Pub Date : 2024-02-01DOI: 10.1615/heattransres.2024048932
Rabah GOMRI, Nadim KAROUN
In this work, a comparative study of the flow boiling heat transfer coefficient of carbon dioxide (CO2) in evaporation is presented. The main objective of the this work is to analyze and evaluate 1886 experimental points of the CO2 heat transfer coefficient with the help of two evaporation correlations (Fang et al., 2013 and Fang et al., 2017); the correlation of Fang et al., 2017 gives the best results.
{"title":"Flow boiling heat transfer Coefficient used for the Design of the Evaporator of a Refrigeration Machine using CO2 as Working Fluid","authors":"Rabah GOMRI, Nadim KAROUN","doi":"10.1615/heattransres.2024048932","DOIUrl":"https://doi.org/10.1615/heattransres.2024048932","url":null,"abstract":"In this work, a comparative study of the flow boiling heat transfer coefficient of carbon dioxide (CO2) in evaporation is presented. The main objective of the this work is to analyze and evaluate 1886 experimental points of the CO2 heat transfer coefficient with the help of two evaporation correlations (Fang et al., 2013 and Fang et al., 2017); the correlation of Fang et al., 2017 gives the best results.","PeriodicalId":50408,"journal":{"name":"Heat Transfer Research","volume":"19 1","pages":""},"PeriodicalIF":1.7,"publicationDate":"2024-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139765945","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"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 : 2024-02-01DOI: 10.1615/heattransres.2024051370
Altug Karabey, Kenan Yakut
Rapid advancements in technology constantly keep the need for thermal systems, which have high performance, on the agenda and direct the attention of researcher-engineers to studies on improving heat transfer. The spray cooling process depends on many parameters including nozzle diameter, surface area, surface geometry, critical heat flux, mass flow, gravity, spraying angle, and surface slope. One would need results from many experiments to better analyze the spray structure. In the present study, by using the rectangular-finned heat sinks optimized for spray cooling and those called “general”, the heat and flow characteristics in spray cooling were analyzed. Water was used as the cooling fluid and the cooling fluid was atomized by using an air-supported atomized. The experiments were conducted with six air-liquid ratio (ALR) values, three different jet heights, three different spraying times, three different fin heights, and three different fin widths. The results are presented in Nusselt number-air liquid ratio (Nu-ALR) and jet thickness-jet velocity (tjet-Ujet) diagrams. It was determined that air-liquid ratio (ALR) value tended to decrease with increasing Nusselt numbers. For the determined air-liquid ratio (ALR) values, Nusselt numbers decreased as the fin height increased. It was concluded that Nusselt numbers tended to decrease in all fin widths as the air-liquid ratio (ALR) value increased. In addition, considering the parameters examined for the rectangular-finned heat sink, separate correlations were developed for Nusselt number, spray angle, and jet thickness.
{"title":"Analyzing The Heat and Flow Characteristics In Spray Cooling By Using An Optimized Rectangular Finned Heat Sink","authors":"Altug Karabey, Kenan Yakut","doi":"10.1615/heattransres.2024051370","DOIUrl":"https://doi.org/10.1615/heattransres.2024051370","url":null,"abstract":"Rapid advancements in technology constantly keep the need for thermal systems, which have high performance, on the agenda and direct the attention of researcher-engineers to studies on improving heat transfer. The spray cooling process depends on many parameters including nozzle diameter, surface area, surface geometry, critical heat flux, mass flow, gravity, spraying angle, and surface slope. One would need results from many experiments to better analyze the spray structure. In the present study, by using the rectangular-finned heat sinks optimized for spray cooling and those called “general”, the heat and flow characteristics in spray cooling were analyzed. Water was used as the cooling fluid and the cooling fluid was atomized by using an air-supported atomized. The experiments were conducted with six air-liquid ratio (ALR) values, three different jet heights, three different spraying times, three different fin heights, and three different fin widths. The results are presented in Nusselt number-air liquid ratio (Nu-ALR) and jet thickness-jet velocity (tjet-Ujet) diagrams. It was determined that air-liquid ratio (ALR) value tended to decrease with increasing Nusselt numbers. For the determined air-liquid ratio (ALR) values, Nusselt numbers decreased as the fin height increased. It was concluded that Nusselt numbers tended to decrease in all fin widths as the air-liquid ratio (ALR) value increased. In addition, considering the parameters examined for the rectangular-finned heat sink, separate correlations were developed for Nusselt number, spray angle, and jet thickness.","PeriodicalId":50408,"journal":{"name":"Heat Transfer Research","volume":"37 1","pages":""},"PeriodicalIF":1.7,"publicationDate":"2024-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139766067","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"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 : 2024-01-01DOI: 10.1615/heattransres.2023050345
