共查询到19条相似文献，搜索用时 406 毫秒
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为获得二甲基甲酰胺(DMF)与氯仿(CHCl3)精馏分离的基础热力学数据,实验采用改进型的Rose平衡釜测定了DMF-CHCl3体系在760mmHg下的汽液相平衡数据,并分别用NRTL和Margules模型对实验数据进行关联。结果表明:实验数据满足热力学一致性的检验,且NRTL和Margules模型的计算结果与实测结果偏差小,平均绝对误差分别为0.0026和0.0010,平均相对误差分别为1.81%和1.23%,可满足工业精馏工艺过程设计的需要。 相似文献
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利用定态流法对超临界CO2流体萃取咖啡因水溶液进行研究,测定咖啡因水溶液在CO2中的溶解度数据,并采用P-R状态方程对文献中SVE体系咖啡因的溶解度数据和实验测定的溶解度数据进行关联,得到相应的二元相互作用参数．计算值和实验值比较结果表明：P—R状态方程模型计算值和实验数据吻合较好． 相似文献
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为了提高制冷剂R1234yf的循环性能,取代温室气体潜能值高的R134a,开发出性能优越的汽车空调制冷剂。本文提出了一种新型环保混合制冷剂LMR01,其由三种制冷剂R1234yf/R152a/R134a（质量百分比为80/10/10）按一定比例混合而成,并通过实验对比分析了变工况下三种制冷剂R1234yf、LMR01和R134a的热力学性能。结论如下：R1234yf和LMR01的COP比R134a分别小6.5%和2.5%;LMR01的COP相比R1234yf提升4%;R1234yf和LMR01的排气温度分别比R134a小11℃和7.5℃;R1234yf的制冷量比R134a小约7%;LMR01的制冷量和R134a相似,非常有利于直接充灌;LMR01的温度滑移很小,可看作共沸混合物;环保性能高,ODP为0,GWP为145,符合F-gas法规;可燃性低,安全性能高。对LMR01的研究可进一步提升汽车空调环保制冷剂的推广。 相似文献
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石玉冰 《濮阳职业技术学院学报》2011,24(3)
本文在Teju-Rice粘度模型的基础上,研究了非电解质水溶液二元交互作用参数的关联方法,导出了具有预测特性适用于非电解质水溶液的粘度模型。利用该模型方程可由各组分物性预测低压下各种温度和不同组成的非电解质水溶液的粘度。用该模型计算了6个体系346个数据点的不同温度和组成的二元水溶液、3个体系164个数据点的不同温度和组成的三元水溶液的粘度,计算值与实验值的总平均相对偏差分别为3.959%和4.061%,计算值与实验数据吻合很好。 相似文献
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《实验室研究与探索》2016,(9):20-23
为提高换热效率,从传热和压降的耦合角度出发,针对R125/R600a混合工质蒸发器建立了结构优化的理论数学模型,分析了管径、蒸发温度对管长优化结果的影响,并对理论模型进行验证。结果发现,R125/R600a混合工质蒸发器存在一最优管长,且最优长度随管径的增大而增加;随着蒸发温度的增大最优管长也呈现增大趋势。由此可见,小管径的蒸发器最优管长更短,结构更为紧凑,制造成本更低,而换热效率更高,同时制冷剂的流动摩擦阻力也会更小。研究结果对空调、冰箱、热泵系统的工质选用及运行工况的选择具有借鉴作用。 相似文献
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《宜宾学院学报》2019,(12):110-116
对我国2004-2015年国内游客数据建立模型,用2016年和2017年的数据检验模型的预测精度.首先对其建立灰色GM(1,1)模型并预测,模型精度为97.465%,预测平均绝对残差为182.986 4.利用无偏灰色模型对其进行修正,与灰色模型相比,预测平均绝对残差减少了0.629 4.然后又建立了传统灰色马尔科夫模型和无偏灰色马尔科夫模型,两种模型的精度都达到了99%,预测平均绝对残差分别为11.022 3和7.105 6,因此,两种模型的拟合和预测效果都大大提高.最后利用相对最优模型无偏灰色马尔科夫模型预测我国2018-2020年的国内游客数分别为:5 639.366 8百万人次、6 363.854百万人次、7 181.415 7百万人次. 相似文献
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通过利用线性与非线性最小二乘法 ,得出了关于水的密度、粘度、热容、导热系数和表面张力等物理性质的计算公式。与文献上这些性质的实验值比较 ,计算偏差较小 ;其中计算水的热容的公式比文献公式优越 ;这些物性关联式可用于工程计算 相似文献
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不同温度下纯液体和液体混合物介电常数的计算 总被引：1，自引：0，他引：1
根据液体介电常数随温度的变化规律 ,发现介电常数ε- 1 /3与温度T之间存在着线性关系ε- 1 /3=B1 B2 T对纯液体和液体混合物不同温度下介电常数的计算结果表明 ,计算值与实验值的一致性令人满意 ,平均误差0 79% .用两个数据点确定式中的两个常数 ,即可预测其它温度下的介电常数 ,对纯液体和液体混合物的预测结果表明 ,预测值接近实验值 ,平均误差 0 83 % 相似文献
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A homogeneous theoretical model is developed to predict the performance of R22 and R290 in adiabatic capillary tubes. The model is based on conservation equations of mass, momentum and energy. Metastable both liquid and two-phase flow regions are considered in the model. In metastable two-phase region, superheated liquid is introduced into the metastable mixture viscosity and two methods are presented to evaluate it. The model is validated by comparing the predicted pressure and temperature profile and mass flow rate with several investigators′ experimental data of R22 and one of its alternatives R290 reported in literature. All of the predicted mass flow rates are within ±8% of measured values. Comparisons are also made between the present model and other investigators′ models or sizing correlation. The model can be used for design or simulation calculation of adiabatic capillary tubes. 相似文献
