Low-temperature heat capacities and standard molar enthalpy of formation of N-methylnorephedrine C11H17NO（s）

This paper reports that low-temperature heat capacities of N-methylnorephedrine C11H17NO（s） have been measured by a precision automated adiabatic calorimeter over the temperature range from T=78K to T=400K. A solid to liquid phase transition of the compound was found in the heat capacity curve in the temperature range of T=342-364 K. The peak temperature, molar enthalpy and entropy of fusion of the substance were determined. The experimental values of the molar heat capacities in the temperature regions of T=78-342 K and T=364-400 K were fitted to two poly- nomial equations of heat capacities with the reduced temperatures by least squares method. The smoothed molar heat capacities and thermodynamic functions of N-methylnorephedrine C11H17NO（s） relative to the standard refer- ence temperature 298.15 K were calculated based on the fitted polynomials and tabulated with an interval of 5 K. The constant-volume energy of combustion of the compound at T=298.15 K was measured by means of an isoperibol precision oxygen-bomb combustion calorimeter. The standard molar enthalpy of combustion of the sample was calculated. The standard molar enthalpy of formation of the compound was determined from the combustion enthalpy and other auxiliary thermodynamic data through a Hess thermochemical cycle.

Speed of Sound and Ideal-Gas Heat Capacity at Constant Pressure for HFC-125

The gaseous speed of sound, the ideal gas heat capacity at constant pressure, and the second Virial coefficient were determined for pentafluoroethane (HFC 125). A total of 49 data points of speed of sound for gaseous HFC 125 were measured for temperatures from 273 to 313 K and pressures from 32 to 479 kPa with a cylindrical, variable path acoustic interferometer. The ideal gas heat capacity at constant pressure and the second acoustic Virial coefficient were determined over the temperature range from the speed of sound measurements and were correlated as functions of temperature. An analytical expression for the second Virial coefficient derived using the square well intermolecular potential model was compared with the data.

Studies of Thermodynamic Properties and Relative Stability of Polybrominated Xanthones by Density Functional Theory

The thermodynamic properties of xanthone（XTH） and 135 polybrominated xanthones（PBXTHs） in the standard state have been calculated at the B3LYP/6-31G＊ level using Gaussian 03 program.The isodesmic reactions were designed to calculate the standard enthalpy of formation（△fHθ） and standard free energy of formation（△fGθ） of PBXTH congeners.The relations of these thermodynamic parameters with the number and position of Br atom substitution（NPBS） were discussed,and it was found that there exist high correlation between thermodynamic parameters（entropy（Sθ）,△fHθ and △fGθ） and NPBS.According to the relative magnitude of their △fGθ,the relative stability order of PBXTH congeners was theoretically proposed.The relative rate constants of formation reactions of PBXTH congeners were calculated,Moreover,the values of molar heat capacity at constant pressure（Cp,m） from 200 to 1000 K for PBXTH congeners were also calculated,and the temperature dependence relation of them was obtained,suggesting very good relationships between Cp,m and temperature（T,T^1 and T^2） for almost all PBXTH congeners.

DFT Study on Some Properties of Polybrominated Phenoxathiin 10-Oxides

With the B3LYP calculation method of density functional theory（DFT）and the 6-31G＊ basis set,full optimization calculation was made for phenoxathiin10-oxide（PTO）and 135 polybromine phenoxathiin 10-oxides（PBPTOs）with the Gaussian 03 program and molar heat capacity in constant volume（CVθ）value of each molecule in the standard state was obtained.The relation between CVθ and the substitution position and number of bromine atom（NPBS）was studied,and the results indicated good correlation（R2 = 1.000）between CVθ and NPBS of PBPTO compounds.Based on the output file of Gaussian 03 program,molar heat capacity at constant pressure（Cp,m）of PBPTO compounds from 200 to 1,000 K was calculated with the statistical thermodynamics program,and the correlation equation between Cp,m and temperature（T,T-1 and T-2）was obtained with the least-squares method,and the correlation coefficient of the correlation equation（R2）was 1.000.In addition,based on the partition function of each molecule calculated by vibration analysis,the relative rate constant of formation of each molecule was calculated.

