International Journal of Heat and Fluid Flow最新文献

{"title":"Solar air heaters vertically integrated in building structures: An experimental investigation","authors":"Abdelhamid Moumeni ,&nbsp;Bachir Bouchekima ,&nbsp;Ahmet Yüksel ,&nbsp;Abdessamia Hadjadj ,&nbsp;Müslüm Arici","doi":"10.1016/j.ijheatfluidflow.2025.109904","DOIUrl":"10.1016/j.ijheatfluidflow.2025.109904","url":null,"abstract":"<div><div>This study investigates the energy and exergy performance of a solar air heating system designed with a novel vertical configuration incorporating rows of 50 internal obstacles, developed to enhance thermal efficiency in building applications. Experimental tests were performed under real outdoor conditions to evaluate both thermal and exergetic behavior. The results showed that solar radiation and ambient temperature followed typical diurnal trends, with peak solar irradiance reaching approximately 740 W/m² and ambient temperatures rising to 30 °C during midday. The maximum thermal efficiency of the system with obstacles was recorded at 82 %, which is notably higher than values reported in previous studies, such as 72 % and 73.31 % for systems enhanced with nano-coated absorbers. Furthermore, the system with internal obstacles maintained a significantly higher useful heat gain compared to the configuration without obstacles, especially during late afternoon hours when solar radiation declined, demonstrating improved thermal inertia and sustained performance. The exergetic efficiency values ranged between 0.01 and 0.22, aligning with trends observed in earlier literature, and reflecting the inherent limitations of low-temperature solar systems in converting available energy into work. Integration of the enhanced solar air heater into a prototype test room resulted in a more stable and uniform indoor temperature distribution, with a temperature difference of approximately 6 °C compared to the baseline system. These findings suggest that the proposed configuration not only improves energy capture and retention but also contributes to passive thermal comfort in buildings, thereby addressing a key gap in the development of sustainable, energy-efficient heating technologies.</div></div>","PeriodicalId":335,"journal":{"name":"International Journal of Heat and Fluid Flow","volume":"116 ","pages":"Article 109904"},"PeriodicalIF":2.6,"publicationDate":"2025-05-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144178448","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"A novel integrated system of photovoltaic panel and water still with photovoltaic cooling and heat storage functions","authors":"Yuan Jiang,&nbsp;Guilian Liu,&nbsp;Xiaohong Yan","doi":"10.1016/j.ijheatfluidflow.2025.109910","DOIUrl":"10.1016/j.ijheatfluidflow.2025.109910","url":null,"abstract":"<div><div>Integrating a water still directly behind the photovoltaic (PV) panel can effectively utilize the waste heat generated by the PV panel to produce fresh water without requiring additional land area. However, the direct installation of a water still behind the PV panel may hinder its heat dissipation, leading to an increase in PV temperature and a reduction in photoelectric conversion efficiency. A novel PV-water still system with a cooling channel and a heat storage tank is proposed, which can achieve the cooling of PV panel and heat storage simultaneously. The coupling mechanisms between the photovoltaic conversion, heat storage and water distillation processes in the novel system are unclear and need to be investigated. This study investigates the transient performance characteristics of the proposed system under different heat storage parameters and environmental conditions, and reveals the influence mechanisms of the heat storage on the photovoltaic conversion and water distillation processes. Results indicate that the heat storage tank mitigates fluctuations in PV temperature and reduces the peak PV temperature by more than 20 K, which increases the daily solar-electricity efficiency of the system by approximately 10 %. Although the daily water yield of the system is diminished by the heat storage tank due to the decreased evaporation temperature, but the stored heat may enhance the water distillation at cold and cloudy days under real conditions. Improving the heat dissipation of the outer surface of water still proves beneficial for both enhancing water distillation rates and cooling efficiencies of PV panels. Compared with air cooling, exposing the outer surface of water still to large water body can increase the daily solar-electricity conversion efficiency by 2.5 % while simultaneously increase the daily water yield by 130 %.