Pub Date : 2024-12-26DOI: 10.1016/j.ijheatfluidflow.2024.109725
Viacheslav Papkov , Boyan Zhang , Han Su , Haojie Chen , Dmitry Pashchenko
This paper deals with the numerical simulation of laminar flow over a porous cylinder under endothermic steam methane reforming reactions. The two-dimensional RANS approach is used to understand the effect of endothermic chemical reactions on the Kármán vortex street and heat transfer coefficient for a wide range of governing temperatures relevant to industrial applications of steam methane reforming. To achieve this goal, a set of calculations is performed for both transient and steady-state regimes, as well as for reactive and non-reactive flows. It was observed that steam methane reforming reactions have an effect on the Kármán vortex parameters. An increase in the catalytic cylinder temperature leads to an increase in the size of the single vortex and the length of the period. Under the analyzed conditions, for a cylinder temperature of 1200 K, the effect of chemical reactions on the Kármán vortex is maximal because the reaction rates strongly depend on temperature. Visualizations of the Kármán vortex formation for reactive and non-reactive flows are provided. Particular attention is paid to the analysis of the heat transfer coefficients on the cylinder surface. It was shown that endothermic chemical reactions significantly increase the heat supplied from the surface to the reacting flow.
{"title":"Numerical modeling of laminar flow over a porous cylinder under endothermic steam methane reforming reaction","authors":"Viacheslav Papkov , Boyan Zhang , Han Su , Haojie Chen , Dmitry Pashchenko","doi":"10.1016/j.ijheatfluidflow.2024.109725","DOIUrl":"10.1016/j.ijheatfluidflow.2024.109725","url":null,"abstract":"<div><div>This paper deals with the numerical simulation of laminar flow over a porous cylinder under endothermic steam methane reforming reactions. The two-dimensional RANS approach is used to understand the effect of endothermic chemical reactions on the Kármán vortex street and heat transfer coefficient for a wide range of governing temperatures relevant to industrial applications of steam methane reforming. To achieve this goal, a set of calculations is performed for both transient and steady-state regimes, as well as for reactive and non-reactive flows. It was observed that steam methane reforming reactions have an effect on the Kármán vortex parameters. An increase in the catalytic cylinder temperature leads to an increase in the size of the single vortex and the length of the period. Under the analyzed conditions, for a cylinder temperature of 1200 K, the effect of chemical reactions on the Kármán vortex is maximal because the reaction rates strongly depend on temperature. Visualizations of the Kármán vortex formation for reactive and non-reactive flows are provided. Particular attention is paid to the analysis of the heat transfer coefficients on the cylinder surface. It was shown that endothermic chemical reactions significantly increase the heat supplied from the surface to the reacting flow.</div></div>","PeriodicalId":335,"journal":{"name":"International Journal of Heat and Fluid Flow","volume":"112 ","pages":"Article 109725"},"PeriodicalIF":2.6,"publicationDate":"2024-12-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143140867","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"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 : 2024-12-26DOI: 10.1016/j.ijheatfluidflow.2024.109732
Vinh Nguyen Duy , Tan Nguyen Tien , Dien Vu Minh , Quang Khong Vu
This study investigates the effects of the heat transfer performance of the fluids and their supplied pressure on TEGs’ performance. Consequently, experiments are conducted to evaluate the fluids as mentioned and the impact of various pressures on the bars from 2 to 6. In addition, the TEG’s working temperature is adjusted to adapt each fluid’s characteristics to find the maximum power point tracker. In general, the study’s results reveal that the power of the TEG significantly depends on the features of the fluids. Indeed, freshwater shows superior heat exchange efficiency compared to other liquids. When fixing the temperature of the cold side about 30 °C, the maximum power for the fluids corresponding to the different hot side temperature is 9.8, 30, 35, and 44 W, and for the fluids of water, ethylene glycol, lubricant, and glycerin, respectively. In addition, when the flow rate changes from 1 to 5 L/min, the voltage and output capacity of the thermoelectric device tend to increase gradually. In conclusion, working fluids’ boundary conditions and characteristics dramatically affect the TEG performance.
