Blunt-nose body structures are widely used in vehicles for better heat distribution due to supersonic/hypersonic flight. However, such a body shape contributes to an increase of shock wave drag owing to the strong bow shock wave generated in its front flow field. Various alternative techniques to modify the flowfield in front of the fore-bodies are theoretically and practically proved to have obvious effects on minimizing the excessive aeroheating and higher wave drag problems. A couple of active controlled configurations including spikes and their combinations with aerodisk and injection are extensively investigated utilizing experimental and numerical methods. The drag and heat reduction effects achieved with different structural parameters and freestream conditions are elaborated in detail. Actually, in the design of optimal weight structures and thermal protection systems for cruise and re-entry vehicles, there exist considerable problems in which the fluid-thermal-structural coupling problems are critical. Such as the thermal and mechanical behavior of mechanical spike coupled with the aerodynamic flow problem. The present paper is intended to systematically analyze the active flow field control technology of spikes and their combinations by surveying and summarizing the related studies in this field. Moreover, the coupling problem encountered in high speed conditions are also taken into consideration with a systematic explication. This paper concludes with outlooks and recommendations on the noteworthy issues that need further investigations in the future.
{"title":"Active control devices of spiked body for drag and heat flux reduction in supersonic/hypersonic flows: State-of-the-art review","authors":"Yu-shan Meng, Zhong-wei Wang, Wei Huang, Yao-bin Niu, Zan Xie, Chao-yang Liu","doi":"10.1016/j.icheatmasstransfer.2024.108317","DOIUrl":"10.1016/j.icheatmasstransfer.2024.108317","url":null,"abstract":"<div><div>Blunt-nose body structures are widely used in vehicles for better heat distribution due to supersonic/hypersonic flight. However, such a body shape contributes to an increase of shock wave drag owing to the strong bow shock wave generated in its front flow field. Various alternative techniques to modify the flowfield in front of the fore-bodies are theoretically and practically proved to have obvious effects on minimizing the excessive aeroheating and higher wave drag problems. A couple of active controlled configurations including spikes and their combinations with aerodisk and injection are extensively investigated utilizing experimental and numerical methods. The drag and heat reduction effects achieved with different structural parameters and freestream conditions are elaborated in detail. Actually, in the design of optimal weight structures and thermal protection systems for cruise and re-entry vehicles, there exist considerable problems in which the fluid-thermal-structural coupling problems are critical. Such as the thermal and mechanical behavior of mechanical spike coupled with the aerodynamic flow problem. The present paper is intended to systematically analyze the active flow field control technology of spikes and their combinations by surveying and summarizing the related studies in this field. Moreover, the coupling problem encountered in high speed conditions are also taken into consideration with a systematic explication. This paper concludes with outlooks and recommendations on the noteworthy issues that need further investigations in the future.</div></div>","PeriodicalId":332,"journal":{"name":"International Communications in Heat and Mass Transfer","volume":"159 ","pages":"Article 108317"},"PeriodicalIF":6.4,"publicationDate":"2024-11-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142653839","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 : 2024-11-12DOI: 10.1016/j.icheatmasstransfer.2024.108314
Shunyang Li , Li Wan , Nan Gui , Xingtuan Yang , Jiyuan Tu , Shengyao Jiang
The thermodynamic properties of the pseudopotential lattice Boltzmann model are typically assessed using the mechanical stability condition. However, this condition is derived based on simple multiphase interfaces, limiting its applicability to circular interfaces such as droplets and bubbles. To address this limitation, this paper introduces a generalized mechanical stability condition that allows for the investigation of thermodynamic properties for multiphase interfaces. The equilibrium densities of the liquid and gas phases under the equilibrium pressure for simple multiphase interfaces are determined. The results indicate that thermodynamic consistency is achieved when the index of the pressure tensor ϵ is appropriately set. For the Carnahan-Starling equation of state, the optimal ϵ is 1.87. For the Peng-Robinson equation of state, the optimal ϵ is 1.73. The equilibrium gas pressure for circular interfaces, , is derived. It is found that deviates from the Kelvin equation significantly, with being eight times larger than the expected value. To rectify this, a modified pseudopotential model is proposed. This model achieves thermodynamic consistency without the need for tuning ϵ, and allows for tunable by adjusting the effective mass. Comparison with the current pseudopotential model reveals that the proposed model is closer to the Kelvin equation, with being four times larger than the expected value. Nevertheless, it is noted that the Kelvin equation cannot be strictly guaranteed, as the interface collapses or deforms due to insufficient surface tension. These findings suggest that an overestimated gas pressure is essential in the pseudopotential model to maintain the liquid-gas interface, albeit with a deviation from thermodynamic laws.