</div></div>","PeriodicalId":335,"journal":{"name":"International Journal of Heat and Fluid Flow","volume":"116 ","pages":"Article 109910"},"PeriodicalIF":2.6,"publicationDate":"2025-05-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144178449","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Dynamic characteristics analysis of supercritical CO2 power cycle under system volume effects","authors":"Tianyang Qin ,&nbsp;Yuwei Sun ,&nbsp;Xinping Yan ,&nbsp;Chengqing Yuan","doi":"10.1016/j.ijheatfluidflow.2025.109905","DOIUrl":"10.1016/j.ijheatfluidflow.2025.109905","url":null,"abstract":"<div><div>Developing an accurate system-level transient model for the recompression supercritical CO₂ power cycle is essential for understanding its dynamic behavior and enhancing operational efficiency. While prior research has extensively addressed the modeling of heat exchangers and turbomachinery, the dynamic impact of system cavities, such as heat exchanger casings and interconnecting pipes, has been largely neglected. This study introduces a comprehensive dynamic system-level model developed in Modelica language, which uniquely incorporating lumped parameter cavity modules to evaluate the impact of cavity volume and location on system performance. By systematically varying the volumes and positions of eight representative cavities, the analysis reveals that the five cavities from the turbine outlet to the main compressor inlet consistently enhance thermal efficiency, while the remaining three cavities from the recompressor outlet to the turbine inlet reduce thermal efficiency but shorten stabilization times. Specifically, the cavity between the low-temperature recuperator and the cooler increases thermal efficiency by 0.23 % at 40 % load, while the cavity between the low- and high-temperature recuperators shortens recovery time by 10 s. These results highlight the previously underappreciated role of cavity dynamics in closed-loop, single-phase systems like the supercritical CO₂ cycle. This work provides new insights into the transient characteristics of such systems and offers a foundation for improving system design, control strategies, and the reliability of supercritical CO₂ power technologies.</div></div>","PeriodicalId":335,"journal":{"name":"International Journal of Heat and Fluid Flow","volume":"116 ","pages":"Article 109905"},"PeriodicalIF":2.6,"publicationDate":"2025-05-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144169061","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Effects of n-decane pyrolysis on supercritical jet impingement heat transfer employed in thermal management of scramjet engines","authors":"Qirun Zhou ,&nbsp;Yong Li ,&nbsp;Jun Xia ,&nbsp;Yingchun Zhang ,&nbsp;Bolun Zhang ,&nbsp;Jiajie Zhang ,&nbsp;Suxia Ma","doi":"10.1016/j.ijheatfluidflow.2025.109902","DOIUrl":"10.1016/j.ijheatfluidflow.2025.109902","url":null,"abstract":"<div><div>Traditional regenerative cooling methods can no longer meet the advancing demands of scramjets, prompting current research to explore novel cooling strategies. Jet impingement cooling, known for its high heat transfer performance, has shown promise in applications involving high heat flux densities. Therefore, jet impingement cooling holds considerable potential for cooling applications in scramjets. This study investigates the flow and heat transfer characteristics of jet impingement cooling under supercritical conditions, using n-decane as the working medium while considering the impact of thermal pyrolysis on flow and heat transfer. Through numerical simulations, this research examines the effects of different flow conditions and pyrolysis reactions on jet impingement cooling. The results indicate that jet impingement under thermal pyrolysis reduces the maximum temperature of the heating surface by approximately 8.2% and decreases the fluid temperature within the channel by about 22.1%. Additionally, the study reveals that the presence of an initial crossflow, under the same total flow rate, enhances the utilization of chemical heat sink effects generated by thermal pyrolysis. In short, this paper provides a reference for the study of jet impingement cooling with thermal pyrolysis used in scramjet thermal management.