Pub Date : 2024-11-15DOI: 10.1016/j.icheatmasstransfer.2024.108301
V.R. Voller , I. Vus̆anović
In general, modeling the solidification/melting in a rectangular cavity requires an accounting of the buoyancy driven fluid motion and associated convective heat transport. This study asks the question—Under what conditions can the contribution of the convective heat transport be ignored? To answer this question, we consider the problem of the solidification of a pure material in a rectangular cavity. Dimensionless governing equations for this problem are obtained. A numerical parametric study is performed, varying the Prandtl number, the Grashof number, thermal diffusivity ratio, scaled wall temperatures, and cavity aspect ratio. For 55 separate cases, steady state predictions of the fraction of solid in the cavity are obtained. These values are compared to steady state solid fraction predictions from a heat conduction alone model, i.e., a model that neglects convection. This analysis leads to a proposal of dimensionless group which provides a criterion for when convection is important. We find that when the value of , calculations based solely on conduction are sufficient.
一般来说，矩形空腔中的凝固/熔化建模需要考虑浮力驱动的流体运动和相关的对流热传输。本研究提出的问题是：在什么条件下可以忽略对流热传输的贡献？为了回答这个问题，我们考虑了矩形空腔中纯材料的凝固问题。我们得到了该问题的无量纲控制方程。通过改变普朗特数、格拉肖夫数、热扩散率、壁面温度比例和空腔长宽比，进行了数值参数研究。在 55 种不同情况下，获得了空腔中固体比例的稳态预测值。将这些值与单纯热传导模型（即忽略对流的模型）预测的稳态固体分数进行比较。通过分析，我们提出了一个无量纲组 V，它为对流何时变得重要提供了一个标准。我们发现，当 V 值≤4000 时，仅基于传导的计算就足够了。
{"title":"A criterion for determining when convection needs to be considered in calculations of solidification/melting in thermal cavities","authors":"V.R. Voller , I. Vus̆anović","doi":"10.1016/j.icheatmasstransfer.2024.108301","DOIUrl":"10.1016/j.icheatmasstransfer.2024.108301","url":null,"abstract":"<div><div>In general, modeling the solidification/melting in a rectangular cavity requires an accounting of the buoyancy driven fluid motion and associated convective heat transport. This study asks the question—Under what conditions can the contribution of the convective heat transport be ignored? To answer this question, we consider the problem of the solidification of a pure material in a rectangular cavity. Dimensionless governing equations for this problem are obtained. A numerical parametric study is performed, varying the Prandtl number, the Grashof number, thermal diffusivity ratio, scaled wall temperatures, and cavity aspect ratio. For 55 separate cases, steady state predictions of the fraction of solid in the cavity are obtained. These values are compared to steady state solid fraction predictions from a heat conduction alone model, i.e., a model that neglects convection. This analysis leads to a proposal of dimensionless group <span><math><mi>V</mi></math></span> which provides a criterion for when convection is important. We find that when the value of <span><math><mrow><mi>V</mi><mo>≤</mo><mn>4000</mn></mrow></math></span>, calculations based solely on conduction are sufficient.</div></div>","PeriodicalId":332,"journal":{"name":"International Communications in Heat and Mass Transfer","volume":"159 ","pages":"Article 108301"},"PeriodicalIF":6.4,"publicationDate":"2024-11-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142653664","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 : 2024-11-14DOI: 10.1016/j.icheatmasstransfer.2024.108320
Muhammad Naeem Aslam , Nadeem Shaukat , Arshad Riaz
In this article, we have conducted the study for the flow and thermal transfer of magneto-hydrodynamic squeezing nanofluid in the middle of two collateral plates extending to infinity using artificial neural network (ANN). The fluid employed in this research is a combination of Ethylene Glycol and water, and we delve into the utilization of a hybrid nanoparticle consisting of Fe3O4 and MoS2 particles. To solve the governing differential equations, we used unsupervised heuristic based physics informed neural network (H-PINN) based fitness function In this research, the weights and biases of neural network were optimized using a hybridization of heuristic algorithms to achieve high accuracy. The fitness values obtained from proposed approach ranging from to. The optimal results were then compared with numerical solutions obtained by using Runge-Kutta order-4 method through BVP4c tool as a reference solution, demonstrating the effectiveness of the unsupervised ANN method. The absolute error between the reference solution and proposed heuristic based physics informed neural networks approaches are ranging from, and. Our findings demonstrate a strong agreement with the numerical approach, with the maximum discrepancy in the profiles of flow speed and energy profiles. Notably, we observed that an increase in the squeeze number and the Hartman number resulted in a reduction in the velocity profile.