{"title":"Thermodynamic properties of pseudopotential lattice Boltzmann model for simple multiphase interfaces","authors":"Shunyang Li , Li Wan , Nan Gui , Xingtuan Yang , Jiyuan Tu , Shengyao Jiang","doi":"10.1016/j.icheatmasstransfer.2024.108314","DOIUrl":"10.1016/j.icheatmasstransfer.2024.108314","url":null,"abstract":"<div><div>The thermodynamic properties of the pseudopotential lattice Boltzmann model are typically assessed using the mechanical stability condition. However, this condition is derived based on simple multiphase interfaces, limiting its applicability to circular interfaces such as droplets and bubbles. To address this limitation, this paper introduces a generalized mechanical stability condition that allows for the investigation of thermodynamic properties for multiphase interfaces. The equilibrium densities of the liquid and gas phases under the equilibrium pressure for simple multiphase interfaces <span><math><msub><mi>p</mi><mn>0</mn></msub></math></span> are determined. The results indicate that thermodynamic consistency is achieved when the index of the pressure tensor <em>ϵ</em> is appropriately set. For the Carnahan-Starling equation of state, the optimal <em>ϵ</em> is 1.87. For the Peng-Robinson equation of state, the optimal ϵ is 1.73. The equilibrium gas pressure for circular interfaces, <span><math><msub><mi>p</mi><mrow><mi>g</mi><mo>,</mo><mi>c</mi></mrow></msub></math></span>, is derived. It is found that <span><math><msub><mi>p</mi><mrow><mi>g</mi><mo>,</mo><mi>c</mi></mrow></msub></math></span> deviates from the Kelvin equation significantly, with <span><math><mo>ln</mo><mfenced><mrow><msub><mi>p</mi><mrow><mi>g</mi><mo>,</mo><mi>c</mi></mrow></msub><mo>/</mo><msub><mi>p</mi><mn>0</mn></msub></mrow></mfenced></math></span> being eight times larger than the expected value. To rectify this, a modified pseudopotential model is proposed. This model achieves thermodynamic consistency without the need for tuning <em>ϵ</em>, and allows for tunable <span><math><msub><mi>p</mi><mrow><mi>g</mi><mo>,</mo><mi>c</mi></mrow></msub></math></span> by adjusting the effective mass. Comparison with the current pseudopotential model reveals that the proposed model is closer to the Kelvin equation, with <span><math><mo>ln</mo><mfenced><mrow><msub><mi>p</mi><mrow><mi>g</mi><mo>,</mo><mi>c</mi></mrow></msub><mo>/</mo><msub><mi>p</mi><mn>0</mn></msub></mrow></mfenced></math></span> being four times larger than the expected value. Nevertheless, it is noted that the Kelvin equation cannot be strictly guaranteed, as the interface collapses or deforms due to insufficient surface tension. These findings suggest that an overestimated gas pressure is essential in the pseudopotential model to maintain the liquid-gas interface, albeit with a deviation from thermodynamic laws.</div></div>","PeriodicalId":332,"journal":{"name":"International Communications in Heat and Mass Transfer","volume":"159 ","pages":"Article 108314"},"PeriodicalIF":6.4,"publicationDate":"2024-11-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142653783","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}
Currently, most methods for heat exchangers to achieve flow drag reduction or heat transfer enhancement are passive control strategies. However, the passive control strategy achieves either drag reduction or heat transfer enhancement, and it is difficult to achieve both drag reduction and heat transfer enhancement. In practical application, if both drag reduction and heat transfer can be achieved simultaneously, the energy consumption of the heat exchanger will be reduced, and the heat exchange area will be saved. For this reason, a micro cuboid vortex generator (MCVG) that can oscillate in the normal direction is located in a rectangular channel in the present work. The open-source software OpenFOAM was used to conduct large eddy numerical simulation research. The effects of oscillation at different heights on the fluid velocity, turbulent vortex structure, skin-friction coefficient, and Nusselt number are numerically investigated. The numerical results indicate that the MCVG with normal oscillation reduced the streamwise velocity upstream of its location, with a maximum reduction of 5.04 %. The streamwise velocity downstream of the MCVG is more affected, with all reductions exceeding 27 %. The MCVG with normal oscillation increased the normal velocity of the entire streamwise direction. Compared with the normal velocity upstream of the oscillation area, the normal velocity varies more dramatically downstream of the MCVG. Adding a MCVG with normal oscillation in the channel increased the skin-friction drag in the oscillation area and reduced the skin-friction drag downstream of the MCVG. The average skin-friction drag of the wall decreases up to 6.87 %. In addition, adding a MCVG with normal oscillation in the channel can also achieve enhanced heat transfer, and the average Nusselt number of the wall can be increased by up to 6.12 %. The comprehensive performance coefficient can be increased by up to 7.01 %.
