Experimental Thermal and Fluid Science最新文献

{"title":"A correction approach of external wall surface temperature measurements in sub-millimeter and high length-diameter ratios tubes","authors":"Zhenhua Wang ,&nbsp;Yu Feng ,&nbsp;Huihang Zhang ,&nbsp;Shuai Xu ,&nbsp;Jiang Qin","doi":"10.1016/j.expthermflusci.2025.111528","DOIUrl":"10.1016/j.expthermflusci.2025.111528","url":null,"abstract":"<div><div>The heat transfer characteristics of working medium in sub-millimeter and high length-diameter ratios tubes have broad application potential in various fields. However, accurately measuring the external wall surface temperature remains challenging due to several factors. In the non-axial end region, property variations of the working medium and non-uniform tube wall thickness complicate the measurement of external wall temperatures that reflect true heat transfer characteristics. In the axial end region, the external wall temperature is affected by the axial heat dissipation. This study introduces a correction approach for external wall temperature measurement. In the non-axial end region, multiple thermocouples are circumferentially welded to the tube surface. The heat transfer coefficients at these weld locations are averaged to represent the comprehensive heat transfer characteristics across the tube’s cross-section. By combining these measurements with fluid temperatures that better reflect the local flow state, correction values for the inner wall temperature are derived, enabling accurate determination of the external wall temperatures. In the axial end region, corrections are applied by compensating for heat transfer to the condenser. Experimental validation demonstrates the effectiveness of the proposed method. After circumferential temperature correction, the average relative error of external wall temperature measurements decreases from −10.1 % to 1.1 %. Similarly, axial temperature correction reduces the average relative error from 32.4 % to 13 %. These results confirm the accuracy and robustness of the correction approach, offering a reliable solution for heat transfer characterization in sub-millimeter and high length-diameter ratios tubes.</div></div>","PeriodicalId":12294,"journal":{"name":"Experimental Thermal and Fluid Science","volume":"169 ","pages":"Article 111528"},"PeriodicalIF":2.8,"publicationDate":"2025-05-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144139433","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}

{"title":"Flow structure around a fixed-supported flexible wing during flutter","authors":"Si Peng ,&nbsp;Md. Mahbub Alam ,&nbsp;Yu Zhou","doi":"10.1016/j.expthermflusci.2025.111525","DOIUrl":"10.1016/j.expthermflusci.2025.111525","url":null,"abstract":"<div><div>This work aims to investigate experimentally the flow structure around a flexible wing undergoing flutter. The nominal angle <em>α</em>₀ of attack examined is 0° − 10°, and the chord-based Reynolds number <em>Re_c</em> is 6.4 × 10⁴ − 1.9 × 10⁵, corresponding to the reduced velocity <em>U</em>_r of 23––70. Three types of flutter are identified, i.e. classical-like (0°−2°), light-stall-like (2°−6°) and deep-stall-like (6° − 8°) flutters, which exhibit features similar to classical, light- and deep-stall flutters associated with spring-supported rigid wings. However, appreciable differences are presently captured in both structural vibration and flow structure between the flexible and rigid wings, which are discussed in detail. Conceptual flow structure models are proposed to summarize the flow structures around the flexible wing undergoing the three types of flutters and their distinct characteristics compared to their counterparts of a rigid wing. Hysteresis phenomena, including dynamic overshoot and undershoot are observed during flutter, and the underlying flow physics is discussed in detail.</div></div>","PeriodicalId":12294,"journal":{"name":"Experimental Thermal and Fluid Science","volume":"168 ","pages":"Article 111525"},"PeriodicalIF":2.8,"publicationDate":"2025-05-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144134597","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}

