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- MakaleYalnız künye2023Scopus SJRQ1Analysis of the mechanical behavior and prediction of the plastic zone of a large-diameter buried gas pipeline under ground overload
Xu, Qian; Zhong, Liqiong; Shu, Mengjie; Zou, Zhenwei; Yang, Gang; Zheng, Qiang; Chen, Xingli; Akkurt, Nevzat; Zhang, Hui; Qiang, Yujie
Plastic failure of pipelines caused by ground overload is increasing. The one-dimensional model based on mechanical nodal parameters cannot predict the plastic failure characteristics of the three-dimensional structure of the pipeline. In order to predict the evolution of the plastic failure of the pipeline with the yield strength as the evaluation criterion, a multidimensional model is needed to consider the changes in the external loads and the changes in the mechanical properties of the pipeline along the circumferential and axial directions. In this study, a finite element calculation model for a large-diameter gas pipeline underground overload was established to investigate the law of stress change in the plastic zone. The nonlinear surface fitting method was used to establish the angle fitting model of the plastic zone and the depth fitting model of the plastic zone. The variation of the area of the plastic zone was described, and the reliability of the results was verified. In addition, the accuracy of the fitting model and the cost of the finite element calculation were evaluated. The results showed that the pipeline entered plasticity at a ground load of P = 25 MPa, and the plastic zone developed continuously in the axial and circumferential directions as the ground load increased. The angle and depth increased to 36° and 1.8 m, respectively, at P = 50 MPa. The average absolute errors for the plastic zone depth fitting model and the plastic zone angle fitting model were 6.42% and 6.64%, respectively, both of which can provide an accurate description of the plastic zone. The calculation results of the plastic zone angle fitting model could meet requirements of data processing and analysis. The plastic zone depth fitting model could be used to obtain solutions with higher accuracy, but it increases the cost of finite element simulation.
AtıfScopus6OpenAlex6
İncele - MakaleYalnız künye2023Scopus SJRQ1Carbide slag recycling to fabricate shape-stable phase change composites for thermal energy storage
Xiong, Yaxuan; Wang, Huixiang; Ren, Jing; Nevzat, Akkurt; Xu, Qian; Nie, Binjian; Li, Chuan; Ding, Yulong
The mining and processing of traditional skeleton materials inevitably generates carbon emissions and pollutes the surrounding environment. To make full use of industrial solid waste, this work innovatively used carbide slag as skeleton material and Na2CO3 as phase change material (PCM) to fabricate shape-stable phase change composites (SSPCCs) via the cold-compression & hot-sintering method. Seven SSPCCs were fabricated with different mass ratios of carbide slag to Na2CO3. Then, the thermal energy storage (TES) performance, mechanical property, micromorphology, chemical compatibility as well as thermal cycling stability were investigated. The results showed that the carbide slag could combine with Na2CO3 to fabricate SSPCCs; Sample CN5 achieved the optimal performance with the mass ratio 52.5:47.5 of carbide slag to Na2CO3; Sample CN5 achieved a TES density of 993 J/g in the range of 100 to 900 °C, a compressive strength of 22.02 MPa and a maximal thermal conductivity of 0.62 W/(m·K); Both carbide slag and Na2CO3 were distributed uniformly in sample CN5, while good thermal stability after the 100 heating/cooling cycles and good chemical compatibility between the carbide slag components and the Na2CO3 were observed.
AtıfScopus34OpenAlex30İncele - MakaleYalnız künye2022Scopus SJRQ1Dynamic response model and equivalent solution method of large-diameter buried energy transportation pipeline under moving load
Xu, Qian; Yang, Gang; Li, Zhuorui; Zou, Zhenwei; Zheng, Qiang; Zhong, Liqiong; Chen, Xingli; Akkurt, Nevzat; Du, Yanping; Xiong, Yaxuan
Long-distance energy pipeline pass under roads, subjecting them to repeated stress and posing pipeline safety problems. To simulate the effects of vehicles driving over energy transmission pipeline, this paper examines large-caliber buried pipelines in the suburbs. In this study, a mechanical action model of vehicle-soil-pipeline (VSP) interactions to transform the process of a vehicle driving into the dynamic process of a load changing with time in the specified area was created. The VSP model was used to analyze the influence of moving load and position on the structural characteristics of the pipeline section. An equivalent solution method with high precision and high calculation efficiency was proposed. The results showed that as the loading position approaches the pipeline or the load increases, the stress value at the top of the pipeline gradually exceeded the stress value at the bottom of the pipeline and became the area with the maximum stress value. The minimum stress location also changed from the lower half near the pipeline bottom (Point D-135°) to the upper half near the pipeline top (Point B-45°or Point H-315°). Using the polynomial fitting method, the stress values of the maximum points were equivalently converted. Under the premise of considering pipeline safety, the most suitable functional relationship for the moving load equivalent model was obtained.
