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

{"title":"Non-Gray Radiation Exchange: The Internal Fractional Function Reconsidered","authors":"J. Lienhard","doi":"10.1115/IMECE2018-86386","DOIUrl":"https://doi.org/10.1115/IMECE2018-86386","url":null,"abstract":"The radiation fractional function is the fraction of black body radiation below a given value of λT. Edwards and others have distinguished between the traditional, or “external”, radiation fractional function and an “internal” radiation fractional function. The latter is used for simplified calculation of net radiation from a non-gray surface when the temperature of an effectively black source is not far from the surface’s temperature, without calculating a separate total absorptivity. This paper examines the analytical approximation involved in the internal fractional function, with results given in terms of the incomplete zeta function. A rigorous upper bound on the difference between the external and internal emissivity is obtained. Calculations using the internal emissivity are compared to exact calculations for several models and materials. A new approach to calculating the internal emissivity is developed, yielding vastly improved accuracy over a wide range of temperature differences. The internal fractional function can be useful for certain simplified calculations.","PeriodicalId":307820,"journal":{"name":"Volume 8B: Heat Transfer and Thermal Engineering","volume":"42 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":"131388999","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":"An Experimental Setup for Multiple Air Jet Impingement Over a Surface","authors":"F. Barbosa, J. Silva, P. Ribeiro, S. Teixeira, D. Soares, Duarte Santos, M. Cerqueira, J. Teixeira","doi":"10.1115/IMECE2018-87995","DOIUrl":"https://doi.org/10.1115/IMECE2018-87995","url":null,"abstract":"Air jet impingement technology receives considerable attention due to its high performance for heat transfer enhancement in thermal equipment, providing high heat transfer rates. Due to its inherent characteristics of high average heat transfer coefficients and uniformity of the heat transfer over the impinging surface, this technology is implemented in a variety of engineering applications and industrial processes, such as reflow soldering, drying of textile, cooling of turbojet engine blades and fusion reactors. Multiple jet impingement involves several variables such as: jets arrangement, jet diameter, nozzle-to-surface distance, nozzle shape, jet-to-jet spacing, jet velocity and Reynolds number, among others. However, the total control of all these parameters is still one of the remarkable issues of the thermal design of jet impingement systems. In some industries that have implemented this technology in their processes, such as reflow soldering, the range of values of these variables are established through empiricism and “trial and error” techniques. To improve the process and to reduce time and costs, it is fundamental to define accurately all the process parameters in order to obtain an optimized design with a high degree of control of the heat transfer over the target surface. To perform an accurate and complete study of the multiple jet impingement variables for a specific application, the development of both experimental and numerical studies is fundamental in order to obtain reliable results. In that sense, this work reports the project and construction of a purpose-built test facility which has been commissioned, using a PIV system. This experimental setup is based on the oven used in the reflow soldering process. The optimization of the multiple jets geometry which is integrated in the experimental setup is herein described and discussed both experimentally and numerically. The numerical simulation of the jet impingement inside the oven was conducted using the ANSYS software, specially designed to predict the fluid behavior. Regarding the relevance of the multiple jet impingement, this work intends to improve the knowledge in this field and to give reliable and scientifically proved answers to the industries that apply this technology in their processes.","PeriodicalId":307820,"journal":{"name":"Volume 8B: Heat Transfer and Thermal Engineering","volume":"9 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":"123268307","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":"Microstructural and Thermal Characterization of Diamond Nanofluids","authors":"F. Mashali, Ethan Languri, G. Mirshekari, J. Davidson, D. Kerns","doi":"10.1115/IMECE2018-87496","DOIUrl":"https://doi.org/10.1115/IMECE2018-87496","url":null,"abstract":"Conventional heat transfer fluids such as water, ethylene glycol, and mineral oil, that are used widely in industry suffer from low thermal conductivity. On the other hand, diamond has shown exceptional thermal properties with a thermal conductivity higher