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A micro-sized tube heat exchanger(MTHE) was fabricated, and its performance in heat transfer and pressure drop was experimentally studied. The single-phase forced convection heat transfer correlation on the sides of the MTHE tubes was proposed and compared with previous experimental data in the Reynolds number range of 500—1 800. The average deviation of the correlation in calculating the Nusselt number was about 6.59%. The entrance effect in the thermal entrance region was discussed. In the same range of Reynolds number, the pressure drop and friction coefficient were found to be considerably higher than those predicted by the conventional correlations. The product of friction factor and Reynolds number was also a constant, but much higher than the conventional. 相似文献
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Investigation of oil-air two-phase mass flow rate measurement using Venturi and void fraction sensor 总被引：6，自引：0，他引：6
INTRODUCTION Accurate measurement of multiphase fluids flow rates in the petroleum industry is of great importance. The most reliable measurement technique for multi-phase flow is separating the mixture and using con-ventional devices for measuring single-phase flow. However, in many cases the separation is not practical from both technical and economical points of view. An alternative solution is the multiphase flow me-tering system, usually consisting of a combination of devices for ph… 相似文献
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A cold-model vertical multi-tube circulating fluidized bed evaporator was designed and built to conduct a visualization study on the pressure drop of a liquid-solid two-phase flow and the corresponding particle distribution.Water and polyformaldehyde particle (POM) were used as the liquid and solid phases,respectively.The effects of operating parameters such as the amount of added particles,circulating flow rate,and particle size were systematically investigated.The results showed that the addition of the particles increased the pressure drop in the vertical tube bundle.The maximum pressure drop ratios were18.65%,21.15%,18.00%,and 21.15%within the experimental range of the amount of added particles for POM1,POM2,POM3,and POM4,respectively.The pressure drop ratio basically decreased with the increase in the circulating flow rate but fluctuated with the increase in the amount of added particles and particle size.The difference in pressure drop ratio decreased with the increase in the circulating flow rate.As the amount of added particles increased,the difference in pressure drop ratio fluctuated at low circulating flow rate but basically decreased at high circulating flow rate.The pressure drop in the vertical tube bundle accounted for about 70%of the overall pressure drop in the up-flow heating chamber and was the main component of the overall pressure within the experimental range.Three-dimensional phase diagrams were established to display the variation ranges of the pressure drop and pressure drop ratio in the vertical tube bundle corresponding to the operating parameters.The research results can provide some reference for the application of the fluidized bed heat transfer technology in the industry. 相似文献
