Готові списки джерел за темами / Diffusion cooling

Добірка наукової літератури з теми "Diffusion cooling"

Автор: Grafiati

Опубліковано: 10 грудня 2022

Оновлено: 29 січня 2023

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Статті в журналах з теми "Diffusion cooling"

Dunlap, W. J. "Natureʼs diffusion experiment: The cooling-rate cooling-age correlation". Geology 28, № 2 (лютий 2000): 139–42. http://dx.doi.org/10.1130/0091-7613(2000)028<0139:nsdetc>2.3.co;2.

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Dunlap, W. J. "Nature's diffusion experiment: The cooling-rate cooling-age correlation." Geology 28, no. 2 (2000): 139. http://dx.doi.org/10.1130/0091-7613(2000)28<139:ndetcc>2.0.co;2.

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Robson, R. E. "Diffusion cooling in a magnetic field." Physical Review E 61, no. 1 (January 1, 2000): 848–54. http://dx.doi.org/10.1103/physreve.61.848.

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Vlasov, M. N., and M. C. Kelley. "Specific features of eddy turbulence in the turbopause region." Annales Geophysicae 32, no. 4 (April 15, 2014): 431–42. http://dx.doi.org/10.5194/angeo-32-431-2014.

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Abstract. The turbopause region is characterized by transition from the mean molecular mass (constant with altitude) to the mean mass (dependent on altitude). The former is provided by eddy turbulence, and the latter is induced by molecular diffusion. Competition between these processes provides the transition from the homosphere to the heterosphere. The turbopause altitude can be defined by equalizing the eddy and molecular diffusion coefficients and can be located in the upper mesosphere or the lower thermosphere. The height distributions of chemical inert gases very clearly demonstrate the transition from turbulent mixing to the diffusive separation of these gases. Using the height distributions of the chemical inert constituents He, Ar, and N2 given by the MSIS-E-90 model and the continuity equations, the height distribution of the eddy diffusion coefficient in the turbopause region can be inferred. The eddy diffusion coefficient always strongly reduces in the turbopause region. According to our results, eddy turbulence above its peak always cools the atmosphere. However, the cooling rates calculated with the eddy heat transport coefficient equaled to the eddy diffusion coefficient were found to be much larger than the cooling rates corresponding to the neutral temperatures given by the MSIS-E-90 model. The same results were obtained for the eddy diffusion coefficients inferred from different experimental data. The main cause of this large cooling is the very steep negative gradient of the eddy heat transport coefficient, which is equal to the eddy diffusion coefficient if uniform turbulence takes place in the turbopause region. Analysis of wind shear shows that localized turbulence can develop in the turbopause region. In this case, eddy heat transport is not so effective and the strong discrepancy between cooling induced by eddy turbulence and cooling corresponding to the temperature given by the MSIS-E-90 model can be removed.

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Yu, Ping, Ren Bo Song, Wen Ming Xiong, Wei Feng Huo, Chen Wei, Zhi Jun Liu, and Shuai Qin. "Phase Transformation Law of Nb Microalloyed Steel at Different Cooling Rates." Materials Science Forum 1035 (June 22, 2021): 396–403. http://dx.doi.org/10.4028/www.scientific.net/msf.1035.396.

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Through the Gleeble3500 thermal simulation test machine, the phase transformation law of Nb microalloyed steel was studied and tested. After the compression deformation, it was cooled to room temperature at different speeds. Obtain the dynamic continuous cooling transformation diagram and the scanning structure diagram of the test steel, and then analyze the phase composition under different cooling speeds through JMatPro material performance simulation. The results show that: at a lower cooling speed (0.1°C/s), austenite decomposition is a diffusion-type phase change that takes place in a high-temperature region, and carbon atoms can diffuse sufficiently. At a moderate cooling rate (1°C/s), the bainite phase transition is a semi-diffusion phase transition in which carbon atoms are displaced in a non-cooperative thermally activated transition mode. When the cooling rate is high (15°C/s), the martensitic transformation is a non-diffusion-type transformation carried out in the low temperature region, and the atoms are directly transferred from the austenite lattice to the martensite lattice. With the increase of the cooling rate and the decrease of the transition temperature, from low-speed cooling→medium-speed cooling→high-speed cooling, respectively, the diffusion type phase transition→semi-diffusion type phase transition→the non-diffusion type phase transition. At different cooling rates, the continuous cooling transition diagram simulated by JMatPro is basically the same as the phase transition in the dynamic continuous cooling transition diagram of the test steel, which proves that the simulation prediction of the dynamic continuous cooling transition of the test steel by the JMatPro software has high accuracy and applicability.

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Elsayed, Ahmed M., Farouk M. Owis, and M. Madbouli Abdel Rahman. "Film Cooling Optimization Using Numerical Computation of the Compressible Viscous Flow Equations and Simplex Algorithm." International Journal of Aerospace Engineering 2013 (2013): 1–24. http://dx.doi.org/10.1155/2013/859465.

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Film cooling is vital to gas turbine blades to protect them from high temperatures and hence high thermal stresses. In the current work, optimization of film cooling parameters on a flat plate is investigated numerically. The effect of film cooling parameters such as inlet velocity direction, lateral and forward diffusion angles, blowing ratio, and streamwise angle on the cooling effectiveness is studied, and optimum cooling parameters are selected. The numerical simulation of the coolant flow through flat plate hole system is carried out using the “CFDRC package” coupled with the optimization algorithm “simplex” to maximize overall film cooling effectiveness. Unstructured finite volume technique is used to solve the steady, three-dimensional and compressible Navier-Stokes equations. The results are compared with the published numerical and experimental data of a cylindrically round-simple hole, and the results show good agreement. In addition, the results indicate that the average overall film cooling effectiveness is enhanced by decreasing the streamwise angle for high blowing ratio and by increasing the lateral and forward diffusion angles. Optimum geometry of the cooling hole on a flat plate is determined. In addition, numerical simulations of film cooling on actual turbine blade are performed using the flat plate optimal hole geometry.