</div></div>","PeriodicalId":335,"journal":{"name":"International Journal of Heat and Fluid Flow","volume":"116 ","pages":"Article 109902"},"PeriodicalIF":2.6,"publicationDate":"2025-05-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144169062","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"A detailed numerical analysis of the flow field characteristics of vortex acoustic streaming around a cylindrical tube","authors":"Yanfeng Yang ,&nbsp;Fugui Shi ,&nbsp;Chaofan Xiao","doi":"10.1016/j.ijheatfluidflow.2025.109906","DOIUrl":"10.1016/j.ijheatfluidflow.2025.109906","url":null,"abstract":"<div><div>In this study, a detailed numerical analysis was conducted to investigate the vortex acoustic streaming around a cylindrical tube using the Reynolds stress method. The evolution of acoustic streaming structures across a wide range of parameters was investigated, and the general relationships between acoustic streaming intensity and acoustic parameters were summarized. It was discovered that low-frequency and intense sound waves (20 Hz, 149.33 dB) can generate distorted acoustic streaming with an axisymmetric distribution surrounding the cylindrical tube. This acoustic streaming internally evolves into a flow field characterized by jet-like vortices, with near-wall velocities reaching as high as 710 mm/s. On the contrary, high-frequency (5 kHz) acoustic streaming no longer has the characteristic of axisymmetric distribution. The inhomogeneity of the sound field leads to changes in the vortex scale, with near-wall velocities reaching only 1 mm/s. The acoustic streaming vortex outside the cylindrical tube gradually presents different flow field structure changes as sound pressure level and frequency increase. Moreover, the streaming intensity under different acoustic parameters is analyzed using a dimensionless approach. It is found that a specific function relationship between dimensionless acoustic streaming intensity and Strouhal number exists, and the empirical formula is given.</div></div>","PeriodicalId":335,"journal":{"name":"International Journal of Heat and Fluid Flow","volume":"116 ","pages":"Article 109906"},"PeriodicalIF":2.6,"publicationDate":"2025-05-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144146852","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Study on thermo-fluid-chemical coupling simulation and characteristic fields evolution during in-situ pyrolysis of tar-rich coal","authors":"Meijing Chen,&nbsp;Yongbo Du,&nbsp;Chang’an Wang,&nbsp;Yujie Hou,&nbsp;Tianlin Yuan,&nbsp;Liujun Chang,&nbsp;Lei Deng,&nbsp;Defu Che","doi":"10.1016/j.ijheatfluidflow.2025.109903","DOIUrl":"10.1016/j.ijheatfluidflow.2025.109903","url":null,"abstract":"<div><div>Underground in-situ pyrolysis of tar-rich coal is an effective approach to expand the supply channels of oil and gas while ensuring energy security, and it has currently aroused wide attention in the academic community. The coupling of multiple interdependent physical fields causes the in-situ pyrolysis process and related phenomena. However, existing studies usually only have focused on a single process. The study proposed a three-dimensional (3D) model for the in-situ pyrolysis of tar-rich coal employing external high-temperature fluids. Numerical simulation was used to achieve the transient calculation of the coupling model of chemical reaction, fluid flow, and heat transfer. The impacts of medium type, medium temperature, inlet rate, well patterns, and the number of horizontal fractures were investigated by characterizing the temperature and concentration fields. The results indicate that, under the basic working condition, the pyrolysis reaction of tar-rich coal in the formation has been completed after ∼28.5 months of heat injection. Both N₂ and CO₂ are heat carriers with greater advantages in heat transfer as compared to H₂O (g). The threshold of injection rate is 5 m·s⁻¹. The heat transfer effect of coal seams with 4 injection wells is obviously better than that of 1 and 2 injection wells. The number of 3 horizontal fractures is superior to 1 and 2 fractures, which can effectively enhance heat transfer and promote the thermal decomposition. The present study has emphatically investigated the evolution of characteristic fields of tar-rich coal seams under thermo-fluid-chemical coupling conditions during the in-situ pyrolysis process, providing substantial reference significance to guide the in-situ conversion mining.