Pub Date : 2024-11-18DOI: 10.1016/j.icheatmasstransfer.2024.108367
Praveen James Sanga , Prabal Datta , Arbind Kumar
A numerical study on forced convection turbulent flow in a top-curved surface vented cavity is conducted to investigate the influence of uncertainties in the viscosity formulas using two different types of nanofluid i.e., water-Al2O3 and water-CuO. The Brinkman and Maiga et al. correlations for viscosity are employed to examine their effect on heat transfer and skin friction for a range of Reynolds number. A finite volume method using RNG k-ε turbulent model is considered for solving governing equations numerically. The outcomes of the present study exhibit significant difference in the average Nusselt number and average skin friction on the top-curved heated wall surface of the cavity for two viscosity models employed. For water-Al2O3 nanofluid, these differences are strongly dependent on volume fraction of nanoparticles as well as on the Reynolds number. In contrast, for water-CuO nanofluid, the difference in average Nusselt number is solely depended on Reynolds number while the average skin friction difference is vigorously reliant on volume fraction of the nanoparticles as well as on the Reynolds number.
{"title":"Effect of Brinkman and Maiga's correlations of viscosity on forced convection turbulent flow","authors":"Praveen James Sanga , Prabal Datta , Arbind Kumar","doi":"10.1016/j.icheatmasstransfer.2024.108367","DOIUrl":"10.1016/j.icheatmasstransfer.2024.108367","url":null,"abstract":"<div><div>A numerical study on forced convection turbulent flow in a top-curved surface vented cavity is conducted to investigate the influence of uncertainties in the viscosity formulas using two different types of nanofluid i.e., water-Al<sub>2</sub>O<sub>3</sub> and water-CuO. The Brinkman and Maiga et al. correlations for viscosity are employed to examine their effect on heat transfer and skin friction for a range of Reynolds number. A finite volume method using RNG k-ε turbulent model is considered for solving governing equations numerically. The outcomes of the present study exhibit significant difference in the average Nusselt number and average skin friction on the top-curved heated wall surface of the cavity for two viscosity models employed. For water-Al<sub>2</sub>O<sub>3</sub> nanofluid, these differences are strongly dependent on volume fraction of nanoparticles as well as on the Reynolds number. In contrast, for water-CuO nanofluid, the difference in average Nusselt number is solely depended on Reynolds number while the average skin friction difference is vigorously reliant on volume fraction of the nanoparticles as well as on the Reynolds number.</div></div>","PeriodicalId":332,"journal":{"name":"International Communications in Heat and Mass Transfer","volume":"159 ","pages":"Article 108367"},"PeriodicalIF":6.4,"publicationDate":"2024-11-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142704901","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-11-18DOI: 10.1016/j.icheatmasstransfer.2024.108334
Ying Guo, Pengjie Shi, Jianjun Ma, Fengjun Liu
To extend the applicability and accuracy of the generalized thermoelasticity theory of thermoelasticity theory for one-dimensional problems involving a moving heat source, this study proposes a fractional-order thermoelasticity coupling theoretical model based on the Green-Lindsay theory and the Caputo-Fabrizio fractional-order derivative. The model's uniqueness and reciprocity are well established. To show its application, we analyzed the thermoelastic coupled dynamic response of a fixed-end rod subjected to a moving heat source. Using Laplace transforms and its numerical inverse method, the distribution patterns of non-dimensional displacement, temperature, and stress were obtained. A comprehensive analysis was conducted to investigate the effects of the fractional coefficient, two thermal relaxation time factors, and moving heat source speed on non-dimensional displacement, temperature, and stress. The findings reveal that the fractional coefficient and the speed of the moving heat source significantly influence all non-dimensional physical variables. While the two distinct thermal relaxation time factors have a minimal influence on the non-dimensional temperature, they exert a more pronounced effect on non-dimensional displacement and stress.
