Volume 8B: Heat Transfer and Thermal Engineering最新文献

{"title":"Effect of Inter-Connector on Thermo-Hydraulic Characteristics of Parallel and Counter Flow Mini-Channel Heat Sink","authors":"Amitav Tikadar, Saad K. Oudah, A. S. Salman, A. Morshed, T. C. Paul, J. Khan","doi":"10.1115/IMECE2018-88273","DOIUrl":"https://doi.org/10.1115/IMECE2018-88273","url":null,"abstract":"A numerical investigation of three-dimensional conjugate heat transfer was performed to quantify the thermal and hydraulic performance of an inter-connected parallel and counter flow mini-channel heat sink under laminar flow condition and within the single-phase regime. The aspect ratio (height/width) and the hydraulic diameter of the mini-channel were 0.33 and 750μm respectively. Three different widths of the inter-connector were selected to analyze the effect of cross flow for Reynolds number ranging from 150 to 1044, at a constant heat flux (20 W/cm2). To understand the fluid flow and heat transfer mechanism inside the inter-connector and their effects on overall thermal performance of the heat sink, Nusselt number (Nu), friction factor, pumping power, and overall thermal resistance were analyzed. Results show that the inter-connector has significantly higher effect on counter flow mini-channel heat sink than parallel flow mini-channel heat sink.","PeriodicalId":307820,"journal":{"name":"Volume 8B: Heat Transfer and Thermal Engineering","volume":"46 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-11-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"132931376","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Rotating Film Cooling Performance of the Hole Near the Leading Edge on the Suction Side of the Turbine Blade","authors":"Zhihong Zhou, Haiwang Li, Haichao Wang, Guoqin Zhao, Feng Han, Min Wu","doi":"10.1115/IMECE2018-86929","DOIUrl":"https://doi.org/10.1115/IMECE2018-86929","url":null,"abstract":"This paper reports the experimental and numerical studies on the effects of rotating speed and blowing ratio on the film cooling performance of the hole near the leading edge on the suction side of the turbine blade. The chord and height of the blade are 60mm and 80mm respectively. The film hole with diameter of 0.8mm is located in the mid span on the suction side at axial location of 8%. The injection angle of the hole is 45° to the suction surface of the blade and is nearly perpendicular to the axial direction. Both experimental and numerical studies were carried out with rotating speeds of 300rpm, 450rpm and 600rpm, and with blowing ratios of 0.5, 1.0, 1.5 and 2.0. CO2 was used as the coolant. Experimental data was measured by applying the Thermochromic Liquid Crystal (TLC) technique and the Stroboscopic Imaging Technique. Mainstream and coolant were heated to 308K and 318K respectively. Numerical studies were performed to assist the analysis of the experimental results. The SST turbulence model was applied in the simulations. Results show that the film cooling performance of the hole near the leading edge is different from that of the hole further downstream on the suction side. This is because the direction of the jet is nearly perpendicular to the axial direction, which increases the effect of the Coriolis force. Besides, the mainstream from leading edge also has effects on film cooling performance. With the increase of the blowing ratio, the film coverage area and spatially averaged film cooling effectiveness increase first and then decrease. The maximum film coverage and averaged film cooling effectiveness appear at blowing ratio of 1.0 and rotating speed of 300rpm. Moreover, the upward deflection angle of the film trajectory increases slightly with the increase of the blowing ratio. Higher rotating speed intensifies the deflection of the film trajectory. Therefore, the film coverage and the averaged film cooling effectiveness decrease rapidly.","PeriodicalId":307820,"journal":{"name":"Volume 8B: Heat Transfer and Thermal Engineering","volume":"70 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-11-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114831861","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Fundamental Study of Multiple Slopes Exhibited by Measured Thermal Contact Conductance (TCC) Versus Load Data for Metal-Metal Contacts","authors":"Navni N. Verma, S. Mazumder","doi":"10.1115/IMECE2018-86722","DOIUrl":"https://doi.org/10.1115/IMECE2018-86722","url":null,"abstract":"Experimental data of thermal contact conductance (TCC) between two metallic rough surfaces versus the applied load (pressure) distinctly exhibit non-linear behavior that can be split into two regimes with two distinct slopes. When the load is small, the