{"title":"An active control strategy for simultaneously achieving turbulent drag reduction and heat transfer enhancement in heat exchangers: Oscillation of micro cuboid vortex generators","authors":"Jintao Niu, Jiansheng Wang, Xueling Liu, Liwei Dong","doi":"10.1016/j.icheatmasstransfer.2024.108315","DOIUrl":"10.1016/j.icheatmasstransfer.2024.108315","url":null,"abstract":"<div><div>Currently, most methods for heat exchangers to achieve flow drag reduction or heat transfer enhancement are passive control strategies. However, the passive control strategy achieves either drag reduction or heat transfer enhancement, and it is difficult to achieve both drag reduction and heat transfer enhancement. In practical application, if both drag reduction and heat transfer can be achieved simultaneously, the energy consumption of the heat exchanger will be reduced, and the heat exchange area will be saved. For this reason, a micro cuboid vortex generator (MCVG) that can oscillate in the normal direction is located in a rectangular channel in the present work. The open-source software OpenFOAM was used to conduct large eddy numerical simulation research. The effects of oscillation at different heights on the fluid velocity, turbulent vortex structure, skin-friction coefficient, and Nusselt number are numerically investigated. The numerical results indicate that the MCVG with normal oscillation reduced the streamwise velocity upstream of its location, with a maximum reduction of 5.04 %. The streamwise velocity downstream of the MCVG is more affected, with all reductions exceeding 27 %. The MCVG with normal oscillation increased the normal velocity of the entire streamwise direction. Compared with the normal velocity upstream of the oscillation area, the normal velocity varies more dramatically downstream of the MCVG. Adding a MCVG with normal oscillation in the channel increased the skin-friction drag in the oscillation area and reduced the skin-friction drag downstream of the MCVG. The average skin-friction drag of the wall decreases up to 6.87 %. In addition, adding a MCVG with normal oscillation in the channel can also achieve enhanced heat transfer, and the average Nusselt number of the wall can be increased by up to 6.12 %. The comprehensive performance coefficient can be increased by up to 7.01 %.</div></div>","PeriodicalId":332,"journal":{"name":"International Communications in Heat and Mass Transfer","volume":"159 ","pages":"Article 108315"},"PeriodicalIF":6.4,"publicationDate":"2024-11-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142653779","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 : 2024-11-11DOI: 10.1016/j.icheatmasstransfer.2024.108202
Yin Yemao , Qian Zuoqin , Cheng Junlin , Qiu Yuanchao , Bi Xiong , Wang Qiang , Liu Jie
A rectangular microchannel featuring staggered and truncated fins was formulated and numerically simulated in this study. The influence of stagger distance, fin angle, and fin height on overall performance was analyzed. The phenomenon was obtained that increasing the stagger distance could significantly decrease the pressure drop, while enhancing the thermal behavior with an initially increase and then decrease trend. This can be ascribed to the disturbance induced by the staggered fins, promoting the diversion of flowlines and enhancing heat transfer through improved blending of hot and cold fluids. Increasing the fin angle can increase thermal performance while simultaneously leading to a significant increase in pressure drop. Increasing the fin height resulted in greater thermal enhancement and flow resistance, with the maximum thermal enhancement observed when there is a certain gap at the upper end of the fins. Subsequently, the effects of these three parameters were further investigated by RSM. The results indicated that the impact of the parameters on heat transfer and overall performance followed an increasing-then-decreasing trend. By optimizing the parameters, the best combination was found to be , , , and the maximum of 1.33 was achieved at .