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Zheng, Hong Liang, Lin Li, Xin Xin Yuan, and Xue Lei Tian. "A Calculation Model of Carbon Diffusion Coefficient in the Austenite for Spheroidal Graphite Cast Iron." Materials Science Forum 789 (April 2014): 593–98. http://dx.doi.org/10.4028/www.scientific.net/msf.789.593.

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This paper presents the relationship between the carbon atom diffusion coefficient in the austenite and the temperature during the nodular cast iron solidification under different cooling rates or with different carbon contents. Pouring the wedge-shaped casting explores the influence of cooling rate on the diffusion coefficient. The other part explores the change of the diffusion coefficient with different carbon contents by water quenching to save the organization in the solidification. Results show that both the cooling rate and the carbon content can affect the diffusion coefficient, and it decreases as the cooling rate increases. More attempts were also done to correlate the diffusion coefficient with the temperature in different carbon content. It has been found that the diffusion coefficient decreases as the temperature increase.

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Zhang, Bo, Li-Bing Lin, Ji-Quan Li, Na-Ru Zhang, and Hong-Hu Ji. "Effect of forward expansion angle on film cooling characteristics of shaped holes." Open Physics 18, no. 1 (July 18, 2020): 302–14. http://dx.doi.org/10.1515/phys-2020-0130.

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AbstractAccording to the design requirements of high-temperature combustion chamber, an advanced shaped hole structure was designed for film cooling. Numerical method was applied in this study to investigate the flow and heat transfer characteristics of shaped holes and compared with those of cylindrical holes. The influence of the forward expansion angle of shaped holes on the flow and heat transfer was studied. The results show that compared to cylindrical holes, the diffused structure of shaped holes decreases the momentum of jet flow, improves the adhesion characteristics of the cooling air film, increases the diffusion of the coolant air outflow and improves the cooling efficiency between adjacent columns of holes in the lateral direction. When the forward expansion angle increases, the expansion section induced the flow vortex, which reduces the radial velocity of coolant flow and enhances the diffusion of cooling air film both in streamwise and spanwise directions. However, as the forward expansion angle increases further, the scale of vortex inside the shaped hole grows. Too large vortex inside the shaped hole increases the coolant eject angle, which weakens the film covering effect. Additionally, the shaped hole results in an increase in lateral spreading and enhances the cooling effect between adjacent columns of the film hole. The enhancement of the film cooling characteristics is due to the change in the shape of the film hole, resulting in the enhancement of the flow vortex, which induces complicated secondary flow.

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Krechun, M. M. "Galvanic interconnects for thermoelectric cooling modules." Фізика і хімія твердого тіла 20, no. 1 (April 1, 2019): 83–88. http://dx.doi.org/10.15330/pcss.20.1.88.

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The paper studies the use of galvanic technologies in thermoelectricity. The technological features of applying anti-diffusion coatings on bismuth telluride based thermoelectric material (TEM) by electroplating method are considered. The advantages and disadvantages of the properties of anti-diffusion structures obtained by the electrochemical method are determined.

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Ramsak, Matjaz, and Leopold Skerget. "Heat diffusion in fractal geometry cooling surface." Thermal Science 16, no. 4 (2012): 955–68. http://dx.doi.org/10.2298/tsci1204955r.

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Дисертації з теми "Diffusion cooling"

Jakob, Uli. "Investigations into solar powered diffusion-absorption cooling machines." Thesis, De Montfort University, 2005. http://hdl.handle.net/2086/10747.

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Solar thermal driven or assisted absorption cooling machines are gaining increasing importance due to the continually growing demand for airconditioning in domestic housing as well as office and hotel buildings. Presently there are no thermally driven absorption cooling machines available on the market that can provide a smaller cooling capacity than 10kW for cooling buildings. For this reason, two single-effect solar heated ammonia/water (NHJlH20) Diffusion-Absorption Cooling Machines (DACM) with a design cooling capacity of 2.SkW at evaporator temperatures between -10°C and +soC were designed, built and operated. The indirectly heated, solar powered generator (bubble pump) is the main new feature of this cooling machine. Data acquisition was conducted under laboratory conditions as well as under simulated field conditions for vacuum-tube collectors. The first pilot plant showed that coefficient of performance values (COP) range from 0.1 to 0.2 and the evaporator cooling capacity of the pilot plant could reach 1.SkW, but that the operation stability was insufficient. The second optimised and compacted pilot plant showed stable and continuous temperature and pressure levels. The reached COPs were between 0.2 and O.S and the continuous cooling performance between 1.0kW and 1.6kW. A maximum cooling performance of 2.0kW could be reached if the evaporator temperature was set to the relatively high value of 2SoC. The Diffusion-Absorption Cycle has been modelled using the constant characteristic equation of sorption chillers. An expanded, steady-state model which includes additional specific components of the DACM was developed based on the exact solution of the internal mass and energy balances of each component as well as the heat transfer between external and internal temperature levels. The internal enthalpies are calculated at each time interval using the simulation environment INSEL. The compared experimental and simulated data showed a good accordance.

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Zuniga, Humberto. "Study of Discharge Coefficient and Trends in Film Cooling Effectiveness of Conical Holes with Increasing Diffusion Angles." Master's thesis, University of Central Florida, 2006. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/3578.