{"title":"Dynamic response of thermoelasticity based on Green-Lindsay theory and Caputo-Fabrizio fractional-order derivative","authors":"Ying Guo, Pengjie Shi, Jianjun Ma, Fengjun Liu","doi":"10.1016/j.icheatmasstransfer.2024.108334","DOIUrl":"10.1016/j.icheatmasstransfer.2024.108334","url":null,"abstract":"<div><div>To extend the applicability and accuracy of the generalized thermoelasticity theory of thermoelasticity theory for one-dimensional problems involving a moving heat source, this study proposes a fractional-order thermoelasticity coupling theoretical model based on the Green-Lindsay theory and the Caputo-Fabrizio fractional-order derivative. The model's uniqueness and reciprocity are well established. To show its application, we analyzed the thermoelastic coupled dynamic response of a fixed-end rod subjected to a moving heat source. Using Laplace transforms and its numerical inverse method, the distribution patterns of non-dimensional displacement, temperature, and stress were obtained. A comprehensive analysis was conducted to investigate the effects of the fractional coefficient, two thermal relaxation time factors, and moving heat source speed on non-dimensional displacement, temperature, and stress. The findings reveal that the fractional coefficient and the speed of the moving heat source significantly influence all non-dimensional physical variables. While the two distinct thermal relaxation time factors have a minimal influence on the non-dimensional temperature, they exert a more pronounced effect on non-dimensional displacement and stress.</div></div>","PeriodicalId":332,"journal":{"name":"International Communications in Heat and Mass Transfer","volume":"159 ","pages":"Article 108334"},"PeriodicalIF":6.4,"publicationDate":"2024-11-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142704347","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The onset of mixed convection of cold water in a horizontal channel is studied using linear stability analysis. The two walls of the channel are modeled using slip conditions and are maintained at different constant temperatures. A model with a parabolic relationship is used to predict the variation of density with temperature in the range around its maximum density. The finite difference method is used to solve numerically the linearized equations, and the critical eigenvalue is obtained using the iterative Newton-Raphson method. The effects of the dimensionless temperature ratio γ and the slip parameter Ω on the onset of thermal instabilities are studied. The obtained results showed that these two parameters induced modifications in the critical Rayleigh number and the corresponding critical wavenumber. The results also indicated that beyond a certain value of dimensionless temperature ratio the slip parameter of the upper wall no longer influences the critical threshold for the onset of mixed convection.
{"title":"Linear stability of Rayleigh-Bénard-Poiseuille flow of water near 4°C in a channel bounded by slip walls","authors":"Aymen Benbeghila , Riadh Ouzani , Ammar Benderradji , Zineddine Alloui , Sofiane Khelladi","doi":"10.1016/j.icheatmasstransfer.2024.108370","DOIUrl":"10.1016/j.icheatmasstransfer.2024.108370","url":null,"abstract":"<div><div>The onset of mixed convection of cold water in a horizontal channel is studied using linear stability analysis. The two walls of the channel are modeled using slip conditions and are maintained at different constant temperatures. A model with a parabolic relationship is used to predict the variation of density with temperature in the range around its maximum density. The finite difference method is used to solve numerically the linearized equations, and the critical eigenvalue is obtained using the iterative Newton-Raphson method. The effects of the dimensionless temperature ratio γ and the slip parameter Ω on the onset of thermal instabilities are studied. The obtained results showed that these two parameters induced modifications in the critical Rayleigh number and the corresponding critical wavenumber. The results also indicated that beyond a certain value of dimensionless temperature ratio the slip parameter of the upper wall no longer influences the critical threshold for the onset of mixed convection.</div></div>","PeriodicalId":332,"journal":{"name":"International Communications in Heat and Mass Transfer","volume":"160 ","pages":"Article 108370"},"PeriodicalIF":6.4,"publicationDate":"2024-11-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142698876","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Using Ultrasound Doppler Velocimetry (UDV), magnetoconvection on a heated vertical flat plate is investigated with and without the influence of a transverse applied magnetic field, created by two strong permanent magnets placed sidewise to the plate. The relative positions of the two magnets lead to a configuration wherein the resultant magnetic field is in a direction that is normal to the temperature gradient field as well as to the flow. The working fluid is an aqueous salt solution ( concentration of 5 % by weight) prepared in de-ionized water. In the measurement region, a quasi-uniform magnetic field distribution of 281 was obtained with the magnets in a custom-built magnet holder. COMSOL-based simulations were carried out for the experimental configuration to confirm the magnetic field distribution. To the best of our knowledge, the present study is the first attempt to successfully demonstrate the use of UDV for the non-intrusive mapping of the velocity boundary layer (VBL) in the vicinity of the heated flat plate, under a transverse magnetic field for a fluid. Simultaneously, a thermal probe (k-type thermocouple) is used to obtain the temperature profile inside the boundary layers. Measurements are carried out for a range of temperature differences ( = 5, 10, and 15 °C), corresponding to Rayleigh numbers (Ra) between 5.22 × 107 to 2.11 × 108, and Hartmann number () of . Experimental observations reveal the maximum velocity near the hot wall and an increase in the average Nusselt number (Nu) due to the effect of the externally applied magnetic field, even at low . A plausible explanation for the observed trend has been provided based on the measurements made. The experimentally measured average Nusselt numbers compare well with standard correlations available in the open literature.
