In this study, a bubble nucleation model for different hydrophobic sections within grooved surfaces is developed by molecular dynamics method to explore the effects of different hydrophobic sites on bubble nucleation on the surface of hydrophobic/hydrophilic hybrid wettability grooves. The results indicate that the time for bubble nucleation is delayed with an increase in the hydrophobic surface area. The order of bubble nucleation time from fastest to slowest is as follows: the BphoSphi (hydrophobic bottom wall and hydrophilic sidewall) surface, the BphiSSpho (hydrophilic bottom wall and hydrophobic single-sidewall) surface, the BphiDSpho (hydrophilic bottom wall and hydrophobic double-sidewall) surface, and the Apho (all-hydrophobic) surface. Additionally, the effect of varying hydrophobic areas at the groove bottom on bubble nucleation is investigated. The results show that the HBphoSphi (half hydrophobic bottom wall and hydrophilic sidewall) surface and the BphoSphi surface are almost the same, whereas the bubble nucleation time for the QBphoSphi (quarter hydrophobic bottom wall and hydrophilic sidewall) surface is significantly later. A slight change in the hydrophobic area at the bottom of the groove has a minimal effect on heat transfer, but an excessively small hydrophobic area is unfavorable for bubble nucleation.
{"title":"Effect of trapezoidal groove hydrophobic sites on bubble nucleation: A molecular dynamics study","authors":"Jingtao Wang, Mingyuan Yang, Yuting Jia, Xiaosong Cui, Hongliang Chang","doi":"10.1016/j.icheatmasstransfer.2025.108751","DOIUrl":"10.1016/j.icheatmasstransfer.2025.108751","url":null,"abstract":"<div><div>In this study, a bubble nucleation model for different hydrophobic sections within grooved surfaces is developed by molecular dynamics method to explore the effects of different hydrophobic sites on bubble nucleation on the surface of hydrophobic/hydrophilic hybrid wettability grooves. The results indicate that the time for bubble nucleation is delayed with an increase in the hydrophobic surface area. The order of bubble nucleation time from fastest to slowest is as follows: the B<sub>pho</sub>S<sub>phi</sub> (hydrophobic bottom wall and hydrophilic sidewall) surface, the B<sub>phi</sub>SS<sub>pho</sub> (hydrophilic bottom wall and hydrophobic single-sidewall) surface, the B<sub>phi</sub>DS<sub>pho</sub> (hydrophilic bottom wall and hydrophobic double-sidewall) surface, and the A<sub>pho</sub> (all-hydrophobic) surface. Additionally, the effect of varying hydrophobic areas at the groove bottom on bubble nucleation is investigated. The results show that the HB<sub>pho</sub>S<sub>phi</sub> (half hydrophobic bottom wall and hydrophilic sidewall) surface and the B<sub>pho</sub>S<sub>phi</sub> surface are almost the same, whereas the bubble nucleation time for the QB<sub>pho</sub>S<sub>phi</sub> (quarter hydrophobic bottom wall and hydrophilic sidewall) surface is significantly later. A slight change in the hydrophobic area at the bottom of the groove has a minimal effect on heat transfer, but an excessively small hydrophobic area is unfavorable for bubble nucleation.</div></div>","PeriodicalId":332,"journal":{"name":"International Communications in Heat and Mass Transfer","volume":"163 ","pages":"Article 108751"},"PeriodicalIF":6.4,"publicationDate":"2025-02-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143454390","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 : 2025-02-20DOI: 10.1016/j.icheatmasstransfer.2025.108730
Ola Talal Mayoof , Nabil J. Yasin , Ayad S. Abedalh
Energy conservation is a key focus in various industries, particularly in HVAC systems. Air conditioning, being one of the most energy-intensive systems, requires significant efforts to reduce energy consumption. U-shaped heat pipe heat exchangers (U-HPHE) offer an effective and cost-efficient solution for applications with high energy demands. The purpose of this study is to investigate whether U-shaped heat pipe heat exchangers (U-HPHE) can lower HVAC system energy usage while preserving desired temperatures. U-HPHE units, containing a working fluid at a 50 % fill ratio, were tested for their impact on HVAC performance, specifically for dehumidification and Coefficient of Performance (COP) improvements. The heat pipes were placed horizontally around the cooling coil and tested in one- and two-row configurations, each with seven pipes. Fresh air temperatures and velocities were varied between 35 and 55 °C and 2–3 m/s. Results showed that using acetone-filled U-HPHE improved temperature differences in both evaporator and condenser. Higher inlet air temperatures, especially with acetone-filled heat pipes, increased heat recovery and effectiveness. The maximum heat recovery was achieved at an intake air temperature of 55 °C and an air velocity of 2 m/s, reaching 535 W and an effectiveness of 0.56.