{"title":"Heuristic based physics informed neural network (H-PINN) approach to analyze nanotribology for viscous flow of ethylene glycol and water under magnetic effects among parallel sheets","authors":"Muhammad Naeem Aslam , Nadeem Shaukat , Arshad Riaz","doi":"10.1016/j.icheatmasstransfer.2024.108320","DOIUrl":"10.1016/j.icheatmasstransfer.2024.108320","url":null,"abstract":"<div><div>In this article, we have conducted the study for the flow and thermal transfer of magneto-hydrodynamic squeezing nanofluid in the middle of two collateral plates extending to infinity using artificial neural network (ANN). The fluid employed in this research is a combination of Ethylene Glycol and water, and we delve into the utilization of a hybrid nanoparticle consisting of Fe<sub>3</sub>O<sub>4</sub> and MoS<sub>2</sub> particles. To solve the governing differential equations, we used unsupervised heuristic based physics informed neural network (H-PINN) based fitness function<span><math><mo>.</mo></math></span> In this research, the weights and biases of neural network were optimized using a hybridization of heuristic algorithms to achieve high accuracy. The fitness values obtained from proposed approach ranging from<span><math><mspace></mspace><msup><mn>10</mn><mrow><mo>−</mo><mn>05</mn></mrow></msup></math></span> to<span><math><mspace></mspace><msup><mn>10</mn><mrow><mo>−</mo><mn>08</mn></mrow></msup></math></span>. The optimal results were then compared with numerical solutions obtained by using Runge-Kutta order-4 method through BVP4c tool as a reference solution, demonstrating the effectiveness of the unsupervised ANN method. The absolute error between the reference solution and proposed heuristic based physics informed neural networks approaches are ranging from<span><math><mspace></mspace><mn>2.36</mn><mo>×</mo><msup><mn>10</mn><mrow><mo>−</mo><mn>04</mn></mrow></msup><mspace></mspace><mtext>to</mtext><mspace></mspace><mn>3.46</mn><mo>×</mo><msup><mn>10</mn><mrow><mo>−</mo><mn>06</mn></mrow></msup></math></span>, <span><math><mn>2.77</mn><mo>×</mo><msup><mn>10</mn><mrow><mo>−</mo><mn>05</mn></mrow></msup><mspace></mspace><mtext>to</mtext><mspace></mspace><mn>1.20</mn><mo>×</mo><msup><mn>10</mn><mrow><mo>−</mo><mn>05</mn></mrow></msup></math></span> and<span><math><mspace></mspace><mn>1.10</mn><mo>×</mo><msup><mn>10</mn><mrow><mo>−</mo><mn>06</mn></mrow></msup><mspace></mspace><mtext>to</mtext><mspace></mspace><mn>6.53</mn><mo>×</mo><msup><mn>10</mn><mrow><mo>−</mo><mn>07</mn></mrow></msup></math></span>. Our findings demonstrate a strong agreement with the numerical approach, with the maximum discrepancy in the profiles of flow speed and energy profiles. Notably, we observed that an increase in the squeeze number and the Hartman number resulted in a reduction in the velocity profile.</div></div>","PeriodicalId":332,"journal":{"name":"International Communications in Heat and Mass Transfer","volume":"159 ","pages":"Article 108320"},"PeriodicalIF":6.4,"publicationDate":"2024-11-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142653667","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 : 2024-11-14DOI: 10.1016/j.icheatmasstransfer.2024.108319
Chao Yuan , Shenghan Jin , Hongqiang Li , Zhongbin Liu , Jinqing Peng , Houpei Li
R450A has a low Global Warming Potential, which is considered a replacement for R134a. This study measures the pressure gradient and heat transfer coefficient of both R134a and R450A during boiling in a multiport microchannel tube. The mass fluxes change from 100 to 200 kg-m−2 s−1, heat fluxes from 2 to 4 kW-m−2, and inlet saturation temperatures from 10 to 30 °C. Both refrigerants exhibit increased HTC with rising vapor quality, peaking at moderate vapor qualities (0.4 to 0.6). R450A shows higher increase in heat transfer coefficient at higher heat fluxes compared to R134a. Heat transfer coefficient enhances about 75 % when mass flux doubled for both refrigerants. The pressure gradient increases with vapor quality for both refrigerants, with R450A showing higher dP/dz. due to its lower vapor density and saturation pressure at the same saturation temperature. Higher mass flux results in higher and steeper pressure gradient. Lower saturation temperatures increase the pressure gradient due to lower vapor density. Kim and Mudawar model and Mishima and Hibiki model are both recommend for predicting pressure gradient. Liu and Winterton has low MAE and ME when comparing the predictions to measurements in this study, showing it is a relatively accurate model for predicting HTC for both R134a and R450A.
