redlich_kwong.py 文件源码

def get_Z(self, T, p):
        #A = self.a * p / self.R**2 / T**2.5
        #B = self.b * p / self.R / T
        A = self.get_A(T, p)
        B = self.get_B(T, p)

        # Solve the cubic equation for compressibility factor z
        # Z^3 - Z^2 + (A-B-B**2)*Z - A*B = 0
        coeffs = [1, -1, A-B-B**2, -A*B]
        roots = np.roots(coeffs)

        real_roots = roots[np.isreal(roots)].real
        valid_roots = real_roots[real_roots > p*self.b/self.R/T]

        return valid_roots

    # dZ/dT at const. p