def calGasVisEq1(params, T):
    """ 
    gas viscosity equation 1 - Pa.s
    args:
        params: 
            equation parameters list [A,B,C,D]
        T: temperature [K]
    """
    # try/except
    try:
        A = params[0]
        B = params[1]
        C = params[2]
        D = params[3]
        _res = A*1e-6*(T**B)/(1+C*(1/T)+D*(T**-2))
        return _res
    except Exception as e:
        raise