{"title":"An experimental and Comparative performance of a thermal electric generator system using different heat exchanger fluids","authors":"Vinh Nguyen Duy , Tan Nguyen Tien , Dien Vu Minh , Quang Khong Vu","doi":"10.1016/j.ijheatfluidflow.2024.109732","DOIUrl":"10.1016/j.ijheatfluidflow.2024.109732","url":null,"abstract":"<div><div>This study investigates the effects of the heat transfer performance of the fluids and their supplied pressure on TEGs’ performance. Consequently, experiments are conducted to evaluate the fluids as mentioned and the impact of various pressures on the bars from 2 to 6. In addition, the TEG’s working temperature is adjusted to adapt each fluid’s characteristics to find the maximum power point tracker. In general, the study’s results reveal that the power of the TEG significantly depends on the features of the fluids. Indeed, freshwater shows superior heat exchange efficiency compared to other liquids. When fixing the temperature of the cold side about 30 °C, the maximum power for the fluids corresponding to the different hot side temperature is 9.8, 30, 35, and 44 W, and for the fluids of water, ethylene glycol, lubricant, and glycerin, respectively. In addition, when the flow rate changes from 1 to 5 L/min, the voltage and output capacity of the thermoelectric device tend to increase gradually. In conclusion, working fluids’ boundary conditions and characteristics dramatically affect the TEG performance.</div></div>","PeriodicalId":335,"journal":{"name":"International Journal of Heat and Fluid Flow","volume":"112 ","pages":"Article 109732"},"PeriodicalIF":2.6,"publicationDate":"2024-12-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143140158","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"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 : 2024-12-26DOI: 10.1016/j.ijheatfluidflow.2024.109711
Tao Li , Zhengquan Chen , Wenxuan Zhao , Jianing Yuan , Chunxiang Wang , Yuchun Zhang
Due to the ever-growing development and construction of municipalities, the underground tunnel structures raises the probability of traffic accidents and the fire risks. The effects of different longitudinal ventilation velocities and air curtain spouting angles (ASA) on the temperature distribution and maximum ceiling temperature rise in a scaled bifurcated tunnel were investigated experimentally and numerically with different heat release rates. Induced by synergistic effect of longitudinal ventilation and air curtain, the maximum ceiling temperature in the fire zone was shifted. The high temperature ranges of ceiling expanded as ASA increased. The smoke sealing effect (SSE) of different ASA ranged from 0.6 to 0.82, and the 15 ° showed a more stable SSE. Besides, based on the Li model, the factor of ASA was introduced for predicting the maximum ceiling temperature rise, which is consistent with the experimental data. Comparison between the experiments and the simulations showed good agreement.
{"title":"Study on the smoke sealing efficiency of air curtain and maximum ceiling temperature rise under longitudinal ventilation in bifurcated tunnel","authors":"Tao Li , Zhengquan Chen , Wenxuan Zhao , Jianing Yuan , Chunxiang Wang , Yuchun Zhang","doi":"10.1016/j.ijheatfluidflow.2024.109711","DOIUrl":"10.1016/j.ijheatfluidflow.2024.109711","url":null,"abstract":"<div><div>Due to the ever-growing development and construction of municipalities, the underground tunnel structures raises the probability of traffic accidents and the fire risks. The effects of different longitudinal ventilation velocities and air curtain spouting angles (ASA) on the temperature distribution and maximum ceiling temperature rise in a scaled bifurcated tunnel were investigated experimentally and numerically with different heat release rates. Induced by synergistic effect of longitudinal ventilation and air curtain, the maximum ceiling temperature in the fire zone was shifted. The high temperature ranges of ceiling expanded as ASA increased. The smoke sealing effect (SSE) of different ASA ranged from 0.6 to 0.82, and the 15 ° showed a more stable SSE. Besides, based on the Li model, the factor <span><math><mi>θ</mi></math></span> of ASA was introduced for predicting the maximum ceiling temperature rise, which is consistent with the experimental data. Comparison between the experiments and the simulations showed good agreement.</div></div>","PeriodicalId":335,"journal":{"name":"International Journal of Heat and Fluid Flow","volume":"112 ","pages":"Article 109711"},"PeriodicalIF":2.6,"publicationDate":"2024-12-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143140154","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"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 : 2024-12-25DOI: 10.1016/j.ijheatfluidflow.2024.109735
Xinshan Sun, Zhan Liu, Shenrui Ji, Kaifeng Yuan