用微扰理论计算磁场对低浓度磁性胶粒体系热力学性质的影响

The interaction of magnetic colloidal particles includes the interaction of colloidal particles and the interaction of the moment of magnetism.The interaction of the moment of magnetism is regard as perturbation.According to the low density system of magnetic colloidal particles in water,a theoretic model is set up based on perturbation theory.The relations between internal energy,specific heat of magnetic colloidal particles system and temperature,density of colloidal particles are calculated.The calculated results are useful in explaining the magnetic memory effect.

变容积量热器法测量液体比热容实验研究

基于准稳态理论，建立了一种可以实时改变工作腔体容积的非流动型量热器，并自行搭建了比热容测量系统。通过测量温度为273．15～293．15K常压下纯水的比热容，对实验系统的测量精度及可靠性进行了检测。结果显示．该实验系统的相对偏差绝对平均值为0．35％，验证了该套实验系统设计原理的正确性及实验装置的准确性。此外，测量了4种配比下．含油制冷剂R134a在温度为273．15～293．15K，其饱和液体的比定压热容和比定容热容。

气体定压比热容测量实验教学系统开发

为了满足大学工程热力学课程的实验教学要求,针对传统实验装置因加热温差范围过大而导致实验结果不准确的问题,设计开发了一套新型气体定压比热容测定实验系统.设计的新型气体定压比热容测定实验系统通过结合预热段、保温、两次测量算法改进等方式,使实验结果更加准确可靠,真实地反映了实验原理,具有较高的精度,完全满足本科研究性实验教学要求.

流体液相定压比热容方程

An equation for the specific heat capacity of liquids which contains four constants hasbeen developed in this paper by means of analysis of data of heat capacities and properties offunction curves and its form is simple and convenient for use. It is testified that the equationhas good extrapolating property and so cp values of subcooled liquids which are deficient canbe predicted by that of saturated liquids and vice versa.

1,1,1,2,3,3,3─七氟丙烷的气相声速

分析了气相声速与理想气体比定压热容的热力学关系，用超声变程干涉仪测定了１，１，１，２，３，３，３－七氟丙烷（ＨＦＣ－２２７ｅａ）的 ７２组气相声速值，温度范围 ２７３－３３３ Ｋ，压力范围 ２６－３１５ ｋＰａ，测量不确定度小于 ０．０５％。根据这些实验数据，确定了ＨＦＣ－２２７ｅａ的理想气体比定压热容和声速第二维里系数，并分别拟合得到了与温度的函数，理想气体比定压热容的不确定度小于 ０．５％．使用方阱势能模型导出了 ＨＦＣ－２２７ｅａ的第二维里系数，并与文献值进行了比较。

DSC法测定联苯的热力学性质与纯度

利用差示扫描量热仪（DSC）对联苯的熔点、熔融焓、结晶焓进行测定，实验结果显示在不同升温／降温速率下DSC法对联苯的熔点的测定结果影响较大，而对熔融焓和结晶焓并无影响．测定联苯固体比定压热容（283．15～323．15K）、液体比定压热容（363．15～443．15K），并将比定压热容与温度进行关联，导出计算比定压热容的方程．同时介绍利用DSC测得联苯纯度的方法．

HFC-125气相声速和理想气体比定压热容的研究

分析了气相声速与理想气体比定压热容的热力学关系 ,用超声变程干涉仪测定了HFC -12 5的 4 9组气相声速值 ,温度范围 2 73- 313K ,压力范围 32 - 4 79kPa。根据这些实验数据 ,获得了HFC - 12 5的理想气体比定压热容和声速第二维里系数 ,并分别拟合得到了理想气体比定压热容和声速第二维里系数与温度的函数关系。使用方阱势能模型导出了HFC - 12 5的第二维里系数 。

空气比热容比的标准值与测量的误差

在绝热膨胀过程中,用电磁阀、大口径管(φ≥4mm)迅速放气和关闭。对空气的比热容比γ的标准值进行了详细的论证计算1.3990<γ<1.4025,并对实测值的误差进行了分析讨论。