{"title":"Experimental investigation for utilization of U-shaped heat pipe heat exchanger in the air-conditioning system","authors":"Ola Talal Mayoof , Nabil J. Yasin , Ayad S. Abedalh","doi":"10.1016/j.icheatmasstransfer.2025.108730","DOIUrl":"10.1016/j.icheatmasstransfer.2025.108730","url":null,"abstract":"<div><div>Energy conservation is a key focus in various industries, particularly in HVAC systems. Air conditioning, being one of the most energy-intensive systems, requires significant efforts to reduce energy consumption. U-shaped heat pipe heat exchangers (U-HPHE) offer an effective and cost-efficient solution for applications with high energy demands. The purpose of this study is to investigate whether U-shaped heat pipe heat exchangers (U-HPHE) can lower HVAC system energy usage while preserving desired temperatures. U-HPHE units, containing a working fluid at a 50 % fill ratio, were tested for their impact on HVAC performance, specifically for dehumidification and Coefficient of Performance (COP) improvements. The heat pipes were placed horizontally around the cooling coil and tested in one- and two-row configurations, each with seven pipes. Fresh air temperatures and velocities were varied between 35 and 55 °C and 2–3 m/s. Results showed that using acetone-filled U-HPHE improved temperature differences in both evaporator and condenser. Higher inlet air temperatures, especially with acetone-filled heat pipes, increased heat recovery and effectiveness. The maximum heat recovery was achieved at an intake air temperature of 55 °C and an air velocity of 2 m/s, reaching 535 W and an effectiveness of 0.56.</div></div>","PeriodicalId":332,"journal":{"name":"International Communications in Heat and Mass Transfer","volume":"163 ","pages":"Article 108730"},"PeriodicalIF":6.4,"publicationDate":"2025-02-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143444713","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The corrosion of the heat exchanger in the actual operation process will make the heat exchange wall rough, and the rough heat exchange wall will cause local fouling deposition in the channel. Based on the constructed local crystallization fouling model, this study compares the local fouling deposition of smooth channel and triangular roughness element channel, and analyzes the relative spacing of triangular roughness elements and the effect of different working condition parameters in detail. Results indicate that compared to smooth channels, triangular roughness elements significantly influence fouling deposition, appearing an extreme value in local fouling resistance. As the relative spacing decreases, the average value of the local fouling resistance initially decreases, reaching its minimum at a spacing of 0.125, before slightly increasing and stabilizing. For the average value of fouling resistance, the increase of inlet velocity or the decrease of calcium carbonate concentration will reduce it; an increase in wall temperature will increase it. Additionally, the thickness of the fouling layer decreases with increasing inlet velocity, decreases with lower concentration of calcium carbonate, and increases with rising wall temperature, both in the smooth zone outside the roughness element and in the roughness element affected zone.