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Previous studies indicate that increasing the diffusion angle in conical film-cooling holes leads to an improvement in their film cooling effectiveness. Discharge coefficient and film cooling effectiveness measurements are conducted to characterize this behavior. Part of the focus of this investigation is to find out how this trend develops and attempt to ascertain the optimum cone angle, if possible. Six test plates, each with one row of eight conical-shaped cooling holes of equal diffusion angles of 0, 1, 2, 3, 6, or 8 [degrees], with respect to the hole axis are used in this study. The ratios of the hole exit areas to the inlet areas range from 1 to 2.85. Coolant injection angle for all holes is at 35 degrees to the horizontal, in the direction of the main flow. Coefficients of discharge of all holes are reported under flow conditions. Temperature sensitive paint, TSP, is the technique used to find the temperature distribution downstream of the cooling holes and determine the laterally averaged film-cooling effectiveness. Data are obtained for blowing ratios ranging from 0.5 to 1.5, at a constant density ratio of 1.26. Results and trends are compared with established literature, which also recommends that a cylindrical entry length for diffused holes should be at least 4 diameters long. The effect that an added entry length has on the 3-degree conical plate's cooling effectiveness is also explored. Data are compared to baseline cylindrical holes, as well as to fan-shaped film holes found in open literature. Results indicate that the conical holes with larger diffusion angles provide strikingly even film protection and outperform fan shaped and cylindrical holes under certain conditions over extended downstream distances. Also, the addition of a cylindrical entry length to a conical hole, by providing a manageable metering diameter, should ease their usage while providing the full benefits of the conical geometry which may one day lead to numerous industrial applications.
M.S.M.E.
Department of Mechanical, Materials and Aerospace Engineering;
Engineering and Computer Science
Mechanical Engineering

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Potgieter, Marthinus Christiaan. "The evaluation of a solar-driven aqua-ammonia diffusion absorption heating and cooling cycle / M.C. Potgieter." Thesis, North-West University, 2013. http://hdl.handle.net/10394/9689.

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Several steps are followed in order to evaluate the cycle as the title suggests. The diffusion absorption refrigerator (DAR) cycle performance is evaluated when using helium or hydrogen as auxiliary gas. A slight increase in COP is found when using helium, but it is not sufficient to justify the cost. A secondary simulation of an alternate dual-pressure cycle using a pump is done as feasibility comparison with the same parameters as the diffusion cycle. It was found that the second cycle is not acceptable due to high evaporator temperatures needed to ensure liquid enters the pump instead of partially evaporated solution. This would greatly increase the work input required for what essentially becomes a compressor. Optimisation of the DAR is evaluated by simulating the use of a rectification column and the effects of different design points on overall performance. Meteorological data for Potchefstroom, South Africa is used to perform a yearly analysis on the simulated cycle and to specify a suitable design point. The use of a radiative cooling system as heat sink for the system is then investigated and incorporated into the system model. Finally, the performance characteristics of the simulated DAR cycle are discussed, verified and compared with available data from similar research. It is shown that a 40% solution aqua-ammonia-hydrogen cycle driven by 526 kW of solar thermal energy at 130°C and a system pressure of 1.5 MPa can easily achieve a COP over 0.4 with an air-cooled absorber at 40°C and a water-cooled condenser at 35°C. A 231 kW refrigeration capacity at an average evaporator temperature of –20°C is achieved, satisfying the requirements for a domestic refrigeration system.
Thesis (MIng (Mechanical Engineering))--North-West University, Potchefstroom Campus, 2013.

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Laot, Christelle Marie. "Gas transport properties in polycarbonate - Influence of the cooling rate, physical aging, and orientation." Diss., Virginia Tech, 2001. http://hdl.handle.net/10919/29844.

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The objective of this research work was to understand the molecular mechanism of gas transport through amorphous glassy polymers. Especially, emphasis was placed on determining whether or not gas transport in amorphous glassy polymers is directly correlated with the free volume content. Free volume arguments are indeed commonly used to explain the gas transport process. The gas transport properties of bisphenol-A polycarbonate films were examined as a function of the cooling rate, physical aging, and orientation. Such conditions affect the free volume content and its size and shape distribution. Results obtained from permeation experiments were accompanied with dynamic mechanical and density measurements. The experimental results suggest that the diffusion coefficient of small gas molecules in glassy polycarbonate is influenced by the local dynamics or mobility of the polymer chains rather than by the overall free volume content. Indeed, the diffusion coefficient of nitrogen for instance was reduced in fast-cooled samples, despite of the fact that those samples possessed a greater overall free volume content. Fast cooling rates may generate highly restricted conformations which hinder local motions, and therefore tend to increase the activation energy of diffusion. As expected, the greater the free volume content, the greater was the solubility coefficient. The increase in the polymer relaxation times with aging time is believed to restrict the local chain motions, leading to enhanced activation energies of diffusion, and therefore to reduced diffusion coefficients. The change in the solubility coefficients with physical aging revealed that the aging process might not affect all the cavity sizes in polycarbonate equally. According to free volume arguments, one would anticipate that the physical aging of fast-cooled samples (which possess more free volume) should be enhanced compared to that of slowly-cooled samples. Quite interestingly, the decrease in the diffusion coefficient with aging was found to occur much slower in fast-cooled samples, despite of the higher initial free volume content. In contrast, properties directly related to the free volume content, such as density or isothermal DMTA measurements actually showed a greater aging rate in the sample containing the greatest amount of free volume. Slow-cooled samples that are in a low energy conformational state may loose their internal degrees of freedom more rapidly, due to the closer interchain packing and the possibly restricted segmental motions. Studies dealing with orientation and gas transport were complicated by several factors. For instance the fact that the permeation experiments were performed perpendicularly to the orientation of the chains and not along the orientation axis limited the sensitivity of the gas transport properties to orientation. This work points out that dynamic rather than static models should be developed to predict the gas transport phenomenon.
Ph. D.

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Raphael, Iain. "Cooling hot property? : an assessment of the impact of property marking on residential burglary crime reduction, crime displacement or diffusion of benefits and public confidence." Thesis, University of Portsmouth, 2015. https://researchportal.port.ac.uk/portal/en/theses/cooling-hot-property(f5a6e97a-bdf6-4722-adcd-1119a57c6b7f).html.