{"title":"Sidewall-attached vortex hidden in a pump sump: evolution process and induced pressure oscillation","authors":"Bowen Zhang ,&nbsp;Lei Ma ,&nbsp;Li Cheng ,&nbsp;Baoshan Zhu ,&nbsp;Heng Zhao ,&nbsp;Yonglin Qin","doi":"10.1016/j.expthermflusci.2025.111524","DOIUrl":"10.1016/j.expthermflusci.2025.111524","url":null,"abstract":"<div><div>In scenarios with a low roof, there is a significant risk of generating rare and concealed sidewall-attached vortices (SAVs) within closed pump sumps. A high-speed visualization experiment was conducted using a transparent circulating hydraulic device with a closed pump sump to capture the spatiotemporal evolution of SAV. High-frequency dynamic pressure sensors were employed to record pressure fluctuations caused by SAVs under various flow conditions. The findings reveal that the evolution of SAVs exhibits three distinct behaviors and structures: right-drift, left-drift, and twin-vortex structure. The scale of the vortex core attached to the sidewall exhibits a characteristic of first expanding, then contracting, and then expanding again with the spatiotemporal evolution of SAV. The pressure drop characteristics due to SAVs exhibit significant differences in pressure fluctuation intensity, with a pressure coefficient amplitude of 3.62 × 10⁻⁵ when vortices are present. Both wavelet packet transform and continuous wavelet spectrum indicate that the induced frequency of SAV is low, with a characteristic frequency of 0.200 Hz. Furthermore, the intensity of pressure fluctuation induced by SAVs increases with higher flow rates. And once the flow rate exceeds 0.7 times the design flow rate, the characteristic low-frequency amplitude induced by SAV exceeds the rotating frequency amplitude and occupies an absolute dominant position.</div></div>","PeriodicalId":12294,"journal":{"name":"Experimental Thermal and Fluid Science","volume":"168 ","pages":"Article 111524"},"PeriodicalIF":2.8,"publicationDate":"2025-05-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144089767","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}

{"title":"Investigating direct-contact heat transfer of a spherical-cap liquid/vapour two-phase bubble evaporating in immiscible liquid: An experimental study","authors":"Ahmed R. Kareem ,&nbsp;Hameed B. Mahood ,&nbsp;Ali S. Baqir","doi":"10.1016/j.expthermflusci.2025.111522","DOIUrl":"10.1016/j.expthermflusci.2025.111522","url":null,"abstract":"<div><div>For the first time, this study presents the experimental investigation into the direct-contact heat transfer of a single spherical-cap liquid/vapour two-phase bubble evaporating in an immiscible liquid medium. The experiments were conducted using a rectangular Perspex column with dimensions of 600 mm × 100 mm × 100 mm. N-pentane droplets, with a diameter of 3.5 mm at saturation temperature (∼36 °C), served as the dispersed phase, while distilled water at three different initial temperatures, creating three temperature differences (ΔT), which is equivalent to Jacobs number (<em>Ja</em> = 18, 30 and 45), was used as the continuous phase. The experiments were performed at an active height in the continuous phase (<em>H</em>) of 500 mm. A high-speed camera operating at 250 frames per second was utilised to record the evaporation process of the droplets along the continuous phase active height. The captured images were analysed using FASTCAM (PFV-4) and AutoCAD (3D) software for precise data evaluation. The formation of the spherical-cap two-phase bubble was observed under various operating conditions. Based on the experimental output, the thickness of the yet-to-be vaporised liquid averaged over the area of the flat base of the two-phase spherical cap bubble (δ), the size of the evaporating spherical-cap two-phase bubble <span><math><mrow><mfenced><mrow><msub><mi>D</mi><mi>e</mi></msub><mo>/</mo><msub><mi>D</mi><mi>o</mi></msub></mrow></mfenced></mrow></math></span>, and the convective heat transfer coefficient, expressed in terms of the Nusselt number (<em>Nu</em>), were determined and analysed. As anticipated, the experimental results demonstrated that <em>Nu</em> increased with a rise in the Reynolds number (<em>Re</em>) and <span><math><mrow><mfenced><mrow><msub><mi>D</mi><mi>e</mi></msub><mo>/</mo><msub><mi>D</mi><mi>o</mi></msub></mrow></mfenced></mrow></math></span> with a significant inverse effect from the Jacobs number (<em>Ja</em>). Additionally, δ was found to decrease exponentially over time, and <em>Nu</em> increased as δ decreased. An empirical correlation for <em>Nu</em> as a function of Pecklet number (<em>Pe</em>) and <em>Ja</em> was developed and compared successfully with the experimental data with a maximum error of about 8 % at <em>Ja</em> = 30.</div></div>","PeriodicalId":12294,"journal":{"name":"Experimental Thermal and Fluid Science","volume":"168 ","pages":"Article 111522"},"PeriodicalIF":2.8,"publicationDate":"2025-05-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144084497","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}

