def mesh2str(mesh):
    """Converts a mesh number to string
    
    This subroutine converts an integer mesh number to a string.
    FDS specifies mesh numbers as zero-padded integers with 4 digits.
    
    Parameters
    ----------
    mesh : int
        Integer mesh number
    
    Returns
    -------
    str
        Mesh number as a string zero-padded to 4 digits
    """
    
    meshStr = "%04.0f"%(mesh)
    return meshStr