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For the year ending March 2014 the Office for National Statistics (ONS) estimated there were 573,000 domestic burglaries in England and Wales. Using the Home Office Integrated Offender Management Value for Money Toolkit valuation (2011) the cost to society of this is £1.9 billion. The financial and resulting emotional cost is a heavy burden for the UK. Better understanding crime prevention approaches and their impact on reducing residential burglary is of obvious relevance to policing, government and society as a whole. This study examined the wider impact of traceable liquid property marking strategies on reducing residential burglary and other acquisitive crime. It monitored levels of crime in trial areas. It observed if crime displacement or diffusion of benefits effects occurred to a distance of 750m, in 250m intervals, surrounding the trial areas. By doing so it added to the body of knowledge that surrounds situational crime prevention. It also surveyed households, which were participants of the trial, some 6 months following the deployment to measure any impact on their confidence in policing and on their fear of crime. To do this, 10 x London trial sites, comprising of 500 households areas were purposively selected that had both a persistent and a long-term chronic residential burglary offence rate. Two such sites were selected on each of five London Boroughs. The residential homes within these areas were then visited by a police officer or a PCSO and occupants had their property marked using a unique traceable liquid property marking solution. This strategy was supported by stickers saying their property had been marked being placed on external display on front and back doors and windows, signs being put up on street furniture in the surrounding area telling people they were entering a property marked area and the use of press and media releases to wider market the approach to offenders. Trap cars and houses were utilised and arrests advertised to ‘prove’ the approach to offenders. Finally control areas of similar characteristics to the trial areas were identified and observed on each of the 5 x borough sites. Once the marking had been implemented to the point of 85% saturation (where able), key data was observed over a 12-month period and compared against the previous year. These included: o Residential burglary crime levels within the target area. o Residential burglary crime levels in displacement zones of 250m, 500m, and 750m, surrounding the targeted area. o Robbery, theft of motor vehicle (M/V), theft from motor vehicle and total notifiable offences (TNO’s) offence levels within the target and displacement areas to measure displacement effects. o An online survey of the trial households of police satisfaction and fear of crime levels. o Interviews with key staff that implemented the trial. The study deduces that the following effects occurred within the trial areas: o A 45% reduction in residential burglaries, a 21% reduction in robberies, no significant change in M/V crime and 22% less TNO’s. Once offset against the control area performance the results indicated: o Overall average residential burglary was reduced by 21% with the best BOCU achieving an 88% reduction. o Personal robbery offences reduced by 16% and overall TNO’s by 20%. o There was no statistically significant change in M/V crime offence levels. o There was no significant crime or offence displacement within the target areas and indeed clear diffusion of benefits effects occurred. When the trial areas were widened to include the 250m, 500m and 750m displacement zones the following results were found to 750m: o A 23% reduction in residential burglaries, a 15% reduction in robberies, a 3% reduction in theft of M/V, 1% reduction in theft from M/V and a 9% less TNO’s. Once offset against the control area performance the results indicated: o Residential burglary reduced by 12% in the 250m-displacement zones, increased by 7% in the 500m zones, decreased by 19% in the 750m zones and cumulatively resulted in a 17% reduction. o Robbery increased by 8% in the 250m-displacement zones, decreased by 7% in the 500m zones, increased by 13% in the 750m zones and cumulatively resulted in a 5% increase. o Theft of M/V increased by 27% in the 250m-displacement zones, increased by 4% in the 500m zones, increased by 5% in the 750m zones and cumulatively resulted in a 10% increase. o Theft from M/V increased by 24% in the 250m-displacement zones, increased by 16% in the 500m zones, increased by 11% in the 750m zones and cumulatively resulted in a 15% increase. o TNO’s increased by 3% in the 250m displacement zones, decreased by 4% in the 500m zones, increased by 5% in the 750m zones and cumulatively resulted in a 1% increase. The results of the on-line survey found the following: o 51% of householders felt safer in their area. o 52% of householders felt safer in their home. o 33% had an improved opinion of the police. The study concludes that traceable liquid property marking is highly effective at reducing residential burglary. It found that when deployed with high levels of saturation to an area, diffusion of benefits effects for this crime type are likely to occur out to at least 750m from that area. This strategy led to a reduction in the fear of crime and if distributed by the police family, leads to an increase in public confidence for at least 6 months after the distribution period. However in achieving these positive impacts there will be offence displacement outside the targeted area, where offenders will move from residential burglary to other offences types. The most likely change is into theft of and from M/V crime. These crimes are arguably less harmful and impactive on crime victims and occurred at a lower rate than the residential burglary offences prevented.

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Ganguly, Jibamitra, Massimiliano Tirone, and Kenneth Domanik. "Cooling rates of LL, L and H chondrites and constraints on the duration of peak thermal conditions: Diffusion kinetic modeling and implications for fragmentation of asteroids and impact resetting of petrologic types." PERGAMON-ELSEVIER SCIENCE LTD, 2016. http://hdl.handle.net/10150/621538.

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We have carried out detailed thermometric and cooling history studies of several LL-, L- and H-chondrites of petrologic types 5 and 6. Among the selected samples, the low-temperature cooling of St. Severin (LL6) has been constrained in an earlier study by thermochronological data to an average rate of similar to 2.6 degrees C/My below 500 degrees C. However, numerical simulations of the development of Fe-Mg profiles in Opx-Cpx pairs using this cooling rate grossly misfit the measured compositional profiles. Satisfactory simulation of the latter and low temperature thermochronological constraints requires a two-stage cooling model with a cooling rate of similar to 50-200 degrees C/ky from the peak metamorphic temperature of similar to 875 degrees C down to 450 degrees C, and then transitioning to very slow cooling with an average rate of similar to 2.6 degrees C/My. Similar rapid high temperature cooling rates (200-600 degrees C/ky) are also required to successfully model the compositional profiles in the Opx-Cpx pairs in the other samples of L5, L6 chondrites. For the H-chondrite samples, the low temperature cooling rates were determined earlier to be 10-20 degrees C/My by metallographic method. As in St. Severin, these cooling rates grossly misfit the compositional profiles in the Opx-Cpx pairs. Modeling of these profiles requires very rapid cooling, similar to 200-400 degrees C/ky, from the peak temperatures (similar to 810-830 degrees C), transitioning to the metallographic rates at similar to 450-500 degrees C. We interpret the rapid high temperature cooling rates to the exposure of the samples to surface or near surface conditions as a result of fragmentation of the parent body by asteroidal impacts. Using the thermochronological data, the timing of the presumed impact is constrained to be similar to 4555-4560 My before present for St. Severin. We also deduced similar two stage cooling models in earlier studies of H-chondrites and mesosiderites that could be explained, using the available geochronological data, by impact induced fragmentation at around the same time. Diffusion kinetic analysis shows that if a lower petrological type got transformed by the thermal effect of shock impacts to reflect higher metamorphic temperature, as has been suggested as a possibility, then the peak temperatures would have had to be sustained for at least 10 ky and 80 ky, respectively, for transformation to the petrologic types 6 and 4. Finally, we present a model that reconciles textural data supporting an onion-shell parent body of H-chondrites with rapid cooling rate at high temperature caused by impact induced disturbance, and also discuss alternatives to the onion shell parent body model. (C) 2016 Elsevier Ltd. All rights reserved.

