International Journal of Heat and Mass Transfer最新文献

{"title":"Investigation on flow and heat transfer of fluid in self-driven circulation system for transpiration cooling","authors":"Yumei Lv ,&nbsp;Wanfan Wu ,&nbsp;Yulong Ma ,&nbsp;Yun Luan ,&nbsp;Fei He ,&nbsp;Jianhua Wang","doi":"10.1016/j.ijheatmasstransfer.2023.124775","DOIUrl":"https://doi.org/10.1016/j.ijheatmasstransfer.2023.124775","url":null,"abstract":"<div><p>Transpiration cooling has attracted extensive attention from industry as an efficient thermal protection strategy to cope with the extreme thermal environment during hypersonic vehicle flight. Unfortunately, the investigation on transpiration cooling in combination with internal coolant piping layout is inadequate. Here, we propose a self-driven natural circulation system as the internal coolant channel in the lower layer of the transpiration cooling structure, aiming to achieve comprehensive thermal management. Meanwhile, a time-resolved Quantitative Light Sheet technique is applied in experimental research on the natural circulation system. Through investigating the flow, heat transfer and phase transition characteristics of the fluid in the system, it is concluded that this system utilizes the heat flux difference loaded on the pipe wall to drive the coolant to circulate in the loop, and the maximum wall heat flux reaches about 15.4 kW/m², realizing internal self-adaptive cooling. Additionally, this proposed system ensures that the phase transition occurs in the lower pipes of the transpiration structure to avoid heat transfer deterioration. Besides, the system releases 57,600 cm³ steam within 100 s under the 500 W/m² heat flux difference of pipes acting as coolant for transpiration cooling. Thus, this work provides an innovative reference for combined application of transpiration cooling and self-driven natural circulation system.</p></div>","PeriodicalId":336,"journal":{"name":"International Journal of Heat and Mass Transfer","volume":"218 ","pages":"Article 124775"},"PeriodicalIF":5.2,"publicationDate":"2023-10-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S0017931023009201/pdfft?md5=cd1d5e34f30e2af8c4543cfb2ea87beb&pid=1-s2.0-S0017931023009201-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"92017431","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}

{"title":"Identification of aerothermal heating for thermal protection systems taking into account the thermal resistance between layers","authors":"Rafał Brociek ,&nbsp;Edyta Hetmaniok ,&nbsp;Christian Napoli ,&nbsp;Giacomo Capizzi ,&nbsp;Damian Słota","doi":"10.1016/j.ijheatmasstransfer.2023.124772","DOIUrl":"https://doi.org/10.1016/j.ijheatmasstransfer.2023.124772","url":null,"abstract":"<div><p>In this paper the aerothermal heating of a reusable launch vehicle is reconstructed on the basis of temperature measurements taken in the thermal protection system of this vehicle. The discussed integrated thermal protection system is composed of three layers. Mathematical model, describing the problem, takes into account the dependence on temperature of the material parameters as well as the thermal resistances occurring in the contact zones of the layers, which is a novelty in the proposed approach. For solving the direct problem, the implicit scheme of the finite difference method is applied. Next, by using the solution of the direct problem, the Tikhonov functional is created, which describes the error of the current approximate solution. Whereas for determining the solution of the inverse problem the Levenberg-Marquardt method, modified and adapted to the Tikhonov functional, is used. The paper presents the mathematical model of the problem and the method of solution together with the selected examples illustrating its exactness and stability. In order to better examination of the solution method some various values of parameters are taken in the demonstrated examples.</p></div>","PeriodicalId":336,"journal":{"name":"International Journal of Heat and Mass Transfer","volume":"218 ","pages":"Article 124772"},"PeriodicalIF":5.2,"publicationDate":"2023-10-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S0017931023009171/pdfft?md5=b80f3262469949e3ed0b0cbbdc3e65df&pid=1-s2.0-S0017931023009171-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"92129646","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}