{"title":"Investigation on the thermohydraulic performance of a microchannel heat exchanger incorporating staggered truncated fins","authors":"Yin Yemao , Qian Zuoqin , Cheng Junlin , Qiu Yuanchao , Bi Xiong , Wang Qiang , Liu Jie","doi":"10.1016/j.icheatmasstransfer.2024.108202","DOIUrl":"10.1016/j.icheatmasstransfer.2024.108202","url":null,"abstract":"<div><div>A rectangular microchannel featuring staggered and truncated fins was formulated and numerically simulated in this study. The influence of stagger distance, fin angle, and fin height on overall performance was analyzed. The phenomenon was obtained that increasing the stagger distance could significantly decrease the pressure drop, while enhancing the thermal behavior with an initially increase and then decrease trend. This can be ascribed to the disturbance induced by the staggered fins, promoting the diversion of flowlines and enhancing heat transfer through improved blending of hot and cold fluids. Increasing the fin angle can increase thermal performance while simultaneously leading to a significant increase in pressure drop. Increasing the fin height resulted in greater thermal enhancement and flow resistance, with the maximum thermal enhancement observed when there is a certain gap at the upper end of the fins. Subsequently, the effects of these three parameters were further investigated by RSM. The results indicated that the impact of the parameters on heat transfer and overall performance followed an increasing-then-decreasing trend. By optimizing the parameters, the best combination was found to be <span><math><mi>L</mi><mo>=</mo><mn>0.18</mn><mspace></mspace><mi>mm</mi></math></span>, <span><math><mi>A</mi><mo>=</mo><msup><mn>42.5</mn><mo>°</mo></msup></math></span>, <span><math><mi>H</mi><mo>=</mo><mn>0.16</mn><mspace></mspace><mi>mm</mi></math></span>, and the maximum <span><math><mi>PEC</mi></math></span> of 1.33 was achieved at <span><math><mo>Re</mo><mo>=</mo><mn>416</mn></math></span>.</div></div>","PeriodicalId":332,"journal":{"name":"International Communications in Heat and Mass Transfer","volume":"159 ","pages":"Article 108202"},"PeriodicalIF":6.4,"publicationDate":"2024-11-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142653776","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 : 2024-11-11DOI: 10.1016/j.icheatmasstransfer.2024.108292
B.A.H.M. Bamunuarachchi , Jinghao Jin , Hyung Ju Lee , Chang Kyoung Choi , Seong Hyuk Lee
Graphene has been widely recognized for its ability to enhance the efficiency and stability of solar cells, promoting extensive research into its application in thin films. This study employs the droplet deposition technique, utilizing the evaporation of a sessile droplet, to optimize the uniformity of particle deposition, with an emphasis on controlling film thickness and mitigating common challenges, such as the ‘coffee-ring’ effect. We evaluate the key performance parameters, including thickness distribution and surface characteristics, to develop strategies for improving deposition techniques. Side-view imaging offers insights into the changes in contact angle, diameter, and volume during evaporation. Also, we analyze particle distribution and thin-film thickness through top-view and cross-sectional images. Our findings reveal that larger graphene particles exhibit slower movement toward the contact line due to their increased mass, causing improved uniformity at higher concentrations and a reduction in the “coffee-ring” effect observed at lower concentrations. At high weight percentages, particle accumulation at the droplet's center results in increased thickness because of stronger cohesive forces. In contrast, reducing particle size at concentrations above 5 wt% promotes enhanced inter-particle interactions, yielding a homogeneous pattern and decreased thickness, while increasing surface tension and contact angle owing to the hydrophobic nature of graphene.