{"title":"Ultrasound Doppler velocimetry study of magnetoconvection on the heated vertical flat plate at low Hartmann number","authors":"Ravi Kant , Avishek Ranjan , Atul Srivastava , Sarthak Sonkar","doi":"10.1016/j.icheatmasstransfer.2024.108297","DOIUrl":"10.1016/j.icheatmasstransfer.2024.108297","url":null,"abstract":"<div><div>Using Ultrasound Doppler Velocimetry (UDV), magnetoconvection on a heated vertical flat plate is investigated with and without the influence of a transverse applied magnetic field, created by two strong permanent magnets placed sidewise to the plate. The relative positions of the two magnets lead to a configuration wherein the resultant magnetic field is in a direction that is normal to the temperature gradient field as well as to the flow. The working fluid is an aqueous salt solution (<span><math><mi>NaCl</mi></math></span> concentration of 5 % by weight) prepared in de-ionized water. In the measurement region, a quasi-uniform magnetic field distribution of 281 <span><math><mi>mT</mi></math></span> was obtained with the magnets in a custom-built magnet holder. COMSOL-based simulations were carried out for the experimental configuration to confirm the magnetic field distribution. To the best of our knowledge, the present study is the first attempt to successfully demonstrate the use of UDV for the non-intrusive mapping of the velocity boundary layer (VBL) in the vicinity of the heated flat plate, under a transverse magnetic field for a <span><math><mo>Pr</mo><mo>></mo><mn>1</mn></math></span> fluid. Simultaneously, a thermal probe (<em>k</em>-type thermocouple) is used to obtain the temperature profile inside the boundary layers. Measurements are carried out for a range of temperature differences (<span><math><mi>Δ</mi><mi>T</mi><mspace></mspace></math></span> = 5, 10, and 15 °C), corresponding to Rayleigh numbers (<em>Ra</em>) between 5.22 × 10<sup>7</sup> to 2.11 × 10<sup>8</sup>, and Hartmann number (<span><math><mi>Ha</mi></math></span>) of <span><math><mn>2.3</mn></math></span>. Experimental observations reveal the maximum velocity near the hot wall and an increase in the average Nusselt number (<em>Nu</em>) due to the effect of the externally applied magnetic field, even at low <span><math><mi>Ha</mi></math></span>. A plausible explanation for the observed trend has been provided based on the measurements made. The experimentally measured average Nusselt numbers compare well with standard correlations available in the open literature.</div></div>","PeriodicalId":332,"journal":{"name":"International Communications in Heat and Mass Transfer","volume":"160 ","pages":"Article 108297"},"PeriodicalIF":6.4,"publicationDate":"2024-11-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142699573","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-11-17DOI: 10.1016/j.icheatmasstransfer.2024.108361
Yunzhen Du , Kunling Peng , Jizheng Duan , Meiling Qi , Yanwei Chen , Changwei Hao , Wenshan Duan , Lei Yang , Sheng Zhang , Ping Lin
As nanoelectronics devices continue to shrink in size and increase in integration, managing heat effectively becomes essential for maintaining their stable operation. Two-dimensional (2D) materials, characterized by their superior thermal conductivity, and mechanical flexibility are considered excellent options for thermal management purposes. This study explores the thermal transport properties of 2D sandwich material MoSi2N4(MoN)n(n = 0–4) using Density Functional Theory and Neural Network Potential. We found that adding a layer of (MoN) on MoSi2N4 to form MoSi2N4(MoN)1 results in a significant decrease in thermal conductivity. We have provided a reasonable explanation for this phenomenon, discovering that it is due to the addition of a layer of (MoN) significantly shortening the phonon lifetime and the average free path of phonons. Furthermore, the addition of a layer of (MoN) leads to an increase in anharmonicity. However, when we continue to add more layers of (MoN), we find that the thermal conductivity no longer shows a significant decrease, but only a slight reduction. This indicates that as more layers of (MoN) are added, the scattering mechanisms reach saturation. These findings reveal the unique thermal behavior of 2D sandwich materials and offer valuable insights for their application in heat energy utilization and thermal management technologies.
