共查询到20条相似文献,搜索用时 46 毫秒
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采用过氧化物交联剂动态硫化聚丙烯(PP)/三元乙丙橡胶(EPDM)/苯乙烯-乙烯-丁烯-苯乙烯(SEBS)三元体系,并研究了交联剂对三元体系性能的影响.结果表明,随着过氧化物交联剂用量增加,体系的拉伸强度和熔体流动速率增加,断裂伸长率和撕裂强度降低,压缩永久形变呈现先降低然后略有增加的变化趋势,当交联剂用量为8份时达到最小值(70℃和125℃分别为21.9%和28.6%),比未添加SEBS时分别降低12%和23.1%,说明复配SEBS对弹性改善效果明显;体系表观黏度随着剪切速率的增加而降低,呈现剪切变稀现象,动态硫化后的表观黏度比未硫化时有明显降低.所得材料中检测不到卤素和重金属,符合无卤化和绿色环保要求. 相似文献
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《Drying Technology》2013,31(5):899-916
Abstract A thin-layer superheated steam drier was constructed with the objective of determining the drying characteristics, drying rates, and the effect of superheated steam on product quality in thin-layers. Results from superheated steam drying experiments with sugar-beet pulp, potatoes, Asian noodles, and spent grains indicate that drying times and rates increase with increasing steam temperature. For sugar-beet pulp it was also found that these changes were more significant than increases seen by hot-air drying under the same conditions and that drying rates were not affected by velocity for hot air but were increased for superheated steam. When quality aspects were examined, superheated steam dried Asian noodles saw both beneficial changes to recovery, adhesiveness, and gumminess while parameters of maximum cutting stress, resistance to compression, and surface firmness saw deleterious effects. Spent grains saw high levels of starch gelatinization and retention of fibre content. 相似文献
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A thin-layer superheated steam drier was constructed with the objective of determining the drying characteristics, drying rates, and the effect of superheated steam on product quality in thin-layers. Results from superheated steam drying experiments with sugar-beet pulp, potatoes, Asian noodles, and spent grains indicate that drying times and rates increase with increasing steam temperature. For sugar-beet pulp it was also found that these changes were more significant than increases seen by hot-air drying under the same conditions and that drying rates were not affected by velocity for hot air but were increased for superheated steam. When quality aspects were examined, superheated steam dried Asian noodles saw both beneficial changes to recovery, adhesiveness, and gumminess while parameters of maximum cutting stress, resistance to compression, and surface firmness saw deleterious effects. Spent grains saw high levels of starch gelatinization and retention of fibre content. 相似文献
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The effect of superheated steam vacuum drying (SSVD) on the drying time and mechanical properties of rubberwood was studied. Rubberwood boards with dimensions of 1000 mm × 76.2 mm × 25.4 mm were dried at 86.7–89.3 kPa vacuum pressure (14.6–12.0 kPa absolute) and temperatures of 60, 70, and 80°C. Superheated steam at 110°C was injected intermittently to relieve stress buildup in wood and eliminate cracking. The prong test was used to evaluate the initial acceptability of the dried wood and the mechanical properties of wood were measured. From this study, the total drying time was reduced from 168 h to less than 20 h (MC reduction from 0.80 to 0.06 db). In addition, compared to the reference values shown in the parentheses, the shear parallel-to-grain, the compression parallel-to-grain, the compression perpendicular-to-grain, the modulus of rupture (MOR), the modulus of elasticity (MOE), and the hardness for the optimum drying temperature of 70°C were 28.87 (11.0) MPa, 59.09 (32.0) MPa, 21.09 (5.0) MPa, 101.97 (66.0) MPa, 9838.5 (9240.0) MPa, and 6475 (4350) N, respectively. Thus, the vacuum-dried wood showed a 32% increase in hardness, a 12% increase in compression parallel-to-grain, and an 88% increase in shear parallel-to-grain. 相似文献
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《Drying Technology》2013,31(10):2231-2253
Abstract A two-dimensional mathematical model developed for vacuum-contact drying of wood was adapted to simulate superheated steam vacuum drying. The moisture and heat equations are based on the water potential concept whereas the pressure equation is formulated considering unsteady-state mass conservation of dry air. A drying test conducted on sugar maple sapwood in a laboratory vacuum kiln was used to infer the convective mass and heat transfer coefficients through a curve fitting technique. The average air velocity was 2.5 m s?1 and the dry-bulb temperature varied between 60 and 66°C. The ambient pressure varied from 15 to 11 kPa. Simulation results indicate that heat and mass transfer coefficients are moisture content dependent. The simulated drying curve based on transfer coefficients calculated from boundary layer theory poorly fits experimental results. The functional relation for the relative permeability of wood to air is a key parameter in predicting the pressure evolution in wood in the course of drying. In the case of small vacuum kilns, radiant heat can contribute substantially to the total heat transfer to the evaporative surface at the early stages of drying. As for conventional drying, the air velocity could be reduced at the latter stage of drying with little or no change to the drying rate. 相似文献