{"title":"Enhanced thin-film deposition uniformity during droplet evaporation: Effects of graphene particle size and concentration","authors":"B.A.H.M. Bamunuarachchi , Jinghao Jin , Hyung Ju Lee , Chang Kyoung Choi , Seong Hyuk Lee","doi":"10.1016/j.icheatmasstransfer.2024.108292","DOIUrl":"10.1016/j.icheatmasstransfer.2024.108292","url":null,"abstract":"<div><div>Graphene has been widely recognized for its ability to enhance the efficiency and stability of solar cells, promoting extensive research into its application in thin films. This study employs the droplet deposition technique, utilizing the evaporation of a sessile droplet, to optimize the uniformity of particle deposition, with an emphasis on controlling film thickness and mitigating common challenges, such as the ‘coffee-ring’ effect. We evaluate the key performance parameters, including thickness distribution and surface characteristics, to develop strategies for improving deposition techniques. Side-view imaging offers insights into the changes in contact angle, diameter, and volume during evaporation. Also, we analyze particle distribution and thin-film thickness through top-view and cross-sectional images. Our findings reveal that larger graphene particles exhibit slower movement toward the contact line due to their increased mass, causing improved uniformity at higher concentrations and a reduction in the “coffee-ring” effect observed at lower concentrations. At high weight percentages, particle accumulation at the droplet's center results in increased thickness because of stronger cohesive forces. In contrast, reducing particle size at concentrations above 5 wt% promotes enhanced inter-particle interactions, yielding a homogeneous pattern and decreased thickness, while increasing surface tension and contact angle owing to the hydrophobic nature of graphene.</div></div>","PeriodicalId":332,"journal":{"name":"International Communications in Heat and Mass Transfer","volume":"159 ","pages":"Article 108292"},"PeriodicalIF":6.4,"publicationDate":"2024-11-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142653775","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 : 2024-11-11DOI: 10.1016/j.icheatmasstransfer.2024.108284
Roksana Urbaniak , Beata Hadała , Rafał Stanik , Janusz Konstanty , Anna Olejnik
During copper smelting, copper concentrates containing organic carbon compounds are subjected to the roasting process in a fluidised-bed furnace. The roasted concentrate formed in the process contains substances which deposit on the surfaces of the tubes present inside the furnace. The deposits contribute to the reduction of the heat flux absorbed from the bed. This study investigates the morphology, chemical composition and thermophysical properties of the deposits. The impact of the increase in the deposit thickness on the increase in the deposit surface temperature and the reduction of the heat flux absorbed by water was determined. A deposit taken from an industrial facility was analysed. It was established that, for a deposit with a thickness of 40 mm, there was an approximately 80 % decline in the absorbed energy as compared to a clean tube surface.
{"title":"Investigations of the impact of deposit thickness on the amount of heat transferred during roasting copper concentrates in a fluidised bed","authors":"Roksana Urbaniak , Beata Hadała , Rafał Stanik , Janusz Konstanty , Anna Olejnik","doi":"10.1016/j.icheatmasstransfer.2024.108284","DOIUrl":"10.1016/j.icheatmasstransfer.2024.108284","url":null,"abstract":"<div><div>During copper smelting, copper concentrates containing organic carbon compounds are subjected to the roasting process in a fluidised-bed furnace. The roasted concentrate formed in the process contains substances which deposit on the surfaces of the tubes present inside the furnace. The deposits contribute to the reduction of the heat flux absorbed from the bed. This study investigates the morphology, chemical composition and thermophysical properties of the deposits. The impact of the increase in the deposit thickness on the increase in the deposit surface temperature and the reduction of the heat flux absorbed by water was determined. A deposit taken from an industrial facility was analysed. It was established that, for a deposit with a thickness of 40 mm, there was an approximately 80 % decline in the absorbed energy as compared to a clean tube surface.</div></div>","PeriodicalId":332,"journal":{"name":"International Communications in Heat and Mass Transfer","volume":"159 ","pages":"Article 108284"},"PeriodicalIF":6.4,"publicationDate":"2024-11-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142653778","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}
Pub Date : 2024-11-11DOI: 10.1016/j.icheatmasstransfer.2024.108296
Kumar Amit, Ashwani Assam, Abhishek Raj
Exploring the intricate interplay of heat transfer dynamics within two- and three-dimensional microchannels with static heat-spots, this study uncovers compelling insights into temperature distribution under varying wall conditions (adiabatic and constant wall temperature). The findings shed light on critical factors shaping heat transfer mechanisms. Key findings reveal that a channel with adiabatic walls experiences significantly higher temperatures than constant wall temperature cases, with a four-heat-spot configuration along the channel centerline yielding the highest temperatures. A stenosed channel experiences a larger temperature increase compared to the non-stenosed channel by a factor of 12–13 %. The study concludes with application to bio-fluid mechanics by studying hemodynamic condition in a bifurcated three-dimensional artery models. The location of heat-spots significantly influences the temperature distribution in the channel. A higher temperature rise appears in the case where heat-spot is located at the inlet of the narrower branch for the case of adiabatic wall conditions. These revelations hold promising implications for fields like medical science, where subtle temperature variations can indicate presence of inflammatory response in the blood vessel.