{"title":"Thermal conductivity in MoSi₂N₄(MoN)ₙ: Insights into phonon scattering and transport","authors":"Yunzhen Du , Kunling Peng , Jizheng Duan , Meiling Qi , Yanwei Chen , Changwei Hao , Wenshan Duan , Lei Yang , Sheng Zhang , Ping Lin","doi":"10.1016/j.icheatmasstransfer.2024.108361","DOIUrl":"10.1016/j.icheatmasstransfer.2024.108361","url":null,"abstract":"<div><div>As nanoelectronics devices continue to shrink in size and increase in integration, managing heat effectively becomes essential for maintaining their stable operation. Two-dimensional (2D) materials, characterized by their superior thermal conductivity, and mechanical flexibility are considered excellent options for thermal management purposes. This study explores the thermal transport properties of 2D sandwich material MoSi<sub>2</sub>N<sub>4</sub>(MoN)<sub>n</sub>(<em>n</em> = 0–4) using Density Functional Theory and Neural Network Potential. We found that adding a layer of (MoN) on MoSi<sub>2</sub>N<sub>4</sub> to form MoSi<sub>2</sub>N<sub>4</sub>(MoN)<sub>1</sub> results in a significant decrease in thermal conductivity. We have provided a reasonable explanation for this phenomenon, discovering that it is due to the addition of a layer of (MoN) significantly shortening the phonon lifetime and the average free path of phonons. Furthermore, the addition of a layer of (MoN) leads to an increase in anharmonicity. However, when we continue to add more layers of (MoN), we find that the thermal conductivity no longer shows a significant decrease, but only a slight reduction. This indicates that as more layers of (MoN) are added, the scattering mechanisms reach saturation. These findings reveal the unique thermal behavior of 2D sandwich materials and offer valuable insights for their application in heat energy utilization and thermal management technologies.</div></div>","PeriodicalId":332,"journal":{"name":"International Communications in Heat and Mass Transfer","volume":"159 ","pages":"Article 108361"},"PeriodicalIF":6.4,"publicationDate":"2024-11-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142653843","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-11-16DOI: 10.1016/j.icheatmasstransfer.2024.108343
Ahmed M. Hassan , Mohammed Azeez Alomari , Qusay H. Al-Salami , Faris Alqurashi , Mujtaba A. Flayyih , Abdellatif M. Sadeq
This study investigates the cooling of a central processing unit (CPU) using a nano-encapsulated phase change material (NEPCM)-water mixture in a trapezoidal cavity with rotating cylinders and baffles. A numerical model based on the finite element method (FEM) is employed to solve the governing equations. The system is subjected to a sinusoidal temperature profile from the CPU and a constant magnetic field. Key parameters examined include Reynolds number (Re: 10–100), Richardson number (Ri: 0.1–10), Hartmann number (Ha: 5–80), NEPCM volume fraction (ϕ: 0.015–0.035), Lewis number (Le: 0.1–10), buoyancy ratio (Nz: 1–5), NEPCM fusion temperature (θf: 0.1–0.9), and Stefan number (Ste: 0.1–0.9). Results show that increasing Re and Ri significantly enhances heat and mass transfer, with the average Nusselt number (Nuav) increasing by up to 80.5 % and average Sherwood number (Shav) by up to 147.9 %. The magnetic field suppresses convection, reducing Nuav by 12.7 % and Shav by 39.5 % as Ha increases. Increasing ϕ improves heat transfer (Nuav up by 32.5 %) with minimal effect on mass transfer. Le strongly influences mass transfer, with Shav increasing by 284.6 % as Le increases. The NEPCM fusion temperature exhibits a non-monotonic effect on Nuav, with an optimal value at θf = 0.5. In conclusion, the study reveals complex interactions between parameters, with Re, Ri, and Le having the most significant impacts on system performance. These findings provide valuable insights for optimizing CPU cooling systems using NEPCM-water mixtures and magnetohydrodynamic (MHD) effects.
本研究探讨了在带有旋转圆柱和挡板的梯形空腔中使用纳米封装相变材料（NEPCM）-水混合物冷却中央处理器（CPU）的问题。采用基于有限元法 (FEM) 的数值模型来求解控制方程。系统受到来自中央处理器的正弦温度曲线和恒定磁场的影响。研究的主要参数包括雷诺数 (Re：10-100)、理查德森数 (Ri：0.1-10)、哈特曼数 (Ha：5-80)、NEPCM 体积分数 (j：0.015-0.035)、路易斯数 (Le：0.1-10)、浮力比 (Nz：1-5)、NEPCM 融合温度 (θf：0.1-0.9) 和斯特凡数 (Ste：0.1-0.9)。结果表明，增加 Re 和 Ri 能显著增强传热和传质，平均努塞尔数 (Nuav) 最多增加 80.5%，平均舍伍德数 (Shav) 最多增加 147.9%。磁场抑制了对流，随着 Ha 的增加，Nuav 降低了 12.7%，Shav 降低了 39.5%。增加 ϕ 可以改善传热（Nuav 增加 32.5%），但对传质的影响很小。Le 对传质影响很大，随着 Le 的增加，Shav 增加了 284.6%。NEPCM 熔融温度对 Nuav 的影响是非单调的，最佳值为 θf = 0.5。总之，研究揭示了参数之间复杂的相互作用，其中 Re、Ri 和 Le 对系统性能的影响最大。这些发现为使用 NEPCM 水混合物和磁流体动力 (MHD) 效应优化 CPU 冷却系统提供了宝贵的见解。