Traditional air-cooling systems cannot meet special requirements of high-density computing power data centers (DCs). The single-phase immersion cooling (SPIC) is considered as one of the best ways to effectively cool high-density computing power DC cabinets. In this study, a SPIC unit was experimentally investigated with dielectric fluid Noah 3000D under a designed heat load of 20 kW. The impact of the cooling water flow rate qv2 on the thermal characteristics, flow resistance and power consumption of the SPIC unit were investigated. The results show that the temperatures of both the coolant and cooling water decrease with the increase of qv2, but the temperature difference of coolant increases with the increase of qv2. An increase in coolant temperature difference means an increase in temperature non-uniformity. The increase in qv2 also leads to an increase in system flow resistance. In this experiment, the pressure loss of the heat exchanger and pipelines on the coolant side, account for about 56 % and 44 %, respectively. The power usage effectiveness of the cooling system in DC (cPUE) and coefficient of performance (COP) of the SPIC unit vary in the range of 1.08–1.09 and 5.69–7.21, respectively. Moreover, it is found that simply increasing qv2 cannot significantly improve the heat exchange of SPIC units, but will increase system’s energy consumption to a certain extent. The present study mainly focuses on the laboratory experimental test on the SPIC unit, and the related conclusions are significant to the design and operation of SPIC units in high-density computing power DCs.
{"title":"Experimental study on thermal performance of a single-phase immersion cooling unit for high-density computing power data center","authors":"Xinshan Sun, Zhan Liu, Shenrui Ji, Kaifeng Yuan","doi":"10.1016/j.ijheatfluidflow.2024.109735","DOIUrl":"10.1016/j.ijheatfluidflow.2024.109735","url":null,"abstract":"<div><div>Traditional air-cooling systems cannot meet special requirements of high-density computing power data centers (DCs). The single-phase immersion cooling (SPIC) is considered as one of the best ways to effectively cool high-density computing power DC cabinets. In this study, a SPIC unit was experimentally investigated with dielectric fluid Noah 3000D under a designed heat load of 20 kW. The impact of the cooling water flow rate <em>q<sub>v</sub></em><sub>2</sub> on the thermal characteristics, flow resistance and power consumption of the SPIC unit were investigated. The results show that the temperatures of both the coolant and cooling water decrease with the increase of <em>q<sub>v</sub></em><sub>2</sub>, but the temperature difference of coolant increases with the increase of <em>q<sub>v</sub></em><sub>2</sub>. An increase in coolant temperature difference means an increase in temperature non-uniformity. The increase in <em>q<sub>v</sub></em><sub>2</sub> also leads to an increase in system flow resistance. In this experiment, the pressure loss of the heat exchanger and pipelines on the coolant side, account for about 56 % and 44 %, respectively. The power usage effectiveness of the cooling system in DC (cPUE) and coefficient of performance (COP) of the SPIC unit vary in the range of 1.08–1.09 and 5.69–7.21, respectively. Moreover, it is found that simply increasing <em>q<sub>v</sub></em><sub>2</sub> cannot significantly improve the heat exchange of SPIC units, but will increase system’s energy consumption to a certain extent. The present study mainly focuses on the laboratory experimental test on the SPIC unit, and the related conclusions are significant to the design and operation of SPIC units in high-density computing power DCs.</div></div>","PeriodicalId":335,"journal":{"name":"International Journal of Heat and Fluid Flow","volume":"112 ","pages":"Article 109735"},"PeriodicalIF":2.6,"publicationDate":"2024-12-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143140868","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Heat exchangers have long been widely used tools in various industries. The close association of heat exchangers with energy consumption motivates engineers to strive for high thermal efficiency through modifications in size and cost minimization in the design process. Active, passive, and compound techniques are employed to enhance heat transfer. Twisted tubes and inserts fall within the category of passive swirl flow devices. These devices enhance heat transfer by generating secondary flows and disrupting the thermal boundary layer. Twisted tubes have the potential to further augment heat transfer and improve the efficiency of heat exchangers by enlarging the surface area, mixing fluid flow, and amplifying turbulence. This review specifically focuses on twisted tubes with elliptical/oval cross-sections. Geometrical parameters such as twist pitch (number of twists) and cross-section characteristics significantly influence heat transfer enhancement in twisted tubes. In this review, studies that involve the combination of twisted elliptical/oval tubes with other passive techniques, such as inserts (wire coils, twisted tapes), and nanofluids, as well as active techniques, are also discussed. This work aims to contribute to enhancing heat exchanger performance through the application of the twisted tube technique.
