def compute_murphree_stage_efficiency(mu, alpha, L, V):
    """
    Return the sectional murphree efficiency, E_mv.
    
    Parameters
    ----------
    mu: float
        Viscosity [mPa*s]
    alpha: float
        Relative volatility.    
    L: float
        Liquid flow rate by mol.
    V: float
        Vapor flow rate by mol.
    
    Notes
    -----
    The efficiency is given by [2]_. See source code for details.
    
    """
    S = alpha*V/L # Stripping factor
    e = 0.503*mu**(-0.226)*(S if S > 1 else 1/S)**(-0.08 )
    if e < 1: return e
    else: return 1