{"title":"A multiobjective optimization of 3D - slot jet configuration for enhancement of film cooling in an annular combustor liner","authors":"Ananda Prasanna Revulagadda ,&nbsp;Rampada Rana ,&nbsp;Batchu Suresh ,&nbsp;C. Balaji ,&nbsp;Arvind Pattamatta","doi":"10.1016/j.ijheatmasstransfer.2023.124745","DOIUrl":"https://doi.org/10.1016/j.ijheatmasstransfer.2023.124745","url":null,"abstract":"&lt;div&gt;&lt;p&gt;This study reports the results of a combined experimental and numerical investigation of the performance of a three-dimensional film cooling slot configuration and its optimization using an evolutionary-based genetic algorithm. The primary objective of the optimization is to maximize the area-averaged film cooling effectiveness (&lt;span&gt;&lt;math&gt;&lt;msub&gt;&lt;mrow&gt;&lt;mi&gt;η&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mi&gt;a&lt;/mi&gt;&lt;mi&gt;d&lt;/mi&gt;&lt;mo&gt;.&lt;/mo&gt;&lt;mi&gt;a&lt;/mi&gt;&lt;mi&gt;v&lt;/mi&gt;&lt;mi&gt;g&lt;/mi&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;/math&gt;&lt;/span&gt;) and minimize its standard deviation (&lt;span&gt;&lt;math&gt;&lt;msub&gt;&lt;mrow&gt;&lt;mi&gt;σ&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mi&gt;η&lt;/mi&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;/math&gt;&lt;/span&gt;) at a fixed coolant mass flux for a single liner. The experimental study is conducted on flow and heat transfer characteristics to validate the numerical model under laboratory conditions (low temperature and pressure). A design space is created using the Latin hypercube sampling technique, and it is solved using steady-state RANS simulations with the validated numerical model to estimate the &lt;span&gt;&lt;math&gt;&lt;msub&gt;&lt;mrow&gt;&lt;mi&gt;η&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mi&gt;a&lt;/mi&gt;&lt;mi&gt;d&lt;/mi&gt;&lt;mo&gt;.&lt;/mo&gt;&lt;mi&gt;a&lt;/mi&gt;&lt;mi&gt;v&lt;/mi&gt;&lt;mi&gt;g&lt;/mi&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;/math&gt;&lt;/span&gt; and &lt;span&gt;&lt;math&gt;&lt;msub&gt;&lt;mrow&gt;&lt;mi&gt;σ&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mi&gt;η&lt;/mi&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;/math&gt;&lt;/span&gt; under actual engine conditions (high temperature and pressure). A surrogate model is developed using the kriging technique to predict the objective functions with the geometrical parameters of the slot. Following this, the optimum configuration is identified using the genetic algorithm. The geometrical parameters are slot jet diameter (&lt;em&gt;d&lt;/em&gt;), slot jet pitch (&lt;em&gt;p&lt;/em&gt;), lip taper angle (&lt;em&gt;α&lt;/em&gt;), and lip length (&lt;em&gt;L&lt;/em&gt;). The numerical results show that the optimum configuration outperforms the two reference configurations of the baseline combustor. At a blowing ratio &lt;span&gt;&lt;math&gt;&lt;mo&gt;(&lt;/mo&gt;&lt;mi&gt;B&lt;/mi&gt;&lt;mi&gt;R&lt;/mi&gt;&lt;mo&gt;)&lt;/mo&gt;&lt;/math&gt;&lt;/span&gt; of 1, the optimum configuration enhances the &lt;span&gt;&lt;math&gt;&lt;msub&gt;&lt;mrow&gt;&lt;mi&gt;η&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mi&gt;a&lt;/mi&gt;&lt;mi&gt;d&lt;/mi&gt;&lt;mo&gt;.&lt;/mo&gt;&lt;mi&gt;a&lt;/mi&gt;&lt;mi&gt;v&lt;/mi&gt;&lt;mi&gt;g&lt;/mi&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;/math&gt;&lt;/span&gt; by 8% and reduces the &lt;span&gt;&lt;math&gt;&lt;msub&gt;&lt;mrow&gt;&lt;mi&gt;σ&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mi&gt;η&lt;/mi&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;/math&gt;&lt;/span&gt; by 6.6% compared to reference -1 configuration. Similarly, compared to reference -2, the optimum configuration enhances the &lt;span&gt;&lt;math&gt;&lt;msub&gt;&lt;mrow&gt;&lt;mi&gt;η&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mi&gt;a&lt;/mi&gt;&lt;mi&gt;d&lt;/mi&gt;&lt;mo&gt;.&lt;/mo&gt;&lt;mi&gt;a&lt;/mi&gt;&lt;mi&gt;v&lt;/mi&gt;&lt;mi&gt;g&lt;/mi&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;/math&gt;&lt;/span&gt; by 19.8% and reduces the &lt;span&gt;&lt;math&gt;&lt;msub&gt;&lt;mrow&gt;&lt;mi&gt;σ&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mi&gt;η&lt;/mi&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;/math&gt;&lt;/span&gt; by 5.2.