状态方程法求算气体的剩余焓与剩余熵

流体剩余焓与剩余熵计算是化工过程设计中十分重要的计算,但现有教科书中缺少P-R方程与S-R-K方程剩余焓与剩余熵的计算方法与计算公式;化工生产中,绝大多数物流都是多组分混合物,而关于维里方程法气体混合物的剩余焓与剩余熵计算也缺少详细的论述。借助于通用立方形方程剩余焓与剩余熵计算式,推导出P-R方程和S-R-K方程的剩余焓与剩余熵的计算公式;采用Prausnitz混合规则,推导出维里方程求算混合气体的剩余焓与剩余熵的计算式与方法,使流体热力学性质计算方法更加完善。     

用SRK方程与PR方程求算双组分混合气体热力学性质

流体热力学性质的计算是化工热力学中的一类重要计算,立方型方程经常用于这类计算中。SRK方程与PR方程是在RK方程基础上发展而来的,具有比RK方程更好的计算精度。但现有教材中没有给出PR方程和SRK方程的剩余焓、剩余熵的计算公式,缺失了流体热力学性质计算的系统性。本文通过立方型状态方程的一般形式推导出PR方程和SRK方程的剩余焓、剩余熵的计算公式,利用Excel电子表格计算双组分混合气体的热力学性质。计算过程简捷明了,利于学生更好地理解混合物热力学性质的计算过程。     

用BENDER状态方程计算N2—Ar—O2体系的热力学参数

Ｂｅｎｄｅｒ状态方程可用于Ｎ２－Ａｒ－Ｏ２三元体系，进行力学性质计算精度较高，本文根据Ｂｅｎｄｅｒ方程推导出焓、熵、比热等热力学参数的计算公式，对Ｎ２、Ａｒ、Ｏ２及共混合物进行计算，并与实验数据进行比较，结果令人满意。     

用BENDER状态方程计算N_2—Ar—O_2体系的热力学参数

Ｂｅｎｄｅｒ状态方程可用于Ｎ_２—Ａｒ—Ｏ_２三元体系，进行热力学性质计算精度较高．本文根据Ｂｅｎｄｅｒ方程推导出焓、熵、比热等热力学参数的计算公式，对Ｎ_２、Ａｒ、Ｏ_２及其混合物进行计算，并与实验数据进行比较，结果令人满意．     

形状因子对应态原理预测流体的热力学性质

采用形状因子对应态原理,由纯流体的蒸汽压和饱和汽液相密度方程得到的保形参数,由此推算其它区域内的Ｐ－Ｖ－Ｔ性质、第二ｖｉｒｉａｌ系数、焓、熵、热容和混合物的汽液平衡等热力学性质,计算结果与文献值符合较一致     

Matlab在“化工热力学”教学中的应用

“化工热力学”是一门重要的应用型课程，将Matlab引入教学中可以增加课程的趣味性，也可以锻炼学生的工程思维能力。采用Matlab对普遍化第二Virial系数法求解纯组分压缩因子、剩余焓（熵）、过程的焓变以及混合物的体积进行编程，结果表明，Matlab可有效解决“化工热力学”相关计算问题，提升学生的工程计算能力。     

含氢、氮、氩、甲烷等组分的液氨混合物的热力学性质计算

本文根据严格的推导,得出了计算溶解于液氨中的氢、氮、氩、甲烷等组分偏摩尔焓、熵的计算公式,根据推导出的公式,建立了计算液氨混合物热力学性质的数学模型。     

真实气体等压热容的关联

根据真实气体热容与剩余焓的关系,导出了计算真实气体热容的普遍化关联式,将该关联式的计算结果与采用文献方法的计算结果进行了比较,结果表明,该关联式的计算误差一般在5％之内,比文献方法准确性高且更简单方便。     

关于Excel在化工热力学计算中应用的探讨

摩尔体积、压缩因子、剩余熵、剩余焓与逸度等的计算是流体热力学性质计算的重要内容,在化工热力学课程中要用较多的课时讲授,而这些计算往往比较复杂,经常涉及试差计算与迭代计算,又经常要进行针对不同流体的相同内容的计算,使得计算异常繁杂,课堂内难于讲授清楚。本文介绍了微软电子表格Excel在流体热力学性质计算中的应用。该计算简单明了,且不易出错,便于课堂内知识传授,是一种值得推广的教学与实用计算方法。     

链状流体的分子热力学模型(Ⅱ)──混合物汽液平衡

实际链状流体混合物的亥氏函数表示为参考流体（硬球链流体混合物）的贡献和由于链节间的方阱位能相互作用的贡献之和．前者直接用作者先前建立的硬球链流体混合物的分子热力学模型计算,不含混合规则;后者采用Alder等人的结果,用vanderWaals单流体理论计算混合物的能量参数.对于不含氢键作用的二元混合物,有一可调相互作用参数,需由实验数据拟合得到．本模型可以满意地关联小分子混合物和高分子溶液的汽液平衡。     

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。     

EVALUATION OF PENG ROBINSON EQUATION OF STATE IN CALCULATING THERMOPHYSICAL PROPERTIES OF COMBUSTION GASES

A set of simple equations of the thermodynamic and transport properties of the combustion gases of a gas turbine have been derived based upon the critically evaluated data and two equations of state: The virial equation of state and Peng-Robinson (PR) equation of state.

