多块修正技术——块修正技术的一般化推广

块修正技术可以大大加速数值法求解传热传质与流动问题时的收敛速度,双块修正技术使许多问题的收敛速度进一步提高.本文将块修正技术作了一般化推广,推导了多块(任意块数)修正技术的计算公式,研究了修正块数对不同问题收敛速度的影响,并找得了最佳修正块数与所研究问题的性质及网格结点数之间的一般关系.文中还研究了块修正与行TDMA迭代扫描次数之间的相互配合关系,并确定了每次块修正技术之后最佳的行(或列)TDMA迭代扫描次数.     

密闭爆发器实验中热散失修正方法研究

介绍了国内外密闭爆发器热散失修正方法的现状,分别分析了克劳-格里姆肖法、压力损失及其修正方法和发射药燃烧全过程压力曲线的修正方法及密闭爆发器实验过程中热散失修正研究方法的优缺点,提出了学术构想与思路。     

数值方法在平板准稳态法测量有机玻璃热物性实验中的应用

利用数值方法对平板准稳态法实验获得的有机玻璃试样的导热率及比热容进行了修正。在修正的过程中,使用了步进法,以计算曲线的热、冷端温差及其热、冷端温升速率与实验曲线相等为计算终止条件,最终获得修正的导热率及比热容。其修正幅度分别为1.7%和2. 8%,且修正后的数值均在相关文献的报道范围之内。     

合成硝基麝香三元体系的固液平衡

通过试验测定了合成硝基麝香二元体系的固液平衡数据,回归并修正了UNIFAC模型的相互作用参数,使UNIFAC模型具有更高的预测功能;为了评价修正后的UNIFAC模型对合成硝基麝香三元体系的预测功能,利用试验测定的溶解度数据和修正后的UNIFAC模型计算值进行了比较,结果表明相互作用参数的修正是理想的.     

基于相对压力冲量的火药能量释放规律

为了研究火药实际能量的释放规律,通过对几何燃烧模型的分析和修正,建立了相对压力冲量形式的修正模型,并在不同装填密度、不同类型的火药和定容、变容条件下进行了理论和实验分析.结果表明,修正模型更好地体现了火药实际能量的释放规律,说明修正模型所建立的理论及处理方案是合理的.     

换热管中心距增大后对管板计算厚度的修正

比照GB 150标准中有关开孔削弱系数的计算公式,分析论证了换热器管板强度削弱系数与换热管中心距之间的相互关系,推导得出了管板计算厚度修正式和修正系数的计算方法,通过实例说明了对管板计算厚度进行修正的意义。提出了GB 151换热器标准中增加"当换热管中心距增大后,允许对管板计算厚度进行修正"的建议。     

密闭爆发器实验中发射药燃烧全过程压力曲线的修正方法

分析了造成密闭爆发器实验时压力损失的两个因素,从造成压力曲线损失的理论关系式出发,无须测量密闭爆发器的壁温曲线,仅根据压力曲线得到了一种适用于火药燃烧的全过程的压力修正方法.该方法能反映出燃气热力参数及余容对压力损失的影响.通过爆发器实验,与传统的修正方法比较,不仅能修正得到火药力和余容,还能修正燃烧全过程的压力曲线以及燃速曲线.新建立的修正方法简单,更具有实用价值.     

基于压力脉冲理论的通风阻力误差修正

针对气压计基点测定法测定矿井通风阻力时存在较大误差的现象,对阻力测定操作步骤及计算公式进行详细分析,根据长期的现场操作经验和对大量测试数据的处理,明确了阻力误差存在的主要原因,在考虑井下压力脉冲的影响下,提出用修正模型修正原有的阻力计算公式,用具体实例对修正模型进行验证,结果表明修正后的通风阻力精确度有了显著的提高。     

入口温度对换热器污垢热阻的影响及其修正

为提高污垢热阻测量精度,在分析污垢热阻温差监测法的基础上,研究了循环冷却水入口温度对换热器污垢热阻的影响。通过对污垢热阻测量模型参数进行推算,利用最小二乘法原理对污垢热阻数据进行处理,确定了在线测量污垢热阻的修正方法。修正前污垢热阻数据表明了循环冷却水入口温度与换热器污垢热阻之间呈反比例的关系。针对无垢和有垢两种情况,分别对污垢热阻测量模型进行了修正,结果表明:对于某电厂现场数据和实验室数据,修正效果均使污垢热阻测量值更加准确,证明了修正公式的可靠性。     

流动沸腾传热渐进模型的一种修正形式

在对文献模型进行分析的基础上,提出流动沸腾传热渐进模型的一个修正形式。探讨了该形式的合理性,并对该修正形式与实验数据的吻合情况进行了检测。结果显示,该修正形式能较好地预测窄矩形流道内流动沸腾传热的传热系数     

Determination of the thermal diffusivity and thermal conductivity of layers of polypropylene and polyamide fibers

Conclusions The proposed procedure for measuring and calculating coefficients of thermal diffusivity and thermal conductivity makes it possible to raise considerably the accuracy in determining these quantities for fibrous materials.Measurement of the thermophysical characteristics of polypropylene and polyamide staple fibers has shown that, while in air the thermal conductivity of the fibrous mass is close to the arithmetically mean value from the thermal conductivities of air and fiber, the sorption of organic substances apparently markedly increases the effective viscosity in the system.Translated from Khimicheskie Volokna, No. 4, pp. 38–40, July–August, 1983.     