</div></div>","PeriodicalId":335,"journal":{"name":"International Journal of Heat and Fluid Flow","volume":"116 ","pages":"Article 109903"},"PeriodicalIF":2.6,"publicationDate":"2025-05-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144169060","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Restricted nonlinear simulations of flow over riblets: Characterizing drag reduction and its breakdown","authors":"Xiaowei Zhu ,&nbsp;Bianca Viggiano ,&nbsp;Benjamin A. Minnick ,&nbsp;Dennice F. Gayme","doi":"10.1016/j.ijheatfluidflow.2025.109862","DOIUrl":"10.1016/j.ijheatfluidflow.2025.109862","url":null,"abstract":"<div><div>The restricted nonlinear (RNL) model is employed as low-order representation of turbulent flow over riblets at <span><math><mrow><mi>R</mi><msub><mrow><mi>e</mi></mrow><mrow><mi>τ</mi></mrow></msub><mo>≈</mo><mn>395</mn></mrow></math></span>. Comparisons with direct numerical simulations (DNS) verify the ability of the model to accurately capture low-order statistics, as well as trends in drag-alteration and secondary motion as a function of riblet geometry and spacing. We demonstrate the ability of the RNL model to reproduce additional flow features by decomposing the roughness function to isolate contributions from the total stress and comparing its predictions to DNS data. An analysis of the spectra of Reynolds shear stress shows that the RNL model captures Kelvin-Helmholtz-like rollers linked to riblet drag reduction breakdown but slightly over predicts the total stresses. The reproduction of the overall trends in stresses and flow features linked to the breakdown of riblet induced drag-reduction suggests that the nonlinearity and scale interactions retained in the RNL system are adequate to capture the key mechanisms underlying turbulent flow over a range of riblet geometries. These results also indicate that examining the limitations of the model may provide insight into the critical nonlinear interactions underlying drag alteration due to riblets.</div></div>","PeriodicalId":335,"journal":{"name":"International Journal of Heat and Fluid Flow","volume":"116 ","pages":"Article 109862"},"PeriodicalIF":2.6,"publicationDate":"2025-05-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144138672","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Sparsity-promoting methods for isolating dominant linear amplification mechanisms in wall-bounded flows","authors":"Scott T.M. Dawson,&nbsp;Jaime Prado Zayas,&nbsp;Barbara Lopez-Doriga","doi":"10.1016/j.ijheatfluidflow.2025.109872","DOIUrl":"10.1016/j.ijheatfluidflow.2025.109872","url":null,"abstract":"<div><div>This work proposes a method to identify and isolate the physical mechanisms that are responsible for linear energy amplification in fluid flows. This is achieved by applying a sparsity-promoting methodology to the resolvent form of the governing equations, solving an optimization problem that balances retaining the amplification properties of the original operator with minimizing the number of terms retained in the simplified sparse model. This results in simplified operators that often have very similar pseudospectral properties as the original equations. The method is demonstrated on both incompressible and compressible wall-bounded parallel shear flows, where the results obtained from the proposed method appear to be consistent with known mechanisms and simplifying assumptions, such as the lift-up mechanism, and (for the compressible case) Morkovin’s hypothesis and the strong Reynolds analogy. This provides a framework for the application of this method to problems for which knowledge of pertinent amplification mechanisms is less established.</div></div>","PeriodicalId":335,"journal":{"name":"International Journal of Heat and Fluid Flow","volume":"115 ","pages":"Article 109872"},"PeriodicalIF":2.6,"publicationDate":"2025-05-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144135147","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Heat transfer performance of inlet/outlet manifold configurations and bottom wall cavities composite in microchannel heat sinks","authors":"Qianjun Mao ,&nbsp;Yue Gu","doi":"10.1016/j.ijheatfluidflow.2025.109894","DOIUrl":"10.1016/j.ijheatfluidflow.2025.109894","url":null,"abstract":"<div><div>High temperature and thermal non-uniformity distribution of electronic devices limited their application and safety. Therefore, three inlet/outlet manifold configurations were proposed: C, I, and Z-type. Additionally, six types of bottom wall