than five times of copper and about zero electrical conductivity. To investigate the effectiveness of nanodiamond particles in traditional heat transfer fluids, we study deaggregated ultra-dispersed diamonds (UDD) using X-ray diffraction analysis (XRD) and transmission electron microscopy (TEM). Furthermore, nanodiamond nanofluids were prepared at different concentrations in deionized (DI) water as the base fluid. Particle size distribution was investigated using TEM and the average particle size have been reported around 6 nm. The thermal conductivity of nanofluids was measured at different concentrations and temperatures. The results indicate up to 15% enhancement in thermal conductivity compared with the base fluid and thermal conductivity increases with temperature and particle loading. The viscosity raise in the samples have been negligible.","PeriodicalId":307820,"journal":{"name":"Volume 8B: Heat Transfer and Thermal Engineering","volume":"45 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":"127710919","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":"Future Scenarios for Emissions From Energy and Power Production in the Rocky Mountain Region","authors":"R. Nsanzineza, J. Milford","doi":"10.1115/IMECE2018-87614","DOIUrl":"https://doi.org/10.1115/IMECE2018-87614","url":null,"abstract":"Across the U.S., electricity production from coal-fired generation is declining while use of renewables and natural gas is increasing. This trend is expected to continue in the future. In the Rocky Mountain region, this shift is expected to reduce emissions from electricity production while increasing emissions from the production and processing of oil and gas, with significant implications for the level, location, and timing of the air pollution emissions that are associated with these activities. In turn, these emissions changes will affect air quality in the region, with impacts on ground-level ozone of particular concern. This study aims to evaluate the tradeoffs in emissions from both power plants and oil and gas basins resulting from contrasting scenarios for shifts in electricity and oil and gas production through the year 2030. The study also incorporates federal and state-level regulations for CH4, NOx, and VOC emissions sources. These regulations are expected to produce significant emissions reductions relative to baseline projections, especially in the oil and gas production sector. Annual emissions from electricity production are estimated to decrease in all scenarios, due to a combination of using more natural gas power plants, renewables, emissions regulations, and retiring old inefficient coal power plants. However, reductions are larger in fall, winter, and spring than in summer, when ozone pollution is of greatest concern. Emissions from oil and gas production are estimated to either increase or decrease depending on the location, scenario, and the number of sources affected by regulations. The net change in emissions thus depends on pollutant, location, and time of year.","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":"116310067","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":"High Porosity and High Pore Density Thin Copper Foams for Compact Electronics Cooling","authors":"S. Panse, Prashant Singh, S. Ekkad","doi":"10.1115/IMECE2018-86355","DOIUrl":"https://doi.org/10.1115/IMECE2018-86355","url":null,"abstract":"Porous media like open celled metal foams inherently provide a high heat transfer area per unit volume due to their interconnected cellular structure and are lightweight. High pore density metal foam because of its small overall dimensions and micro feature size shows promise in thermal packaging of compact electronics. An experimental study was carried out to evaluate thermal performance of high porosity (95%) and high pore density (90 PPI) copper foam of size 20 mm × 20 mm × 3 mm in buoyancy induced flow conditions and compared with a baseline smooth surface. The enhanced surface showed about 15% enhancement in average heat transfer coefficient over the baseline case. To optimize the performance further, the foam sample was cut into strips of 20 mm × 5 mm × 3 mm and attached symmetrically on the central 20 mm2 base surface area with inter-spacing of 2.5 mm. This new configuration led to further 15% enhancement in heat transfer even with 25% lesser heat transfer area. This is significant as heat transfer is seen as a strong function of permeability to flow through the structure over heat conduction through it. To test this hypothesis, a third configuration was tested in which the strips were further cut into blocks of 4 mm × 4 mm × 3 mm and attached in a 3 × 3 array on to the base surface. Here, only 36% of the central 20 mm2 base surface area was covered with foam. The heat transfer performance was found to be within ± 10% of the initial metal foam configuration, thereby, supporting the