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A two-dimensional mathematical model developed for vacuum-contact drying of wood was adapted to simulate superheated steam vacuum drying. The moisture and heat equations are based on the water potential concept whereas the pressure equation is formulated considering unsteady-state mass conservation of dry air. A drying test conducted on sugar maple sapwood in a laboratory vacuum kiln was used to infer the convective mass and heat transfer coefficients through a curve fitting technique. The average air velocity was 2.5 m s-1 and the dry-bulb temperature varied between 60 and 66°C. The ambient pressure varied from 15 to 11 kPa. Simulation results indicate that heat and mass transfer coefficients are moisture content dependent. The simulated drying curve based on transfer coefficients calculated from boundary layer theory poorly fits experimental results. The functional relation for the relative permeability of wood to air is a key parameter in predicting the pressure evolution in wood in the course of drying. In the case of small vacuum kilns, radiant heat can contribute substantially to the total heat transfer to the evaporative surface at the early stages of drying. As for conventional drying, the air velocity could be reduced at the latter stage of drying with little or no change to the drying rate. 相似文献
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本文通过室内单管模型对某水敏感性稠油油藏的现场油砂进行了不同流体岩心流动实验,对比了岩心在相同温度条件下的热水、饱和蒸汽、过热蒸汽三种不同流体下的渗透率恢复率。通过X衍射分析,研究了岩心中粘土矿物与过热蒸汽作用下的变化规律。实验结果表明:过热蒸汽具有永久改善水敏性储层渗透率的特点,对水敏性储层渗透率恢复明显高于热水、普通蒸汽。在室内研究的基础上,进行了注过热蒸汽吞吐开发矿场试验,对比前期普通蒸汽开发效果,注过热蒸汽吞吐可提高日产量4~6倍,效果显著。 相似文献
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This exploratory study evaluated the possibility of drying 50-mm-thick western red cedar with superheated steam. Since there are no industrial facilities in Canada drying western red cedar with superheated steam, the study was designed to explore the potential of this technology in terms of lumber quality, moisture content distribution, and drying time. The experiments showed that the 50-mm-thick product can be dried in less than three days without jeopardizing lumber quality (in comparison with the two weeks that is currently required in conventional kilns), and the percentage of pieces that remained wet after drying was within the 10% to 15% range that is typically tolerated in industry. 相似文献
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Modeling of the transfer between a porous medium and its surroundings is commonly made using transfer coefficients that are theoretically well known only under boundary layer hypothesis. The resolution of Navier–Stokes equations in the surroundings of the product in order to get information about the boundary conditions avoids the classical use of these transfer coefficients. In this article, a modeling and a simulation of superheated steam drying of a rectangular piece of porous medium is proposed using a coupling method between a porous medium code and a CFD software. In some cases of superheated steam drying, even if a thermal boundary layer exists, a mass boundary layer cannot be defined. Moreover, boiling occurs during the process. An analysis of the interfacial transfer coupled with the analysis of the temperature, moisture content, and pressure profiles inside the porous medium is proposed. 相似文献
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Arnaud Erriguible Philippe Bernada Fr d ric Couture Michel Roques 《Drying Technology》2006,24(8):941-951
Modeling of the transfer between a porous medium and its surroundings is commonly made using transfer coefficients that are theoretically well known only under boundary layer hypothesis. The resolution of Navier-Stokes equations in the surroundings of the product in order to get information about the boundary conditions avoids the classical use of these transfer coefficients. In this article, a modeling and a simulation of superheated steam drying of a rectangular piece of porous medium is proposed using a coupling method between a porous medium code and a CFD software. In some cases of superheated steam drying, even if a thermal boundary layer exists, a mass boundary layer cannot be defined. Moreover, boiling occurs during the process. An analysis of the interfacial transfer coupled with the analysis of the temperature, moisture content, and pressure profiles inside the porous medium is proposed. 相似文献