{"title":"Characteristics of local deposition of CaCO3 fouling on rough wall surfaces of heat exchanger channels","authors":"Zhimin Han, Xiangyu Zhou, Hongyu Zhang, Zhiming Xu","doi":"10.1016/j.icheatmasstransfer.2025.108718","DOIUrl":"10.1016/j.icheatmasstransfer.2025.108718","url":null,"abstract":"<div><div>The corrosion of the heat exchanger in the actual operation process will make the heat exchange wall rough, and the rough heat exchange wall will cause local fouling deposition in the channel. Based on the constructed local crystallization fouling model, this study compares the local fouling deposition of smooth channel and triangular roughness element channel, and analyzes the relative spacing of triangular roughness elements and the effect of different working condition parameters in detail. Results indicate that compared to smooth channels, triangular roughness elements significantly influence fouling deposition, appearing an extreme value in local fouling resistance. As the relative spacing decreases, the average value of the local fouling resistance initially decreases, reaching its minimum at a spacing of 0.125, before slightly increasing and stabilizing. For the average value of fouling resistance, the increase of inlet velocity or the decrease of calcium carbonate concentration will reduce it; an increase in wall temperature will increase it. Additionally, the thickness of the fouling layer decreases with increasing inlet velocity, decreases with lower concentration of calcium carbonate, and increases with rising wall temperature, both in the smooth zone outside the roughness element and in the roughness element affected zone.</div></div>","PeriodicalId":332,"journal":{"name":"International Communications in Heat and Mass Transfer","volume":"163 ","pages":"Article 108718"},"PeriodicalIF":6.4,"publicationDate":"2025-02-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143454470","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 : 2025-02-20DOI: 10.1016/j.icheatmasstransfer.2025.108719
Benan Cai , Jianxin Zhang , Yuqi Zhao , Xunjian Che , Jianchuang Sun , Jiameng Tian , Weihua Cai
To investigate the flash evaporation of aqueous ethanol in vacuum environment, a correction factor is introduced to modify the flash evaporation rate equation. The modified method is based on the Lagrangian-Eulerian model that couples the momentum and mass transfer of continuous and discrete phases. The results for droplets temperature exhibit average errors of less than 3.28 K compared to experimental data, thereby verifying accuracy of the method. Through the analysis of the flash evaporation behavior of two-component droplets, two distinct stages can be identified. “The first stage of flashing” is characterized by high flash evaporation rate, rapid temperature decline, and short duration, while “the second stage of flashing” is opposite to the Stage I. As the droplet size increases and the initial ethanol concentration decreases, it is observed that the duration of Stage I increases. This phenomenon extends the duration of high flash evaporation rate, thereby enhancing the mass transfer to the vapor, leads to larger decline of ethanol mass fraction. Increasing the spray temperature or decreasing the vacuum pressure can also enhance the mass transfer and flash evaporation rate. However, spray temperature shows a more significant effect on the flash evaporation rate and evaporated mass than that of vacuum pressure.
{"title":"Numerical investigation on vacuum spray flash evaporation of ethanol-water solution","authors":"Benan Cai , Jianxin Zhang , Yuqi Zhao , Xunjian Che , Jianchuang Sun , Jiameng Tian , Weihua Cai","doi":"10.1016/j.icheatmasstransfer.2025.108719","DOIUrl":"10.1016/j.icheatmasstransfer.2025.108719","url":null,"abstract":"<div><div>To investigate the flash evaporation of aqueous ethanol in vacuum environment, a correction factor is introduced to modify the flash evaporation rate equation. The modified method is based on the Lagrangian-Eulerian model that couples the momentum and mass transfer of continuous and discrete phases. The results for droplets temperature exhibit average errors of less than 3.28 K compared to experimental data, thereby verifying accuracy of the method. Through the analysis of the flash evaporation behavior of two-component droplets, two distinct stages can be identified. “The first stage of flashing” is characterized by high flash evaporation rate, rapid temperature decline, and short duration, while “the second stage of flashing” is opposite to the Stage I. As the droplet size increases and the initial ethanol concentration decreases, it is observed that the duration of Stage I increases. This phenomenon extends the duration of high flash evaporation rate, thereby enhancing the mass transfer to the vapor, leads to larger decline of ethanol mass fraction. Increasing the spray temperature or decreasing the vacuum pressure can also enhance the mass transfer and flash evaporation rate. However, spray temperature shows a more significant effect on the flash evaporation rate and evaporated mass than that of vacuum pressure.</div></div>","PeriodicalId":332,"journal":{"name":"International Communications in Heat and Mass Transfer","volume":"163 ","pages":"Article 108719"},"PeriodicalIF":6.4,"publicationDate":"2025-02-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143454471","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 : 2025-02-20DOI: 10.1016/j.icheatmasstransfer.2025.108736
Bing Yi , Jiawei Liu , Rui Liu , Xiang Peng
Topology optimization has the advantages of large design freedom and optimization searching space. Hence, it has been introduced into the topology optimization of structures with excellent thermal conductive properties with given volume constraints. However, the optimized structures contain a lot of complex geometry, which increases the difficulty and cost of manufacturing. To address these challenges by balancing the manufacturing cost and thermal conductivity property, a perimeter-constrained topology optimization method for thermal conduction structures is proposed. First, the structural boundaries are extracted by using the modified two-step filter and projection process, which directly relates to the manufacturing costs. Subsequently, the perimeter constraint is integrated into the formulation of the topology optimization model based on Solid Isotropic Material with Penalization (SIMP), and the thermal compliance is set as the objective function. Then, the sensitivity analysis is derived for both the constraints and objective function, and the method of moving asymptotes (MMA) is used to solve the model iteratively. Finally, several numerical examples are conducted to show the performance of the proposed method for topology optimization of heat conduction structure under various boundary conditions. The average temperature of the examples only improved by 2–3 K under the condition that the perimeter is reduced by 50 % of the conventional results. The results validate the effectiveness of the proposed method for the ability to balance the manufacturing costs and the thermal conductivity property of the optimized structure according to the requirements of the designers.