{"title":"Comprehensive review of heat transfer and fluid flow characteristics of elliptical/oval twisted tubes","authors":"Aliakbar Sheikhi Azizi , S. Morteza Mousavi , Kambiz Vafai , A.Ali Rabienataj Darzi","doi":"10.1016/j.ijheatfluidflow.2024.109639","DOIUrl":"10.1016/j.ijheatfluidflow.2024.109639","url":null,"abstract":"<div><div>Heat exchangers have long been widely used tools in various industries. The close association of heat exchangers with energy consumption motivates engineers to strive for high thermal efficiency through modifications in size and cost minimization in the design process. Active, passive, and compound techniques are employed to enhance heat transfer. Twisted tubes and inserts fall within the category of passive swirl flow devices. These devices enhance heat transfer by generating secondary flows and disrupting the thermal boundary layer. Twisted tubes have the potential to further augment heat transfer and improve the efficiency of heat exchangers by enlarging the surface area, mixing fluid flow, and amplifying turbulence. This review specifically focuses on twisted tubes with elliptical/oval cross-sections. Geometrical parameters such as twist pitch (number of twists) and cross-section characteristics significantly influence heat transfer enhancement in twisted tubes. In this review, studies that involve the combination of twisted elliptical/oval tubes with other passive techniques, such as inserts (wire coils, twisted tapes), and nanofluids, as well as active techniques, are also discussed. This work aims to contribute to enhancing heat exchanger performance through the application of the twisted tube technique.</div></div>","PeriodicalId":335,"journal":{"name":"International Journal of Heat and Fluid Flow","volume":"112 ","pages":"Article 109639"},"PeriodicalIF":2.6,"publicationDate":"2024-12-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143140603","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"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 : 2024-12-24DOI: 10.1016/j.ijheatfluidflow.2024.109707
Xingwen Peng , Wen Yao , Xingchen Li , Xiaoqian Chen
Reconstructing flow and temperature fields from limited sensor measurements is a critical capability for state evaluation, optimization, and control of flow and heat transfer processes. While deep learning has been harnessed for physical field reconstruction and has demonstrated impressive performance, it faces the challenge of achieving enhanced precision and computational efficiency, particularly when dealing with intricate, nonlinear problems. Inspired by the observation that numerous physical phenomena exhibit distinct behaviors within isolated regions of the spatial domain, such as boundary layers and separated flows, we introduce a novel deep learning approach that employs a “divide-and-conquer” strategy. In this methodology, the entire spatial domain is partitioned into various subdomains, each of which is entrusted to a dedicated neural network for precise reconstruction of the flow and temperature fields. Initially, the physical domain is segmented into discrete subdomains using K-means clustering based on cosine distance. Subsequently, individual deep neural networks are constructed to map from limited sensor measurements to the physical field within each subdomain. Finally, the separately reconstructed fields are amalgamated to constitute the ultimate physical field representation. To validate the efficacy of our approach, numerical experiments were conducted across four diverse cases: flow around a cylinder, turbulent channel flow, transonic flow, and conduction involving multiple heat sources. The results demonstrate the superior accuracy and efficiency of the proposed method. In comparison to the non-partitioned approach, our method achieves a minimum reduction of 44.6% in mean absolute error, simultaneously enhancing training efficiency by approximately 30.0% under the premise that the model can utilize multi-GPUs parallel training, all while maintaining a manageable model complexity.