rate of change of TCC with load is linear with a small slope. At intermediate loads, this slope increases. A third slope has been exhibited in some cases at extremely high loads — one in which the slope decreases again. In this study, two types of analysis are conducted on a simplified model system comprised of a single asperity compressed by two flat surfaces. The first analysis assumes one-dimensional heat conduction across the asperity, resulting in a fin-equation type model. In the second analysis, two-dimensional heat conduction through the asperity is considered, and the governing steady state heat conduction equation is solved numerically. Results show that the first two slopes at low and intermediate loads can be captured by both models. However, when the asperity is significantly depressed (high load regime) and deformed, the experimental behavior of the third reduced slope can only be captured by the two-dimensional numerical model. This implies that when the asperity deforms significantly, multi-dimensional heat transport becomes a critical limiting factor for the TCC.","PeriodicalId":307820,"journal":{"name":"Volume 8B: Heat Transfer and Thermal Engineering","volume":"210 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-11-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115758668","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Experimental Investigation of Heat Transfer Enhancement Through Array Jet Impingement on Various Configurations of High Porosity Thin Metal Foams","authors":"Srivatsan Madhavan, Prashant Singh, S. Ekkad","doi":"10.1115/IMECE2018-86432","DOIUrl":"https://doi.org/10.1115/IMECE2018-86432","url":null,"abstract":"High porosity metal foams are known for providing high heat transfer rates, as they provide significant increase in wetted surface area as well as highly tortuous flow paths to coolant flowing over fibers. Further, jet impingement is also known to offer high convective cooling, particularly on the footprints of the jets on the target to be cooled. Jet impingement, however, leads to large special gradients in heat transfer coefficient, leading to increased thermal stresses. In this study, we have tried to use high porosity thin metal foams subjected to array jet impingement, for a special crossflow scheme. One aim of using metal foams is to achieve cooling uniformity also, which is tough to achieve for impingement cooling. High porosity (92.65%) and high pore density (40 pores per inch, 3 mm thick) foams have been used as heat transfer enhancement agents. In order to reduce the pumping power requirements imposed by full metal foam design, we developed two striped metal foam configurations. For that, the jets were arranged in 3 × 6 array (x/d = 3.42, y/d = 2), such that the crossflow is dominantly sideways. This crossflow scheme allowed usage of thin stripes, where in one configuration we studied direct impingement onto stripes of metal foam and in the other, we studied impingement onto metal and crossflow interacted with metal foams. Steady state heat transfer experiments have been conducted for a jet plate configuration with varying jet-to-target plate distance z/d = 0.75, 2 and 4. The baseline case was jet impingement onto a smooth target surface. Jet diameter-based Reynolds number was varied between 3000 to 11000. Enhancement in heat transfer due to impingement onto thin metal foams has been evaluated against the enhancement in pumping power requirements. For a specific case of z/d = 0.75 with the base surface fully covered with metal foam, metal foams have enhanced heat transfer by 2.42 times for a concomitant pressure drop penalty of 1.67 times over the flow range tested.","PeriodicalId":307820,"journal":{"name":"Volume 8B: Heat Transfer and Thermal Engineering","volume":"33 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-11-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123616407","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Design and Evaluation of the Fresnel-Lens Based Solar Concentrator System Through a Statistical-Algorithmic Approach","authors":"H. Qandil, Weihuan Zhao","doi":"10.1115/IMECE2018-87023","DOIUrl":"https://doi.org/10.1115/IMECE2018-87023","url":null,"abstract":"A novel non-imaging Fresnel-lens-based solar concentrator-receiver system has been investigated to achieve high-efficiency photon and heat outputs with minimized effect of chromatic aberrations. Two types of non-imaging Fresnel lenses, a spot-flat lens and a dome-shaped lens, are designed through a statistical algorithm incorporated in MATLAB. The algorithm optimizes the lens design via a statistical ray-tracing methodology of the incident light, considering the chromatic