.ClaRa.SubSystems.Furnace.HopperSlice_L4_AdditionalAir.GasHeatTransfer_Top .ClaRa.SubSystems.Furnace.HopperSlice_L4_AdditionalAir.GasHeatTransfer_Topmodel GasHeatTransfer_Top = ClaRa.Basics.ControlVolumes.Fundamentals.HeatTransport.Gas_HT.Radiation.Radiation_gas2Gas_L2;