%. Furthermore, under actual engine conditions, a numerical study is conducted on a subsequent row of liners to determine the optimum length of the cooling ring. The numerical results show that the optimum slot configuration cools an additional liner length (&lt;span&gt;&lt;math&gt;&lt;mi&gt;G&lt;/mi&gt;&lt;mo&gt;/&lt;/mo&gt;&lt;mi&gt;S&lt;/mi&gt;&lt;/math&gt;&lt;/span&gt;) of 5.5 compared to the reference-1 slot and results in a reduction of one pair of cooling rings in the combustor, which contributes to a 16.","PeriodicalId":336,"journal":{"name":"International Journal of Heat and Mass Transfer","volume":"218 ","pages":"Article 124745"},"PeriodicalIF":5.2,"publicationDate":"2023-10-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S0017931023008906/pdfft?md5=76a9016aa748d5095bebfdef208123b7&pid=1-s2.0-S0017931023008906-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"92017428","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}

{"title":"Prediction of supercritical CO2 heat transfer behaviors by combining transfer learning and deep learning based on multi-fidelity data","authors":"Xinhuan Shi ,&nbsp;Yongji Liu ,&nbsp;Longxian Xue ,&nbsp;Wei Chen ,&nbsp;Minking K. Chyu","doi":"10.1016/j.ijheatmasstransfer.2023.124802","DOIUrl":"https://doi.org/10.1016/j.ijheatmasstransfer.2023.124802","url":null,"abstract":"<div><p>The flow and heat transfer characteristics of supercritical CO₂ are important for heat exchanger design and the safe operation of supercritical CO₂ power cycles. However, it is difficult to predict the supercritical heat transfer behaviors due to the non-monotonic temperature distribution in the case of the heat transfer deterioration (HTD) phenomenon. For low-cost, fast and accurate prediction of the supercritical heat transfer behavior, this study proposed a transfer learning model based on multi-fidelity data to achieve fast prediction with acceptable accuracy over a wide range of working conditions. This method fully utilized the low fidelity data (empirical correlations) and the medium fidelity data (numerical results) to generate a large amount of data for pretraining, in which the Latin Hypercube Sampling (LHS) method combined with the HTD correlation was used for sampling. For fine-tuning, high fidelity data from experiments was employed. Compared to the deep learning model trained directly with high fidelity dataset, the transfer learning model demonstrated vastly improved predictive performance on both the test and validation datasets. Additionally, the coefficient of determination <em>R</em>² was discussed to preventing from “physical overfitting”. Instead of excessively pursuing the high <em>R</em>² (close to 1), the validity of the prediction should be concerned, especially when using the non-smooth experimental data as the dataset for model training. Moreover, the trained models and the relative files are available at <em>Supplementary materials</em>.</p></div>","PeriodicalId":336,"journal":{"name":"International Journal of Heat and Mass Transfer","volume":"218 ","pages":"Article 124802"},"PeriodicalIF":5.2,"publicationDate":"2023-10-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S001793102300947X/pdfft?md5=71767446426d9a8a7a582be938ef6c31&pid=1-s2.0-S001793102300947X-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"92017429","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}

{"title":"Thermo-electrohydrodynamic convection in a rotating shell with central force field","authors":"Yann Gaillard,&nbsp;Peter S.B. Szabo,&nbsp;Vadim Travnikov,&nbsp;Christoph Egbers","doi":"10.1016/j.ijheatmasstransfer.2023.124760","DOIUrl":"https://doi.org/10.1016/j.ijheatmasstransfer.2023.124760","url":null,"abstract":"<div><p>Thermally driven convection in a rotating shell of dielectric fluid is investigated. An imposed central electric force field induces thermo-electrohydrodynamic convection by the dielectrophoretic force in the presence of a radial temperature gradient. Depending on the strength of the dielectrophoretic force regular to irregular convective modes are observed that are reminiscent of the classical Rayleigh-Bénad convection. While the rotation has an influence on the nature of the convective modes, a force ratio is developed to characterise the evolving pattern formation. A time evolution