aberration of solar spectrum, the lens-receiver spacing and aperture sizes, and the optimum number of prism grooves. An equal-groove-width of the Poly-methyl-methacrylate (PMMA) prisms is adopted in the model. The main target is to maximize ray intensity on the receiver’s aperture, and therefore, achieve the highest possible heat flux and output concentration temperature. The algorithm outputs prism and system geometries of the Fresnel-lens concentrator. The lenses coupled with solar receivers are simulated by COMSOL Multiphysics. It combines both optical and thermal analyses for the lens and receiver to study the optimum lens structure for high solar flux output. The optimized solar concentrator-receiver system can be applied to various devices which require high temperature inputs, such as concentrated photovoltaics (CPV), high-temperature stirling engine, etc.","PeriodicalId":307820,"journal":{"name":"Volume 8B: Heat Transfer and Thermal Engineering","volume":"32 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-11-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129640480","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Shape Optimization of Microchannels Using Surrogate Modelling","authors":"Muhammad Ansab Ali, T. Khan, Saqib Salam, E. A. Hajri","doi":"10.1115/IMECE2018-87780","DOIUrl":"https://doi.org/10.1115/IMECE2018-87780","url":null,"abstract":"To minimize the computational and optimization time, a numerical simulation of 3D microchannel heat sink was performed using surrogate model to achieve the optimum shape. Latin hypercube sampling method was used to explore the design space and to construct the model. The accuracy of the model was evaluated using statistical methods like coefficient of multiple determinations and root mean square error. Thermal resistance and pressure drop being conflicting objective functions were selected to optimize the geometric parameters of the microchannel. Multi objective shape optimization of design was conducted using genetic algorithm and the optimum design solutions are presented in the Pareto front. The application of the surrogate methods has predicted the performance of the heat sink with the sufficient accuracy employing significantly lower computational resources.","PeriodicalId":307820,"journal":{"name":"Volume 8B: Heat Transfer and Thermal Engineering","volume":"14 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-11-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114929891","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Strain Effect on Thermal Transport in Carbon Nanotube-Graphene Junctions","authors":"Jungkyu Park, P. Pena","doi":"10.1115/IMECE2018-87764","DOIUrl":"https://doi.org/10.1115/IMECE2018-87764","url":null,"abstract":"We employ molecular dynamics simulations to explore the effect of tensile strain on the thermal conductivity of carbon nanotube (CNT)-graphene junction structures. Two different types of CNT-graphene junctions are simulated; a perfect seamless junction between CNT and graphene with complete sp2 covalent bonds, and a CNT-graphene junction with mixed sp2/sp3 covalent bonds are studied. The most interesting phenomenon observed in the present research study is that the thermal conductivity of CNT-graphene junction structures increases with an increase in mechanical strain. For the case of CNT-graphene junction structure with pillar height of 50 nm and inter-pillar distance of 15 nm, the thermal conductivity is improved by 22.4% when 0.1 tensile strain is imposed. It is observed that the thermal conductivity improvement is enhanced when a larger graphene floor is placed between junctions since larger graphene floor allows larger deformation (larger tensile strain) in the junction. In addition, the thermal conductivity of CNT-graphene junction structures with pure sp2 bonds is observed to be higher than the thermal conductivity of CNT-graphene junction structures with mixed sp2/sp3 bonds regardless of the amount of tensile strain. The obtained results will contribute to the development of flexible electronics by providing a theoretical background on the thermal transport of three dimensional carbon nanostructures under deformation.","PeriodicalId":307820,"journal":{"name":"Volume 8B: Heat Transfer and Thermal Engineering","volume":"6 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-11-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126991291","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Adiabatic Analysis of Rotary Displacer Stirling Engine","authors":"A. Bagheri, William C. Mullins, Phillip R. Foster, H. Bostanci","doi":"10.1115/IMECE2018-87758","DOIUrl":"https://doi.org/10.1115/IMECE2018-87758","url":null,"abstract":"Utilizing