{"title":"Integrating perimeter constraints into topology optimization of thermal conduction structures considering the manufacturing efficiency","authors":"Bing Yi , Jiawei Liu , Rui Liu , Xiang Peng","doi":"10.1016/j.icheatmasstransfer.2025.108736","DOIUrl":"10.1016/j.icheatmasstransfer.2025.108736","url":null,"abstract":"<div><div>Topology optimization has the advantages of large design freedom and optimization searching space. Hence, it has been introduced into the topology optimization of structures with excellent thermal conductive properties with given volume constraints. However, the optimized structures contain a lot of complex geometry, which increases the difficulty and cost of manufacturing. To address these challenges by balancing the manufacturing cost and thermal conductivity property, a perimeter-constrained topology optimization method for thermal conduction structures is proposed. First, the structural boundaries are extracted by using the modified two-step filter and projection process, which directly relates to the manufacturing costs. Subsequently, the perimeter constraint is integrated into the formulation of the topology optimization model based on Solid Isotropic Material with Penalization (SIMP), and the thermal compliance is set as the objective function. Then, the sensitivity analysis is derived for both the constraints and objective function, and the method of moving asymptotes (MMA) is used to solve the model iteratively. Finally, several numerical examples are conducted to show the performance of the proposed method for topology optimization of heat conduction structure under various boundary conditions. The average temperature of the examples only improved by 2–3 K under the condition that the perimeter is reduced by 50 % of the conventional results. The results validate the effectiveness of the proposed method for the ability to balance the manufacturing costs and the thermal conductivity property of the optimized structure according to the requirements of the designers.</div></div>","PeriodicalId":332,"journal":{"name":"International Communications in Heat and Mass Transfer","volume":"163 ","pages":"Article 108736"},"PeriodicalIF":6.4,"publicationDate":"2025-02-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143444714","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The severe thermo-physical properties variations of supercritical fluids in the vicinity of the critical point lead to difficulty in heat transfer prediction. In this paper, a novel prediction model for supercritical CO2 (sCO2) cooling heat transfer is proposed, integrating a Direct Numerical Simulation (DNS) database with the CatBoost algorithm. A high-precision heat transfer prediction database was established based on DNS data (8192 data points in total). The feature parameters were screened utilizing the random forest feature importance method. More importantly, a newly dimensionless parameter, , was selected as one of the feature parameters. represents the impact of near-wall acceleration caused by buoyancy, and it demonstrated the highest feature importance during training and screening processes. Based on the selected ten characteristic parameters, a robust data-driven heat transfer prediction model for sCO2 was developed. The CatBoost algorithm outperformed the other three widely used machine learning algorithm s across training sets, testing sets, and actual predictions, achieving a mean absolute percentage error reduction of up to 22.69 %. Through comparison with 6 traditional heat transfer correlations, the results showed that the CatBoost-based sCO2 cooling heat transfer prediction model exhibits superior training speed and predictive accuracy, with a maximum relative error of merely 6.57 %. Moreover, when validated through experimental data with large Reynolds number, this model still has the highest accuracy, with 91.3 % of the data sets having a prediction accuracy within ±30 % for the Nusselt number.