{"title":"Influence of Turbulent gaseous jet configuration on entrainment – A Comparative Schlieren study","authors":"Ben Binyamin Ben David Holtzer,&nbsp;Leonid Tartakovsky","doi":"10.1016/j.expthermflusci.2025.111523","DOIUrl":"10.1016/j.expthermflusci.2025.111523","url":null,"abstract":"<div><div>The reported study is motivated by the recently published data on significant Particulate Matter (PM) formation in hydrogen-fed Internal Combustion Engines. These works showed that PM formation is dominated by the entrained lubricant involvement in the combustion which is governed by the hydrogen jet. However, there is a lack of the knowledge about the hollow-cone jet entrainment characteristics at different stages of the jet development and a comparison of the entrainment characteristics with the round jet. Schlieren optical imaging accompanied by the smoke-wire visualization of the ambient entrainment into the jet is suggested for the first time to study the entrainment characteristics of the hollow-cone jet. The following novel findings are attained in the reported study. We show that the hollow-cone jets exhibit different vapor front entrainment behavior, compared to the round jet. Moreover, the study found that the distance between the jet Turbulent Non-Turbulent Interface to the vapor layer is a major factor affecting the entrainment in the free jet region. Additionally, the geometry influence was found to be more important than the injection system properties like injection-pressure and mass flow rate.</div></div>","PeriodicalId":12294,"journal":{"name":"Experimental Thermal and Fluid Science","volume":"168 ","pages":"Article 111523"},"PeriodicalIF":2.8,"publicationDate":"2025-05-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144071485","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}

{"title":"Experimental investigation of flow characteristics in tailpipe of a pulsation reactor","authors":"Chunliang Zhang,&nbsp;Stefan Odenbach","doi":"10.1016/j.expthermflusci.2025.111509","DOIUrl":"10.1016/j.expthermflusci.2025.111509","url":null,"abstract":"<div><div>Flow characteristics within the tailpipe of a pulsation reactor are crucial for understanding and optimizing system performance, particularly in relation to heat transfer, acoustic interactions, and flow dynamics. This study examines the fluid flow velocity in the tailpipe of a laboratory-scale pulsation reactor using phase-locked PIV measurements. The results provide spatially and temporally resolved velocity profiles under different operating conditions, along with (phase-averaged) mean flow velocity measurements. The findings confirm a periodic velocity variation in the tailpipe that correlates with the pulsation cycle. The velocity field and oscillatory velocity amplitude in the core flow region are analyzed, revealing that the mean velocity and oscillatory amplitude vary significantly with the air–fuel equivalence ratio. Under stable pulsation conditions, an increase in the air–fuel equivalence ratio leads to a decrease in velocity amplitude, while the mean velocity increases. This indicates that optimizing operating conditions can influence not only the combustion process but also the flow characteristics. Additionally, CFD simulations are conducted to complement the PIV measurements by providing further insights into the velocity distribution and flow field dynamics.</div></div>","PeriodicalId":12294,"journal":{"name":"Experimental Thermal and Fluid Science","volume":"168 ","pages":"Article 111509"},"PeriodicalIF":2.8,"publicationDate":"2025-05-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144107107","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}