{"title":"A divide-and-conquer deep learning approach to reconstruct flow and temperature fields","authors":"Xingwen Peng , Wen Yao , Xingchen Li , Xiaoqian Chen","doi":"10.1016/j.ijheatfluidflow.2024.109707","DOIUrl":"10.1016/j.ijheatfluidflow.2024.109707","url":null,"abstract":"<div><div>Reconstructing flow and temperature fields from limited sensor measurements is a critical capability for state evaluation, optimization, and control of flow and heat transfer processes. While deep learning has been harnessed for physical field reconstruction and has demonstrated impressive performance, it faces the challenge of achieving enhanced precision and computational efficiency, particularly when dealing with intricate, nonlinear problems. Inspired by the observation that numerous physical phenomena exhibit distinct behaviors within isolated regions of the spatial domain, such as boundary layers and separated flows, we introduce a novel deep learning approach that employs a “divide-and-conquer” strategy. In this methodology, the entire spatial domain is partitioned into various subdomains, each of which is entrusted to a dedicated neural network for precise reconstruction of the flow and temperature fields. Initially, the physical domain is segmented into discrete subdomains using K-means clustering based on cosine distance. Subsequently, individual deep neural networks are constructed to map from limited sensor measurements to the physical field within each subdomain. Finally, the separately reconstructed fields are amalgamated to constitute the ultimate physical field representation. To validate the efficacy of our approach, numerical experiments were conducted across four diverse cases: flow around a cylinder, turbulent channel flow, transonic flow, and conduction involving multiple heat sources. The results demonstrate the superior accuracy and efficiency of the proposed method. In comparison to the non-partitioned approach, our method achieves a minimum reduction of 44.6% in mean absolute error, simultaneously enhancing training efficiency by approximately 30.0% under the premise that the model can utilize multi-GPUs parallel training, all while maintaining a manageable model complexity.</div></div>","PeriodicalId":335,"journal":{"name":"International Journal of Heat and Fluid Flow","volume":"112 ","pages":"Article 109707"},"PeriodicalIF":2.6,"publicationDate":"2024-12-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143140870","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"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 : 2024-12-24DOI: 10.1016/j.ijheatfluidflow.2024.109731
Lucong Han, Yuying Yan
Microwave vacuum drying (MVD) is widely adopted in the food industry helping maintain high product quality but the impact of shrinkage on heat and mass transfer is often overlooked. In the present study, the popular fruit, pitaya, was selected for a case study; a heat-moisture-mechanical (HMM) coupling multiphase porous medium model is developed to comprehensively analyse the effect of shrinkage on heat and mass transfer during the MVD. The findings indicate that the HMM model shows a faster decrease in moisture content, with the maximum deviation of 144.85%, and a larger evaporation rate peak, with a deviation of 36.76%. The average temperature predicted by the HMM model was lower than that of the HM model during the early drying stage, with a maximum temperature difference of 5.76℃. Throughout the drying process, axial shrinkage was greater than radial shrinkage. The HMM model can effectively predict the influence of material property parameters on the shrinkage process, in which the hygroscopic expansion coefficient exhibits the most significant impact on volumetric strain (reaching up to 10.1%). The model can more accurately simulate the food MVD process and provides technical support for optimizing the drying process and enhancing product quality.
{"title":"Heat-moisture-mechanical bidirectional coupling multiphase porous media model for microwave vacuum drying of pitaya","authors":"Lucong Han, Yuying Yan","doi":"10.1016/j.ijheatfluidflow.2024.109731","DOIUrl":"10.1016/j.ijheatfluidflow.2024.109731","url":null,"abstract":"<div><div>Microwave vacuum drying (MVD) is widely adopted in the food industry helping maintain high product quality but the impact of shrinkage on heat and mass transfer is often overlooked. In the present study, the popular fruit, pitaya, was selected for a case study; a heat-moisture-mechanical (HMM) coupling multiphase porous medium model is developed to comprehensively analyse the effect of shrinkage on heat and mass transfer during the MVD. The findings indicate that the HMM model shows a faster decrease in moisture content, with the maximum deviation of 144.85%, and a larger evaporation rate peak, with a deviation of 36.76%. The average temperature predicted by the HMM model was lower than that of the HM model during the early drying stage, with a maximum temperature difference of 5.76℃. Throughout the drying process, axial shrinkage was greater than radial shrinkage. The HMM model can effectively predict the influence of material property parameters on the shrinkage process, in which the hygroscopic expansion coefficient exhibits the most significant impact on volumetric strain (reaching up to 10.1%). The model can more accurately simulate the food MVD process and provides technical support for optimizing the drying process and enhancing product quality.</div></div>","PeriodicalId":335,"journal":{"name":"International Journal of Heat and Fluid Flow","volume":"112 ","pages":"Article 109731"},"PeriodicalIF":2.6,"publicationDate":"2024-12-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143140869","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-12-23DOI: 10.1016/j.ijheatfluidflow.2024.109726
Reza Beigzadeh, Saber Soltanian, Donya Tofangchi
Optimizing the performance of heat exchangers is critical for enhancing energy efficiency in industrial applications. Traditional methods often fail to balance heat transfer enhancement and pressure loss. This study addresses this gap by integrating Computational Fluid Dynamics (CFD) and Genetic Algorithms (GA) to optimize circular baffle heat exchangers, targeting both Nusselt number (Nu) and friction factor (f). CFD simulations were conducted over Reynolds numbers from 30,000 to 70,000, with water as the working fluid. Key geometric parameters, baffle diameter ratio (di/D), spacing ratio (S/D), and hole count (N) were investigated. The results show that reducing the baffle spacing from S/D = 5.56 to S/D = 2.381 led to a 42 % increase in Nu, while f increased by 89 %. Using GA, optimal configurations were identified, achieving a maximum Nu of 1588.1 and a corresponding f of 12.522 at Re = 70,000. This novel approach bridges the gap between maximizing heat transfer and minimizing pressure drop, providing a new pathway for efficient heat exchanger design.