analytical models at the initial stages of Stirling engine (SE) development is a common approach since the cost could be excessive when experimental (i.e., building prototypes) or even numerical (i.e., using Computational Fluid Dynamics (CFD)) approaches are taken first. One of the well-known analyses in this area is the adiabatic analysis that assumes working fluid to be an ideal gas, and adiabatic expansion and compression processes in the power cylinder. Although adiabatic analysis neglects pressure loss in the cycle, it still predicts operating envelope and performance with a better accuracy compared to isothermal (Schmidt) analysis. This study considers the adiabatic analysis that was originally developed for conventional, reciprocating displacer SE configuration, and aims to adapt it for an innovative, rotary displacer SE configuration. The analysis enables to present pressure-volume diagrams, and estimates the amount of generated work and the efficiency. The results, when compared to that of the ideal Schmidt analysis, indicate up to 4.6% lower values of the generated work, suggesting a significant difference between the two ideal assumptions.","PeriodicalId":307820,"journal":{"name":"Volume 8B: Heat Transfer and Thermal Engineering","volume":"28 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-11-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"127347222","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Heat Transfer Modeling of Nanoparticle Packings on a Substrate","authors":"A. Yuksel, E. Yu, M. Cullinan, J. Murthy","doi":"10.1115/IMECE2018-88642","DOIUrl":"https://doi.org/10.1115/IMECE2018-88642","url":null,"abstract":"The temperature evolution of nanoparticle packings on a substrate under high laser power is investigated both experimentally and via numerical simulations. Numerical modeling of temperature distributions in copper nanoparticle packings on a glass substrate is performed and results are compared with experiment under 2.6 kW/cm2 laser power. A coupled electromagnetic-heat transfer model is implemented to understand the nanoparticle temperature distribution. Very good agreement between the coupled electromagnetic-heat transfer model and the experimental results is obtained by matching the interfacial thermal conductance, G, between the nanoparticles using the experimental result in the coupled electromagnetic-heat transfer model.","PeriodicalId":307820,"journal":{"name":"Volume 8B: Heat Transfer and Thermal Engineering","volume":"25 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-11-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"121656140","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Experimental Study of Convective Heat Transfer in Standard and Cross-Drilled Brake Discs With Radial Vane and X-Lattice Cores","authors":"Hongbin Yan, Shangsheng Feng, Wei‐Tao Wu, T. Lu, G. Xie","doi":"10.1115/IMECE2018-86195","DOIUrl":"https://doi.org/10.1115/IMECE2018-86195","url":null,"abstract":"To improve the cooling performance of disc brake systems, cross-drilled holes penetrating across the rubbing discs are separately introduced into a commercial radial vane brake disc (as reference) and a novel X-lattice cored brake disc. Prototype samples of both the reference and cross-drilled brake discs are fabricated. A rotating test rig is designed and constructed to characterize and compare the cooling performance of the brake discs with infrared thermography. Within the typical operating range of a vehicle, e.g., 200–1000 rpm, the experimental results show that the introduction of cross-drilled holes can substantially enhance brake disc cooling. For the radial vane brake disc, the overall Nusselt number is enhanced by 31%–44%; for the X-lattice cored brake disc, the cross-drilled holes only lead to 9%–18% enhancement. As the radial vane brake disc and the X-lattice cored brake disc with cross-drilled holes exhibit similar cooling performance, flow through the cross-drilled holes has a more prominent effect on the former than the latter. Corresponding fluid flow and heat transfer mechanisms underlying the enhanced heat transfer by cross-drilled holes and the different effects of cross-drilled holes on the two distinct brake discs are explored. The experimental comparison and the thermo-fluidic physics presented in this paper are beneficial for engineers to further improve disc brake cooling.","PeriodicalId":307820,"journal":{"name":"Volume 8B: Heat Transfer and Thermal Engineering","volume":"41 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-11-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"124975767","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}