{"title":"Experimental study of R134a and its alternative mixture R450A flow boiling in a microchannel tube","authors":"Chao Yuan , Shenghan Jin , Hongqiang Li , Zhongbin Liu , Jinqing Peng , Houpei Li","doi":"10.1016/j.icheatmasstransfer.2024.108319","DOIUrl":"10.1016/j.icheatmasstransfer.2024.108319","url":null,"abstract":"<div><div>R450A has a low Global Warming Potential, which is considered a replacement for R134a. This study measures the pressure gradient and heat transfer coefficient of both R134a and R450A during boiling in a multiport microchannel tube. The mass fluxes change from 100 to 200 kg-m<sup>−2</sup> s<sup>−1</sup>, heat fluxes from 2 to 4 kW-m<sup>−2</sup>, and inlet saturation temperatures from 10 to 30 °C. Both refrigerants exhibit increased HTC with rising vapor quality, peaking at moderate vapor qualities (0.4 to 0.6). R450A shows higher increase in heat transfer coefficient at higher heat fluxes compared to R134a. Heat transfer coefficient enhances about 75 % when mass flux doubled for both refrigerants. The pressure gradient increases with vapor quality for both refrigerants, with R450A showing higher dP/dz. due to its lower vapor density and saturation pressure at the same saturation temperature. Higher mass flux results in higher and steeper pressure gradient. Lower saturation temperatures increase the pressure gradient due to lower vapor density. Kim and Mudawar model and Mishima and Hibiki model are both recommend for predicting pressure gradient. Liu and Winterton has low MAE and ME when comparing the predictions to measurements in this study, showing it is a relatively accurate model for predicting HTC for both R134a and R450A.</div></div>","PeriodicalId":332,"journal":{"name":"International Communications in Heat and Mass Transfer","volume":"159 ","pages":"Article 108319"},"PeriodicalIF":6.4,"publicationDate":"2024-11-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142653665","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 : 2024-11-13DOI: 10.1016/j.icheatmasstransfer.2024.108318
Yun Seok Choi , Sung Jin Kim , Il Woong Park , Hyun Sun Park , Yeon-Gun Lee
Advancements in technology have led to electronics with higher power densities, which strains the sustainability of these devices. In this context, using metal foams in pool boiling can provide solutions by enhancing heat transfer. The porous structure of metal foams affects the boiling parameters such as critical heat flux (CHF) and boiling heat transfer coefficient (BHTC). To study these effects, copper foams of varying thicknesses and PPI were used, and they were attached to smooth silicon surfaces to simulate chip cooling. This research focused on thin foams with 1 mm thickness, which had been sparsely explored in the previous studies. In the ten samples, the CHF increased by up to 85.8 %, and the BHTC increased by up to 141.1 %. Vapor bubble dynamics on copper foam surfaces, which were affected by the foam thickness and PPI, were analyzed. The experimental results show that copper foams significantly enhance pool boiling heat transfer. However, thicker foams increase the frequency of bubble trapping, causing localized overheating which leads to deterioration of heat transfer performance. There was also an optimal PPI value for each foam thickness, which is 40 PPI for the 1 mm thickness and 30 PPI for the 3 mm thickness.