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Agyare, Benjamin A. "INVESTIGATION OF ATOMIC MOTION IN OPTICAL LATTICES VIA INTENSITY CORRELATION MEASUREMENT." Miami University / OhioLINK, 2007. http://rave.ohiolink.edu/etdc/view?acc_num=miami1186171967.

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Dardour, Houda. "Étude des machines frigorifiques à absorption et à absorption-diffusion utilisant un mélange d'alcanes : étude systémique et modélisation rigoureuse de l'absorbeur." Thesis, Pau, 2012. http://www.theses.fr/2012PAUU3013/document.

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Le présent travail est consacré en premier lieu à l'investigation des limites de fonctionnement et de performances des machines frigorifiques à absorption et absorption-diffusion utilisant des mélanges d'alcanes comme fluides de travail et l'analyse en second lieu du processus d'absorption le long d'un absorbeur à film tombant en présence d'un gaz inerte. Dans le cas d'un refroidissement à l’eau les meilleures performances réalisées sont celles d'une machine utilisant le binaire C₃H₈/n-C₉H₂₀ avec un COP de l'ordre de 0.51 dans l'intervalle de la température de la chaleur motrice [110-125℃]. Une machine à absorption-diffusion utilisant ce même mélange en combinaison avec l’hydrogène permet de réaliser un COP de l'ordre de 0.44 pour une température de la chaleur motrice ne dépassant pas 120℃. Une étude approfondie est par suite menée sur l’absorption en présence d’un gaz inerte. Les résultats des l’étude ont montré entre autres que les deux résistances aux transferts de chaleur et de matière sont toutes les deux prédominantes en phase vapeur et ont révélé un taux d'absorption de l'ordre de 34% à travers une surface d'échange de 0.15m². Pour évaluer la réponse du système aux variations de ses principaux paramètres caractéristiques une étude paramétrique a été menée. Cette étude a permis d'appréhender le comportement complexe du processus d'absorption en présence d'un gaz inerte
This work is aimed primarily to investigate the feasibility limits and the performance of absorption and absorption-diffusion cooling machines using light alkane mixture as working pairs and secondarily to analyze the absorption process along a falling film absorber in the presence of an inert gas. It is shown that in the case of water cooling the best performances are those of an absorption machine using the C₃H₈/n-C₉H₂₀ binary mixture with a COP of about 0.51 in the heat driving temperature range 110-125℃. A COP of about 0.44 is attained with an absorption-diffusion cooling machine using the same mixture in combination with hydrogen with a heat driving temperature of 120℃. A detailed study of the absorption process with the C₃H₈/n-C₉H₂₀ pair and hydrogen as inert gas is conducted. The study results show that the heat and the mass transfer resistances are both prevalent in the vapor phase. An absorption rate of about 34% through an exchange surface of 0.15m² is calculated. A parametric study is carried out to evaluate the system response to the changes of its main characteristic parameters. This study allows a better understanding of the complex behavior of the absorption process in the presence of an inert gas

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Chen, Yiqiang. "High-resolution microstructural and microanalysis studies to better understand the thermodynamics and diffusion kinetics in an advanced Ni-based superalloy RR1000." Thesis, University of Manchester, 2015. https://www.research.manchester.ac.uk/portal/en/theses/highresolution-microstructural-and-microanalysis-studies-to-better-understand-the-thermodynamics-and-diffusion-kinetics-in-an-advanced-nibased-superalloy-rr1000(1d4e96e0-b362-484e-82cb-bec18cab850b).html.

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The commercial polycrystalline superalloy RR1000 developed for turbine disc applications contains a large number of alloying elements. This complex alloy chemistry is required in order to produce appropriate microstructures and the required mechanical properties, such that the most important strengthener γʹ displays complex alloy chemistry. The broad aim of this project is to develop an approach to measuring the composition of γʹ precipitates at a broad range of length scales from nanometres to hundreds of nanometres, and subsequently develop a better understanding of the role of thermodynamics and diffusion kinetics on γʹ phase separation and precipitate growth. A solution of the absorption-corrected EDX spectroscopy to spherical particles was developed in our work, therefore enabling the quantitative analysis of precipitates' composition using an absorption-corrected Cliff-Lorimer approach. By performing this quantification, size-dependent precipitate compositional variations were obtained. Examination of this quantitative approach was compared to thermodynamic calculations of primary γ' precipitates possessing equilibrium compositions. Given the development of semi-quantitative compositional measurements for spherical γʹ precipitates and that cooling is one of the most common and critical regimes in physical metallurgy of Ni-based superalloys, this approach was then applied to study the local compositional variations that are induced in γ' precipitates when the alloy RR1000 undergoes different cooling rates. These measured compositions have been compared to detailed thermodynamic calculations and provide new experimental evidence of the importance of the dominant role of aluminium antisite diffusion in determining the low-temperature growth kinetics of fine-scale γ' precipitates. We have applied a similar analysis approach to study the compositional variations of γʹ cores within the class of secondary precipitates upon cyclic coarsening and reversal coarsening. It was shown that supersaturated Co in secondary γʹ exhibits an overall trend towards the equilibrium but Co content can significantly increase as γʹ coarsens. It was demonstrated that the limited elemental diffusivity in γ and γʹ compared to the observed coarsening rate in the coarsening regime results in the long-lasting Co supersaturation in γʹ and builds up elemental enhancements or depletions. These inhomogeneous elemental distributions produce compressive elastic constraints on large-scale secondary γʹ, therefore inducing morphological instability of these γʹ and causing the reversal coarsening. These results enable us to better understand the role that both thermodynamics and limited diffusion kinetics plays in controlling the complex microstructures of γ' precipitates.