{"title":"Numerical analysis of MHD combined convection for enhanced CPU cooling in NEPCM-filled a trapezoidal cavity","authors":"Ahmed M. Hassan , Mohammed Azeez Alomari , Qusay H. Al-Salami , Faris Alqurashi , Mujtaba A. Flayyih , Abdellatif M. Sadeq","doi":"10.1016/j.icheatmasstransfer.2024.108343","DOIUrl":"10.1016/j.icheatmasstransfer.2024.108343","url":null,"abstract":"<div><div>This study investigates the cooling of a central processing unit (CPU) using a nano-encapsulated phase change material (NEPCM)-water mixture in a trapezoidal cavity with rotating cylinders and baffles. A numerical model based on the finite element method (FEM) is employed to solve the governing equations. The system is subjected to a sinusoidal temperature profile from the CPU and a constant magnetic field. Key parameters examined include Reynolds number (<em>Re</em>: 10–100), Richardson number (<em>Ri</em>: 0.1–10), Hartmann number (<em>Ha</em>: 5–80), NEPCM volume fraction (<em>ϕ</em>: 0.015–0.035), Lewis number (<em>Le</em>: 0.1–10), buoyancy ratio (<em>Nz</em>: 1–5), NEPCM fusion temperature (<em>θ</em><sub><em>f</em></sub>: 0.1–0.9), and Stefan number (<em>Ste</em>: 0.1–0.9). Results show that increasing <em>Re</em> and <em>Ri</em> significantly enhances heat and mass transfer, with the average Nusselt number (<em>Nu</em><sub><em>av</em></sub>) increasing by up to 80.5 % and average Sherwood number (<em>Sh</em><sub><em>av</em></sub>) by up to 147.9 %. The magnetic field suppresses convection, reducing <em>Nu</em><sub><em>av</em></sub> by 12.7 % and <em>Sh</em><sub><em>av</em></sub> by 39.5 % as <em>Ha</em> increases. Increasing <em>ϕ</em> improves heat transfer (<em>Nu</em><sub><em>av</em></sub> up by 32.5 %) with minimal effect on mass transfer. <em>Le</em> strongly influences mass transfer, with <em>Sh</em><sub><em>av</em></sub> increasing by 284.6 % as <em>Le</em> increases. The NEPCM fusion temperature exhibits a non-monotonic effect on <em>Nu</em><sub><em>av</em></sub>, with an optimal value at <em>θ</em><sub><em>f</em></sub> = 0.5. In conclusion, the study reveals complex interactions between parameters, with <em>Re</em>, <em>Ri</em>, and <em>Le</em> having the most significant impacts on system performance. These findings provide valuable insights for optimizing CPU cooling systems using NEPCM-water mixtures and magnetohydrodynamic (MHD) effects.</div></div>","PeriodicalId":332,"journal":{"name":"International Communications in Heat and Mass Transfer","volume":"159 ","pages":"Article 108343"},"PeriodicalIF":6.4,"publicationDate":"2024-11-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142653948","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The significant potential for stage efficiency improvement is in steam turbines of solar thermal power plants, which operate in difficult atmospheric conditions contributing to the high pressure in the condenser and steam impurities. Presented study aims to examine the influence of three steam impurities on the condensing flow through turbine stage rotor. Firstly, the modified condensation model is validated using experimental data. Next, the flow characteristics and losses of pure steam and steam containing heterogeneous particles in three-dimensional turbine are investigated separately, and the effects of particles on the flow process and system performance are analyzed. Finally, the effect of backpressure on the condensation flow and the turbine performance is investigated. The results reveal that homogeneous condensation predominantly occurs at higher blade height, NaCl particles have the most significant impact on condensation. At a particle concentration of , the thermal efficiency of heterogeneous condensation on solid particles and tiny droplets increases by 1.6 % and 2.3 %, respectively, compared to homogeneous condensation. Conversely, NaCl particles exhibit a reduction of 0.2 %. Lastly, by strategically raising the backpressure, it is feasible to decrease the humidity on the final stage blades, enhancing thermal efficiency and ultimately optimizing tower solar power generation system operation.