{"title":"Heat transfer characteristics of pulsatile flow through microchannel with heat-spots: Mimicking heat generation in the blood vessels","authors":"Kumar Amit, Ashwani Assam, Abhishek Raj","doi":"10.1016/j.icheatmasstransfer.2024.108296","DOIUrl":"10.1016/j.icheatmasstransfer.2024.108296","url":null,"abstract":"<div><div>Exploring the intricate interplay of heat transfer dynamics within two- and three-dimensional microchannels with static heat-spots, this study uncovers compelling insights into temperature distribution under varying wall conditions (adiabatic and constant wall temperature). The findings shed light on critical factors shaping heat transfer mechanisms. Key findings reveal that a channel with adiabatic walls experiences significantly higher temperatures than constant wall temperature cases, with a four-heat-spot configuration along the channel centerline yielding the highest temperatures. A stenosed channel experiences a larger temperature increase compared to the non-stenosed channel by a factor of 12–13 %. The study concludes with application to bio-fluid mechanics by studying hemodynamic condition in a bifurcated three-dimensional artery models. The location of heat-spots significantly influences the temperature distribution in the channel. A higher temperature rise appears in the case where heat-spot is located at the inlet of the narrower branch for the case of adiabatic wall conditions. These revelations hold promising implications for fields like medical science, where subtle temperature variations can indicate presence of inflammatory response in the blood vessel.</div></div>","PeriodicalId":332,"journal":{"name":"International Communications in Heat and Mass Transfer","volume":"159 ","pages":"Article 108296"},"PeriodicalIF":6.4,"publicationDate":"2024-11-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142653781","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 : 2024-11-11DOI: 10.1016/j.icheatmasstransfer.2024.108312
Seonwoong Byun , Sewon Lee , Changhyun Baek , Jinyoung Kim , Yongchan Kim
Falling film evaporators have been widely utilized due to their high heat-transfer efficiency and low refrigerant charge. However, there is limited research on the impact of distributor design variables on the heat transfer coefficient (HTC) in falling film evaporators. This study investigates the effects of these variables–hole diameter, hole pitch, and distributor height–on the heat transfer characteristics of water in falling film evaporators using three-dimensional simulations. Hole diameter had the most significant influence on HTC, with a sensitivity of 63.1 %, followed by hole pitch at 46.3 %, and distributor height at 0.9 %. Smaller hole diameters enhanced the HTC, but for diameters greater than 2 mm, the effects of hole diameter and pitch on the axial HTC became negligible. The HTC increased with hole pitch up to the dry-out owing to the jet impingement. The influence of distributor height on HTC was minor, particularly at a hole diameter of 1 mm. The optimal design for the highest average HTC at a film Reynolds number of 200 was determined to be a hole diameter of 1 mm, a hole pitch of 37.5 mm, and a distributor height of 30 mm, resulting in a 50 % improvement in performance compared to the least effective design.