{"title":"Enhancing heat transfer efficiency in heat exchangers: A fusion of computational fluid dynamics and genetic algorithm for circular baffle optimization","authors":"Reza Beigzadeh, Saber Soltanian, Donya Tofangchi","doi":"10.1016/j.ijheatfluidflow.2024.109726","DOIUrl":"10.1016/j.ijheatfluidflow.2024.109726","url":null,"abstract":"<div><div>Optimizing the performance of heat exchangers is critical for enhancing energy efficiency in industrial applications. Traditional methods often fail to balance heat transfer enhancement and pressure loss. This study addresses this gap by integrating Computational Fluid Dynamics (CFD) and Genetic Algorithms (GA) to optimize circular baffle heat exchangers, targeting both Nusselt number (Nu) and friction factor (f). CFD simulations were conducted over Reynolds numbers from 30,000 to 70,000, with water as the working fluid. Key geometric parameters, baffle diameter ratio (di/D), spacing ratio (S/D), and hole count (N) were investigated. The results show that reducing the baffle spacing from S/D = 5.56 to S/D = 2.381 led to a 42 % increase in Nu, while f increased by 89 %. Using GA, optimal configurations were identified, achieving a maximum Nu of 1588.1 and a corresponding f of 12.522 at Re = 70,000. This novel approach bridges the gap between maximizing heat transfer and minimizing pressure drop, providing a new pathway for efficient heat exchanger design.</div></div>","PeriodicalId":335,"journal":{"name":"International Journal of Heat and Fluid Flow","volume":"112 ","pages":"Article 109726"},"PeriodicalIF":2.6,"publicationDate":"2024-12-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143140871","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"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 : 2024-12-21DOI: 10.1016/j.ijheatfluidflow.2024.109716
Shuangjie Yan , Jianjun Liu , Baitao An
This paper presents an investigation of mini-ribs that are arranged on the endwall to enhance heat transfer in pin–fin cooling channel on gas turbine vane trailing edge or double wall cooling. The mini-rib structure in this study consists of two types, straight rib and V-rib, and each type contains full length rib (#SR, #VR) and two broken ribs with different broken positions (#BSR1, #BSR2, #BVR1, #BVR2). The height-to-diameter ratio of the pin–fin is 2, and the ratio of mini-rib height to the diameter of the pin–fin is equal to 0.1. Numerical simulations with SST turbulence model are conducted to acquire the heat transfer and flow characteristics, and the effect of mini-rib types and broken positions on heat transfer enhancement performance is analyzed. The results are shown that the disturbance of the boundary layer near the wall by mini-rib resulted in better heat transfer on the endwall. Two types of mini-rib, full-length straight rib and V-rib, are arranged on the endwall in pin–fin cooling channel, which can effectively enhance the horseshoe vortex system around pin–fin. Compared with smooth endwall (#B), mini-ribs expand the high heat transfer region. The effect of different broken positions on the two types of mini-rib is obviously different. The endwall heat transfer with straight rib arrangement is greatly affected by the broken positions, and the flow resistance is less affected. However, the conclusion of V-rib is opposite. Overall thermal performance of #SR, #VR and #BSR1 is relatively high, which is 21% to 26% higher than that of #B. Arrangements of #SR, #VR, and #BSR1 are suitable for situations with high thermal loads and less concern for flow losses, while #BVR1 is suitable for situations where a certain heat transfer improvement is required but flow losses need to be limited.
