Sürdürülebilir Kalkınma Amaçları
Yayınlar
- MakaleAçık Erişim2022Scopus SJRQ12D MHD Mixed Convection in a Zigzag Trapezoidal Thermal Energy Storage System Using NEPCM
Abderrahmane, Aissa; Younis, Obai; Al-Khaleel, Mohammad; Laidoudi, Houssem; Akkurt, Nevzat; Guedri, Kamel; Marzouki, Riadh
In a magnetic field, two-dimensional (2D) mixed convection is investigated within a zigzagged trapezoidal chamber. The lower side of the trapezoidal chamber is irregular, in particular, a zigzagged wall with different zigzag numbers N. The fluid particles move in the room due to the motion of the upper wall, while the porosity-enthalpy approach represents the melting process. The thermal parameters of the fluid are enhanced by what is called a nano-encapsulated phase change material (NEPCM) consisting of polyurethane as the shell and a nonadecane as the core, while water is used as the base fluid. In order to treat the governing equations, the well-known Galerkin finite element method (GFEM) is applied. In addition, the heat transfer (HT) and the dynamic behavior of flow are treated in terms of average Nusselt number and contours of streamlines. The main results show that the melt band curve of heat capacity behaves almost parabolically at smaller values of Reynolds number (Re) and larger values of Hartmann number (Ha). Moreover, minimizing the zigzag number is better in order to obtain a higher heat transfer rate.
AtıfScopus30OpenAlex34
İncele - MakaleYalnız künye2021Scopus SJRQ2Characterization of Various Carbon-Based Polypropylene Nanocomposites
Kaya, Ozge; Buran, Dincer; Akkurt, Nevzat; Yapici, Kerim; Sarac, Mehmet Fahri
Pure and three types of carbon additives including graphite, graphene, and multi-walled carbon nanotube added into polypropylene (PP) composites as a vibration damping component and sound insulator material in the automotive sector were investigated by using vibrational damping, dynamic mechanical analysis (DMA), tensile, hardness and acoustic behavior tests. According to the obtained results, porosity and distribution of carbon in the polymer matrix are key parameters on the composite parameters causing its reduction of tensile strength and its brittle behavior. Moreover, it seems that 0.01 wt.% graphene and 1 wt.% graphite added PP composites show the highest impact damping properties and also increase the storage and loss modulus of the composite while decreasing the glass transition temperature. The loss factor obtained from DMA and vibration damping test indicated the damping capacity in the interphase of carbon added PP composites depends only on the load applied and not sensitivity upon the natural frequency of the composite system. Depending on the morphological differentiation, graphene added PP composites decrease the sound transmission loss while the 0.1 wt.% MWCNT added PP composites increase sound transmission loss which makes it an alternative vibration damping component.
AtıfScopus6WoS6İncele - 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 SJRQ2Effect of roof and ceiling configuration on energy performance of a metamaterial-based cool roof for low-rise office building in China
Tang, Saihong; Akkurt, Nevzat; Zhang, Kai; Chen, Lufang; Ma, Mingquan
Cool roofs with higher solar reflectance and emittance can effectively reduce building energy consumption. However, it is still limited to use at night on account of the development of roof materials during the past decades. The newly proposed metamaterial-based cool roof (MCR) greatly improves the possibility of the radiative cooling in the daytime. To study the influence of MCR on the energy consumption for the office building, a small single-floor office was adopted to analyse the cooling performance of MCR by using EnergyPlus. In this study, the optimization analysis was conducted based on the proposed dimensionless thermal resistance (θRTR) and roof pitch (Δ). Then the annual electricity saving potential of the office building with MCR was evaluated in details based on the selected cities from all five climate zones in China. The results show that more annual electricity saving can be achieved under the optimized values of θR7 = 1.53 and Δ = 20°. Furthermore, more than 15.7% of annual cooling electricity saving can be achieved while the optimized θRTR and Δ are applied.
AtıfScopus13WoS12OpenAlex15İncele - MakaleYalnız künye2021Scopus SJRQ2Effects of Optimized Operating Parameters on Combustion Characteristics and NOx Emissions of a Burner based on Orthogonal Analysis
Xu, Qian; Akkurt, Nevzat; Yang, Gang; Zhu, Lidong; Shi, Kejian; Wang, Kang; Zou, Zhenwei; Liu, Zhihui; Wang, Jiulong; Du, Zhiwei
To optimize the structure of the burner, improve the combustion performance, and reduce the emission of NOx, a self-circulating low NOx combustion technology was used to design a new type of flue gas self-circulating low NOx burner. Based on previous research on the numerical model of combustion and the composition of mixed gas on combustion and NOx emissions, the effect of various factors on the ejection coefficient of the flue gas self-circulating structure was analyzed using the orthogonal test method, and the burner operating parameters, such as preheating temperature and excess air coefficient, were deeply studied through the three-dimensional finite element numerical model in this paper. The results show that the diameter ratio of the nozzle and the length of the cylindrical section of the flue gas self-circulating structure have great influence on its ejection and mixing ability. The optimal ejection coefficient was 0.4829. Overall, the amount of NOx emissions greatly increased from 6.23×10−6 (volume fraction) at the preheating temperature 973 K to 3.5×10−3 at preheating temperature 1573 K. When the excess air coefficient decreased from 1.2 to 1, the maximum combustion temperature decreased from 2036.3 K to 1954.22 K, and the NOx emissions decreased from 352.29×10−6 to 159.73×10−6.