{"title":"A supercritical carbon dioxide cooling heat transfer machine learning prediction model based on direct numerical simulation","authors":"Dingchen Wu , Mingshan Wei , Ran Tian , Yihang Zhao , Jianshe Guo","doi":"10.1016/j.icheatmasstransfer.2025.108753","DOIUrl":"10.1016/j.icheatmasstransfer.2025.108753","url":null,"abstract":"<div><div>The severe thermo-physical properties variations of supercritical fluids in the vicinity of the critical point lead to difficulty in heat transfer prediction. In this paper, a novel prediction model for supercritical CO<sub>2</sub> (sCO<sub>2</sub>) cooling heat transfer is proposed, integrating a Direct Numerical Simulation (DNS) database with the CatBoost algorithm. A high-precision heat transfer prediction database was established based on DNS data (8192 data points in total). The feature parameters were screened utilizing the random forest feature importance method. More importantly, a newly dimensionless parameter, <span><math><msup><mo>Re</mo><mrow><mo>−</mo><mn>0.9</mn></mrow></msup><msub><mi>π</mi><mi>A</mi></msub></math></span>, was selected as one of the feature parameters. <span><math><msup><mo>Re</mo><mrow><mo>−</mo><mn>0.9</mn></mrow></msup><msub><mi>π</mi><mi>A</mi></msub></math></span> represents the impact of near-wall acceleration caused by buoyancy, and it demonstrated the highest feature importance during training and screening processes. Based on the selected ten characteristic parameters, a robust data-driven heat transfer prediction model for sCO<sub>2</sub> was developed. The CatBoost algorithm outperformed the other three widely used machine learning algorithm s across training sets, testing sets, and actual predictions, achieving a mean absolute percentage error reduction of up to 22.69 %. Through comparison with 6 traditional heat transfer correlations, the results showed that the CatBoost-based sCO2 cooling heat transfer prediction model exhibits superior training speed and predictive accuracy, with a maximum relative error of merely 6.57 %. Moreover, when validated through experimental data with large Reynolds number, this model still has the highest accuracy, with 91.3 % of the data sets having a prediction accuracy within ±30 % for the Nusselt number.</div></div>","PeriodicalId":332,"journal":{"name":"International Communications in Heat and Mass Transfer","volume":"163 ","pages":"Article 108753"},"PeriodicalIF":6.4,"publicationDate":"2025-02-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143454484","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}
Regenerative cooling technology is crucial for addressing the severe thermal protection challenges faced by engines in hypersonic vehicles. The steam reforming reaction of hydrocarbon fuels is an effective method for significantly enhancing the fuel's heat absorption capacity. Current research has not fully examined the correlation of convective heat transfer coefficients and their relationship with the endothermic capacity of steam reforming reactions. In this study, the catalyst coating is simplified as a surface with no thickness, and a multidimensional numerical simulation model for the steam reforming reaction of n-decane at supercritical pressure is proposed, applicable under constant wall heat flux. The model has been validated against experimental results, showing a maximum relative error in fuel conversion of 12 %. Gnielinski correlation is tested to be applicable for convective heat transfer predictions in range of 7000 ≤ Re ≤ 180,000, and fuel conversion less than 20 %. An augmentation ratio, defined as the ratio of total to physical heat sink increase per unit tube length, is introduced. Using this ratio, the predicted total heat transfer coefficient shows a deviation of no more than 16 %.
{"title":"Modeling and analysis of supercritical hydrocarbon fuel heat and mass transfer with catalytic steam reforming","authors":"Shuai Xu , Junbo He , Yu Feng , Fuqiang Chen , Jiang Qin","doi":"10.1016/j.icheatmasstransfer.2025.108703","DOIUrl":"10.1016/j.icheatmasstransfer.2025.108703","url":null,"abstract":"<div><div>Regenerative cooling technology is crucial for addressing the severe thermal protection challenges faced by engines in hypersonic vehicles. The steam reforming reaction of hydrocarbon fuels is an effective method for significantly enhancing the fuel's heat absorption capacity. Current research has not fully examined the correlation of convective heat transfer coefficients and their relationship with the endothermic capacity of steam reforming reactions. In this study, the catalyst coating is simplified as a surface with no thickness, and a multidimensional numerical simulation model for the steam reforming reaction of n-decane at supercritical pressure is proposed, applicable under constant wall heat flux. The model has been validated against experimental results, showing a maximum relative error in fuel conversion of 12 %. Gnielinski correlation is tested to be applicable for convective heat transfer predictions in range of 7000 ≤ <em>Re</em> ≤ 180,000, and fuel conversion less than 20 %. An augmentation ratio, defined as the ratio of total to physical heat sink increase per unit tube length, is introduced. Using this ratio, the predicted total heat transfer coefficient shows a deviation of no more than 16 %.</div></div>","PeriodicalId":332,"journal":{"name":"International Communications in Heat and Mass Transfer","volume":"163 ","pages":"Article 108703"},"PeriodicalIF":6.4,"publicationDate":"2025-02-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143454387","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 : 2025-02-19DOI: 10.1016/j.icheatmasstransfer.2025.108752