of the convection showed mode merging, quasi-stationary states and irregular to axis-symmetric patterns. These patterns are further analysed by a spatial Fourier decomposition to calculate the mode number and drift rates related to the rotational and di-electrophoretic forcing. The heat transfer is evaluated by the Nusselt number, <em>Nu</em>, and showed a significant influence by the intensity of the respective forcing. With the use of the force ratio, ϒ, and the potential mode energy, <span><math><msub><mrow><mi>E</mi></mrow><mrow><mi>m</mi></mrow></msub></math></span>, the convective modes could be classified into four distinct regimes that suggests two power laws for <span><math><mi>N</mi><mi>u</mi><mo>∼</mo><mi>R</mi><msubsup><mrow><mi>a</mi></mrow><mrow><mi>E</mi></mrow><mrow><mn>0.17</mn><mo>±</mo><mn>0.01</mn></mrow></msubsup></math></span> and <span><math><mi>N</mi><mi>u</mi><mo>∼</mo><msup><mrow><mn>0.7</mn></mrow><mrow><mo>−</mo><mn>0.204</mn><mo>/</mo><msub><mrow><mi>E</mi></mrow><mrow><mi>m</mi></mrow></msub></mrow></msup></math></span> for values of <span><math><mi>ϒ</mi><mo>≤</mo><mn>0.7</mn></math></span>.</p></div>","PeriodicalId":336,"journal":{"name":"International Journal of Heat and Mass Transfer","volume":"218 ","pages":"Article 124760"},"PeriodicalIF":5.2,"publicationDate":"2023-10-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S0017931023009055/pdfft?md5=1d39fd046f2f2692516d6481b3d3de87&pid=1-s2.0-S0017931023009055-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"92005851","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}

{"title":"Flow regimes and heat transfer mechanisms affecting supercritical transition in microchannels","authors":"Trevor A. Whitaker,&nbsp;Joseph W. Cochran,&nbsp;Jacob D. Hochhalter,&nbsp;Sameer R. Rao","doi":"10.1016/j.ijheatmasstransfer.2023.124749","DOIUrl":"https://doi.org/10.1016/j.ijheatmasstransfer.2023.124749","url":null,"abstract":"<div><p>Supercritical carbon dioxide (sCO₂) exhibits unique thermophysical and transport properties, which have the potential to enhance a wide range of thermal systems. Significant property variations accompanying the pseudocritical transition preclude accurate and generalized predictions of heat transfer, particularly at the microscale. A novel method for investigating fundamental fluid flow and heat transfer mechanisms through heat transfer coefficient measurements and side-view high-speed (8000 fps) schlieren imaging was developed. Experiments are conducted in a square microchannel (<span><math><msub><mrow><mi>D</mi></mrow><mrow><mi>h</mi></mrow></msub><mo>=</mo><mn>500</mn><mspace></mspace><mrow><mi>μ</mi><mtext>m</mtext></mrow></math></span>) at reduced pressure near unity (<span><math><msub><mrow><mi>P</mi></mrow><mrow><mi>R</mi></mrow></msub><mo>=</mo><mn>1.05</mn></math></span>) over a range of heat and mass fluxes (<span><math><msubsup><mrow><mi>q</mi></mrow><mrow><mi>c</mi></mrow><mrow><mo>″</mo></mrow></msubsup><mo>=</mo><mn>1.3</mn><mo>−</mo><mn>82.6</mn><mtext> W</mtext><mspace></mspace><msup><mrow><mtext>cm</mtext></mrow><mrow><mo>−</mo><mn>2</mn></mrow></msup></math></span>; <span><math><mi>G</mi><mo>=</mo><mn>280</mn><mo>−</mo><mn>1380</mn><mtext> kg</mtext><mspace></mspace><msup><mrow><mtext>m</mtext></mrow><mrow><mo>−</mo><mn>2</mn></mrow></msup><mspace></mspace><msup><mrow><mtext>s</mtext></mrow><mrow><mo>−</mo><mn>1</mn></mrow></msup></math></span>). Non-uniform density profiles within the boundary layer and distinct, freely mixed liquid-like and gas-like packets at various stages of pseudocritical transition were observed. Three flow regimes were identified as a function of heat flux with unique convection boundary layer characteristics. Transport of liquid-like and the production of gas-like sCO₂ at the wall were found to be the primary mechanisms affecting heat transfer and were quantified using a modified form of the Richardson number. The experimental approach and mechanistic insight developed herein provide a basis for high-fidelity heat transfer models for the design of supercritical fluid systems.</p></div>","PeriodicalId":336,"journal":{"name":"International Journal of Heat and Mass Transfer","volume":"218 ","pages":"Article 124749"},"PeriodicalIF":5.2,"publicationDate":"2023-10-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S0017931023008943/pdfft?md5=b04697c65345a4ac1868c4d17de71b68&pid=1-s2.0-S0017931023008943-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"92017425","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}