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Dooris, Matthew David. "Apparent Total Evaporative Resistance Values From Human Trials Over a Range of Metabolic and Heat Stress Levels." Scholar Commons, 2011. http://scholarcommons.usf.edu/etd/3078.

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Failure to maintain thermal equilibrium can cause uncontrollable increases in body core temperature beyond critical upper limits. In selecting clothing, consideration must be given to the heat transfer properties of clothing that may restrict the cooling capacity of the human body under heat stress conditions, most importantly, apparent total evaporative resistance (Re,T,a). This study calculated and compared Re,T,a for five clothing ensembles under varying heat stress conditions, including three relative humidity (RH) levels and three stages of heat stress to determine if Re,T,a values varied or remained the same with changes in heat stress conditions. A four-way mixed model analysis of variance demonstrated significant differences for estimated Re,T,a values among ensembles, RH levels, heat stress stages, and interactions among ensembles and RH levels and ensembles and heat stress stages (p < 0.0001). No significant interaction among RH levels and heat stress stages was found (p = 0.67). A Tukey's Honestly Significant Difference multiple comparison test was used to identify where significant differences occurred (p < 0.05). The results of the study indicated that Re,T,a values do change with RH levels and stages of heat stress and that the theoretical framework for explaining heat-exchange in hot environments is not yet well-established. Also confirmed was the dominance of the convection pathway over the diffusion pathway in hot environments.

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Книги з теми "Diffusion cooling"

S, Wichman I., and United States. National Aeronautics and Space Administration., eds. Influence of a simple heat loss profile on a pure diffusion flame. [Washington, DC: National Aeronautics and Space Administration, 1996.

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1934-, Hoffman Joe D., and United States. National Aeronautics and Space Administration., eds. The prediction of nozzle performance and heat transfer in hydrogen/oxygen rocket engines with transpiration cooling, film cooling, and high area ratios. [Washington, DC]: National Aeronautics and Space Administration, 1994.

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On the influence of a fuel side heat-loss ("soot") layer on a planar diffusion flame. [Washington, DC: National Aeronautics and Space Administration, 1994.

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Частини книг з теми "Diffusion cooling"

Robson, Robert E., Ronald D. White, and Malte Hildebrandt. "Boundary Conditions, Diffusion Cooling, and a Variational Method." In Fundamentals of Charged Particle Transport in Gases and Condensed Matter, 209–26. Boca Raton, FL : CRC Press, Taylor & Francis Group, [2017] |: CRC Press, 2017. http://dx.doi.org/10.4324/9781315120935-13.

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Wierszyłłowski, Ignacy. "The Influence of Increased Cr Content and Austenite Grain Size on the Kinetics of Phase Transformations when Cooling Hypo-Eutectoid Steel." In Defect and Diffusion Forum, 421–26. Stafa: Trans Tech Publications Ltd., 2006. http://dx.doi.org/10.4028/3-908451-36-1.421.

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Suzuki, Hideyuki. "Multigroup Flux Limited Diffusion Scheme Code for Cooling Simulations of Protoneutron Stars." In Numerical Astrophysics, 287–88. Dordrecht: Springer Netherlands, 1999. http://dx.doi.org/10.1007/978-94-011-4780-4_91.

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Fiedler, Torben, Joachim Rösler, Martin Bäker, Felix Hötte, Christoph von Sethe, Dennis Daub, Matthias Haupt, Oskar J. Haidn, Burkard Esser, and Ali Gülhan. "Mechanical Integrity of Thermal Barrier Coatings: Coating Development and Micromechanics." In Notes on Numerical Fluid Mechanics and Multidisciplinary Design, 295–307. Cham: Springer International Publishing, 2020. http://dx.doi.org/10.1007/978-3-030-53847-7_19.

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Abstract To protect the copper liners of liquid-fuel rocket combustion chambers, a thermal barrier coating can be applied. Previously, a new metallic coating system was developed, consisting of a NiCuCrAl bond-coat and a Rene 80 top-coat, applied with high velocity oxyfuel spray (HVOF). The coatings are tested in laser cycling experiments to develop a detailed failure model, and critical loads for coating failure were defined. In this work, a coating system is designed for a generic engine to demonstrate the benefits of TBCs in rocket engines, and the mechanical loads and possible coating failure are analysed. Finally, the coatings are tested in a hypersonic wind tunnel with surface temperatures of 1350 K and above, where no coating failure was observed. Furthermore, cyclic experiments with a subscale combustion chamber were carried out. With a diffusion heat treatment, no large-scale coating delamination was observed, but the coating cracked vertically due to large cooling-induced stresses. These cracks are inevitable in rocket engines due to the very large thermal-strain differences between hot coating and cooled substrate. It is supposed that the cracks can be tolerated in rocket-engine application.

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Engelfried, Robert. "Permissible diffusion resistance of polymer coatings against water vapour and its diffusion effective film thickness." In Natural Draught Cooling Towers, 347–52. CRC Press, 2004. http://dx.doi.org/10.1201/b17001-51.

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"Isothermal and Continuous Cooling Transformation Diagrams." In Steels, 197–211. 2nd ed. ASM International, 2015. http://dx.doi.org/10.31399/asm.tb.spsp2.t54410197.