AtıfScopus16OpenAlex13İncele - MakaleYalnız künye2022Scopus SJRQ1Numerical evaluation of the coupled/uncoupled effectiveness of a fluid-solid-thermal multi-field model for a long-distance energy transmission pipeline
Wang, Kang; Xie, Kai; Zhang, Hui; Qiang, Yujie; Du, Yanping; Xiong, Yaxuan; Zou, Zhenwei; Zhang, Mingbao; Zhong, Liqiong; Akkurt, Nevzat
As the main component of energy transmission, long-distance energy transmission pipeline (LETP), whose safety problem is becoming more and more prominent with the development of the oil and gas transportation industry, is susceptible to the traffic loading, temperature loading, pressure loading and other loadings. In this paper, the mechanical characteristics of LETP under the interaction of temperature loading and pressure loading are investigated. Based on the theory of multi-field coupling, the mathematical model of fluid-solid-thermal coupling of fluid-filled pipelines under the combined effect of temperature and pressure loadings is established and verified. Meanwhile, an equivalent model is proposed to accurately calculate the stress of any pipeline segment in LETP. The results show that the coupling of temperature loading and the pressure loading is significantly affected by the end-side constraints of the pipelines. For strong end-side constraint, the coupling effect of temperature and pressure loadings has a significant effect on the calculated equivalent stress. The difference between the stress solution under coupling effect and decoupling effect is above 30 MPa. However, for weak end-side constraints, the error is within 10 MPa. The equivalent stress can be approximated by the decoupling solution instead of the coupling solution.
AtıfScopus15OpenAlex15İncele - MakaleYalnız künye2022Scopus SJRQ1Heat and mass transfer mechanism and control strategy of clean low carbon combustion technology in the novel-type coke oven flue with MILD combustion
Xu, Qian; Shen, Meng; Xie, Kai; Zhang, Hui; Akkurt, Nevzat; Wang, Jiulong; Xiong, Yaxuan; Shi, Kejian; Chen, Xingli; Lv, Qian
In the field of emission reduction, considering the limitations of single clean combustion technology and joint control of carbon emission, the application of Technology of Mixed-Gas (TMG), Technology of Low-calorific Value Gas (TLVG) and Technology of Low Oxygen Combustion (TLOC) in the Novel-type Coke Oven Flue with MILD Combustion (MILD-NCOF) was realized. By adjusting the ratio of coke oven gas to blast furnace gas (α), the ratio of flue gas to gas (β) and the ratio of flue gas to air (γ), the heat and mass transfer mechanism of combustion process in MILD-NCOF was researched, the dual emission control system and the regulation strategy of pollutant and carbon emissions were established. The results showed that with the increase of α, β and γ, the fluidity of gas and the reaction rate of combustible components in the fire path were improved, the heat and mass transfer was enhanced, and the effect of dual emission reduction of pollutants and carbon emissions was improved. When the mixing ratio α was 0.6, Tave was reached at 1594.93 K. The NOx concentration at the outlet was 116.34 mg/m3, and the sum of the molar concentrations of CO and CO2 at the outlet was reduced to 1.440 × 10−1. When the mixing ratio β was 2.4, Tave was reached at 1518.73 K, the NOx concentration at the outlet was 128.42 mg/m3, and the sum of the molar concentrations of CO and CO2 at the outlet was 1.127 × 10−1. When the mixing ratio γ was 0.6, Tave was reached at 1627.28 K, the NOx concentration at the outlet was 142.73 mg/m3, and the sum of the molar concentrations of CO and CO2 was reduced to 1.128 × 10−1, which could meet the dual standards of clean production and low-carbon environmental protection of MILD-NCOF.