cavity structures for manifold microchannel heat sinks were proposed, namely straight bottom wall, square-wavy bottom wall, wavy bottom wall, zigzag bottom wall, right-angled triangle bottom wall in type one, and right-angled triangle bottom wall in type two. The results indicate that the I-type inlet/outlet manifold configuration offers the most uniform flow distribution. Among the six manifold microchannel heat sinks (I-type), the square-wavy bottom wall (I-type) demonstrates the best thermal performance, bottom wall temperature uniformity, and comprehensive temperature uniformity. Additionally, eleven square-wavy bottom wall (I-type) designs were developed for optimization studies in heat transfer. Regarding thermal performance, bottom wall temperature uniformity, and comprehensive temperature uniformity, the optimal square-wavy bottom wall (I-type) exhibits an overall thermal resistance of 0.721, a temperature uniformity factor of 0.424, and a comprehensive temperature uniformity factor of 0.636. Compared to the straight bottom wall (I-type), the optimal square-wavy bottom wall (I-type) reduces the overall thermal resistance, temperature uniformity factor, and comprehensive temperature uniformity factor by 30.3 %, 37.0 %, and 36.4 %, respectively. In addition, the optimal square-wavy bottom wall (I-type) reduces the temperature uniformity factor by 35.1 % at high power (285 W/cm²). This research offers a valuable guideline for designing manifold microchannel heat sinks in high-power electronic devices.</div></div>","PeriodicalId":335,"journal":{"name":"International Journal of Heat and Fluid Flow","volume":"115 ","pages":"Article 109894"},"PeriodicalIF":2.6,"publicationDate":"2025-05-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144123748","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Partial sheltering effects on spanwise wake interference of unequal-height tandem finite wall-mounted cylinders","authors":"Ashim Chhetri,&nbsp;Keziah N.D. Hammond,&nbsp;Ebenezer E. Essel","doi":"10.1016/j.ijheatfluidflow.2025.109892","DOIUrl":"10.1016/j.ijheatfluidflow.2025.109892","url":null,"abstract":"<div><div>The effects of partial sheltering on the unsteady flow dynamics of unequal-height tandem finite wall-mounted cylinders fully submerged in a turbulent boundary layer (TBL) were investigated using time-resolved particle image velocimetry. The height ratio of the cylinders was kept constant at <span><math><mrow><mi>h</mi><mo>/</mo><mi>H</mi><mo>=</mo><mn>0.75</mn></mrow></math></span>, where <span><math><mi>h</mi></math></span> and <span><math><mi>H</mi></math></span> are the heights of the upstream cylinder (UC) and downstream cylinder (DC), respectively. The center-to-center spacing between the cylinders was <span><math><mrow><mn>4</mn><mi>d</mi></mrow></math></span>, the Reynolds number based on the cylinder diameter (<span><math><mi>d</mi></math></span>) was <span><math><mrow><mn>5540</mn></mrow></math></span> and the submergence ratio was <span><math><mrow><mi>δ</mi><mo>/</mo><mi>H</mi><mo>=</mo><mn>1.2</mn></mrow></math></span>, where <span><math><mi>δ</mi></math></span> is the TBL thickness. Measurements were also performed for a single cylinder (SC) with a similar aspect ratio (<span><math><mrow><mi>H</mi><mo>/</mo><mi>d</mi><mo>=</mo><mn>7</mn></mrow></math></span>) as the DC. Spatio-temporal characteristics in three streamwise-spanwise planes along the height of the tandem cylinders (TC) and the SC were examined to understand the impact of partial sheltering on the mean wake structure, pumping motion of the reverse flow region, spanwise shear layer growth, and cellular vortex shedding behavior. The results showed that wake interference by the DC enhanced the near-wall pumping motion and integral time scales, while reducing the vortex shedding frequency behind the UC compared to the SC. For the DC, the attachment of the spanwise shear layers from the UC significantly accelerated vortex formation of smaller structures and delayed vortex formation at the unsheltered free end. As a result, the reverse flow region was reduced in the sheltered portion but enhanced near the free end of the DC.</div></div>","PeriodicalId":335,"journal":{"name":"International Journal of Heat and Fluid Flow","volume":"115 ","pages":"Article 109892"},"PeriodicalIF":2.6,"publicationDate":"2025-05-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144115350","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}