{"title":"Impact of distributor design variables on heat transfer characteristics in falling film evaporators using water","authors":"Seonwoong Byun , Sewon Lee , Changhyun Baek , Jinyoung Kim , Yongchan Kim","doi":"10.1016/j.icheatmasstransfer.2024.108312","DOIUrl":"10.1016/j.icheatmasstransfer.2024.108312","url":null,"abstract":"<div><div>Falling film evaporators have been widely utilized due to their high heat-transfer efficiency and low refrigerant charge. However, there is limited research on the impact of distributor design variables on the heat transfer coefficient (HTC) in falling film evaporators. This study investigates the effects of these variables–hole diameter, hole pitch, and distributor height–on the heat transfer characteristics of water in falling film evaporators using three-dimensional simulations. Hole diameter had the most significant influence on HTC, with a sensitivity of 63.1 %, followed by hole pitch at 46.3 %, and distributor height at 0.9 %. Smaller hole diameters enhanced the HTC, but for diameters greater than 2 mm, the effects of hole diameter and pitch on the axial HTC became negligible. The HTC increased with hole pitch up to the dry-out owing to the jet impingement. The influence of distributor height on HTC was minor, particularly at a hole diameter of 1 mm. The optimal design for the highest average HTC at a film Reynolds number of 200 was determined to be a hole diameter of 1 mm, a hole pitch of 37.5 mm, and a distributor height of 30 mm, resulting in a 50 % improvement in performance compared to the least effective design.</div></div>","PeriodicalId":332,"journal":{"name":"International Communications in Heat and Mass Transfer","volume":"159 ","pages":"Article 108312"},"PeriodicalIF":6.4,"publicationDate":"2024-11-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142653762","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}
To effectively control the spontaneous combustion of coal in goaf, this study investigates the developmental mechanisms and bidirectional propagation characteristics of spontaneous coal fires under various influencing factors using oxidation kinetics tests and simulation experiments. The results show that the critical air leakage rate for self-sustained reverse propagation of coal fire is 16.4 m/h, significantly lower than that required for forward propagation. Consequently, under low air leakage conditions in the goaf, fire development exhibits distinct oxygen-seeking behavior. A distinct double-peak temperature phenomenon appears during reverse fire propagation for larger coal particle sizes. The high-temperature zone in the upstream fire area experiences two phases: reverse propagation and wind-following migration. The development of the upstream fire zone significantly affects forward fire propagation. Once the upstream fire reaches a certain extent, it suppresses or even halts further spread. As the particle size of residual coal decreases, the double-peak temperature phenomenon gradually disappears, while forward propagation is significantly inhibited. Upward air leakage direction with increased Inclination significantly accelerates forward propagation, with the fire front reaching a peak rate of 14.8 cm/h at 45°. Meanwhile, reverse fire propagation is suppressed and ceases when the Inclination exceeds 15°. Simultaneously, the fire zone expansion follows a non-linear trend, initially increasing, then decreasing, and rising again, with the largest fire zone and highest risk occurring at inclination angles of 10° and 45°. Downward air leakage direction with increased Inclination accelerates reverse propagation while inhibiting forward spread. The fire expansion rate is faster at steeper angles in the early fire stages(0-6 h). However, in the mid-to-late stages, the fire zone expands more extensively under lower inclination conditions.