Junjie Zhu, Jifen Wang, Xinyi Liu, Kuan Zhao
We investigated the interfacial thermal conductance of the graphene/C3N multilayer in-plane heterostructures by non-equilibrium molecular dynamics simulation. The results showed that the interfacial thermal conductance is 12.97 GW/(m2·K) and the thermal rectification ratio is 23.80% in the bilayer of the multilayer parallel stacked heterostructure. The interfacial thermal conductance and the thermal rectification ratio of the multilayer staggered stacked heterostructure decreased with number of the layers increasing and both convergent as the layers. The phonon participation ratio of two stacking types exhibits a similar trend with interfacial thermal conductance as the number of layers changes. The interfacial thermal conductance of both structures were raised substantially with the temperatures. The interfacial thermal conductance of multilayer heterostructures could be adjusted by altering the defect type, concentration, and distribution proportion and the changes in phonon activities were investigated through phonon density of states and overlap factor S. This work proves the reference for thermal management applications in microelectronic devices.
我们通过非平衡分子动力学模拟研究了石墨烯/C3N多层平面异质结构的界面热导率。结果表明，多层平行堆叠异质结构双层的界面热导率为 12.97 GW/(m2-K)，热整流比为 23.80%。多层交错堆叠异质结构的界面热导率和热整流比随着层数的增加而减小，并随着层数的增加而收敛。随着层数的变化，两种堆叠类型的声子参与比也呈现出与界面热导类似的趋势。两种结构的界面热导率都随着温度的升高而大幅提高。多层异质结构的界面热导率可通过改变缺陷类型、浓度和分布比例来调节，声子活动的变化则通过声子态密度和重叠因子 S 来研究。
{"title":"Molecular dynamics study of the thermal transport properties in the graphene/C3N multilayer in-plane heterostructures","authors":"Junjie Zhu, Jifen Wang, Xinyi Liu, Kuan Zhao","doi":"10.1615/heattransres.2023050345","DOIUrl":"https://doi.org/10.1615/heattransres.2023050345","url":null,"abstract":"We investigated the interfacial thermal conductance of the graphene/C3N multilayer in-plane heterostructures by non-equilibrium molecular dynamics simulation. The results showed that the interfacial thermal conductance is 12.97 GW/(m2·K) and the thermal rectification ratio is 23.80% in the bilayer of the multilayer parallel stacked heterostructure. The interfacial thermal conductance and the thermal rectification ratio of the multilayer staggered stacked heterostructure decreased with number of the layers increasing and both convergent as the layers. The phonon participation ratio of two stacking types exhibits a similar trend with interfacial thermal conductance as the number of layers changes. The interfacial thermal conductance of both structures were raised substantially with the temperatures. The interfacial thermal conductance of multilayer heterostructures could be adjusted by altering the defect type, concentration, and distribution proportion and the changes in phonon activities were investigated through phonon density of states and overlap factor S. This work proves the reference for thermal management applications in microelectronic devices.","PeriodicalId":50408,"journal":{"name":"Heat Transfer Research","volume":"72 1","pages":""},"PeriodicalIF":1.7,"publicationDate":"2024-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139084546","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"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 : 2024-01-01DOI: 10.1615/heattransres.2024051673
Krishan Sharma, Deepu P, Subrata Kumar
In this paper, we study the hydrothermal characteristics of flow inside a rotating helical pipe filled with a saturated homogenous porous medium. The analysis is being carried out for the case of small curvature and torsion. Using perturbation approach, velocity and temperature fields are solved for both uniform wall heat-flux and uniform wall temperature boundary conditions. Perturbation expansion up to third-order is carried out to investigate the effect of rotation on the flow. The influence of rotation on velocity is noticed as early as the first order, and on temperature solution, it has an effect in the third order. The influence of rotation on Nusselt number does not appear till third order, and it is discovered that Nusselt number grows as dimensionless curvature increases.