Xin Wang , Zheqi Xu , Hongyuan Di , Chaojun Wang
Due to reliable accuracy and computational efficiency, full-spectrum correlated k-distribution (FSCK) look-up tables (short for traditional FSCK tables) have continuously gained popularities; however, they are only valid for combustion products and intermediates, such as CO2, H2O, CO and soot. Gas fuels, i.e., CH4, NH3 or their mixture, also display complex spectral or ‘nongray’ behaviors across spectrum. While those gas fuels are commonly consumed during combustion, their spectral behaviors may affect ignition, flame spread and chemical reactions. Therefore, it is necessary to include spectral properties of both CH4 and NH3 into FSCK look-up tables. To achieve this, a separate FSCK look-up tables (short for extended FSCK tables) including only CH4 and NH3 is constructed in this work. The multiplicative mixing scheme is then used to mix k-distributions from traditional FSCK tables and those from extended FSCK tables. A realistic non-premixed flame is used to validate both efficiency and accuracy of extended FSCK tables as well as multiplicative mixing scheme. Results show that absorption from CH4 and NH3 during combustion is strong and cannot be ignored. Results also show that treating spectral properties of CH4 and NH3 to be gray may bring in significant errors.
{"title":"Technical note: Extension of full-spectrum correlated k-distribution look-up tables to CH4 and NH3 for use in combustion modelling","authors":"Xin Wang , Zheqi Xu , Hongyuan Di , Chaojun Wang","doi":"10.1016/j.icheatmasstransfer.2025.108752","DOIUrl":"10.1016/j.icheatmasstransfer.2025.108752","url":null,"abstract":"<div><div>Due to reliable accuracy and computational efficiency, full-spectrum correlated <em>k</em>-distribution (FSCK) look-up tables (short for traditional FSCK tables) have continuously gained popularities; however, they are only valid for combustion products and intermediates, such as CO<sub>2</sub>, H<sub>2</sub>O, CO and soot. Gas fuels, i.e., CH<sub>4</sub>, NH<sub>3</sub> or their mixture, also display complex spectral or ‘nongray’ behaviors across spectrum. While those gas fuels are commonly consumed during combustion, their spectral behaviors may affect ignition, flame spread and chemical reactions. Therefore, it is necessary to include spectral properties of both CH<sub>4</sub> and NH<sub>3</sub> into FSCK look-up tables. To achieve this, a separate FSCK look-up tables (short for extended FSCK tables) including only CH<sub>4</sub> and NH<sub>3</sub> is constructed in this work. The multiplicative mixing scheme is then used to mix <em>k</em>-distributions from traditional FSCK tables and those from extended FSCK tables. A realistic non-premixed flame is used to validate both efficiency and accuracy of extended FSCK tables as well as multiplicative mixing scheme. Results show that absorption from CH<sub>4</sub> and NH<sub>3</sub> during combustion is strong and cannot be ignored. Results also show that treating spectral properties of CH<sub>4</sub> and NH<sub>3</sub> to be gray may bring in significant errors.</div></div>","PeriodicalId":332,"journal":{"name":"International Communications in Heat and Mass Transfer","volume":"163 ","pages":"Article 108752"},"PeriodicalIF":6.4,"publicationDate":"2025-02-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143437011","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 : 2025-02-19DOI: 10.1016/j.icheatmasstransfer.2025.108657
Mair Khan , T. Salahuddin , Sadia Ayub , Basem Al Awan , Meznah M. Alanazi , M. Afzal
Consider a steady flow analysis with temperature dependent viscosity and variable thermal conductivity near a rotating sphere. Additionally, a temperature dependent viscosity and variable thermal conductivity has been assumed for the current analysis. Partial differential equation system is converted into a differential system for distinct regions near the boundary layer region. Power series is used to calculate the solution of the problem. Ordinary differential systems are obtained by using this mythology. The sensitivity parameter shows reducing impact as it is showed for rotating disk problem. Temperature dependent liquid viscosity is analyzed to decrease the base flow profile the range, but for gases opposite impact is noticed. Variable thermal conductivity increase the temperature profile. The comparative results is evaluated for a limited case and good agreement is shown with previously published work.