{"title":"Experimental study on the development and bidirectional propagation characteristics of spontaneous coal combustion in goaf","authors":"Guoqin Wang, Yongliang Yang, Yifan Zhang, Purui Li, Kaiyang Gao","doi":"10.1016/j.icheatmasstransfer.2024.108313","DOIUrl":"10.1016/j.icheatmasstransfer.2024.108313","url":null,"abstract":"<div><div>To effectively control the spontaneous combustion of coal in goaf, this study investigates the developmental mechanisms and bidirectional propagation characteristics of spontaneous coal fires under various influencing factors using oxidation kinetics tests and simulation experiments. The results show that the critical air leakage rate for self-sustained reverse propagation of coal fire is 16.4 m/h, significantly lower than that required for forward propagation. Consequently, under low air leakage conditions in the goaf, fire development exhibits distinct oxygen-seeking behavior. A distinct double-peak temperature phenomenon appears during reverse fire propagation for larger coal particle sizes. The high-temperature zone in the upstream fire area experiences two phases: reverse propagation and wind-following migration. The development of the upstream fire zone significantly affects forward fire propagation. Once the upstream fire reaches a certain extent, it suppresses or even halts further spread. As the particle size of residual coal decreases, the double-peak temperature phenomenon gradually disappears, while forward propagation is significantly inhibited. Upward air leakage direction with increased Inclination significantly accelerates forward propagation, with the fire front reaching a peak rate of 14.8 cm/h at 45°. Meanwhile, reverse fire propagation is suppressed and ceases when the Inclination exceeds 15°. Simultaneously, the fire zone expansion follows a non-linear trend, initially increasing, then decreasing, and rising again, with the largest fire zone and highest risk occurring at inclination angles of 10° and 45°. Downward air leakage direction with increased Inclination accelerates reverse propagation while inhibiting forward spread. The fire expansion rate is faster at steeper angles in the early fire stages(0-6 h). However, in the mid-to-late stages, the fire zone expands more extensively under lower inclination conditions.</div></div>","PeriodicalId":332,"journal":{"name":"International Communications in Heat and Mass Transfer","volume":"159 ","pages":"Article 108313"},"PeriodicalIF":6.4,"publicationDate":"2024-11-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142653782","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 : 2024-11-11DOI: 10.1016/j.icheatmasstransfer.2024.108266
Xiaofeng Song , Xiao Jia , Lei Shi , Yao Wang , Zhigang Gao , Kaiqian Kuang , Zhenchu Ni , Weiguang An
This study delves into the influence of deck height and ambient wind speed on the temperature distribution of key structural components in a double-deck bridge during fire, utilizing scaled-down fire experiments. The experimental results were analyzed to pinpoint the maximum temperature of the upper bridge deck in a windy environment, corresponding to each of the three scenarios: buoyant plume, intermittent flame, and continuous flame. Additionally, a temperature rise prediction equations for the upper bridge deck was derived. It was observed that the maximum temperature of the truss diminishes as the deck height escalates. A model predicting the maximum temperature rise of trusses was formulated through dimensionless analysis. For the majority of operational conditions, the truss temperature initially increases and then decreases with an increase in vertical height. A temperature jump is noted at the peak of the truss, which becomes less pronounced as the deck height increases. By fitting the experimental data, the prediction formulas for the dimensionless temperature rise at the peak of the truss were obtained. The findings presented in this paper offer a theoretical framework and temperature range criteria that can inform the fire protection design and fire risk evaluation of critical structural elements in double-deck bridges.
{"title":"Experimental study on temperature distribution of key structural components of double-deck bridges during fire affected by wind and deck height","authors":"Xiaofeng Song , Xiao Jia , Lei Shi , Yao Wang , Zhigang Gao , Kaiqian Kuang , Zhenchu Ni , Weiguang An","doi":"10.1016/j.icheatmasstransfer.2024.108266","DOIUrl":"10.1016/j.icheatmasstransfer.2024.108266","url":null,"abstract":"<div><div>This study delves into the influence of deck height and ambient wind speed on the temperature distribution of key structural components in a double-deck bridge during fire, utilizing scaled-down fire experiments. The experimental results were analyzed to pinpoint the maximum temperature of the upper bridge deck in a windy environment, corresponding to each of the three scenarios: buoyant plume, intermittent flame, and continuous flame. Additionally, a temperature rise prediction equations for the upper bridge deck was derived. It was observed that the maximum temperature of the truss diminishes as the deck height escalates. A model predicting the maximum temperature rise of trusses was formulated through dimensionless analysis. For the majority of operational conditions, the truss temperature initially increases and then decreases with an increase in vertical height. A temperature jump is noted at the peak of the truss, which becomes less pronounced as the deck height increases. By fitting the experimental data, the prediction formulas for the dimensionless temperature rise at the peak of the truss were obtained. The findings presented in this paper offer a theoretical framework and temperature range criteria that can inform the fire protection design and fire risk evaluation of critical structural elements in double-deck bridges.</div></div>","PeriodicalId":332,"journal":{"name":"International Communications in Heat and Mass Transfer","volume":"159 ","pages":"Article 108266"},"PeriodicalIF":6.4,"publicationDate":"2024-11-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142653780","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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