技术的进步使得电子产品的功率密度越来越高，这对这些设备的可持续性造成了压力。在这种情况下，在水池沸腾中使用金属泡沫可以通过增强传热提供解决方案。金属泡沫的多孔结构会影响沸腾参数，如临界热通量（CHF）和沸腾传热系数（BHTC）。为了研究这些影响，我们使用了不同厚度和 PPI 的铜泡沫，并将它们附着在光滑的硅表面，以模拟芯片冷却。这项研究的重点是厚度为 1 毫米的薄泡沫，而之前的研究对这一厚度的研究较少。在 10 个样品中，CHF 增加了 85.8%，BHTC 增加了 141.1%。实验分析了泡沫铜表面的气泡动力学，气泡动力学受泡沫厚度和 PPI 的影响。实验结果表明，铜泡沫能显著提高池沸腾传热。然而，较厚的泡沫会增加气泡捕获的频率，造成局部过热，从而导致传热性能下降。此外，每种厚度的泡沫都有一个最佳 PPI 值，1 毫米厚度的泡沫为 40 PPI，3 毫米厚度的泡沫为 30 PPI。
{"title":"Experimental investigation on the influence of copper foam characteristics on pool boiling heat transfer","authors":"Yun Seok Choi , Sung Jin Kim , Il Woong Park , Hyun Sun Park , Yeon-Gun Lee","doi":"10.1016/j.icheatmasstransfer.2024.108318","DOIUrl":"10.1016/j.icheatmasstransfer.2024.108318","url":null,"abstract":"<div><div>Advancements in technology have led to electronics with higher power densities, which strains the sustainability of these devices. In this context, using metal foams in pool boiling can provide solutions by enhancing heat transfer. The porous structure of metal foams affects the boiling parameters such as critical heat flux (CHF) and boiling heat transfer coefficient (BHTC). To study these effects, copper foams of varying thicknesses and PPI were used, and they were attached to smooth silicon surfaces to simulate chip cooling. This research focused on thin foams with 1 mm thickness, which had been sparsely explored in the previous studies. In the ten samples, the CHF increased by up to 85.8 %, and the BHTC increased by up to 141.1 %. Vapor bubble dynamics on copper foam surfaces, which were affected by the foam thickness and PPI, were analyzed. The experimental results show that copper foams significantly enhance pool boiling heat transfer. However, thicker foams increase the frequency of bubble trapping, causing localized overheating which leads to deterioration of heat transfer performance. There was also an optimal PPI value for each foam thickness, which is 40 PPI for the 1 mm thickness and 30 PPI for the 3 mm thickness.</div></div>","PeriodicalId":332,"journal":{"name":"International Communications in Heat and Mass Transfer","volume":"159 ","pages":"Article 108318"},"PeriodicalIF":6.4,"publicationDate":"2024-11-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142653660","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 : 2024-11-13DOI: 10.1016/j.icheatmasstransfer.2024.108324
Bhavna Rajput , Sonika Sharma , Bahni Ray , Apurba Das , Prabal Talukdar
Flame-Retardant Clothing serves as a protective shield for firefighters that safeguards them from exposure to heat, flames and other thermal hazards. To achieve an optimal design for the clothing, it is essential to simultaneously account for all the factors affecting the performance of the clothing. The present study employs data from a numerical model to explore heat and moisture transport through clothing subjected to flame exposure. Seventeen non-dimensionless parameters associated with the heat and moisture transport in flame-retardant clothing are obtained. A correlation is developed to link the dimensionless second-degree burn time with other non-dimensional parameters. This correlation provides a means to predict the thermal protective performance (TPP) of the clothing. Additionally, an Artificial Neural Network (ANN) method is employed to determine the TPP of the clothing. Multi-layer feedforward backpropagation networks are utilized to predict the TPP under specified exposure conditions. The findings indicate that both the correlations and the ANN approach adopted in the present study demonstrated promising results. However, the ANN model predictions show better agreement with model data in comparison to the results derived from the developed correlation. The maximum percentage error in the predicted non-dimensional second degree burn time using ANN is limited to 10 %.
阻燃服是消防员的保护罩，可防止他们暴露在高温、火焰和其他热危险中。要实现服装的最佳设计，必须同时考虑影响服装性能的所有因素。本研究利用数值模型中的数据来探讨热量和湿气在暴露于火焰下的服装中的传输。研究获得了 17 个与阻燃服装中热量和湿气传输相关的无量纲参数。建立了一种相关关系，将无量纲二级燃烧时间与其他非量纲参数联系起来。这种相关性为预测服装的热防护性能（TPP）提供了一种方法。此外，还采用了人工神经网络（ANN）方法来确定服装的热防护性能。利用多层前馈反向传播网络来预测特定暴露条件下的 TPP。研究结果表明，本研究中采用的相关性和 ANN 方法都显示出良好的效果。不过，与开发的相关方法得出的结果相比，ANN 模型的预测结果与模型数据的一致性更好。使用 ANN 预测的非二度烧伤时间的最大百分比误差限制在 10%。
{"title":"Performance prediction of flame-retardant clothing using correlations and artificial neural networks: Optimizing firefighter safety","authors":"Bhavna Rajput , Sonika Sharma , Bahni Ray , Apurba Das , Prabal Talukdar","doi":"10.1016/j.icheatmasstransfer.2024.108324","DOIUrl":"10.1016/j.icheatmasstransfer.2024.108324","url":null,"abstract":"<div><div>Flame-Retardant Clothing serves as a protective shield for firefighters that safeguards them from exposure to heat, flames and other thermal hazards. To achieve an optimal design for the clothing, it is essential to simultaneously account for all the factors affecting the performance of the clothing. The present study employs data from a numerical model to explore heat and moisture transport through clothing subjected to flame exposure. Seventeen non-dimensionless parameters associated with the heat and moisture transport in flame-retardant clothing are obtained. A correlation is developed to link the dimensionless second-degree burn time with other non-dimensional parameters. This correlation provides a means to predict the thermal protective performance (TPP) of the clothing. Additionally, an Artificial Neural Network (ANN) method is employed to determine the TPP of the clothing. Multi-layer feedforward backpropagation networks are utilized to predict the TPP under specified exposure conditions. The findings indicate that both the correlations and the ANN approach adopted in the present study demonstrated promising results. However, the ANN model predictions show better agreement with model data in comparison to the results derived from the developed correlation. The maximum percentage error in the predicted non-dimensional second degree burn time using ANN is limited to 10 %.</div></div>","PeriodicalId":332,"journal":{"name":"International Communications in Heat and Mass Transfer","volume":"159 ","pages":"Article 108324"},"PeriodicalIF":6.4,"publicationDate":"2024-11-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142653662","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 : 2024-11-13DOI: 10.1016/j.icheatmasstransfer.2024.108323
