@staticmethod
def T1_ph(p, h):
    """function T1_ph = T1_ph(p, h)

        5 Equations for Region 1, Section. 5.1 Basic Equation, 5.2.1 The Backward Equation T (p, h)

        Eqution 11, Table 6, Page 10
        """
    I1 = [0, 0, 0, 0, 0, 0, 1, 1, 1, 1, 1, 1, 1, 2, 2, 3, 3, 4, 5, 6]
    J1 = [0, 1, 2, 6, 22, 32, 0, 1, 2, 3, 4, 10, 32, 10, 32, 10, 32, 32, 32, 32
        ]
    n1 = [-238.72489924521, 404.21188637945, 113.49746881718, -
        5.8457616048039, -0.0001528548241314, -1.0866707695377e-06, -
        13.391744872602, 43.211039183559, -54.010067170506, 30.535892203916,
        -6.5964749423638, 0.0093965400878363, 1.157364750534e-07, -
        2.5858641282073e-05, -4.0644363084799e-09, 6.6456186191635e-08, 
        8.0670734103027e-11, -9.3477771213947e-13, 5.8265442020601e-15, -
        1.5020185953503e-17]
    Pi = p / 1
    eta = h / 2500
    T = 0
    for i in range(0, 20):
        T = T + n1[i] * Pi ** I1[i] * (eta + 1) ** J1[i]
    return T