hypothesis. Performance was seen to decrease with increase in inclination from 0° to 30° to 90° with respect to the vertical.","PeriodicalId":307820,"journal":{"name":"Volume 8B: Heat Transfer and Thermal Engineering","volume":"139 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":"131473532","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 Dissipator With Aztec Inspired Radial Geometry","authors":"A. Perez-Hernandez, L. Luviano-Ortiz, A. Hernandez-Guerrero, Israel Botello-Arredondo","doi":"10.1115/IMECE2018-88570","DOIUrl":"https://doi.org/10.1115/IMECE2018-88570","url":null,"abstract":"The increase in the power of chips and microchips has resulted in the generation of heat fluxes to be dissipated of the order of 100 W/cm2 in very small areas [1], therefore, dissipating this heat has become a priority for the proper functioning of these dispositives. Thus, the proposition of new geometries and dissipation methods has become an area of great interest in scientific research. This research presents the analysis of a new geometry for a heat sink capable of dissipating very high energy flows by means of liquid cooling. The analyzes are based on previous analyzes of serpentine type geometries, where the heat flux to dissipate was 10 W/cm2 [2]. The operating conditions, such as velocity and pressure drop, as well as heat transfer are analyzed. Water is used as the dissipation fluid at an inlet velocity of 0.1 m/s. The geometry to be analyzed, called “Aztec Geometry,” is a radial type geometry that was originally designed for fuel cells, and has small fins arranged in three radial stripes. The results indicate that the pressure drop is on the order of 85 Pa, which is less than the pressure drop when radial coil microchannels are used (between 100 and 870 Pa). The dissipated heat is larger than the heat dissipated in radial coil microchannels (205 W versus 145 and 194 W), proving that the proposed radial geometry has a greater dissipation capacity at a lower cost than previously proposed geometries in the market.","PeriodicalId":307820,"journal":{"name":"Volume 8B: Heat Transfer and Thermal Engineering","volume":"118 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":"131488107","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":"Two-Dimensional Heat Transfer Considerations for Thermoreflectance Measurements","authors":"D. Sarkar, P. Chakraborty, B. T. Beck, Z. Leseman","doi":"10.1115/IMECE2018-88657","DOIUrl":"https://doi.org/10.1115/IMECE2018-88657","url":null,"abstract":"In the Suspended ThermoReflectance (STR) technique a microcantilever is heated with a laser power at the free end of the microcantilever and as heat propagates through it, another laser is used to measure the temperature along the beam.[1] In this paper, the heat equation is solved for two-dimensional heat flow in the microcantilever to determine the material’s thermal conductivity and heat capacity. Two of the dimensions of the microcantilever, width and length, are significantly greater than the third dimension, the thickness, leading to the two-dimensional approximation. Two boundaries along the length of the structure and one boundary along the width are assumed to be under Dirichlet boundary conditions, while the other boundary has Neumann condition. The Neumann or flux condition has a Gaussian profile due to the nature of laser beam intensity. The heat equation is solved using under 3 different flux conditions: (1) Steady-state, (2) Transient, and (3) Periodic. A steady-state condition mimics the experimental condition when a continuous wave laser is used to heat the microcantilever’s tip. A transient condition is possible when quickly removing or adding the continuous wave laser’s flux from the microcantilever’s tip using a chopper. Finally, a periodic condition can be achieved when an electro-optic modulator is utilized experimentally. Closed form analytical expressions are evaluated against the finite element model and experimental results for microcantilever beams and micro-structures of Si that have lengths on the order of a mm, width on the order of 100 microns, and thicknesses of 1 micron or less.","PeriodicalId":307820,"journal":{"name":"Volume 8B: Heat Transfer and Thermal Engineering","volume":"157 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":"122859694","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":"Flow and Heat Transfer of Mist/Steam Two-Phase Flow in Two-Pass Rectangular Channels With Paralleled and V-Shaped Rib Turbulators","authors":"G. Jiang, Jianmin Gao, Xiaojun Shi, Wang Zhao, Li Yunlong","doi":"10.1115/IMECE2018-88532","DOIUrl":"https://doi.org/10.1115/IMECE2018-88532","url":null,"abstract":"The heat and flow characteristics of mist/steam two-phase flow in U-shaped internal cooling passage of gas turbine blade are studid numerically in this paper. The standard k-ε model was used as the turbulence model combined