排序方式: 共有21条查询结果,搜索用时 15 毫秒
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Brent A. Anderson Spring Sun Ferruh Erdogdu R. Paul Singh 《International Journal of Refrigeration》2004,27(1):156
Recently, several manufacturers of domestic refrigerators have introduced models with “quick thaw” and “quick freeze” capabilities. In this study, the time required for freezing and thawing different meat products was determined for five different models of household refrigerators. Two refrigerators had “quick thaw” compartments and three refrigerators had “quick freeze” capabilities. It was found that some refrigerator models froze and thawed foods significantly faster than others (P<0.05). The refrigerators with the fastest freezing and thawing times were found to be those with “quick thaw” and “quick freeze” capabilities. Heat transfer coefficients ranged from 8 to 15 Wm−2K−1 during freezing, and the overall heat transfer coefficients ranged from 5 to 7 Wm−2 K−1 during thawing. Mathematical predictions for freezing and thawing time in the refrigerators gave results similar to those obtained in experiments. With the results described, manufacturers can improve their design of refrigerators with quick thawing and freezing functions. 相似文献
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Axi-symmetric approach in vertical cans lead to 2-dimensional (2D) model with shorter computational times. For horizontal cans containing liquids, this approach is not possible due to internally evolved natural convection. If an assumption is made to neglect gravitational effect in horizontal direction, it may be possible to use a 2D model. Therefore, the objective of this study was to evaluate this approach numerically and experimentally. In simulations, continuity, energy and momentum equations were solved in 2D and 3D using Ansys CFX 12.1 for horizontal cans containing water and another viscous liquid. In experiments, water filled cans were prepared, and temperature data were compared with simulation results. The results demonstrated the possible use of 2D approach in modelling for liquid containing horizontal cans with significant reduction in computational times. Optimization algorithms of simulation programs are also expected to be used in combination with simulation studies since computation times are reduced significantly. 相似文献
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Presence of headspace during canning is required since an adequate amount allows forming vacuum during the process. Sealing technology may not totally eliminate all entrapped gases, and headspace might affect heat transfer. Not much attention has been given to solve this problem in computational studies, and cans, for example, were mostly assumed to be fully filled with product. Therefore, the objective of this study was to determine velocity and temperature evolution of water and air in cans during heating to evaluate the relevance of headspace in the transport mechanism. For this purpose, canned water samples with a certain headspace were used, and required governing continuity, energy, and momentum equations were solved using a finite volume approach coupled with a volume of fluid element model. Simulation results correlated well with experimental results validating faster heating effects of headspace rather than insulation effects as reported in the literature. The organized velocity motions along the air-water interface were also shown. Practical Application: Canning is a universal and economic method for processing of food products, and presence of adequate headspace is required to form vacuum during sealing of the cans. Since sealing technology may not totally eliminate the entrapped gases, mainly air, headspace might affect heating rates in cans. This study demonstrated the increased heating rates in the presence of headspace in contrast with some studies in the literature. By applying the effect of headspace, required processing time for thermally processed foods can be reduced leading to more rapid processes and lower energy consumptions. 相似文献
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Ferruh Özbudak Burcu Gülmez Temur 《Applicable Algebra in Engineering, Communication and Computing》2007,18(5):433-443
We study the general fibre product of any two Kummer covers of the projective line over finite fields. Under some assumptions,
we obtain an involved condition for the existence of rational points in the fibre product over a rational point of the projective
line so that we determine the exact number of the rational points. Using this, we construct explicit examples of such fibre
products with many rational points. In particular we obtain a record and a new entry for the table (http://www.science.uva.nl/~geer/tables-mathcomp15.ps).
相似文献
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During processing of canned mixtures of solid–liquid foods, conduction and convection occur simultaneously. The literature lacks in a complete simulation study where a large number of solids are dispersed in the liquid phase, e.g. canned peas. Therefore, the objectives of this study were to determine temperature changes inside a can containing solid–liquid food mixtures. For this purpose, dispersed stationary solids (canned peas in water) in a 2D (axi-symmetrical) configuration were applied. Ansys V11 (Ansys Inc., Canonsburg, PA) was used to solve continuity, energy and momentum equations. For experiments, canned pea samples were prepared in 500 g cans, and heating process was conducted in a retort under pasteurization conditions at ≈98 °C. Temperature changes were measured using needle type thermocouples, and simulation results were validated against experimental data. This study is expected to be a significant contribution to the literature for further optimization studies and to form basis of an industrial project to improve canning process of solid–liquid mixtures. 相似文献
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Besides traditional atmospheric frying, high pressure (super-atmospheric) frying might be an alternative approach to the frying of food products. In this study, convective heat transfer coefficient during atmospheric and high pressure frying was compared. For this purpose, a pressure cooker was modified to allow the immersion of a sample into frying oil under pressure and temperature measurement of sample and oil. Heat transfer coefficient versus frying time was determined on potato slabs using changes of total mass of the experimental set-up. At the pressure of 2 bar, the results showed an almost doubled heat transfer coefficient compared to the atmospheric pressure frying. The knowledge of heat transfer coefficient during pressure frying is expected to allow accurate determination of temperature distribution and hence the kinetic calculations to lead to development of an alternative frying process. 相似文献
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Hybrid multi-objective shape design optimization using Taguchi’s method and genetic algorithm 总被引:1,自引:0,他引:1
Ali R. Yıldız Nursel Öztürk Necmettin Kaya Ferruh Öztürk 《Structural and Multidisciplinary Optimization》2007,34(4):317-332
This research is based on a new hybrid approach, which deals with the improvement of shape optimization process. The objective
is to contribute to the development of more efficient shape optimization approaches in an integrated optimal topology and
shape optimization area with the help of genetic algorithms and robustness issues. An improved genetic algorithm is introduced
to solve multi-objective shape design optimization problems. The specific issue of this research is to overcome the limitations
caused by larger population of solutions in the pure multi-objective genetic algorithm. The combination of genetic algorithm
with robust parameter design through a smaller population of individuals results in a solution that leads to better parameter
values for design optimization problems. The effectiveness of the proposed hybrid approach is illustrated and evaluated with
test problems taken from literature. It is also shown that the proposed approach can be used as first stage in other multi-objective
genetic algorithms to enhance the performance of genetic algorithms. Finally, the shape optimization of a vehicle component
is presented to illustrate how the present approach can be applied for solving multi-objective shape design optimization problems. 相似文献