The properties which have been considered were, density, specific heat at constant pressure, enthalpy, entropy, viscosity and thermal conductivity.

The temperature range was (200-2600 K) theoretically while the pressure range was (0.3-1.2 MPa).

A computer program, to evaluate the departure of thermophysical properties using virial and PR equations of state, was used.

The Peng Robinson (PR) equation of state gave better estimated accuracy than the virial equation of state especially in evaluating the departure of thermodynamic properties.     

R32热力学性质计算模型及其分析

提出了R32制冷剂在饱和线(?130~78℃，0.00013~5.76 MPa)范围内饱和蒸气压、液体密度等关联式的计算模型，在此基础上推导了蒸发潜热的计算模型；建立了描述饱和气体线上(?130~78℃，0.00013~5.76 MPa)及过热区(过热度为100℃)范围内描述P-v-T关系的状态方程；在上述模型的基础上推导得到了饱和气体线及过热区范围内焓、熵、比热容的计算模型。将模型计算结果与REFPROP9.0数据源、已发表的状态方程及公开实验数据对比，各关联式计算模型的平均相对偏差均小于0.16%，最大相对偏差不超过3.7%，与已有状态方程和公开数据对比偏差小于8.7%；基于状态方程和热力学关系式推导得到的焓、熵、比热容的计算模型的平均相对偏差均小于5.2%，最大相对偏差不超过9.1%。     

利用P-R方程估算纯组分真实气体的物性

从P-R状态方程出发,用Newton迭代法求出真实气体的摩尔体积,然后用数值方法求P-R方程的过剩焓对温度的偏导数,从而得到真实气体的剩余等压热容,由此计算出真实气体的等压热容。给出了Newton迭代方法和偏导数数值解法。编写求解程序,实际计算了一些烃类物质的等压热容。结果表明计算的误差可满足工程应用。     

AN EMPIRICAL VIRIAL-LIKE CUBIC EQUATION OF STATE FOR PHASE EQUILIBRIUM CALCULATIONS

An empirical cubic equation of state(EOS) was obtained by truncating the virial expansion in reciprocal of molar volume after the third term. The constants of the EOS was generalized in terms of critical temperature, critical pressure and Pitzer's acentric factor.

In pure component applications the EOS exhibited a performance comparable to Peng-Robinson (1976) EOS in the reduced temperature range of 0.5 to 1. The present EOS tends to predict better saturation liquid volumes at reduced temperatures below 0.8, and better estimations for second virial coefficient at high reduced temperatures.

The EOS was successfully employed for vapor liquid equilibrium calculations for some mixtures of normal or slightly polar fluids with traditional one binary parameter mixing rule at moderately high pressures. At low reduced temperatures, where conventional one adjustable parameter applications of the cubic equations compare unfavorably with dual methods based on excess Gibbs energy functions for the liquid phase, a new two constant mixing rule introduced by Stryjek and Vera (1986) was employed for the present equation of state.     

Equation of state for gaseous nitrogen determined from isotropic model potentials

A four‐term virial equation of state was combined with isotropic potential models to predict accurate volumetric and caloric thermodynamic properties of nitrogen in the gas phase. The parameters of the model potentials were determined from a fit to acoustic data alone; no other data was used. For nitrogen, it was only necessary to approximate the fourth virial coefficient at the level of interactions that contained no more than one triplet potential; higher order approximations offered no further advantage. It was shown that the four‐term virial equation was more accurate than the three‐term analogue. It was found that predicted virial coefficients became consistent with experimental values when temperature was >150 ± 30 K; conversely, below this range virial coefficients predicted by the model did not agree with experiment. It was believed that predicted fourth virial coefficient was reliable and accurate only above about 150 K. Predicted compressibility factors deviated by <0.05% at pressures of up to 10–12 MPa, or densities up to 4 mol/dm³ (≈0.4ρ_c), only when temperature was >220 K. Values of enthalpy predicted from the equation of state showed good agreement with experimental data.     

Vapor Pressure,Vaporization Enthalpy,Standard Enthalpy of Formation and Standard Entropy of n-Butyl Carbamate

The vapor pressures of n-butyl carbamate were measured in the temperature range from 372.37 K to 479.27 K and fitted with Antoine equation. The compressibility factor of the vapor was calculated with t...