{"title":"Numerical investigation and optimization of heterogeneous-homogeneous coupled condensation in steam turbines of tower solar power system","authors":"Guojie Zhang , Qiang Zuo , Jiaheng Chen , Zunlong Jin , Sławomir Dykas , Mirosław Majkut , Krystian Smołka","doi":"10.1016/j.icheatmasstransfer.2024.108336","DOIUrl":"10.1016/j.icheatmasstransfer.2024.108336","url":null,"abstract":"<div><div>The significant potential for stage efficiency improvement is in steam turbines of solar thermal power plants, which operate in difficult atmospheric conditions contributing to the high pressure in the condenser and steam impurities. Presented study aims to examine the influence of three steam impurities on the condensing flow through turbine stage rotor. Firstly, the modified condensation model is validated using experimental data. Next, the flow characteristics and losses of pure steam and steam containing heterogeneous particles in three-dimensional turbine are investigated separately, and the effects of particles on the flow process and system performance are analyzed. Finally, the effect of backpressure on the condensation flow and the turbine performance is investigated. The results reveal that homogeneous condensation predominantly occurs at higher blade height, NaCl particles have the most significant impact on condensation. At a particle concentration of <span><math><msup><mn>10</mn><mn>15</mn></msup></math></span> <span><math><mfenced><mrow><mn>1</mn><mo>/</mo><mi>kg</mi></mrow></mfenced></math></span>, the thermal efficiency of heterogeneous condensation on solid particles and tiny droplets increases by 1.6 % and 2.3 %, respectively, compared to homogeneous condensation. Conversely, NaCl particles exhibit a reduction of 0.2 %. Lastly, by strategically raising the backpressure, it is feasible to decrease the humidity on the final stage blades, enhancing thermal efficiency and ultimately optimizing tower solar power generation system operation.</div></div>","PeriodicalId":332,"journal":{"name":"International Communications in Heat and Mass Transfer","volume":"159 ","pages":"Article 108336"},"PeriodicalIF":6.4,"publicationDate":"2024-11-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142653842","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-11-16DOI: 10.1016/j.icheatmasstransfer.2024.108339
Shupeng Liu , Ali B.M. Ali , Muntadher Abed Hussein , Anjan Kumar , Dilsora Abduvalieva , Hadeel Kareem Abdul-Redha , Soheil Salahshour , Nafiseh Emami
The mechanical and thermal properties of porous silicon samples were examined in this investigation in relation to their initial temperature (Temp). The molecular dynamics (MD) numerical simulation method was employed to analyze the results, and LAMMPS software was used to model the porous sample. The simulations conducted in the present study predicted the physical equilibrium of porous silicon samples that were modeled. The research results indicate that the ultimate strength and Young's modulus of porous structures decreased from 26.559 and 52.484 GPa to 25.830 and 52.304 GPa as the Temp increased from 300 to 500 K. The results indicate that the toughness decreased from 10.788 eV/Å3 to 10.195 eV/Å3 as the initial Temp increased to 500 K. Additionally, MSD and diffusion coefficient of porous silicon sample increased from 3.88 nm2 and 27.86 nm2/ns to 8.67 nm2 and 75.56 nm2/ns when the Temp increased from 300 K to 500 K. As the Temp increases to 500 K, the COM increases from 0.236 to 0.41 Å. The total energy of system decreases to −29,259.648 eV when the initial Temp of the porous silicon sample increases to 500 K. Changes in the atomic-scale dynamics and the structural properties of porous silicon network were responsible for this tendency. This study's novelty lies in its focus on the unknown relationship between Temp and porous silicon performance. The results of this study indicate that the Temp had a significant effect on the mechanical and thermal properties of porous silicon samples. These findings are necessary to advance the practical use of porous silicon in various technological fields, especially in Temp-sensitive applications, where understanding its behavior under different thermal conditions is very important.
本研究考察了多孔硅样品的机械性能和热性能与其初始温度（Temp）的关系。采用分子动力学（MD）数值模拟方法对结果进行分析，并使用 LAMMPS 软件对多孔样品进行建模。本研究中进行的模拟预测了所建模的多孔硅样品的物理平衡。研究结果表明，当温度从 300 K 上升到 500 K 时，多孔结构的极限强度和杨氏模量分别从 26.559 和 52.484 GPa 下降到 25.830 和 52.304 GPa。当温度从 300 K 升至 500 K 时，多孔硅样品的 MSD 和扩散系数分别从 3.88 nm2 和 27.86 nm2/ns 增至 8.67 nm2 和 75.56 nm2/ns。这项研究的新颖之处在于它关注温度与多孔硅性能之间的未知关系。研究结果表明，温度对多孔硅样品的机械性能和热性能有显著影响。这些发现对于推动多孔硅在各个技术领域的实际应用是非常必要的，特别是在对温度敏感的应用领域，了解多孔硅在不同热条件下的行为非常重要。