{"title":"Flame structure and flashback process in hydrogen partially premixed flame","authors":"Jaehong Choi ,&nbsp;Hyung chul Kim ,&nbsp;Jong guen Lee ,&nbsp;Youngbin Yoon","doi":"10.1016/j.expthermflusci.2025.111511","DOIUrl":"10.1016/j.expthermflusci.2025.111511","url":null,"abstract":"<div><div>This paper investigated the flame structure and flashback process of partially premixed hydrogen-air flames within a single-nozzle swirl combustor featuring a short mixing length and side-wall fuel injection. Experimental characterization utilized simultaneous OH* chemiluminescence imaging and Particle Image Velocimetry (PIV), complemented by non-reacting CFD simulations to analyze internal nozzle flow and fuel distribution. Three distinct stable flame structures (V, M, and N-M) were identified, with their appearance dependent on global equivalence ratio and airflow velocity. The V-flame (low equivalence ratio) showed the largest flame angle and a single flame surface on ORZ. The M − flame (intermediate equivalence ratio) showed a narrower angle with an inner flame surface and an associated upstream-shifted inner recirculation zone (IRZ). The N-M flame (high equivalence ratio or low u_a) exhibited the narrowest angle, disappearance of the IRZ, and flame anchoring within the nozzle, indicating flashback. Transitions between three flames were analyzed. The V to M transition was primarily driven by the fuel distribution change with increasing equivalence ratio. Conversely, the M to N-M (flashback) transition depended on the balance between flow velocity and flame speed, leading to the displacement and dissipation of the IRZ. These results demonstrate that the interplay between fuel distribution and velocity fields, governed by the side-wall injection configuration in this short mixing length combustor.</div></div>","PeriodicalId":12294,"journal":{"name":"Experimental Thermal and Fluid Science","volume":"168 ","pages":"Article 111511"},"PeriodicalIF":2.8,"publicationDate":"2025-05-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144068930","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}

{"title":"Electrodeposited porous surfaces with capillary effect for enhancing the heat transfer performance of Novec-7100 in spray cooling","authors":"Ho-Ching Lin ,&nbsp;Hui-Chung Cheng ,&nbsp;Yi-Xuan Huang ,&nbsp;Ping-Hei Chen","doi":"10.1016/j.expthermflusci.2025.111514","DOIUrl":"10.1016/j.expthermflusci.2025.111514","url":null,"abstract":"<div><div>This study investigated the spray cooling performance of Novec-7100 on electrodeposited copper surfaces. Test surfaces with microporous structures were fabricated using a two-step electrodeposition method. Different current densities (i.e., 0.3, 0.5, and 1.5 A/cm²) were applied to produce microporous structures with distinct surface properties. The results of this study indicated that the capillary effect of these microporous structures enhanced the heat transfer performance. In the single-phase heat transfer regime, the heat transfer coefficients of the electrodeposited surfaces, which had microporous structures, were higher than that of a plain copper surface. This is because the electrodeposited surfaces had a larger evaporation area, a longer triple-contact line, and stronger droplet impact convection. In the two-phase heat transfer regime, the microporous structures of the electrodeposited surfaces had more numerous sites available for surface and secondary nucleation. Furthermore, the electrodeposited surface that was produced under a current density of 1.5 A/cm² exhibited the best capillary performance; its heat transfer coefficient and critical heat flux were increased by 62% and 66% compared to the plain surface, respectively. Finally, the heat transfer data collected in the single- and two-phase regimes were correlated using modified prediction models incorporating a dimensionless capillary parameter. The errors in the predictions of the models derived for these regimes were within 11.5% and 28%, respectively.</div></div>","PeriodicalId":12294,"journal":{"name":"Experimental Thermal and Fluid Science","volume":"168 ","pages":"Article 111514"},"PeriodicalIF":2.8,"publicationDate":"2025-05-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143937322","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}