{"title":"Temperature dependent viscosity effect and conductivity on the sphere rotating surface","authors":"Mair Khan , T. Salahuddin , Sadia Ayub , Basem Al Awan , Meznah M. Alanazi , M. Afzal","doi":"10.1016/j.icheatmasstransfer.2025.108657","DOIUrl":"10.1016/j.icheatmasstransfer.2025.108657","url":null,"abstract":"<div><div>Consider a steady flow analysis with temperature dependent viscosity and variable thermal conductivity near a rotating sphere. Additionally, a temperature dependent viscosity and variable thermal conductivity has been assumed for the current analysis. Partial differential equation system is converted into a differential system for distinct regions near the boundary layer region. Power series is used to calculate the solution of the problem. Ordinary differential systems are obtained by using this mythology. The sensitivity parameter shows reducing impact as it is showed for rotating disk problem. Temperature dependent liquid viscosity is analyzed to decrease the base flow profile the range, but for gases opposite impact is noticed. Variable thermal conductivity increase the temperature profile. The comparative results is evaluated for a limited case and good agreement is shown with previously published work.</div></div>","PeriodicalId":332,"journal":{"name":"International Communications in Heat and Mass Transfer","volume":"163 ","pages":"Article 108657"},"PeriodicalIF":6.4,"publicationDate":"2025-02-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143444711","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 : 2025-02-19DOI: 10.1016/j.icheatmasstransfer.2025.108724
Kai Ling , Hongbo Yang , Gangling Wu , Huadong Yong
This paper investigates the fluid-solid coupling boiling heat transfer between superconductor and liquid helium using the Multiple-Relaxation-Time (MRT) pseudo potential lattice Boltzmann model. The reliability of the numerical model is verified by Laplace law and thermodynamic consistency of helium medium. This work focuses on pool boiling, with an emphasis on the influence of surface wettability and thermal disturbance in the superconductor. The numerical results reveal the boiling curves of liquid helium with different surface wettability and the four phases of boiling. Additionally, the flow field of liquid helium boiling, including the nucleation, growth, and detachment of a single helium bubble, is simulated and analyzed in detail. And we also study the temperature changes of superconductor under different thermal disturbances and current densities. It can be found that nuclear boiling caused by smaller thermal perturbations has a high cooling efficiency, whereas larger thermal perturbations cause film boiling with a much lower cooling efficiency. Meanwhile, the hydrophobic surface reduces the critical heat flux for liquid helium boiling, which causes liquid helium to initiate film boiling at a lower superheat, severely inhibiting the cooling capacity of liquid helium.
{"title":"Boiling heat transfer of liquid helium induced by thermal disturbance in superconductors","authors":"Kai Ling , Hongbo Yang , Gangling Wu , Huadong Yong","doi":"10.1016/j.icheatmasstransfer.2025.108724","DOIUrl":"10.1016/j.icheatmasstransfer.2025.108724","url":null,"abstract":"<div><div>This paper investigates the fluid-solid coupling boiling heat transfer between superconductor and liquid helium using the Multiple-Relaxation-Time (MRT) pseudo potential lattice Boltzmann model. The reliability of the numerical model is verified by Laplace law and thermodynamic consistency of helium medium. This work focuses on pool boiling, with an emphasis on the influence of surface wettability and thermal disturbance in the superconductor. The numerical results reveal the boiling curves of liquid helium with different surface wettability and the four phases of boiling. Additionally, the flow field of liquid helium boiling, including the nucleation, growth, and detachment of a single helium bubble, is simulated and analyzed in detail. And we also study the temperature changes of superconductor under different thermal disturbances and current densities. It can be found that nuclear boiling caused by smaller thermal perturbations has a high cooling efficiency, whereas larger thermal perturbations cause film boiling with a much lower cooling efficiency. Meanwhile, the hydrophobic surface reduces the critical heat flux for liquid helium boiling, which causes liquid helium to initiate film boiling at a lower superheat, severely inhibiting the cooling capacity of liquid helium.</div></div>","PeriodicalId":332,"journal":{"name":"International Communications in Heat and Mass Transfer","volume":"163 ","pages":"Article 108724"},"PeriodicalIF":6.4,"publicationDate":"2025-02-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143437022","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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