{"title":"Numerical study of changes in the mechanical and thermal property of porous silicon sample with increasing initial temperature: A molecular dynamics approach","authors":"Shupeng Liu , Ali B.M. Ali , Muntadher Abed Hussein , Anjan Kumar , Dilsora Abduvalieva , Hadeel Kareem Abdul-Redha , Soheil Salahshour , Nafiseh Emami","doi":"10.1016/j.icheatmasstransfer.2024.108339","DOIUrl":"10.1016/j.icheatmasstransfer.2024.108339","url":null,"abstract":"<div><div>The mechanical and thermal properties of porous silicon samples were examined in this investigation in relation to their initial temperature (Temp). The molecular dynamics (MD) numerical simulation method was employed to analyze the results, and LAMMPS software was used to model the porous sample. The simulations conducted in the present study predicted the physical equilibrium of porous silicon samples that were modeled. The research results indicate that the ultimate strength and Young's modulus of porous structures decreased from 26.559 and 52.484 GPa to 25.830 and 52.304 GPa as the Temp increased from 300 to 500 K. The results indicate that the toughness decreased from 10.788 eV/Å<sup>3</sup> to 10.195 eV/Å<sup>3</sup> as the initial Temp increased to 500 K. Additionally, MSD and diffusion coefficient of porous silicon sample increased from 3.88 nm<sup>2</sup> and 27.86 nm<sup>2</sup>/ns to 8.67 nm2 and 75.56 nm<sup>2</sup>/ns when the Temp increased from 300 K to 500 K. As the Temp increases to 500 K, the COM increases from 0.236 to 0.41 Å. The total energy of system decreases to −29,259.648 eV when the initial Temp of the porous silicon sample increases to 500 K. Changes in the atomic-scale dynamics and the structural properties of porous silicon network were responsible for this tendency. This study's novelty lies in its focus on the unknown relationship between Temp and porous silicon performance. The results of this study indicate that the Temp had a significant effect on the mechanical and thermal properties of porous silicon samples. These findings are necessary to advance the practical use of porous silicon in various technological fields, especially in Temp-sensitive applications, where understanding its behavior under different thermal conditions is very important.</div></div>","PeriodicalId":332,"journal":{"name":"International Communications in Heat and Mass Transfer","volume":"159 ","pages":"Article 108339"},"PeriodicalIF":6.4,"publicationDate":"2024-11-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142653949","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-11-16DOI: 10.1016/j.icheatmasstransfer.2024.108349
Kaiqi Liang , Zhibin Chen , Kui Jiang
The underexpanded jet induced by loss of vacuum accidents (LOVA) can significantly impact the fusion reactor management, since it poses safety problems associated with hydrogen risks and radioactivity to the environment. To characterize the air ingress process into the high vacuum environment, simulations were performed with OpenFOAM modelling in a representative small-scale fusion facility. The general features of the thermodynamic parameters, such as density, pressure, velocity, and temperature, were analyzed, and also characterized the wall friction velocity and the formation of the Mach disk within the underexpanded jet. Proper orthogonal decomposition (POD) method was applied to compare the fluid dynamic behaviors of the jet subjected to different thermodynamic conditions. The results show that the rapid expansion and acceleration of the jet leads to a decrease in density and an accumulation of the gas along the centerline. The high jet velocity will result in a lower jet temperature and raise the temperature of the surroundings, which also triggers the formation of recirculation zones, and the gradual development of Mach disk structure, also, the higher wall friction velocity will further contribute to the complex air ingress dynamics. Moreover, it is observed that the ideal gas and real gas model appear similar fluid dynamic structures and energy modes during the pressure and velocity development, and only subtle differences appear in the low energy contribution POD modes. The main differences of the energy modes are captured in the momentum field between these different thermodynamic conditions. The observations can contribute to fusion safety management and appropriate thermodynamic modelling selection in such applications.
真空损失事故（LOVA）引起的喷气膨胀不足会对聚变反应堆的管理产生重大影响，因为它会带来与氢风险和环境放射性相关的安全问题。为了描述空气进入高真空环境的过程，我们在一个具有代表性的小型聚变设施中使用 OpenFOAM 建模技术进行了模拟。对密度、压力、速度和温度等热力学参数的一般特征进行了分析，同时还对壁面摩擦速度和未充分膨胀射流内马赫盘的形成进行了描述。应用适当正交分解（POD）方法比较了不同热力学条件下射流的流体动力学行为。结果表明，射流的快速膨胀和加速导致密度下降，气体沿中心线聚集。高射流速度会导致射流温度降低和周围温度升高，这也会引发再循环区的形成和马赫盘结构的逐渐发展，同时，较高的壁面摩擦速度也会进一步导致复杂的进气动力学。此外，在压力和速度发展过程中，理想气体模型和真实气体模型出现了相似的流体动力学结构和能量模式，只有低能量贡献 POD 模式出现了细微差别。能量模式的主要差异体现在这些不同热力学条件下的动量场中。这些观察结果有助于在此类应用中进行聚变安全管理和适当的热力学建模选择。
{"title":"OpenFOAM modelling of air ingress into the high vacuum for fusion reactor safety","authors":"Kaiqi Liang , Zhibin Chen , Kui Jiang","doi":"10.1016/j.icheatmasstransfer.2024.108349","DOIUrl":"10.1016/j.icheatmasstransfer.2024.108349","url":null,"abstract":"<div><div>The underexpanded jet induced by loss of vacuum accidents (LOVA) can significantly impact the fusion reactor management, since it poses safety problems associated with hydrogen risks and radioactivity to the environment. To characterize the air ingress process into the high vacuum environment, simulations were performed with OpenFOAM modelling in a representative small-scale fusion facility. The general features of the thermodynamic parameters, such as density, pressure, velocity, and temperature, were analyzed, and also characterized the wall friction velocity and the formation of the Mach disk within the underexpanded jet. Proper orthogonal decomposition (POD) method was applied to compare the fluid dynamic behaviors of the jet subjected to different thermodynamic conditions. The results show