{"title":"Influences of single-phase/two-phase transpiration cooling on detonation initiation and propagation","authors":"Jianing Kang,&nbsp;Yuguang Jiang,&nbsp;Qi Wang,&nbsp;Jin Zhang,&nbsp;Yong Lin,&nbsp;Wei Fan","doi":"10.1016/j.expthermflusci.2025.111513","DOIUrl":"10.1016/j.expthermflusci.2025.111513","url":null,"abstract":"<div><div>Pulse Detonation Engine (PDE) requires highly efficient cooling technology, especially under high frequency and high Mach number. Transpiration cooling is a promising cooling method considering its high cooling capacity. In this work, the influences of single/two phase transpiration cooling on the Deflagration to Detonation Transition process (DDT) and the propagation of detonation wave are investigated experimentally. Regarding single phase transpiration cooling, the supply pressure and cooling Cooling phase of the cooling gas affect the local equivalence ratio, which affects the flame structure and velocity. When <em>P</em>_c (Supply pressure) = 0.4–1.0 MPa, the effect of supply pressure on flame velocity is not significant (The DDT section, <em>C</em>_s(Cooling phase) ≤ -10°; The detonation propagation section, <em>C</em>_s ≤ -5°). The two-phase transpiration cooling coolant changes the blocking ratio and affects the flame acceleration. The two-phase transpiration cooling has less interference on detonation propagation section. Local divergent flow passage is formed where the transpiration layer ends. The detonation propagation velocity reduces, but the minimum of which is still higher than 90 % CJ velocity. No decoupling or failure of detonation wave occurs.</div></div>","PeriodicalId":12294,"journal":{"name":"Experimental Thermal and Fluid Science","volume":"168 ","pages":"Article 111513"},"PeriodicalIF":2.8,"publicationDate":"2025-05-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143923310","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}

{"title":"Enhanced flow boiling heat transfer in embedded hybrid distributed jet/pin-fin microchannel heat sink","authors":"Jinya Liu,&nbsp;Huiying Wu,&nbsp;Xia Hua,&nbsp;Jiru Wei,&nbsp;Zhenyu Liu","doi":"10.1016/j.expthermflusci.2025.111508","DOIUrl":"10.1016/j.expthermflusci.2025.111508","url":null,"abstract":"<div><div>An embedded hybrid distributed jet/pin–fin microchannel (JPM) heat sink with flow boiling visualization is constructed in the silicon base to enhance the chip-level heat dissipation. The flow boiling heat transfer characteristics of deionized water in JPM heat sink with jet Reynolds numbers (<em>Re</em>_j) of 244 ∼ 732 and inlet subcoolings (Δ<em>T</em>_sub) of 20°C ∼ 60°C are experimentally investigated and compared with those in distributed jet/smooth microchannel (JSM) heat sink. Two-phase flow patterns in JPM and JSM are simultaneously captured by a high-speed microscope camera. It is found that compared with JSM, critical heat fluxes for JPM are significantly enhanced by 27.7 %∼70.8 % due to the effective prevention of reverse flow and local dry-out. Specifically, JPM achieves an extremely high critical heat flux of 1098 W/cm² at a small pressure drop of 4.2 kPa when <em>Re</em>_j = 732 and Δ<em>T</em>_sub = 40°C. Moreover, JPM can increase the heat transfer coefficient by 33.4 %∼51.6 % and decrease the effective thermal resistance by 22.8 %∼32.1 % due to more nucleation sites and larger heat transfer surfaces existing in JPM than in JSM. Meanwhile, better flow boiling stability and base temperature uniformity are obtained for JPM because its pin–fin structures can enhance the flow disturbance, promote the phase uniform distribution, and prevent the reverse flow. Particularly note that, although the enhancement in heat transfer is at the cost of the increase in pressure drop, JPM has superior comprehensive thermal–hydraulic performance than JSM, with <em>PEC</em>s for JPM compared to JSM being 1.18 ∼ 1.29 under different conditions. This study provides a more efficient embedded two-phase electronic cooling scheme by combining pin–fin microchannel with distributed jet impingement.</div></div>","PeriodicalId":12294,"journal":{"name":"Experimental Thermal and Fluid Science","volume":"168 ","pages":"Article 111508"},"PeriodicalIF":2.8,"publicationDate":"2025-05-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143918205","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}