AtıfScopus30OpenAlex36İncele - MakaleYalnız künye2022Scopus SJRQ1Heat transfer performance by forced convection of microencapsulated phase change material-latent functional thermal fluid flowing in a mini-channels heat sink
Xu, Qian; Zhu, Lidong; Yan, Xinyu; Yang, Jingbin; Wang, Zhaoxiao; Liu, DingHai; Yang, Gang; Chen, Xingli; Akkurt, Nevzat; Liu, Lin
Conventional single-phase coolants have not been able to meet the high cooling requirements of electronic devices. Microencapsulated phase change material-latent functional thermal fluid (MPCM-LFTF), a solid–liquid two-phase cooling medium, has the dual advantages of active liquid cooling and passive phase change material cooling. However, it also increases the power consumption in the mini-channels, and the cooling efficiency of MPCM-LFTF in practical applications needs to be further studied. A new MPCM-LFTF was prepared by paraffin melamine resin MPCM and base fluid (absolute ethanol and deionized water) in this work. The heat transfer performance and hydrodynamic properties were investigated using the dimensionless wall temperature and friction factor, respectively. The efficiency factor was introduced to evaluate the cooling efficiency of MPCM-LFTF in mini-channels. The experimental results showed that the addition of MPCM increased the viscosity of MPCM-LFTF, which increased the friction factor. MPCM-LFTF with a mass fraction of 15 % had the best effect of temperature control and reduced the dimensionless wall temperature by 40.5 %. However, considering the characteristics of flow resistance and improved heat transfer, MPCM-LFTF with a mass fraction of 10 % had the highest cooling efficiency and the efficiency factor was 57.0 % higher than that of the base fluid.
AtıfScopus35OpenAlex36İncele - MakaleAçık Erişim2022Scopus SJRQ1Experimental study on heat transfer properties of gravity heat pipes in single/hybrid nanofluids and inclination angles
Wang, Zhaoxiao; Zhang, Hui; Yin, Lei; Yang, Di; Yang, Gang; Akkurt, Nevzat; Liu, Dinghai; Zhu, Lidong; Qiang, Yujie; Yu, Fan
In order to meet the working requirements of heat pipes under complex working conditions and high heat flux density, and propose corresponding thermal management solutions. In this paper, the single and hybrid nanofluids (TiO2-H2O, Al2O3-H2O, Al2O3+TiO2-H2O) with mass fraction of 5% under the gradient of gravity heat pipe at 50°, 60°, 70°, 80°, 90° are studied. The changes in thermal resistance, thermal efficiency and equivalent heat transfer coefficient of water were compared with deionized water. The results are as follows: The overall efficiency of gravity heat pipe ranges from 70% to 85%. Compared with deionized water, the nanofluid can effectively improve the heat transfer. At different inclination angles, the hybrid nanofluid with the same mass fraction shows the reverse trend compared with the single nanofluid by decreasing the thermal resistance of the heat pipe and increasing the heat transfer efficiency. At an inclination angle of 70°, the heat transfer efficiency of the nanofluid Al2O3+TiO2-H2O is 6.8% weaker compared to TiO2-H2O and 4.5% weaker compared to Al2O3-H2O. At a tilt angle of 60°, the heat transfer capacity of Al2O3+TiO2-H2O nanofluid increases by 7.3% compared to TiO2-H2O and by 5.6% compared to Al2O3-H2O.
AtıfScopus47OpenAlex45İncele - MakaleAçık Erişim2022Scopus SJRQ1Experimental study on synergistic enhancement of thermal performance of a closed two-phase thermosyphon by a TiO2nanofluid doped with Al2O3
Xu, Qian; Yang, Gang; Jia, Shuhui; Wang, Zhaoxiao; Akkurt, Nevzat; Zhang, Hui; Zhou, Qiang; Shen, Meng; Yang, Di; Zhu, Lidong
The heat transfer performance of two-phase closed thermosyphon solar collectors (TPCTs) can be improved by adding nanoparticles to the conventional working fluid, but it is necessary to ensure good rheological properties while improving the heat transfer performance. Therefore, spherical (TiO2) nanoparticles with good rheological properties and rod-shaped (Al2O3) nanoparticles with high thermal conductivity were mixed and applied to the TPCT. First, the effects of individual factors such as the concentration of nanoparticles and the operating parameters on the thermal performance of the TPCT were investigated and a regression analysis was performed. Then, the joint effect of inclination angle and filling ratio on the thermal performance of TPCT was further investigated by orthogonal experiment. The results show that doping TiO2 with Al2O3 can further improve the thermal performance of TPCT. For the volume concentration of 0.6% of nanoparticles, filling ratio of 50% and inclination angle of 80°, the best heat transfer performance of TPCT was achieved. Compared with the deionized water (DW), the thermal resistance of the single (TiO2-H2O) and hybrid (Al2O3+TiO2-H2O) nanofluid TPCT is reduced by 10.7% and 13.4%, the thermal efficiency is increased by 11.0% and 13.7%, and the equivalent heat transfer coefficient is increased by 16.2% and 18.7%, respectively.