混合溶液等压比热容的简便测量系统及修正

液体比热容是反映液体特性的重要参量之一,是了解和利用液体的依据。纯净液体的比热容可通过查询获得,而混合溶液的比热容基本需要通过测量获得。本文利用水壶的保温特性,设计了一种可利用电加热法测量混合溶液等压比热容的系统,并通过分析实验中的温度变化获得了本测量系统的修正值,最后利用该系统测量了不同浓度盐溶液的等压比热容。

多元混合理想气体有关问题的研究

用类比推理的方法讨论了多元混合理想气体有关的物理量和方程,给出了一些有意义的结果.

真实气体等压热容的关联

根据热力学原理,在第二维里系数关系式、RK方程与SRK方程基础上导出了真实气体等压热容的关联式。利用这些关联式计算了包括极性气体的3种真实气体在不同压力和温度下的等压热容,并与文献上的实验数据进行了比较。计算结果表明:基于第二维里系数关系式的等压热容关联式简单方便,在p<10MPa与对比体积Vr≥2的条件下,计算误差一般在3%以下;在不接近露点的条件下,基于SRK方程导出的关联式计算误差一般小于4%,基于RK方程导出的关联式对于非极性气体计算误差一般小于4%;本文关联式计算准确性优于剩余热容图法,为工程计算提供了一种便于计算机应用的计算方法。

应用马丁─侯状态方程计算含氨气体混合物的物性参数

本文将马丁—侯状态方程用于计算气体混合物的恒压热容、粘度和导热系数．含氨气体混合物的恒压热容为理想气体混合物热容与真实气体混合物剩余热容之和，根据剩余粘度法计算粘度，剩余导热系数法计算导热系数．三种压力，不同温度条件下气体混合物恒压热容、粘度和导热系数的计算结果表明：计算值与实验值相吻合．并分别拟合了合成氨生产三种工艺含氨气体混合物恒压热容、粘度、导热系数的计算式。

计算液体及其混合物的C_p-C_v的方法

建立了一个能够计算各种温度下液体恒压热容与恒容热容之差的关系式C_p-C_v=RTV^2a/(V^2-AV+B)A和B是两个相关的特性常数,它们的值可由基团贡献法和分子的拓外指数确定.计算结果与实验值相一致.倘若应用A和B的简单混合规则,上述关系式亦适用于液体混合物.

范德瓦尔斯气体的内能及摩尔热容

用热力学的方法讨论了物质内能的一般表达式,从而从普物的角度导出范德瓦尔斯气体的内能及定压摩尔热容与定容摩尔热容的差值。

HFC-32和CF_3I的气相声速

The speed of sound of the gaseous difluoromethane (HFC-32) and trifluoroiodomethane(CF3I) are measured with a cylindrical, variable-path acoustic interferometer operating at156.252 kHz. Temperatures ranged from 273.15 K to 333.15 K for both and pressures rangedfrom 48 kPa to 390 kPa for HFC-32 and from 58 to 276 kPa for CF3I, respectively Theuncertainty of the speed of sound was less than ±0.1%. The ideal-gas heat capacity atconstant pressure and the second acoustic virial coefficients for HFC-32 and CF3I werealso determined over the temperature range from the speed of sound measurements. Theideal-gas heat capacities at constant pressure and second virial coefficients calculated fromthese speed of sound measurements for both were compared with results from the literaturedetermined from PVT measurements and from speed of sound measurements, respectively.The uncertainty of the ideal-gas heat capacities at constant pressure were estimated to beless than ±1%.

空气定压比热容测定实验教学探索

空气定压比热容测定实验是工程热力学的基本实验。该实验涉及温度、压力、流量、热量等基本物理量的测量,数据处理和计算过程中需用到比热容及湿空气等方面的基础知识。在完成数据计算的基础上分析了实验产生误差的原因以及减小误差的方法,并提出了一些实质性的改进建议。该实验符合当前高校本科开展研究型和创新型实验教学的要求。