{"title":"Research on the effective thermal conductivity of nickel-based bi-porous capillary wicks: Modeling and validation","authors":"Yuankun Zhang ,&nbsp;Zhuosheng Han ,&nbsp;Yongsheng Yu ,&nbsp;M.Akbar Rhamdhani ,&nbsp;Yiming Gao ,&nbsp;Chunsheng Guo","doi":"10.1016/j.ijheatmasstransfer.2023.124776","DOIUrl":"https://doi.org/10.1016/j.ijheatmasstransfer.2023.124776","url":null,"abstract":"<div><p>This study proposed an analytical model to predict the effective thermal conductivity (ETC) of bi-sized porous capillary wicks with both interstitial pores (formed inside nickel skeleton) and with large pores created by NaCl as the pore-forming agent. The interstitial-pore model was developed utilizing the sintering neck formation theory and thermal resistance network, which was validated by measured data obtained from samples of multiple particle sizes. It is shown that the model works well for fine nickel powders with the root mean square error (RMSE) of 13.8%, while a large deviation was observed when using the coarse powders. Based on the presented interstitial-pore model, an ETC model for samples containing formation pores was formulated. A total of six types of equations were proposed, considering three packing modes and two shapes of formation pores. Samples with NaCl of various granularities (54–75 μm, 88–125 μm) and proportions (2.5, 5.0, 7.5, and 10.0 wt.%) were made for the model validation. The results demonstrated that the bi-porous ETC models, with both interstitial pores and those formed by NaCl, exhibit good performance when applying the BCC configuration, while small and large formation pores can be characterized by spherical and cubic models respectively.</p></div>","PeriodicalId":336,"journal":{"name":"International Journal of Heat and Mass Transfer","volume":"218 ","pages":"Article 124776"},"PeriodicalIF":5.2,"publicationDate":"2023-10-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S0017931023009213/pdfft?md5=8d031bc619d8dbaa5688324ba6c97c22&pid=1-s2.0-S0017931023009213-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"92017427","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}

{"title":"Experimental and numerical investigations on transient film cooling performances with trenched holes considering mainstream oscillation","authors":"Liwei Ma ,&nbsp;Minmin Wang ,&nbsp;Jinfu Chen ,&nbsp;Hao Su ,&nbsp;Jianhua Wang ,&nbsp;Ran Yao","doi":"10.1016/j.ijheatmasstransfer.2023.124799","DOIUrl":"https://doi.org/10.1016/j.ijheatmasstransfer.2023.124799","url":null,"abstract":"<div><p>By a series of time-resolved experiments and large eddy simulations, the present work exhibits the transient behaviors and unsteady characteristics of film cooling with different trench configurations. The inevitable mainstream oscillation in turbine operation is considered, with a Strouhal number of 0.0128 and an amplitude of 0.50. The results show that: 1) The main instantaneous features are well captured by both experimental and numerical methods, and the transient behaviors of film cooling with trench design can be accurately predicted by the present large eddy simulation, even considering mainstream oscillation. 2) Without mainstream oscillation, film cooling unsteadiness is mainly caused by the temporal evolution of near-wall vortices, and the trench configurations exhibit a strong correlation on the unsteadiness level. The design with a higher trench height can evidently enhance the near-wall stability of film cooling while keeping a high time-averaged film effectiveness. 3) Film cooling unsteadiness is significantly aggravated by the mainstream oscillation. Under the present oscillation condition, the standard deviation of instantaneous film effectiveness is increased over 350.0 %, compared to the non-oscillation data. Meanwhile, the regions with high unsteadiness level are revealed with mainstream oscillation, which is mainly caused by the temporary coverage of cooling air in the target surface.</p></div>","PeriodicalId":336,"journal":{"name":"International Journal of Heat and Mass Transfer","volume":"218 ","pages":"Article 124799"},"PeriodicalIF":5.2,"publicationDate":"2023-10-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S0017931023009444/pdfft?md5=5d0c113f4af89f5ad1fa6e9984aaf87f&pid=1-s2.0-S0017931023009444-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"92005852","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}