AtıfScopus38OpenAlex41İncele - MakaleYalnız künye2021Scopus SJRQ2Effect of the Mixing Structure Parameters of a Self-reflux Burner on Combustion Characteristics and NOx Emission
Xu, Qian; Shen, Meng; Shi, Kejian; Liu, Zhihui; Akkurt, Nevzat; Xiong, Yaxuan; Liu, Lin; Feng, Junxiao; Wang, Jiulong
To solve the problem of low efficiency of NOx emission reduction in self-reflux burners, this study is based on the concept of coordinated control of self-reflux burner structural and thermal parameters. After completing the structural design and optimization of thermal parameters, we continue to adjust the two key structural parameters: the nozzle axis distance and the length of the cylindrical section, to minimize NOx emissions. These are the two parameters that chiefly affect the mixing of flue gas and fuel gas. The results show that increasing nozzle axis distance can delay the mixing of gas and air and create a more uniform oxygen concentration field for the combustion process. The maximum combustion temperature is reduced from 1973.65 K to 1935.88 K and the volume fraction of NOx in the flue gas is reduced from 188.08×10−6 to 143.47×10−6. However, compared with the nozzle axis distance, the length of the cylindrical section of the burner has little effect on the mixing of the flow field. Under different cylindrical section lengths, the maximum combustion temperature does not change more than 3 K, and the volume fraction of NOx in the flue gas changes within 5×10−6.
AtıfScopus3OpenAlex2İncele - MakaleYalnız künye2021Scopus SJRQ1A new type of two-supply, one-return, triple pipe-structured heat loss model based on a low temperature district heating system
Xu, Qian; Wang, Kang; Zou, Zhenwei; Zhong, Liqiong; Akkurt, Nevzat; Feng, Junxiao; Xiong, Yaxuan; Han, Jingxiao; Wang, Jiulong; Du, Yanping
Based on the design concept of a fourth-generation smart pipe network system, this paper innovatively proposes a new TOTS (Two-supply/One-return, triple pipe structure) arrangement method for district heating systems. Moreover, to accurately predict the heat loss due to the pipeline operation of the multi-pipe system, based on the multipole calculation method, a new heat loss theoretical analytical model for the TOTS was created; additionally, a corresponding three-dimensional numerical simulation model was established, which was analyzed and numerically solved. The results showed that in comparison with thermal loss data measured by Danfoss et al., the above analytical and numerical models have a high accuracy, and the deviation is within 2%. Additionally, through calculations, it was found that the distance between the heating pipes is an important factor that affects the total heat loss from the new multi-control heating system and the actual heat exchange between pipes.
AtıfScopus74OpenAlex75İncele - MakaleYalnız künye2020Scopus SJRQ2Synthesis and Characterization of Disodium Hydrogen Phosphate Dodecahydrate-Lauric-Palmitic Acid Used for Indoor Energy Storage Floor Units
Xu, Qian; Akkurt, Nevzat; Zou, Zhenwei; Liu, Yang; Feng, Junxiao; Yu, Chuqiao; Ding, Chong; Xiong, Yaxuan; Zhou, Jingzhi; Zang, Yong
Organic and inorganic phase change materials (PCMs) are considered potential materials for thermal energy storage (TES) with different phase change characteristics. In this study, a novel organic-inorganic composite phase change material (PCM) called disodium hydrogen phosphate dodecahydrate-lauric-palmitic acid (D-LA-PACM) was prepared. Expanded graphite (EG) was selected as the support material, and the novel organic-inorganic form-stable PCM called D-LA-PAPCM/EG was prepared using the vacuum adsorption method. Differential scanning calorimetry, Fourier transform infrared spectroscopy, X-ray diffraction, leakage testing, melting and solidification cycle testing, thermal conductivity testing, scanning electron microscopy observation of the micromorphology, and other characterization methods were used to study the micro structure and morphology, thermal physical parameters, thermal conductivity, stability of the PCMs, and the comprehensive material properties of D-LA-PAPCM under the composite action of EG. Results indicated that the melting and freezing temperatures and latent heats of D-LA-PAPCM/EG were measured to be 31.6°C and 34.3°C and 142.9 and 142.8 J/g, respectively. Although some of the lauric-palmitic acid (LA-PA) and disodium hydrogen phosphate dodecahydrate (DHPD) separated in the multiple porous structures of EG after 1000 cycles, they could still absorb and release latent heats independently, with D-LA-PAPCM/EG still exhibiting good thermal stability. The thermal conductivity of D-LA-PAPCM/EG was 1.361 W/(mK). Therefore, the material and thermal properties of the prepared D-LA-PAPCM/EG indicate that it could be well used as a feasible material for energy-saving phase change floor units in indoor TES systems.
AtıfScopus18OpenAlex18İncele