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含临界区流体的物性计算一直是热力学领域的难点。一般认为,解析式状态方程不可能同时很好地计算远离临界点和靠近临界点流体的热力学性质。该文目的就是验证解析式方程在计算热力学性质特别是接近临界点附近的热力学性质适用性。通过计算机分子模拟数据,研究了各种解析式状态方程计算接近临界区的方阱流体的物性的可能性,结果表明,经过参数重新拟合新的解析式方程,可以很好地计算方阱流体的相平衡、密度等性质,直到对比温度接近临界点0.05处。临界点温度、压力和密度的计算值和分子模拟值也基本符合。该文结果可以为解析式方程计算范围的扩大提供依据,从而说明解析式在工程方面有更加广泛的应用。
Physical calculation of fluid with critical region has always been a difficult area in thermodynamics. It is generally accepted that the analytical equation of state can not simultaneously calculate the thermodynamic properties of the fluid far and near the critical point. The purpose of this paper is to verify the applicability of the analytical equations in the calculation of the thermodynamic properties, especially near the critical point. By computer numerical simulation data, the possibility of calculating the properties of square-well fluid near the critical region by various state-of-state equations is studied. The results show that the square well fluid can be well calculated by re-fitting the new analytical equation Phase balance, density and other properties until the contrast temperature close to the critical point of 0.05. The calculated values of critical temperature, pressure and density are basically in accordance with the molecular simulation values. The result of this paper can provide the basis for expanding the range of analytical equations, which shows that analytic equations are more widely used in engineering.