def METHOD_NAME(build_drum1D):
    m = build_drum1D
    # fix inlets
    m.fs.unit.water_steam_inlet.flow_mol[:].fix()
    m.fs.unit.water_steam_inlet.pressure[:].fix()
    m.fs.unit.water_steam_inlet.enth_mol[:].fix()
    m.fs.unit.feedwater_inlet.flow_mol[:].fix()
    m.fs.unit.feedwater_inlet.enth_mol[:].fix()
    optarg = {"tol": 1e-7, "max_iter": 40}
    solver.options = optarg
    # solve model
    results = solver.solve(m, tee=True)
    # Check for optimal solution
    assert pyo.check_optimal_termination(results)
    assert degrees_of_freedom(m) == 0
    assert pytest.approx(0.6, abs=1e-3) == pyo.value(m.fs.unit.level[0])
    # energy balance
    assert pytest.approx(0, abs=1e-3) == pyo.value(
        m.fs.unit.water_steam_inlet.flow_mol[0]
        * m.fs.unit.water_steam_inlet.enth_mol[0]
        + m.fs.unit.feedwater_inlet.flow_mol[0] * +m.fs.unit.feedwater_inlet.enth_mol[0]
        - m.fs.unit.steam_outlet.flow_mol[0] * m.fs.unit.steam_outlet.enth_mol[0]
        - m.fs.unit.liquid_outlet.flow_mol[0] * m.fs.unit.liquid_outlet.enth_mol[0]
        + m.fs.unit.heat_duty[0]
    )
    # pressure drop
    assert pytest.approx(3662.5483, rel=1e-5) == pyo.value(m.fs.unit.deltaP[0])
    # mass balance
    assert pytest.approx(0, abs=1e-3) == pyo.value(
        m.fs.unit.water_steam_inlet.flow_mol[0]
        + m.fs.unit.feedwater_inlet.flow_mol[0]
        - m.fs.unit.steam_outlet.flow_mol[0]
        - m.fs.unit.liquid_outlet.flow_mol[0]
    )
    assert pytest.approx(
        pyo.value(
            m.fs.unit.water_steam_inlet.flow_mol[0]
            * m.fs.unit.flash.mixed_state[0].vapor_frac
        ),
        abs=1e-3,
    ) == pyo.value(m.fs.unit.steam_outlet.flow_mol[0])