with the DPM model to calculate the influence of mist/steam mass ratio and mist diameter on flow and heat transfer of U-passage with different shaped ribs. The result indicates that under the same working condition, the U-shaped channel with 45 deg. V-shaped ribs has better heat transfer performance than other channels and heat transfer non-uniformity of the U-shaped channel with 75 deg. ribs is the worst among all channels studied in this paper. The heat transfer performance of the U-shaped channel with V-shaped ribs is higher than that of the channel with paralleled ribs. As for the mist/steam cooling in U-shaped passage with same ribs structure, heat transfer non-uniformity increases with the increasing of heat transfer performance. When mists diameter increases from 5μm to 15μm, the heat transfer performance of the Second-Flow-Passage increases obviously and the heat transfer non-uniformity increases at the same time. The heat transfer performance has not been further enhanced when the mists diameter continuously increases after mist diameter are larger than 10μm.","PeriodicalId":307820,"journal":{"name":"Volume 8B: Heat Transfer and Thermal Engineering","volume":"36 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":"114764284","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 Across Crystalline and Amorphous Silicon Surfaces in Contact With Water and the Effects of the Interfacial Liquid Structuring","authors":"Luis E Paniagua-Guerra, C. U. Gonzalez-Valle, B. Ramos-Alvarado","doi":"10.1115/IMECE2018-86497","DOIUrl":"https://doi.org/10.1115/IMECE2018-86497","url":null,"abstract":"The understanding of nanoscale heat transfer across solid-liquid interfaces poses similar challenges as solid-solid interfaces; however, the higher mobility of liquid particles increases the complexity of this problem. It has been observed that liquid particles tend to form organized structures in the vicinity of solid surfaces; additionally, the formation of such structures has been reported to correlate with heat transfer across interfaces. Classical molecular dynamics simulations were used to investigate the behavior of liquid water in contact with crystalline and amorphous silicon. The in-plane and out-of-plane structure of interfacial water was characterized under different artificial wettability conditions, i.e., the silicon-water interaction potentials were calibrated to reproduce a wide range of wettability conditions. The change in the vibrational density of states was analyzed in order to quantify the mismatch between modes on both sides of the solid-liquid interfaces. Linear response theory was used to calculate the thermal boundary conductance at the different interfaces and a correlation was found between surface chemistry and heat transfer.","PeriodicalId":307820,"journal":{"name":"Volume 8B: Heat Transfer and Thermal Engineering","volume":"43 3 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":"130469838","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":"Thermal Stress Associated With Non-Fourier Heat Conduction in Femtosecond Laser Heating of Multilayer Metallic Films","authors":"S. Bag, M. Amin","doi":"10.1115/IMECE2018-86144","DOIUrl":"https://doi.org/10.1115/IMECE2018-86144","url":null,"abstract":"In the present work, the deformation behavior in metallic film subjected to ultra-short laser heating is investigated. Static thermo-elastic behavior is predicted for 100 nm thin film of either single layer or multiple layers. The temperature distribution is estimated from dual-phase lag non-Fourier heat conduction model. The maximum temperature after single pulse is achieved 730 K. The temperature profile for this pulse laser is used to compute elastic stress and distortion field following the minimization of potential energy of the system. In the present work, the simulation has been proposed by developing 3D finite element based coupled thermo-elastic model using dual phase lag effect. The experimental basis of transient temperature distribution in ultra-short pulse laser is extremely difficult or nearly impossible, the model results have been validated with literature reported thermal results. Since the temperature distribution due to pulse laser source varies with time, the stress analysis is performed in incremental mode. Hence, a sequentially coupled thermo-mechanical model is developed that is synchronized between thermal and mechanical analysis in each time steps of transient problem. The maximum equivalent stress is achieved 0.3 GPa. Numerical results show that the predicted thermal stress may exceeds the tensile strength of the material and may lead to crack or damage the thin film.","PeriodicalId":307820,"journal":{"name":"Volume 8B: Heat Transfer and Thermal Engineering","volume":"18 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":"126834172","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}