Jiajie Guo, Liming Song, Zhi Tao, Jun Li
For the purpose to enhance the cooling performance of the squealer tip under stage conditions, an automatic optimization framework was constructed to optimize the cooling holes on a squealer tip, including the utilization of oval-shaped holes. The analysis of the optimization results indicates that the configuration of the cooling holes with positive axial inclination and the reduction in the arrangement interval of holes that are assembled in the front cavity can effectively enhance the film attachment, resulting in augmented film coverage and cooling effectiveness. The coefficient of heat transfer in the region between and downstream the holes is observed to decrease in accordance with the film coverage. Meanwhile, the positive axial inclination guides the jets to accumulate towards the rear of the cavity, enhancing the blocking effect to leakage flow. The film attachment is further improved as the jets outflow along the long axis edge of oval holes, which exhibit low curvature. In general, the implementation of round hole optimization has led to an increase in cooling effectiveness by 54.85 % in comparison to the benchmark. Furthermore, the use of oval holes has resulted in a greater improvement of 67.65 %. The aerodynamic performance has remained uncompromised throughout these modifications.
{"title":"Cooling layout optimization for a turbine blade squealer tip with the application of oval holes","authors":"Jiajie Guo, Liming Song, Zhi Tao, Jun Li","doi":"10.1016/j.icheatmasstransfer.2024.108323","DOIUrl":"10.1016/j.icheatmasstransfer.2024.108323","url":null,"abstract":"<div><div>For the purpose to enhance the cooling performance of the squealer tip under stage conditions, an automatic optimization framework was constructed to optimize the cooling holes on a squealer tip, including the utilization of oval-shaped holes. The analysis of the optimization results indicates that the configuration of the cooling holes with positive axial inclination and the reduction in the arrangement interval of holes that are assembled in the front cavity can effectively enhance the film attachment, resulting in augmented film coverage and cooling effectiveness. The coefficient of heat transfer in the region between and downstream the holes is observed to decrease in accordance with the film coverage. Meanwhile, the positive axial inclination guides the jets to accumulate towards the rear of the cavity, enhancing the blocking effect to leakage flow. The film attachment is further improved as the jets outflow along the long axis edge of oval holes, which exhibit low curvature. In general, the implementation of round hole optimization has led to an increase in cooling effectiveness by 54.85 % in comparison to the benchmark. Furthermore, the use of oval holes has resulted in a greater improvement of 67.65 %. The aerodynamic performance has remained uncompromised throughout these modifications.</div></div>","PeriodicalId":332,"journal":{"name":"International Communications in Heat and Mass Transfer","volume":"159 ","pages":"Article 108323"},"PeriodicalIF":6.4,"publicationDate":"2024-11-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142653952","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 : 2024-11-13DOI: 10.1016/j.icheatmasstransfer.2024.108321
Han Shen , Xinyue Lan , Gongnan Xie , Chi-Chuan Wang
The design of impacting-jet double-layer nested microchannel heat sinks (IJDN-MHS) has been proved to be an effective structure on heat dissipation improvement in electronic components. In order to achieve ideal substrate thermal uniformity for IJDN-MHS, the position research on vertical fin connecting inner/outer cooling circuit in IJDN-MHS has been studied numerically. Moreover, 3D printing test samples are made on the purpose of experimental verification using selective laser melting printing technology. As a result of the analysis, there is a strong correlation between the results of the numerical simulation and the experimental results. Through numerical simulation, it has been determined that the center fin position should be optimized for achieving the best thermal uniformity on the substrate. The model of distance between vertical fin connecting inner/outer cooling circuit and central point in IJDM-MHS equaling 0.27 mm (IJDN-MHS_0.27) has shown the optimal thermal symmetry on substrate. Further, with the streaming fins length increasing to 0.7 mm on the both sides of the vertical fin connecting inner/outer cooling circuit, thermal gradient at the bottom can be significantly controlled, and the peak temperature on substrate also drop to its most extreme limit based on the thermal uniformity on substrate.