{"title":"Convective heat transfer inside a rotating helical pipe filled with saturated porous media","authors":"Krishan Sharma, Deepu P, Subrata Kumar","doi":"10.1615/heattransres.2024051673","DOIUrl":"https://doi.org/10.1615/heattransres.2024051673","url":null,"abstract":"In this paper, we study the hydrothermal characteristics of flow inside a rotating helical pipe filled with a saturated homogenous porous medium. The analysis is being carried out for the case of small curvature and torsion. Using perturbation approach, velocity and temperature fields are solved for both uniform wall heat-flux and uniform wall temperature boundary conditions. Perturbation expansion up to third-order is carried out to investigate the effect of rotation on the flow. The influence of rotation on velocity is noticed as early as the first order, and on temperature solution, it has an effect in the third order. The influence of rotation on Nusselt number does not appear till third order, and it is discovered that Nusselt number grows as dimensionless curvature increases.","PeriodicalId":50408,"journal":{"name":"Heat Transfer Research","volume":"3 1","pages":""},"PeriodicalIF":1.7,"publicationDate":"2024-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139587840","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Flow boiling of FC-72 in a small tube was investigated experimentally. The material of the tube was SUS304 stainless steel with an inner diameter of 1.8 mm and a length of 129 mm. The effect of flow velocity and subcooling on critical heat flux (CHF) was measured in this experiment. The flow velocity, u, was varied from 0.33 to 4.26 m/s, and the inlet subcooling degree was varied from 25 to 36 K. The heat transfer coefficients from the non-boiling to boiling region were then measured. Experimental results showed that CHF increased as flow velocity was raised, but it sharply declined above u = 3.0 m/s because of premature CHF. On the basis of the experimental data, the empirical correlation between the boiling number and Weber number was obtained. The predicted value of this correlation was in agreement with the measured data within 17%.
实验研究了 FC-72 在小管内的流动沸腾。管子材料为 SUS304 不锈钢，内径为 1.8 毫米，长度为 129 毫米。实验测量了流速和过冷度对临界热通量（CHF）的影响。流速 u 在 0.33 至 4.26 m/s 之间变化，入口过冷度在 25 至 36 K 之间变化。实验结果表明，CHF 随流速的增加而增加，但在 u = 3.0 m/s 以上，由于过早出现 CHF，CHF 急剧下降。在实验数据的基础上，得到了沸腾数和韦伯数之间的经验相关性。该相关性的预测值与测量数据的一致性在 17% 以内。
{"title":"Flow boiling critical heat flux in a small tube for FC-72","authors":"Yuki Otsuki, Makoto Shibahara, Qiusheng Liu, Sutopo Fitri","doi":"10.1615/heattransres.2023051482","DOIUrl":"https://doi.org/10.1615/heattransres.2023051482","url":null,"abstract":"Flow boiling of FC-72 in a small tube was investigated experimentally. The material of the tube was SUS304 stainless steel with an inner diameter of 1.8 mm and a length of 129 mm. The effect of flow velocity and subcooling on critical heat flux (CHF) was measured in this experiment. The flow velocity, u, was varied from 0.33 to 4.26 m/s, and the inlet subcooling degree was varied from 25 to 36 K. The heat transfer coefficients from the non-boiling to boiling region were then measured. Experimental results showed that CHF increased as flow velocity was raised, but it sharply declined above u = 3.0 m/s because of premature CHF. On the basis of the experimental data, the empirical correlation between the boiling number and Weber number was obtained. The predicted value of this correlation was in agreement with the measured data within 17%.","PeriodicalId":50408,"journal":{"name":"Heat Transfer Research","volume":"28 1","pages":""},"PeriodicalIF":1.7,"publicationDate":"2024-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139084494","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"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 : 2024-01-01DOI: 10.1615/heattransres.2024053037
Andaç Batur Çolak, Mustafa Bayrak
Estimating the heat transfer parameters of parabolic trough solar collectors with machine learning is crucial for improving the efficiency and performance of these renewable energy systems, optimizing their design and operation, and reducing costs while increasing the use of solar energy as a sustainable power source. In this study, the heat transfer characteristics of two different nanofluids flowing through the porous media in a straight plane underneath thermal jump conditions were investigated by machine learning methods. For the flow in the parabolic trough solar collector, two different nanofluids obtained from silver- and copper-based motor oil are considered. Flow characteristics were obtained by nonlinear surface tension, thermal radiation, and Cattaneo–Christov heat flow, which was used to calculate the heat flow in the thermal boundary layer. A neural network structure was established to estimate the skin friction and Nusselt number determined for the analysis of the flow characteristic. The data used in the multilayer neural network, which was developed using a total of 30 data sets, were divided into three groups as training, validation, and testing. In the input layer of the network model with 15 neurons in the hidden layer, 10 parameters were defined and four different results were obtained for two different nanofluids in the output layer. The prediction performance of the established neural network model has been comprehensively studied by means of several performance parameters. The study findings presented that the established artificial neural network can predict the heat transfer characteristics of two different nanofluids obtained from silver- and copper-based motor oil with deviation rates less than 0.06%.