液体有机物导热系数的估算

在计算液体导热系数的Weber方程和Sato关系式的基础上,根据对有机物液体导热系数影响因素的分析研究,提出了估算有机物导热系数的计算模型;利用该模型计算了22个体系74个数据点的有机物液体的导热系数,计算值与实验值的总平均相对偏差3.18%,计算准确性优于文献方法;计算结果表明,利用被估算物质的摩尔质量、临界温度、正...     

加压下液体物质导热系数的计算

根据液体物质的导热系数与其对比温度和对比压力的关系的文献数据,导出了估算加压下液体有机物导热系数的计算模型;利用该模型计算了9种液体物系223个数据点的导热系数数据,计算值与实验值的总平均相对误差为3.349%,计算值与实验数据吻合很好,计算准确性优于文献方法;本文方法简单方便,只需要物质的临界温度、临界压力和低压下物...     

测油脂导热系数的研究新进展

简要介绍测定油脂导热系数在科学研究和工程设计方面的意义,系统综述目前测定液体导热系数的方法,如:理论推导、稳态法及非稳态法等,并对这些方法的优缺点进行了论述和分析;最后指出了油脂导热系数测定方法存在的问题及其发展趋势。测量实践表明:瞬态平面热源法测量准确可靠,具有巨大的应用前景。     

Effect of humidity on the thermal conductivity of porous zirconia ceramics

This study focuses on the role of the water content on the effective thermal conductivity of porous ceramics placed in different conditions of relative humidity. Fully stabilized zirconia samples with variation in the capacity to take up water were prepared by varying the temperature of the thermal treatment. The pore volume fraction of the dried samples decreases from 56% down to 30%. Thermal conductivity measurements were made on samples placed in a chamber where the relative humidity was fixed between 3% and 99%. For all samples, the experimental values of the effective thermal conductivity increase significantly with the water content. Experimental results agree closely to analytical predictions based on the upper limit of the Hashin and Shtrikman expressions for calculating the thermal conductivity of the pores (constituted by air and water) and Landauer's effective medium expression for calculating the effective thermal conductivity of the material.     

热探针法测量陶瓷粉末导热系数的实验研究

以Al2O3粉末为例,在分析探针法测量原理的基础上,用热探针法对Al2O3粉末的导热系数进行测量,研究在不同含水率和温度下Al2O3粉末导热系数的变化情况。试验结果发现,Al2O3粉末的导热系数随着秸秆密度,温度和含水率的增加而增加,并基本呈线性关系。     

有机物水溶液导热系数的关联

根据对有机物水溶液导热系数影响因素的分析,在Horvath液体导热系数关系式的基础上,导出了估算有机物水溶液导热系数的计算模型;利用该模型计算了14个体系中447个数据点的不同温度和组成的二元水溶液导热系数;结果表明,计算值与实验数据吻合很好,其与实验值的总平均相对偏差为1.03％,计算准确性优于文献方法。本文计算方法简单方便,只需知道水溶液各组分的临界温度、临界体积和导热系数数据,就可以直接预测各种温度和组成的有机物水溶液混合物的导热系数。     

Comparative Method and Choice of Standards for Thermal Conductivity Determinations

An improved version of the comparative method thermal conductivity apparatus was designed. Its accuracy was determined by measuring the conductivity of alumina with standards made of the same alumina and by cross-checking the conductivities of alumina, forsterite, Pyroceram Code 9606, and zirconia. The thermal stabilities of Pyroceram Code 9606 and zirconia were examined to establish their values as thermal conductivity reference materials. It was concluded that: (1) With this apparatus accurate thermal conductivity data can be obtained and (2) Pyroceram Code 9606 can be recommended for use as a primary standard for the low thermal conductivity range.     

STUDY ON HEAT TRANSFER CHARACTERISTICS AND DRYING EXPERIMENT OF SINGLE SEED

Studies in the seeds drying field are presently aimed at macro heat and mass transfer of the whole seeds heap, but for drying of life materials, such as the seeds, the control of their internal temperature is essential. Therefore, the study of the heat transfer process of the internal single seed is pressed. This paper experimentally studied the measuring method of the thermal conductivity for the single broad bean seed, and then obtained an interrelated curve between the thermal conductivity and water contents for single seed. During the drying, the internal temperature could be derived from the surface temperature of the seeds and it contributed to deciding the safe drying temperature of the seeds. Then we derived the thermal conductivity of the seed coat and the cotyledon by testing and calculating the temperature fields of the inner cross section in the seed, which quantitatively indicated the difference of the thermal resistance between the seed coat and the cotyledon. In order to conquer the thermal resistance, appropriate drying conditions could increase the drying speed on the condition that the activity of seeds was maintained. In this paper, the Chinese cabbage seeds are selected to experimentally validate this method through the two-pass infrared radiation vibrated dryer and produces some satisfactory results. These results will contribute to the improvement of the drying quality and the efficiency of the life materials, such as the seeds.     

耐硫甲烷化催化剂的有效导热系数研究

在常压空气气氛下采用稳态法测试了KD306型耐硫甲烷化催化剂的有效导热系数,运用Woodside随机模型,建立了反应状态下有效导热系数的计算模型。研究表明,该催化剂有效导热系数较大,温度、压力影响明显,组成影响较小。