{"title":"Bilayer thermal metadevices that mold transient heat flows","authors":"Qingxiang Ji ,&nbsp;Qi Zhang ,&nbsp;Sébastien Guenneau ,&nbsp;Muamer Kadic ,&nbsp;Changguo Wang","doi":"10.1016/j.ijheatmasstransfer.2023.124744","DOIUrl":"https://doi.org/10.1016/j.ijheatmasstransfer.2023.124744","url":null,"abstract":"<div><p>Thermal manipulation has been widely researched due to its potential in novel functions, such as cloaking, illusion and sensing. To avoid the spatially inhomogeneous and anisotropic heat conductivity tensors (introduced by transformation thermodynamics), several thermal cloaks based on scattering cancellation (SC) approach are designed and experimentally demonstrated. However, the current SC cloak is only effective in the steady-state heat transfer condition as the heat capacity terms are neglected by the requirement of constant external fields. In order to expand the SC cloak to the transient regime, a bilayer scheme is introduced to achieve the accurate solutions of the camouflage equations considering time factors. Indeed, there are two equations to solve with two unknown quantities: first the thermal conductivity and second the product of specific heat capacity by the density. We construct thermal camouflage devices and verify their ability to mold dynamic heat flows both by simulations and experiments. Our proposed method paves an efficient avenue to extend SC approach to dynamic heat transfer regime.</p></div>","PeriodicalId":336,"journal":{"name":"International Journal of Heat and Mass Transfer","volume":"218 ","pages":"Article 124744"},"PeriodicalIF":5.2,"publicationDate":"2023-10-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S001793102300889X/pdfft?md5=3c111433740e7e39aa9a2c43fcbcc8c8&pid=1-s2.0-S001793102300889X-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"92017426","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}

{"title":"A comprehensive critical heat flux mechanism model applicable to narrow rectangular channels","authors":"Meiyue Yan ,&nbsp;Liang-ming Pan ,&nbsp;Zaiyong Ma ,&nbsp;Poh Seng Lee ,&nbsp;Qingche He","doi":"10.1016/j.ijheatmasstransfer.2023.124800","DOIUrl":"https://doi.org/10.1016/j.ijheatmasstransfer.2023.124800","url":null,"abstract":"<div><p>Critical heat flux (CHF) is an essential consideration for the economy and safety of the equipment operation. To understand the CHF triggering mechanism and two-phase evolution characteristics from nucleation boiling until the occurrence of boiling crisis in narrow rectangular channels, a series of CHF visualization experiments were carried out at different gap sizes (1–5 mm), with pressures ranging from 1 to 4 MPa, inlet subcooling ranging from 65 to 120 K, and mass flux ranging from 350 to 2000 kg/(m²·s). Based on the visualization results and energy balance analysis, a comprehensive CHF mechanism model capable of predicting DNB type boiling crisis, Dryout type boiling crisis, and PM (premature) type boiling crisis is proposed. Comparison of the presented CHF mechanism model with the CHF experimental values in one side heated narrow rectangular channels showed that the MRE and RMSE of DNB type boiling crisis are 15.2 % and 21.3 %, of Dryout type boiling crisis are 10.1 % and 12.7 %, and of PM type boiling crisis are 11.8 % and 13.8 %, respectively. The MRE and RMSE of CHF values in double sides heated narrow rectangular channel are about 13.6 % and 15.7 %, respectively, and of non-uniform heated narrow rectangular channel are about 15.9 % and 19.1 %, respectively.</p></div>","PeriodicalId":336,"journal":{"name":"International Journal of Heat and Mass Transfer","volume":"218 ","pages":"Article 124800"},"PeriodicalIF":5.2,"publicationDate":"2023-10-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S0017931023009456/pdfft?md5=c25221e6f46fa71d66e260d52e7d946d&pid=1-s2.0-S0017931023009456-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"92017430","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}