Beispiel #1
0
def test_fuzz_dV_dP_and_d2V_dP2_derivatives():
    from thermo import eos
    eos_list = list(eos.__all__); eos_list.remove('GCEOS')
    eos_list.remove('ALPHA_FUNCTIONS'); eos_list.remove('VDW')
    
    phase_extensions = {True: '_l', False: '_g'}
    derivative_bases_dV_dP = {0:'V', 1:'dV_dP', 2:'d2V_dP2'}
    
    def dV_dP(P, T, eos, order=0, phase=True, Tc=507.6, Pc=3025000., omega=0.2975):
        eos = globals()[eos_list[eos]](Tc=Tc, Pc=Pc, omega=omega, T=T, P=P)
        phase_base = phase_extensions[phase]
        attr = derivative_bases_dV_dP[order]+phase_base
        return getattr(eos, attr)
    
    
    x, y = [], []
    for eos in range(len(eos_list)):
        for T in np.linspace(.1, 1000, 50):
            for P in np.logspace(np.log10(3E4), np.log10(1E6), 50):
                T, P = float(T), float(P)
                for phase in [True, False]:
                    for order in [1, 2]:
                        try:
                            # If dV_dx_phase doesn't exist, will simply abort and continue the loop
                            numer = derivative(dV_dP, P, dx=15., args=(T, eos, order-1, phase))
                            ana = dV_dP(T=T, P=P, eos=eos, order=order, phase=phase)
                        except:
                            continue
                        x.append(numer)
                        y.append(ana)
    assert allclose_variable(x, y, limits=[.02, .04, .04, .05, .15, .45, .95],
                            rtols=[1E-2, 1E-3, 1E-4, 1E-5, 1E-6, 1E-7, 1E-9])
Beispiel #2
0
def test_fuzz_dPsat_dT():
    from thermo import eos
    eos_list = list(eos.__all__); eos_list.remove('GCEOS')
    eos_list.remove('ALPHA_FUNCTIONS'); eos_list.remove('eos_list')
    eos_list.remove('GCEOS_DUMMY')
    
    Tc = 507.6
    Pc = 3025000
    omega = 0.2975
    
    e = PR(T=400, P=1E5, Tc=507.6, Pc=3025000, omega=0.2975)
    dPsats_dT_expect = [938.7777925283981, 10287.225576267781, 38814.74676693623]
    assert_allclose([e.dPsat_dT(300), e.dPsat_dT(400), e.dPsat_dT(500)], dPsats_dT_expect)
    
    # Hammer the derivatives for each EOS in a wide range; most are really 
    # accurate. There's an error around the transition between polynomials 
    # though - to be expected; the derivatives are discontinuous there.
    dPsats_derivative = []
    dPsats_analytical = []
    for eos in range(len(eos_list)):
        for T in np.linspace(0.2*Tc, Tc*.999, 50):
            e = globals()[eos_list[eos]](Tc=Tc, Pc=Pc, omega=omega, T=T, P=1E5)
            anal = e.dPsat_dT(T)
            numer = derivative(e.Psat, T, order=9)
            dPsats_analytical.append(anal)
            dPsats_derivative.append(numer)
    assert allclose_variable(dPsats_derivative, dPsats_analytical, limits=[.02, .06], rtols=[1E-5, 1E-7])
Beispiel #3
0
def test_SRK_Psat():
    eos = SRK(Tc=507.6, Pc=3025000, omega=0.2975, T=299., P=1E6)
    
    # ERROR actually for RK not SRK
    Cs_SRK = [-3.0486334, -5.2157649E-2, 0.55002312, -0.44506984, 3.1735078E-2,
              4.1819219E-2, -1.18709865E-2, 1.79267167E-3, -1.47491666E-4, 
              5.19352748E-6]
              
    def Psat(T, Tc, Pc, omega):
        Tr = T/Tc
        e = SRK(Tc=Tc, Pc=Pc, omega=omega, T=T, P=1E5)
        alpha = e.a_alpha/e.a
        tot = 0
        for k, Ck in enumerate(Cs_SRK[0:4]):
            tot += Ck*(alpha/Tr-1)**((k+2)/2.)
        for k, Ck in enumerate(Cs_SRK[4:]):
            tot += Ck*(alpha/Tr-1)**(k+3)
        P = exp(tot)*Tr*Pc
        return P
    
    Ts = np.linspace(160, 504, 100)
    Psats_lit = [Psat(T, Tc=507.6, Pc=3025000, omega=0.2975) for T in Ts]
    Psats_eos = [eos.Psat(T) for T in Ts]
    assert_allclose(Psats_lit, Psats_eos, rtol=5E-2)
    # Not sure why the fit was so poor for the original author

    fugacity_ls, fugacity_gs = [], []
    for T, P in zip(Ts, Psats_eos):
        eos = SRK(Tc=507.6, Pc=3025000, omega=0.2975, T=T, P=P)
        fugacity_ls.append(eos.fugacity_l)
        fugacity_gs.append(eos.fugacity_g)
        
    assert allclose_variable(fugacity_ls, fugacity_gs, limits=[0, .1, .5], rtols=[3E-2, 1E-3, 3E-4])