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醚类有机污染物结构与毒性关系研究 总被引：2，自引：1，他引：1
廖立敏 《内江师范学院学报》2009,24(10):44-48
采用分子电性相互作用矢量对25种醚类化合物进行了结构表征,并与其对幼鼠的毒性值（pC50）建立定量结构一活性关系（QSAR）模型．利用多元线性回归（MLR）,得到的5变量模型（M1）复相关系数（Ri）为0．918、标准偏差（SD,）为0．128,留一法（LOO）交互校验（CV）预测值的复相关系数（R^2CV1）为0．845、标准偏差（SDcv1）为0．175．用逐步回归的方法筛选3变量进行建模（M2）,复相关系数（R2^2）为0．912、标准偏差（SD2）为0．125,留一法（LOO）交互校验（CV）预测值的复相关系数（R^2CV2）为0．871、标准偏差（SDcv2）为0．152．结果表明模型具有良好的预-测能力与稳定性． 相似文献
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Succinic acid serves as an important intermediatefor producing a wide variety of industrially importantchemicals such as butanediol, tetrahydrofuran,γ-bu-tyrolactone,n-methyl pyrrolidinone, 2-pyrrolidinine,paints, polymers, plastics, food additives and c… 相似文献
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In this paper, a new ternary non-azeotropic mixture of HFC-161/125/143a (0.15/0.45/0.40 in mass fraction), as a promising
mixed refrigerant to R404A, is presented. The ozone depletion potential (ODP) of the new refrigerant is zero and its basic
thermodynamic properties are similar to those of R404A, but its global warming potential (GWP) is much smaller than those
of R507A and R404A. Meanwhile, theoretical calculations show that, under the working condition I (the average evaporation
temperature: −23 °C, the average condensing temperature: 43 °C, the superheat temperature: 28 °C, the subcooling temperature:
5 °C), the volumetric refrigerating effect and specific refrigerating effect of the new mixture are 2.33% and 15.48% higher,
respectively, than those of R404A. The coefficient of performance (COP) of the new mixture is 5.19% higher than that of R404A
and the pressure ratio of the new mixture is 0.82% lower than that of R404A. Equally, under the working condition II (the
average evaporation temperature: −40 °C, the average condensing temperature: 35 °C, the superheating temperature: 30 °C, the
subcooling temperature: 5 °C), the volumetric refrigerating effect and specific refrigerating effect of the new mixture are
2.24% and 20.58% higher, respectively, than those of R404A. The COP of the new mixture is 4.60% higher than that of R404A
and the pressure ratio of the new mixture is similar to that of R404A. The performances of the new mixture and R404A are compared
in a vapor compressor refrigeration apparatus originally designed for R404A under several working conditions (condensing temperatures:
35–45 °C, evaporation temperatures: −40–−20 °C). Experimental results show that the new mixture can obtain a higher COP, by
6.3% to 12.1%, and a lower pressure ratio, by 1.8% to 6.6%, compared to R404A; although the discharge temperature of the new
mixture is slightly higher than that of R404A. The advantages of the new mixture will be further verified in the actual system. 相似文献
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为了避免股票市场中因子之间复杂非线性关系引起的多因子选股模型过拟合现象,基于因子偏离度对股票因子数据进行分析,筛选影响股票收益率的有效因子,通过梯度提升树对股票影响因子的权值进行不断调整和分析,建立一个DEV-GBDT量化选股模型,再根据基于因子偏离度的GBDT多因子选股模型的预测结果进行模拟交易,以沪深300指数成分股2010年1月1日—2019年7月31日数据为例进行实证分析。实验结果表明,DEV-GBDT选股模型的年化收益率达26.14%,比传统GBDT选股模型提高8.61%。基于因子偏离度的GBDT多因子选股模型能有效识别股市影响因子,提高股票预测准确度,帮助投资者获得超额收益。 相似文献