def compute_constants(params):
    """ compute_constants parameters

    Parameters :
    ------------
    params : dict of setup parameters


    Returns :
    ---------
    const : dict of constant parameters
    """
    const = {}
    const['h_ratio'] = params['h_cold'] / params['h_hot']
    const['biot'] = params['h_hot'] * params['width'] / params['lambda']
    const['t_ref'] = params['t_cold'] + (params['t_hot'] - params['t_cold']
        ) * (1.0 / (1.0 + const['h_ratio']))
    const['dx'] = params['typ_size'] / params['res']
    const['lam_ov_rhocp'] = params['lambda'] / (params['rho'] * params['cp'])
    const['dt'] = params['fourier'] * const['dx'] ** 2 / const['lam_ov_rhocp']
    const['total_time'] = params['typ_size'] ** 2 / const['lam_ov_rhocp']
    const['exp_iterations'] = const['total_time'] / const['dt']
    for key in const:
        print(key + ':' + str(const[key]))
    return const