{"title":"Effect of different mini-rib arrangements on endwall heat transfer in pin–fin channel","authors":"Shuangjie Yan , Jianjun Liu , Baitao An","doi":"10.1016/j.ijheatfluidflow.2024.109716","DOIUrl":"10.1016/j.ijheatfluidflow.2024.109716","url":null,"abstract":"<div><div>This paper presents an investigation of mini-ribs that are arranged on the endwall to enhance heat transfer in pin–fin cooling channel on gas turbine vane trailing edge or double wall cooling. The mini-rib structure in this study consists of two types, straight rib and V-rib, and each type contains full length rib (#SR, #VR) and two broken ribs with different broken positions (#BSR1, #BSR2, #BVR1, #BVR2). The height-to-diameter ratio of the pin–fin is 2, and the ratio of mini-rib height to the diameter of the pin–fin is equal to 0.1. Numerical simulations with SST turbulence model are conducted to acquire the heat transfer and flow characteristics, and the effect of mini-rib types and broken positions on heat transfer enhancement performance is analyzed. The results are shown that the disturbance of the boundary layer near the wall by mini-rib resulted in better heat transfer on the endwall. Two types of mini-rib, full-length straight rib and V-rib, are arranged on the endwall in pin–fin cooling channel, which can effectively enhance the horseshoe vortex system around pin–fin. Compared with smooth endwall (#B), mini-ribs expand the high heat transfer region. The effect of different broken positions on the two types of mini-rib is obviously different. The endwall heat transfer with straight rib arrangement is greatly affected by the broken positions, and the flow resistance is less affected. However, the conclusion of V-rib is opposite. Overall thermal performance of #SR, #VR and #BSR1 is relatively high, which is 21% to 26% higher than that of #B. Arrangements of #SR, #VR, and #BSR1 are suitable for situations with high thermal loads and less concern for flow losses, while #BVR1 is suitable for situations where a certain heat transfer improvement is required but flow losses need to be limited.</div></div>","PeriodicalId":335,"journal":{"name":"International Journal of Heat and Fluid Flow","volume":"112 ","pages":"Article 109716"},"PeriodicalIF":2.6,"publicationDate":"2024-12-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143140156","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"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 : 2024-12-20DOI: 10.1016/j.ijheatfluidflow.2024.109713
Sondus Al Qudah , Ali Radwan , Ibrahim I. El-Sharkawy
Improving heat transfer in circular tubes using twisted tape (TT) inserts has attracted researchers’ interest. This has led to exploring different insert shapes, materials, and configurations to understand their impact on heat exchanger performance. This study proposed a new design of TT insert with rings to enhance the heat transfer in circular tubes. Using Response Surface Methodology, a detailed experimental plan with ninety-three runs is created to investigate the effects of four main factors: the inlet flow velocity, twist pitch, TT height, and the TT length in the turbulent flow regime. The experimental investigation was conducted for a Reynolds number (Re) ranging from 33,000 to 46,000, using air as the working fluid. The TT inserts were designed with three different lengths (800 mm, 1000 mm, and 1200 mm), three-pitch distances (90 mm, 180 mm, and 270 mm), and three heights (18 mm, 21 mm, and 24 mm). These variations allowed for a comprehensive evaluation of the heat transfer performance and flow characteristics under turbulent flow conditions. Six different responses, including Nusselt number (Nu), friction factor (f), their respective ratios (Nu/Nuo) and (f/fo), the entropy production ratio (S′/S′o), and Bejan number ratio (Be/Bo) are experimentally evaluated. Various single and multi-objective optimization scenarios are conducted. The experimental results showed that adding the rings to the conventional TT inserts enhances the heat transfer characteristics compared with the TT without rings, especially at larger TT pitch distances. Further, the experimental results showed that the Nu values in the case of using the TT inserts with rings significantly increased by up to 25 % more than smooth pipes at low air velocities with larger pitch distance and by about 43 % at higher velocity and smaller pitch distance. Furthermore, accurate predictive models are obtained to evaluate these six responses in terms of the input design factors.
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