def R_curv(deltaT_sub, r_min, radius, Q_drop):
    """ thermal resistance due drop curvature
    
    Parameters
    ----------
    deltaT_sub: float
                temperature difference to the cooled wall in K
    r_min:      float      
                minimum droplet radius in m    
    radius:     float
                radius of drop in m
    Q_drop:     float
                rate of heat flow through drop in W                
    
    Returns
    ----------
    R_curv:     float
                thermal resistance due drop curvature in K/W
    """
    R_curv = (deltaT_sub*r_min / radius) / Q_drop
    return R_curv