{"title":"A NOVEL MACHINE LEARNING STUDY: MAXIMIZING THE EFFICIENCY OF PARABOLIC TROUGH SOLAR COLLECTORS WITH ENGINE OIL-BASED COPPER AND SILVER NANOFLUIDS","authors":"Andaç Batur Çolak, Mustafa Bayrak","doi":"10.1615/heattransres.2024053037","DOIUrl":"https://doi.org/10.1615/heattransres.2024053037","url":null,"abstract":"Estimating the heat transfer parameters of parabolic trough solar collectors with machine learning is crucial for\u0000improving the efficiency and performance of these renewable energy systems, optimizing their design and operation,\u0000and reducing costs while increasing the use of solar energy as a sustainable power source. In this study, the heat transfer characteristics of two different nanofluids flowing through the porous media in a straight plane underneath thermal jump conditions were investigated by machine learning methods. For the flow in the parabolic trough solar collector,\u0000two different nanofluids obtained from silver- and copper-based motor oil are considered. Flow characteristics were\u0000obtained by nonlinear surface tension, thermal radiation, and Cattaneo–Christov heat flow, which was used to calculate\u0000the heat flow in the thermal boundary layer. A neural network structure was established to estimate the skin friction\u0000and Nusselt number determined for the analysis of the flow characteristic. The data used in the multilayer neural\u0000network, which was developed using a total of 30 data sets, were divided into three groups as training, validation, and\u0000testing. In the input layer of the network model with 15 neurons in the hidden layer, 10 parameters were defined and\u0000four different results were obtained for two different nanofluids in the output layer. The prediction performance of the established neural network model has been comprehensively studied by means of several performance parameters. The study findings presented that the established artificial neural network can predict the heat transfer characteristics of two different nanofluids obtained from silver- and copper-based motor oil with deviation rates less than 0.06%.","PeriodicalId":50408,"journal":{"name":"Heat Transfer Research","volume":"41 1","pages":""},"PeriodicalIF":1.7,"publicationDate":"2024-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141526926","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"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 : 2024-01-01DOI: 10.1615/heattransres.2024051490
Meltem ARISU, Tayfun MENLİK
Energy consumption worldwide continues to increase due to factors such as population growth, rural-to-urban migration, technological advancements, and the rising use of technological products that make life easier. As a result, there is a growing demand for renewable energy sources in energy supply, and technological research is conducted to address energy losses and improve existing systems for more efficient energy use. The Organic Rankine Cycle (ORC) is a thermodynamic cycle used for converting heat energy, similar to the Clausius-Rankine cycle. With evolving technology and increasing energy needs, studies related to the Organic Rankine Cycle are of great interest to researchers. This study examines the impact of adding nano-particles to the working fluids used in the ORC system on its performance. Seven different working fluids were selected, including R141b, R123, R142b (isentropic), R22, and R32 (wet), as well as R114 and R600 (dry). Performance was calculated for 14 different nano-fluids created by adding Al2O3 and TiO2 nano-particles to the working fluids. The EES software was used in the analyses. Among the types of working fluids, it was observed that isentropic working fluids were more suitable for the ORC system, particularly R141b and R123. When considering the working fluid type for the ORC system, it was found that isentropic working fluids achieved higher efficiency, followed by dry-type working fluids. The lowest efficiency values were obtained for R22 and R32 working fluids.