{"title":"Parametric study for thermal uniformity analysis on vertical fin located in novel designed impacting-jet double-layer nested microchannel heat sinks verified by SLM 3D printing method","authors":"Han Shen , Xinyue Lan , Gongnan Xie , Chi-Chuan Wang","doi":"10.1016/j.icheatmasstransfer.2024.108321","DOIUrl":"10.1016/j.icheatmasstransfer.2024.108321","url":null,"abstract":"<div><div>The design of impacting-jet double-layer nested microchannel heat sinks (IJDN-MHS) has been proved to be an effective structure on heat dissipation improvement in electronic components. In order to achieve ideal substrate thermal uniformity for IJDN-MHS, the position research on vertical fin connecting inner/outer cooling circuit in IJDN-MHS has been studied numerically. Moreover, 3D printing test samples are made on the purpose of experimental verification using selective laser melting printing technology. As a result of the analysis, there is a strong correlation between the results of the numerical simulation and the experimental results. Through numerical simulation, it has been determined that the center fin position should be optimized for achieving the best thermal uniformity on the substrate. The model of distance between vertical fin connecting inner/outer cooling circuit and central point in IJDM-MHS equaling 0.27 mm (IJDN-MHS_0.27) has shown the optimal thermal symmetry on substrate. Further, with the streaming fins length increasing to 0.7 mm on the both sides of the vertical fin connecting inner/outer cooling circuit, thermal gradient at the bottom can be significantly controlled, and the peak temperature on substrate also drop to its most extreme limit based on the thermal uniformity on substrate.</div></div>","PeriodicalId":332,"journal":{"name":"International Communications in Heat and Mass Transfer","volume":"159 ","pages":"Article 108321"},"PeriodicalIF":6.4,"publicationDate":"2024-11-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142653950","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 : 2024-11-13DOI: 10.1016/j.icheatmasstransfer.2024.108328
Tianjiao Li , Yue Zhu , Weiyi Zhang , Bingkun Wu , Dong Liu
The comprehension of the distribution of gaseous species and soot particles plays a pivotal role in investigating the combustion process of a flame. A highly effective method to accomplish this is by extracting visible and near-infrared emission information from flames. In this study, we present a novel near-infrared multi-spectral light field imaging model that enables the concurrent extraction of gas and soot property distributions within a flame. A synthetic test of ethylene diffusion flame is assessed using the proposed reconstruction method. The mole fraction of gaseous water, together with the flame temperature and soot volume fraction, are decoupled spectrally using near-infrared and visible wavelengths. The results demonstrate a reliably retrieved temperature range of 1400 K to 2050 K, accurately reconstructing the actual distributions of soot volume fraction and gaseous water mole fraction. Minor influences on the imaging results and property reconstruction are observed due to uncertainties arising from the reconstruction method, absorption function, reconstruction wavelength for H2O mole fraction, and signal-to-noise ratio. This study serves as a theoretical guide for the future development of practical near-infrared multi-spectral light field imaging techniques for rapid and robust flame diagnostic purposes related to soot and gas properties.
