume fraction for S235JR steel at failure for low initial stress triaxiality

P.G. Kossakowski
Archives of Civil Engineering | 2018 | Vol. 64 | No 1 | 101-115
Keywords void volume fraction failure S235JR steel Gurson-Tvergaard-Needleman material model low stresstriaxiality
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Abstract

This paper deals with problems of failure mechanisms of S235JR structural steel. One of the fundamental parameters of the Gurson-Tvergaard-Needleman damage mechanics-based material model is considered in order to describe the behaviour of the material at the plastic range. The analysis was performed on the void volume fraction fF determined at failure of S235JR steel. The case of low initial stress triaxiality η = 1/3 was taken into consideration. Different from the most popular methods such as curve-fitting, the experimental method based on the digital image analysis of the fracture surface of S235JR steel is proposed in order to determine the critical parameter fF.

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Authors and Affiliations

P.G. Kossakowski

Effect of Initial Porosity on Material Response Under Multi-Axial Stress State for S235JR Steel

P.G. Kossakowski
Archives of Civil Engineering | 2012 | No 4 | 445-462
Keywords Initial porosity initial void volume fraction f0 Gurson-Tvergaard-Needleman material model multi-axial stress states high stress triaxiality voids numerical calculations S235JR steel
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Abstract

The effect of the initial porosity on the material response under multi-axial stress state for S235JR steel using the Gurson-Tvergaard-Needleman (GTN) material model was examined. Three levels of initial porosity, defined by the void volume fraction f₀, were considered: zero porosity for fully dense material without pores, average and maximum porosity according to the metallurgical requirements for S235JR steel. The effect of the initial porosity on the material response was noticed for tensile elements under multi-axial stress state defined by high stress triaxiality σₘ/σe = 1.345. This effect was especially noticeable at the range of the material failure. In terms of the load-bearing capacity of the elements, the conservative results were obtained when maximum value of f₀ = 0.0024 was used for S235JR steel under multi-axial stress state, and this value is recommended to use in the calculations in order to preserve the highest safety level of the structure. In usual engineering calculations, the average porosity defined by f₀ = 0.001 may be applied for S235JR.

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Authors and Affiliations

P.G. Kossakowski

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