{"title":"Investigation of the Effect of Using Different Nanofluids on the Performance of the Organic Rankine Cycle","authors":"Meltem ARISU, Tayfun MENLİK","doi":"10.1615/heattransres.2024051490","DOIUrl":"https://doi.org/10.1615/heattransres.2024051490","url":null,"abstract":"Energy consumption worldwide continues to increase due to factors such as population growth, rural-to-urban migration, technological advancements, and the rising use of technological products that make life easier. As a result, there is a growing demand for renewable energy sources in energy supply, and technological research is conducted to address energy losses and improve existing systems for more efficient energy use. The Organic Rankine Cycle (ORC) is a thermodynamic cycle used for converting heat energy, similar to the Clausius-Rankine cycle. With evolving technology and increasing energy needs, studies related to the Organic Rankine Cycle are of great interest to researchers. This study examines the impact of adding nano-particles to the working fluids used in the ORC system on its performance. Seven different working fluids were selected, including R141b, R123, R142b (isentropic), R22, and R32 (wet), as well as R114 and R600 (dry). Performance was calculated for 14 different nano-fluids created by adding Al2O3 and TiO2 nano-particles to the working fluids. The EES software was used in the analyses. Among the types of working fluids, it was observed that isentropic working fluids were more suitable for the ORC system, particularly R141b and R123. When considering the working fluid type for the ORC system, it was found that isentropic working fluids achieved higher efficiency, followed by dry-type working fluids. The lowest efficiency values were obtained for R22 and R32 working fluids.","PeriodicalId":50408,"journal":{"name":"Heat Transfer Research","volume":"65 1","pages":""},"PeriodicalIF":1.7,"publicationDate":"2024-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139459914","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"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 : 2024-01-01DOI: 10.1615/heattransres.2024051252
Anitha Sakthivel, Tiju Thomas
Here we report a numerical analysis of a cylindrical tube heat exchanger equipped with perforated conical rings. This study reports entropy generation, energy consumption and thermal evaluation of heat exchanger by using ternary hybrid nanofluid (as a coolant). The nanomaterials such as Al2O3, Cu, MWCNT (multi walled carbon nanotubes) with various volume fraction (φ=0-0.5%) are used. The mean diameter of the nanoparticles is 42 nm. The geometrical effects of perforated conical rings on the heat transfer rate, effectiveness, performance index, entropy generation and energy consumption are discussed. Mass flow rate is varied from 0.2 kg/s to 1 kg/s. The optimum performance is highlighted with 0.5% of volume fraction along with 0.4 kg/s mass flow rate. It is noted that the entropy generation is 50% lower by using ternary hybrid nanofluid. This study enables to understand the choice and volume fraction of particles, base fluid and flow rate of the fluid motion.
{"title":"Entropy generation and heat transfer performance of cylindrical tube heat exchanger with perforated conical rings: a numerical study","authors":"Anitha Sakthivel, Tiju Thomas","doi":"10.1615/heattransres.2024051252","DOIUrl":"https://doi.org/10.1615/heattransres.2024051252","url":null,"abstract":"Here we report a numerical analysis of a cylindrical tube heat exchanger equipped with perforated conical rings. This study reports entropy generation, energy consumption and thermal evaluation of heat exchanger by using ternary hybrid nanofluid (as a coolant). The nanomaterials such as Al2O3, Cu, MWCNT (multi walled carbon nanotubes) with various volume fraction (φ=0-0.5%) are used. The mean diameter of the nanoparticles is 42 nm. The geometrical effects of perforated conical rings on the heat transfer rate, effectiveness, performance index, entropy generation and energy consumption are discussed. Mass flow rate is varied from 0.2 kg/s to 1 kg/s. The optimum performance is highlighted with 0.5% of volume fraction along with 0.4 kg/s mass flow rate. It is noted that the entropy generation is 50% lower by using ternary hybrid nanofluid. This study enables to understand the choice and volume fraction of particles, base fluid and flow rate of the fluid motion.","PeriodicalId":50408,"journal":{"name":"Heat Transfer Research","volume":"40 1","pages":""},"PeriodicalIF":1.7,"publicationDate":"2024-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139414509","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"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 : 2024-01-01DOI: 10.1615/heattransres.2024051366
Yousuf Alhendal