了解气态物质和烟尘颗粒的分布对研究火焰的燃烧过程起着至关重要的作用。提取火焰的可见光和近红外发射信息是实现这一目标的高效方法。在本研究中，我们提出了一种新型的近红外多光谱光场成像模型，该模型可同时提取火焰中的气体和烟尘特性分布。使用所提出的重建方法对乙烯扩散火焰的合成测试进行了评估。气态水的摩尔分数、火焰温度和烟尘体积分数通过近红外和可见光波长进行光谱解耦。结果表明，可靠检索的温度范围为 1400 K 至 2050 K，准确重建了烟尘体积分数和气态水分子分数的实际分布。由于重建方法、吸收函数、H2O 分子分数的重建波长和信噪比的不确定性，对成像结果和属性重建的影响较小。这项研究为今后开发实用的近红外多光谱光场成像技术提供了理论指导，可用于快速、可靠地诊断与烟尘和气体性质有关的火焰。
{"title":"Water vapor and soot spatial characteristics retrieve of axisymmetric optically-thin laminar diffusion flame based on visible and near-infrared multi-spectral light field imaging","authors":"Tianjiao Li , Yue Zhu , Weiyi Zhang , Bingkun Wu , Dong Liu","doi":"10.1016/j.icheatmasstransfer.2024.108328","DOIUrl":"10.1016/j.icheatmasstransfer.2024.108328","url":null,"abstract":"<div><div>The comprehension of the distribution of gaseous species and soot particles plays a pivotal role in investigating the combustion process of a flame. A highly effective method to accomplish this is by extracting visible and near-infrared emission information from flames. In this study, we present a novel near-infrared multi-spectral light field imaging model that enables the concurrent extraction of gas and soot property distributions within a flame. A synthetic test of ethylene diffusion flame is assessed using the proposed reconstruction method. The mole fraction of gaseous water, together with the flame temperature and soot volume fraction, are decoupled spectrally using near-infrared and visible wavelengths. The results demonstrate a reliably retrieved temperature range of 1400 K to 2050 K, accurately reconstructing the actual distributions of soot volume fraction and gaseous water mole fraction. Minor influences on the imaging results and property reconstruction are observed due to uncertainties arising from the reconstruction method, absorption function, reconstruction wavelength for H<sub>2</sub>O mole fraction, and signal-to-noise ratio. This study serves as a theoretical guide for the future development of practical near-infrared multi-spectral light field imaging techniques for rapid and robust flame diagnostic purposes related to soot and gas properties.</div></div>","PeriodicalId":332,"journal":{"name":"International Communications in Heat and Mass Transfer","volume":"159 ","pages":"Article 108328"},"PeriodicalIF":6.4,"publicationDate":"2024-11-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142653663","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 : 2024-11-13DOI: 10.1016/j.icheatmasstransfer.2024.108287
Sai Luo, JingBo Xu, Chen Wang, Jie Ji
Flame may spread over accidentally leaked liquid fuel, which is essentially related to multi-phase flows and heat transfer. This paper investigates the dynamic evolution behavior and the heat transfer mechanism of flame spread over stationary and flowing diesel fuel with various discharge flow rates. Results show that for flowing fuel cases, there is a considerable long-lasting unsteady flame spread stage, in which the subsurface flow velocity (us) and flame spread rate (Vf) increase as the spread proceeds. This is significantly different from flame spread over stationary fuel, in which us and Vf remain almost unchanged. Driving mechanism of the subsurface flow and variation of momentum balance is analyzed for the explanation. Besides, theoretical analysis is conducted to predict the acceleration, whose results agree with experimental data. Moreover, based on the momentum balance, it is found that us cannot be assumed to be linearly distributed along the fuel thickness, detailed velocity profiles are further clarified. In addition, dynamic variation of the heat transfer process is quantitatively revealed, and there is a transition of the dominant contribution to the heat needed for flame spread. Flame radiation plays a more significant role initially, as flame spreads, liquid convection gradually plays the dominant role.