AtıfScopus7OpenAlex8İncele - 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 - MakaleYalnız künye2020Scopus SJRQ1Study on model uncertainty of water source heat pump and impact on decision making
Zhang, Ying; Akkurt, Nevzat; Yuan, Jiaqi; Xiao, Ziwei; Wang, Qianjiang; Gang, Wenjie
Water source heat pump systems are widely used for cooling and heating due to high efficiency. The energy source can be surface water or underground water. Accurate modeling of water source heat pump systems is the basis for performance prediction, design and control optimization. However, various heat pump models are available to predict the system performance and results obtained can be very different under different models due to the model uncertainty. Without considering these uncertainties, the performance of water source heat pump systems would be overestimated or underestimated and the decision making would be affected. This paper attempts to quantify the model uncertainty of water source heat pump and its impact on the system performance. Thirteen commonly-used models are selected and validated using the manufacture data. By importing these models into the water source heat pump system, the impact of heat pump model uncertainty on the system performance is quantified. It shows that the model uncertainty can result in a deviation of up to 30% in the annual energy consumption. The energy saving potential of water source heat pump systems can vary from -18.43% to 14.78% compared with the chillers & boiler in the hot summer and cold winter area. The priority of water source heat pump systems is also controversial. The difference in the annual average coefficient of performance of the system can be up to 1.22. It demonstrates that the model uncertainty of water source heat pumps affects the system performance significantly and should be taken into account in building energy prediction and design optimization. The models considering the correction of part load ratio are recommended.
AtıfScopus40WoS34OpenAlex45İncele - MakaleYalnız künye2020Scopus SJRQ1Techno-economic analyses of multi-functional liquid air energy storage for power generation, oxygen production and heating
Wang, Chen; Akkurt, Nevzat; Zhang, Xiaosong; Luo, Yimo; She, Xiaohui
Liquid air energy storage (LAES) is increasingly popular for decarbonizing the power network. At off-peak time, ambient air after purification is liquefied and stored; at peak time, the liquid air is discharged to generate power. One of the key challenges for the LAES system is the lower economic benefit as peak electricity is usually the only source of income, leading to a longer payback period of ~15 years. To address this issue, this paper, for the first time, proposes a multifunctional LAES system, which not only generates peak electricity but also provides pure oxygen and heating. The proposed system is composed of an air separation unit (ASU), a nitrogen liquefaction unit (NLU) and a power generation unit (PGU). Thermodynamic and economic analyses are carried out on the proposed system. Compared with the baseline LAES system (NLU + PGU), the multifunctional LAES system has a lower round trip efficiency of ~0.39 due to the extra electricity consumption by the ASU. However, it shows a much better economic performance with additional benefits from pure oxygen and heating. In a project life-span of 30 years, the multifunctional LAES system (10 MW/80 MWh) has a short payback period of ~5.7 years. Furthermore, it has a savings-to-investment ratio of 3.12, which is ~153% higher than that of the baseline LAES system. Investigation on the system operation strategy suggests that the ASU should operate at full time. The proposed system provides a feasible way to improve the economic benefits of the LAES system, thus promoting its wide applications.
AtıfScopus82OpenAlex86İncele - MakaleYalnız künye2020Scopus SJRQ1In-situ synthesis of 3D printable mono- and Bi-metallic (Cu/Ag) nanoparticles embedded polymeric structures with enhanced electromechanical properties
Aktitiz, İsmail; Varol, Remzi; Akkurt, Nevzat; Saraç, Mehmet Fahri
The interest of additive manufacturing with 3D printing increases day by day, which provides improved mechanical, electrical, magnetic and thermal properties of 3D parts. The production of 3D parts with the stereolithography (SLA) method, which allows it to be produced with high precision, resolution and complex geometries, distinguishes itself from other alternative additive manufacturing methods (FDM. SLS. LOM. LMD etc.). However, studies on the preparation of functional 3D polymer nanocomposites with the SLA method are quite limited. This study aims to produce silver (Ag) and/or copper (Cu) based 3D polymer nanocomposites for enhancing its mechanical strength, thermal stability and electrical conductivity. Mono and bimetallic (Cu/Ag) nanoparticles have been in-situ synthesized by selective irradiation of laser beam method using a commercial SLA device. In this method, metal (Cu/Ag) acrylate containing photocurable resin is not only cured but also leads to thermal decomposition of metal ions into nanoparticles to form functional 3D structures. The mechanical, electrical and thermal properties of polymer nanocomposites are characterized in detail. As a result of the analysis, the nanoparticles, with an average diameter of 25–55 nm, are well dispersed in the polymer matrix without agglomeration. The temperature at which 5% weight loss of Ag and Cu based polymer structures is measured as 179.3 °C while the glass transition temperature is found to be 223.81 °C. Most importantly, the resistance values are significantly decreased from 456.62 GΩ (Gigaohm) to 1.50 GΩ by increasing the amount of Ag addition at 3D polymeric structures. Therefore, this study allows the production of polymer nanocomposites not only in complex structures but also in desired properties especially for electrically conductive materials, capacitors and electronic applications.
AtıfScopus32WoS24OpenAlex33İncele