共查询到20条相似文献,搜索用时 578 毫秒
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用混合法测定物质比热容中通常把高温物质放入低温的水中,这时损失大量的热量,增加了测量误差,为减少这部分误差,提出了把低温物质放进高温物质的实验方法和步骤。 相似文献
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混合法测定物质的比热容实验的方法:首先将被测物的质量进行测量,然后把被测物放入水中加热并测量其温度;测量量热器中水的质量,并测出其温度;再把高温被测物放进量热器中搅拌,测量出混合后的终温;然后根据比热容公式计算出被测物的比热容.然而学生实验中发现测量值始终小于理论值,这是由于整个实验过程损失了较多的热量.那么如何减小误差,本文对此提加以探讨. 相似文献
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声扰动形成的分子振动弛豫过程使得气体热容成为依赖于声频率的有效热容,导致随频率变化的声速频散和声弛豫吸收。本文基于单弛豫过程合成算法,提出一种基于两频点声速和声吸收测量值的气体平衡态热容合成方法。该方法两个测量声频点只需在声弛豫吸收显著的频率范围即可分别合成可激发气体分子内外自由度热容,并有效消除声弛豫过程对气体平衡态热容测量结果的影响。对于室温下由CO2、CH4、Cl2、N2和O2组成的多种气体,合成的气体热容值与基于Planck-Einstein公式的热力学理论计算结果相符,相比实验数据最大相对误差为3.51%。合成的转动和振动热容还可应用于气体分子几何结构、振动频率大小和混合气体摩尔分数的检测。 相似文献
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We present a new mathematical method for the analysis of heat capacity and thermal conductivity measurements by the heat pulse technique for the case of samples of finite length with a one-dimensional heat flow. In these experiments a heat pulse is produced by a heater, and the temperature is measured as a function of time at a different location on the sample. Finite length effects are taken care of in a natural way, and the thermal conductivity is obtained very simply. In addition, this method is capable of separating the heat capacities of the sample, of the heater and of the thermometer, which may be of practical importance for the case of thin samples with a small heat capacity. The mathematical analysis is based on Laplace transform techniques similar to those used for electrical transmission lines. The analysis of the experimental data is performed by calculating several moments of the temperature rise in the thermometer as a function of time. The method is particularly suitable for on-line computer experiments. 相似文献
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Based on the fractal distribution of nanoparticles, a fractal model for heat transfer of nanofluids is presented in the Letter. Considering heat convection between nanoparticles and liquids due to the Brownian motion of nanoparticles in fluids, the formula of calculating heat flux of nanofluids by convection is given. The proposed model is expressed as a function of the average size of nanoparticle, concentration of nanoparticle, fractal dimension of nanoparticle, temperature and properties of fluids. It is shown that the fractal model is effectual according to a good agreement between the model predictions and experimental data. 相似文献
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A systematic study of the Hugoniot equation of state, phase transition, and the other thermodynamic properties including the Hugoniot temperature, the electronic and ionic heat capacities, and the Gruneisen parameter for shockcompressed BeO, has been carried out by calculating the total free energy. The method of calculations combines first-principles treatment for 0 K and finite-T electronic contribution and the mean-field-potential approach for the vibrational contribution of the lattice ion to the total energy. Our calculated Hugoniot is in good agreement with the experimental data. 相似文献
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The theoretical derivation of the formula for calculating heat load, given in the treatise titled “The Theory of Heat and Mass Transfer” (edited by A.I. Leont’ev, Bauman State Technical University, Moscow, 1997) is noted to be incorrect. A corrected deduction of the formula, performed using the dimensional method, is considered. A brief review of the whole problem is given. It is noted that the “second crisis of boiling” is due to the effect of the “spheroidal” state in liquids. 相似文献
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真实比热模型中铝粉尘两相爆轰波的数值研究 总被引:1,自引:0,他引:1
采用多流体模型对铝粉尘两相爆轰波进行数值模拟,研究颗粒能量计算方法对起爆和传播过程的影响.以前的固相颗粒能量的计算一般采用固定比热方法,本文采用随温度变化的真实比热.由于铝颗粒及其产物氧化铝的比热变化很大,模拟得到的爆轰波的速度、压力和波后参数变化和采用固定比热存在较大的差异.变比热计算得到的爆轰波压力、传播速度和实验结果更加接近,而固定比热的计算方法会对这些参数造成高估.对爆轰波的形成进行研究,发现起爆距离主要受起爆能量影响,但是相对于固定比热模型,采用变比热模型得到的起爆距离较短. 相似文献
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文中采用微正则分子动力学方法模拟研究了原子数N=60到675之间的6种金原子纳米团簇从固态到液态的熔解过程,得到了势能和热容量随温度的变化关系.其结果表明,所模拟的6种团簇在熔点附近出现负热容,通过对这些团簇熔解前后的势能以及结构变化的分析,探讨了产生负热容的微观机制. 相似文献