{"title":"Experimental study on the dynamic evolution behavior and heat transfer of flame spread over continuously flowing diesel fuel","authors":"Sai Luo, JingBo Xu, Chen Wang, Jie Ji","doi":"10.1016/j.icheatmasstransfer.2024.108287","DOIUrl":"10.1016/j.icheatmasstransfer.2024.108287","url":null,"abstract":"<div><div>Flame may spread over accidentally leaked liquid fuel, which is essentially related to multi-phase flows and heat transfer. This paper investigates the dynamic evolution behavior and the heat transfer mechanism of flame spread over stationary and flowing diesel fuel with various discharge flow rates. Results show that for flowing fuel cases, there is a considerable long-lasting unsteady flame spread stage, in which the subsurface flow velocity (<em>u</em><sub><em>s</em></sub>) and flame spread rate (<em>V</em><sub><em>f</em></sub>) increase as the spread proceeds. This is significantly different from flame spread over stationary fuel, in which <em>u</em><sub><em>s</em></sub> and <em>V</em><sub><em>f</em></sub> remain almost unchanged. Driving mechanism of the subsurface flow and variation of momentum balance is analyzed for the explanation. Besides, theoretical analysis is conducted to predict the acceleration, whose results agree with experimental data. Moreover, based on the momentum balance, it is found that <em>u</em><sub><em>s</em></sub> cannot be assumed to be linearly distributed along the fuel thickness, detailed velocity profiles are further clarified. In addition, dynamic variation of the heat transfer process is quantitatively revealed, and there is a transition of the dominant contribution to the heat needed for flame spread. Flame radiation plays a more significant role initially, as flame spreads, liquid convection gradually plays the dominant role.</div></div>","PeriodicalId":332,"journal":{"name":"International Communications in Heat and Mass Transfer","volume":"159 ","pages":"Article 108287"},"PeriodicalIF":6.4,"publicationDate":"2024-11-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142653661","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.2024.108331
Jinfu Zheng , Changpeng Han , Songtao Hu , Qixiang Qin , Jinda Wang , Hui Zhu , Shimin Liang
The thermal and hydraulic performances of front-end heat exchangers significantly influence the energy efficiency of surface water-source heat pumps. To evaluate the performance of a capillary box heat exchanger (CBHE), a comparative study between the CBHE and a conventional helical coil heat exchanger (HCHE) was conducted under different tube velocities, heat transfer media, and temperatures. The comparison considered not only traditional metrics, such as the heat transfer coefficient, heat transfer efficiency, and pressure drop, but also the volume heat transfer coefficient and two thermal-hydraulic comprehensive performance parameters: the modified Colburn–Fanning factor ratio (JFK) with larger-the-better characteristics and the electricity consumption to extracted or rejected heat quantity ratio (EHR) with smaller-the-better characteristics. The results indicated that the heat transfer coefficient, heat transfer efficiency, and volume heat transfer coefficient of the CBHE were 10.1 W/(m2.°C)–25.58 W/(m2.°C), 34 %–45 %, and 1140 W/(m3.°C)–1416 W/(m3.°C) larger than those of the HCHE, whereas its total pressure drop was only 15 %–21 % of that of the HCHE. Additionally, the JFK and EHR of the CBHE were approximately three times and 11 %–16 %, respectively, those of the HCHE. This study serves as a reference for selecting and designing front-end heat exchangers.
{"title":"Comparative experimental study on the thermal and hydraulic performances of capillary box heat exchanger and helical coil heat exchanger for surface water-source heat pump","authors":"Jinfu Zheng , Changpeng Han , Songtao Hu , Qixiang Qin , Jinda Wang , Hui Zhu , Shimin Liang","doi":"10.1016/j.icheatmasstransfer.2024.108331","DOIUrl":"10.1016/j.icheatmasstransfer.2024.108331","url":null,"abstract":"<div><div>The thermal and hydraulic performances of front-end heat exchangers significantly influence the energy efficiency of surface water-source heat pumps. To evaluate the performance of a capillary box heat exchanger (CBHE), a comparative study between the CBHE and a conventional helical coil heat exchanger (HCHE) was conducted under different tube velocities, heat transfer media, and temperatures. The comparison considered not only traditional metrics, such as the heat transfer coefficient, heat transfer efficiency, and pressure drop, but also the volume heat transfer coefficient and two thermal-hydraulic comprehensive performance parameters: the modified Colburn–Fanning factor ratio (<em>JF</em><sub><em>K</em></sub>) with larger-the-better characteristics and the electricity consumption to extracted or rejected heat quantity ratio (<em>EHR</em>) with smaller-the-better characteristics. The results indicated that the heat transfer coefficient, heat transfer efficiency, and volume heat transfer coefficient of the CBHE were 10.1 W/(m<sup>2.</sup>°C)–25.58 W/(m<sup>2.</sup>°C), 34 %–45 %, and 1140 W/(m<sup>3.</sup>°C)–1416 W/(m<sup>3.</sup>°C) larger than those of the HCHE, whereas its total pressure drop was only 15 %–21 % of that of the HCHE. Additionally, the <em>JF</em><sub><em>K</em></sub> and <em>EHR</em> of the CBHE were approximately three times and 11 %–16 %, respectively, those of the HCHE. This study serves as a reference for selecting and designing front-end heat exchangers.</div></div>","PeriodicalId":332,"journal":{"name":"International Communications in Heat and Mass Transfer","volume":"159 ","pages":"Article 108331"},"PeriodicalIF":6.4,"publicationDate":"2024-11-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142653951","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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