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Isothermal and continuous cooling transformation (CT) diagrams help users map out diffusion-controlled phase transformations of austenite to various mixtures of ferrite and cementite. This chapter discusses the application as well as limitations of these engineering tools in the context of heat treating eutectoid, hypoeutectoid, and proeutectoid steels. It also provides references to large collections of transformation diagrams and includes several diagrams that plot quenching and hardening transformations as a function of bar diameter.

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Nakanishi, Hiizu, and Namiko Mitarai. "Particle Diffusion in the Cooling Process of Granular Gas." In Powders and Grains 2001, 581–83. CRC Press, 2020. http://dx.doi.org/10.1201/9781003077497-143.

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"Ferritic Microstructures." In Steels, 113–31. 2nd ed. ASM International, 2015. http://dx.doi.org/10.31399/asm.tb.spsp2.t54410113.

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This chapter describes the ferritic microstructures that form in carbon steels under continuous cooling conditions. It begins with a review of the Dubé classification system for crystal morphologies. It then explains how cooling-rate-induced changes involving carbon atom diffusion and the associated rearrangement of iron atoms produce the wide variety of morphologies and microstructures observed in ferrite. The chapter also describes a classification system developed specifically for ferritic microstructures and uses it to compare common forms of ferrite, including polygonal or equiaxed ferrite, Widmanstatten ferrite, quasi-polygonal or massive ferrite, acicular ferrite, and granular ferrite.

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De Pascalis, Lorenzo, Giuseppe Starace, and Federica Carluccio. "The Diffusion Absorption Refrigerator Operation and Performance." In Handbook of Research on Advances and Applications in Refrigeration Systems and Technologies, 36–84. IGI Global, 2015. http://dx.doi.org/10.4018/978-1-4666-8398-3.ch002.

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This chapter focuses on the Diffusion Absorption Refrigerator (DAR) cycle and describes a new advanced thermodynamic model which allows good predictions of the chiller performance in terms of efficiency and cooling capacity, starting from a precise evaluation of the thermo-physical properties of the working mixture at each point of the circuit. A steady state thermodynamic analytical model of the thermal pump driving the DAR is also included. In addition, the experimental validation of the model, performed on a prototype built coupling a domestic 750 W-magnetron with a small purposely modified commercial DAR to activate the thermal pump, is here included: a maximum mismatch of 2.32% in the weak mixture mass flow rate and lower than 5% in COP between the predicted and measured data were found.

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"Hardness and Hardenability." In Steels, 335–72. 2nd ed. ASM International, 2015. http://dx.doi.org/10.31399/asm.tb.spsp2.t54410335.

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Abstract The properties of martensite and the mechanisms that govern its formation are the key to understanding hardness and the hardenability of carbon steel. Martensite is a transformation product of austenite that requires rapid cooling to suppress diffusion-dependent transformation pathways. This chapter describes the conditions that must be met for martensite to form. It discusses the role of quenching and the factors that affect cooling rate, including heat transfer, thermal diffusivity, emissivity, and section size. It defines hardenability and explains how to quantify it using the Grossmann-Bain approach or Jominy end-quench testing. It also explains how hardenability can be improved through the addition of boron, phosphorus, and other alloys.

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Тези доповідей конференцій з теми "Diffusion cooling"

Gozzini, S., Claudio Marinelli, E. Mariotti, C. Gabbanini, Alessandro Lucchesini, and L. Moi. "Vapor diffusion and atom cooling by white light." In 1992 Shanghai International Symposium on Quantum Optics, edited by Yuzhu Wang, Yiqiu Wang, and Zugeng Wang. SPIE, 1992. http://dx.doi.org/10.1117/12.130410.

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An, Bai-Tao, Jian-Jun Liu, Si-Jing Zhou, Xiao-Dong Zhang, and Chao Zhang. "Film Cooling Investigation of a Slot-Based Diffusion Hole." In ASME Turbo Expo 2016: Turbomachinery Technical Conference and Exposition. American Society of Mechanical Engineers, 2016. http://dx.doi.org/10.1115/gt2016-56175.

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This paper presents a new configuration of discrete film hole, i.e., the slot-based diffusion hole. Retaining the similar diffusion features to a traditional diffusion hole, the slot-based diffusion hole transforms the cross section of circle for the traditional diffusion hole to a flattened rectangle with respect to the equivalent cross-sectional area. Consequently, the exit width of the new hole is effectively enlarged. To verify the film cooling effectiveness, a low speed flat plate experimental facility incorporated with Pressure Sensitive Paint (PSP) measurement technique was employed to obtain the adiabatic film cooling effectiveness. The experiments were performed with hole pitch to diameter ratio p/D=6 and density ratio DR=1.38. The blowing ratio was varied from M=0.5 to M=2.5. A fan-shaped hole and two slot-based diffusion holes were tested and compared. Three-dimensional numerical simulation was employed to analyze the flow field in detail. The experimental results showed that the area averaged effectiveness of two slot-based diffusion holes is significantly higher than that of the fan-shaped hole when the blowing ratio exceeds 1.0. The slot-based diffusion hole demonstrates the great advantage over the fan-shaped hole at hole exit and maintains this to far downstream. The numerical results showed that the ends shape of the flattened rectangular cross section has large influences on film distribution patterns and downstream vortex structures. The semi-circle and straight line ends shapes lead to a bi-peak and a single-peak effectiveness pattern, respectively. The optimal ends shape can regulate the vortex structures and improve the film cooling effectiveness further.

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Bunker, Ronald S. "FILM COOLING: BREAKING THE LIMITS OF DIFFUSION SHAPED HOLES." In TURBINE-09. Proceedings of International Symposium on Heat Transfer in Gas Turbine Systems. New York: Begellhouse, 2009. http://dx.doi.org/10.1615/ichmt.2009.heattransfgasturbsyst.160.

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Guo, Dong-peng, Ren-tai Yao, and Qing-dang Qiao. "CFD Numerical Simulation of Drift Diffusion of the NPP's Cooling Tower." In 2011 5th International Conference on Bioinformatics and Biomedical Engineering (iCBBE). IEEE, 2011. http://dx.doi.org/10.1109/icbbe.2011.5781253.