When a fluid moves from lower to higher surface tension regions, its bubble or droplet moves in the direction of the temperature gradient (∇T), a process known as Marangoni flow occurs. In this paper, the drop movement in both stagnant and vibrated liquid in a rotating cylinder is analyzed and numerically presented using a computational fluid dynamics (CFD) approach. For two-phase flow, the governing continuum conservation equations are solved using the commercial program Ansys-Fluent. The Volume of Fluid (VOF) method has been found to be a useful research tool for studying multiphase interaction. It tracks the liquid/liquid interface in 2D and 3D domains. As the Marangoni number increases, the inherent velocity of drops decreases, which is consistent with earlier space onboard experimental findings that have been documented in the literature. This work revealed the complex behavior of droplets in zero gravity, where some neglected forces, such as rotational motion and host fluid vibration, that vanish in the presence of gravity, are the main source of the observed behavior. It was discovered that the thermocapillary droplet migration, which was insignificant in the presence of gravity, was significantly influenced by the small frequency amplitude (Am), which decreases with an increase in it. The study also showed that, in a static liquid inside a rotating cylinder, the velocity of thermocapillary droplet migration decreased. Up until this effect vanishes with increasing temperature gradient, increasing the temperature gradient (∇T) also increases the migration speed of the droplet inside the vibrating fluid and a rotating cylinder of different number of Marangoni (Ma
{"title":"Influence of Temperature Gradients and Fluid Vibrations on the Thermocapillary Droplet Behavior in a Rotating Cylinder","authors":"Yousuf Alhendal","doi":"10.1615/heattransres.2024051366","DOIUrl":"https://doi.org/10.1615/heattransres.2024051366","url":null,"abstract":"When a fluid moves from lower to higher surface tension regions, its bubble or droplet moves in the direction of the temperature gradient (∇T), a process known as Marangoni flow occurs. In this paper, the drop movement in both stagnant and vibrated liquid in a rotating cylinder is analyzed and numerically presented using a computational fluid dynamics (CFD) approach. For two-phase flow, the governing continuum conservation equations are solved using the commercial program Ansys-Fluent. The Volume of Fluid (VOF) method has been found to be a useful research tool for studying multiphase interaction. It tracks the liquid/liquid interface in 2D and 3D domains. As the Marangoni number increases, the inherent velocity of drops decreases, which is consistent with earlier space onboard experimental findings that have been documented in the literature. This work revealed the complex behavior of droplets in zero gravity, where some neglected forces, such as rotational motion and host fluid vibration, that vanish in the presence of gravity, are the main source of the observed behavior. It was discovered that the thermocapillary droplet migration, which was insignificant in the presence of gravity, was significantly influenced by the small frequency amplitude (Am), which decreases with an increase in it. The study also showed that, in a static liquid inside a rotating cylinder, the velocity of thermocapillary droplet migration decreased. Up until this effect vanishes with increasing temperature gradient, increasing the temperature gradient (∇T) also increases the migration speed of the droplet inside the vibrating fluid and a rotating cylinder of different number of Marangoni (Ma","PeriodicalId":50408,"journal":{"name":"Heat Transfer Research","volume":"1 1","pages":""},"PeriodicalIF":1.7,"publicationDate":"2024-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139482281","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"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 : 2024-01-01DOI: 10.1615/heattransres.2024052307
Muhammed Musab Gavgali, Aziz Hakan Altun, Eyub Canli
The plate-fin heat sink geometry was modified to have the fin form sinusoidal wave shape in the horizontal direction with twelve variations by amplitude and period changes. Three different wave periods and four different wave amplitudes were used. The purpose was to alter natural convection motion in favor of heat transfer effectiveness. The main performance indicator was the base-plate average temperature. The independent geometric parameters were experimentally examined in terms of the effectiveness of natural convection heat transfer by the measured average temperature values. Heat transfer by radiation was calculated by an analytical algebraic approach in order to obtain the Nusselt number solely based on convective heat transfer. Eight different heat inputs were used for each tested geometry to change the Grashof and Rayleigh numbers in a laminar flow interval. As reference geometries, a flat plate and a heat sink with straight/flat-plate fins were utilized. The heat sinks were also oriented to three different angles by a test stand. Accordingly, thirty six unique experimental cases were examined as a result of 327 trials and 1100 hours of testing. It was realized that the wavy fin geometry enhances natural convection heat transfer compared to the base-plate and flat-plate-fin heat sinks. However, increasing period and amplitude of the wave form more than initial values deteriorated the gains by the modifications on the fins. Since a single-period, 2-mm-amplitude heat sink resulted in the highest Nusselt number for all orientations, an optimum may be sought about this setting. As a general evaluation, computational simulations for spatial resolution of the event physics and dimensional optimization are standing as future study targets.
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