IBRAHIM NAIM RAMADAN, EUGEN VICTOR LAUDACESCU, MARIA POPA, LOREDANA IRENA NEGOITA STUDIES ON BEHAVIOUR OF IN SERVICE TUBULAR MATERIAL USED AT REFINERY PROCESS FURNACES The purpose of the heat transfer analysis at the level of the technological furnace in radiation section was to determine the medium temperature on the outside wall of the pipeline through which the effluent is processed. It is important to keep an outside temperature of the wall of the duct below the maximum allowable temperature at which this carburizing process takes place. Thus, the temperature calculated on the outside pipe wall is 523.5 oC and the maximum allowable temperature of the outside pipe wall is 595.5oC. The carburizing process leads to the modification of the thermal conductivity of the tubing material. Therefore, if steel is enriched with carbon, thermal conductivity decreases.