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Yu, Y., C.-H. Yen, T. I.-P. Shih, M. K. Chyu, and S. Gogineni. "Film Cooling Effectiveness and Heat Transfer Coefficient Distributions Around Diffusion Shaped Holes." In ASME 1999 International Gas Turbine and Aeroengine Congress and Exhibition. American Society of Mechanical Engineers, 1999. http://dx.doi.org/10.1115/99-gt-034.

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Presented in this paper is an experimental study focusing on the effects of diffusion hole-geometry on overall film cooling performance. The study consists of three different but closely related hole shapes: (1) Shape A: straight circular hole with a 30-degree inclined injection, (2) Shape B: same as Shape A but with a 10-degree forward diffusion, and (3) Shape C: same as Shape B with an additional 10-degree lateral diffusion. The blowing ratios tested are 0.5 and 1.0. The density ratio is nominally equal to one. Measurements of the experiment use a transient liquid crystal technique that reveals local distributions of both film effectiveness (η) and heat transfer coefficient (h). The data obtained indicate that Shape C with a combined forward and lateral diffusion produces a significant increase in η and decrease in h as compared to Shape A, the baseline case. These improvements combined yield an about 30% to 50% reduction in heat transfer or thermal load on the film protected surface. Shape B, with forward diffusion only, shows a much less significant change in both film effectiveness and overall heat transfer reduction than Shape C. However, it has the lowest heat transfer coefficient in the vicinity of the injection hole among all the three hole-shapes studied. A flow visualization study using pulsed laser sheet-light reveals that Shape A and Shape B inherit quite similar flow structures. The coolant injected out of Shape C flows much closer to the protected wall than that of Shape A and Shape B.

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Hota, Sai Kiran. "Advection Diffusion Model for Particle Assisted Solar Water Evaporation." In ISES Solar World Congress 2019/IEA SHC International Conference on Solar Heating and Cooling for Buildings and Industry 2019. Freiburg, Germany: International Solar Energy Society, 2019. http://dx.doi.org/10.18086/swc.2019.46.02.

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Lin, Yuanfang, and Yuanqing Huang. "Annular coaxial waveguide CO 2 laser with rf discharge and diffusion cooling." In Photonics Asia 2002, edited by Dianyuan Fan, Keith A. Truesdell, and Koji Yasui. SPIE, 2002. http://dx.doi.org/10.1117/12.481829.

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Pun, W. M., and Dudley Brian Spalding. "INFLUENCE OF THERMAL DIFFUSION ON TRANSPIRATION COOLING AT AN AXI-SYMMETRICAL STAGNATION POINT." In International Heat Transfer Conference 3. Connecticut: Begellhouse, 2019. http://dx.doi.org/10.1615/ihtc3.1930.

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Wang, You-qing, Guiling Wu, Q. L. Chen, and Qiyang Xu. "Theoretical treatment of rf discharges in annular CO 2 lasers with diffusion cooling." In Optoelectronics '99 - Integrated Optoelectronic Devices, edited by Ernest A. Dorko. SPIE, 1999. http://dx.doi.org/10.1117/12.350658.

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Bruce-Black, Joshua E., Frederick T. Davidson, David G. Bogard, and David R. Johns. "Practical Slot Configurations for Turbine Film Cooling Applications." In ASME Turbo Expo 2009: Power for Land, Sea, and Air. ASMEDC, 2009. http://dx.doi.org/10.1115/gt2009-59674.

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Turbine component film cooling is most effective when using a continuous slot to introduce coolant to the surface. However, this is not practical due to the structural weakness that would be inherent with a continuous slot. In this study, several slot-like designs are investigated to establish the film cooling effectiveness. These slot configurations extended only a partial distance through the simulated turbine vane wall, and were fed with impinging cylindrical holes. The configurations were studied on the suction side of a scaled-up turbine vane. In this study varying slot widths, discrete and continuous slots, and diffusing the coolant flow within the slot prior to it being emitted onto the surface of the vane were investigated. Rows of discrete round and shaped holes were also tested for comparison with the slots. The study of varying slot geometries showed that decreasing the width of the slots led to a substantial increase in adiabatic effectiveness. An internal coolant diffusion technique showed promise by maintaining performance levels while potentially providing a design configuration that more readily meets structural demands in real world operating conditions. The coolant flow characteristics were also studied through the use of thermal profiles measurements. These thermal profiles showed significant mainstream ingestion on the top surface of the slot prior to the coolant emitting onto the surface of the vane.

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Звіти організацій з теми "Diffusion cooling"

Allen, Jeffrey, Robert Moser, Zackery McClelland, Md Mohaiminul Islam, and Ling Liu. Phase-field modeling of nonequilibrium solidification processes in additive manufacturing. Engineer Research and Development Center (U.S.), December 2021. http://dx.doi.org/10.21079/11681/42605.

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This project models dendrite growth during nonequilibrium solidification of binary alloys using the phase-field method (PFM). Understanding the dendrite formation processes is important because the microstructural features directly influence mechanical properties of the produced parts. An improved understanding of dendrite formation may inform design protocols to achieve optimized process parameters for controlled microstructures and enhanced properties of materials. To this end, this work implements a phase-field model to simulate directional solidification of binary alloys. For applications involving strong nonequilibrium effects, a modified antitrapping current model is incorporated to help eject solute into the liquid phase based on experimentally calibrated, velocity-dependent partitioning coefficient. Investigated allow systems include SCN, Si-As, and Ni-Nb. The SCN alloy is chosen to verify the computational method, and the other two are selected for a parametric study due to their different diffusion properties. The modified antitrapping current model is compared with the classical model in terms of predicted dendrite profiles, tip undercooling, and tip velocity. Solidification parameters—the cooling rate and the strength of anisotropy—are studied to reveal their influences on dendrite growth. Computational results demonstrate effectiveness of the PFM and the modified antitrapping current model in simulating rapid solidification with strong nonequilibrium at the interface.

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