that the rapid expansion and acceleration of the jet leads to a decrease in density and an accumulation of the gas along the centerline. The high jet velocity will result in a lower jet temperature and raise the temperature of the surroundings, which also triggers the formation of recirculation zones, and the gradual development of Mach disk structure, also, the higher wall friction velocity will further contribute to the complex air ingress dynamics. Moreover, it is observed that the ideal gas and real gas model appear similar fluid dynamic structures and energy modes during the pressure and velocity development, and only subtle differences appear in the low energy contribution POD modes. The main differences of the energy modes are captured in the momentum field between these different thermodynamic conditions. The observations can contribute to fusion safety management and appropriate thermodynamic modelling selection in such applications.</div></div>","PeriodicalId":332,"journal":{"name":"International Communications in Heat and Mass Transfer","volume":"159 ","pages":"Article 108349"},"PeriodicalIF":6.4,"publicationDate":"2024-11-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142653947","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-11-16DOI: 10.1016/j.icheatmasstransfer.2024.108348
Mohamed Alanwar , Ahmed A. Hassan , Mohamed A. Abdelatief , Emad Z. Ibrahim , Mohamed L. Elsayed
Steam ejectors are a promising energy-saving technology. Therefore, enhancing their relatively low entrainment performance is essential for expanding their industrial applications. In the present study, a novel ejector design, in which an annular cavity bypass is used in the primary nozzle, has been proposed to improve the entrainment performance of steam ejectors. CFD simulations by ANSYS Fluent 2020R2 are conducted on the proposed steam ejector to investigate the influence of bypass-related geometric parameters (position, width, and divergence angles before and after the bypass) on its entrainment performance under constant operating conditions. The main finding in the present study is that the proposed ejector performs better than the conventional ejector, where the proposed ejector achieves a maximum enhancement of in entrainment performance and in critical back pressure. The parametric study shows that the best values for the bypass position (), width (), and divergence angles after bypass () and before bypass () are , , , and , respectively. Moreover, the bypass position has the most significant contribution to the entrainment performance improvement, followed by the divergence angle before the bypass. While the divergence angle after the bypass has a minimal effect on the ejector performance and the bypass width demonstrates an insignificant impact.
{"title":"Performance enhancement of steam ejector via novel primary nozzle bypass: CFD analysis","authors":"Mohamed Alanwar , Ahmed A. Hassan , Mohamed A. Abdelatief , Emad Z. Ibrahim , Mohamed L. Elsayed","doi":"10.1016/j.icheatmasstransfer.2024.108348","DOIUrl":"10.1016/j.icheatmasstransfer.2024.108348","url":null,"abstract":"<div><div>Steam ejectors are a promising energy-saving technology. Therefore, enhancing their relatively low entrainment performance is essential for expanding their industrial applications. In the present study, a novel ejector design, in which an annular cavity bypass is used in the primary nozzle, has been proposed to improve the entrainment performance of steam ejectors. CFD simulations by ANSYS Fluent 2020R2 are conducted on the proposed steam ejector to investigate the influence of bypass-related geometric parameters (position, width, and divergence angles before and after the bypass) on its entrainment performance under constant operating conditions. The main finding in the present study is that the proposed ejector performs better than the conventional ejector, where the proposed ejector achieves a maximum enhancement of <span><math><mn>10.4</mn><mo>%</mo></math></span> in entrainment performance and <span><math><mn>4.5</mn><mo>%</mo></math></span> in critical back pressure. The parametric study shows that the best values for the bypass position (<span><math><mi>ψ</mi></math></span>), width (<span><math><mi>δ</mi></math></span>), and divergence angles after bypass (<span><math><mi>θ</mi></math></span>) and before bypass (<span><math><mi>β</mi></math></span>) are <span><math><mn>0.54</mn></math></span>, <span><math><mn>0.146</mn></math></span>, <span><math><msup><mn>7.1</mn><mo>°</mo></msup></math></span>, and <span><math><msup><mn>7.6</mn><mo>°</mo></msup></math></span>, respectively. Moreover, the bypass position has the most significant contribution to the entrainment performance improvement, followed by the divergence angle before the bypass. While the divergence angle after the bypass has a minimal effect on the ejector performance and the bypass width demonstrates an insignificant impact.</div></div>","PeriodicalId":332,"journal":{"name":"International Communications in Heat and Mass Transfer","volume":"159 ","pages":"Article 108348"},"PeriodicalIF":6.4,"publicationDate":"2024-11-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142653953","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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