Thermal Field And Stress Analysis Of Tubular Heat Exchanger

As the key equipment, tubular heat exchanger plays an important role in petrochemical industry. Because the tubular heat exchanger works under mechanical loads and thermal loads which lead to complex stress state, thermal field and stress analysis of tubular heat exchanger has great significance in improving design quality.In this thesis, the theory about thermal field and stress analysis of tubular heat exchanger was summarized and the solution method was given. 3-D parametric finite element model of tubular heat exchanger was built and the steady temperature field analysis of tubular heat exchanger was done. The results show that a large temperature difference can be found on the both sides of tubesheet, the temperature in most region of tubesheet is close to the temperature of tube unit fluid, and the temperature in the region of shell unit surface is close to the temperature of shell unit fluid,"skin effect theory"is verified. Then, the stress analysis of heat exchanger in seven operating conditions was done and stress distribution nephogram in each operating condition was obtained. Moreover, strength was checked according to national standard. The results reveal that the dangerous operating condition occurs in shutdown time, during this time, the tube unit is closed; the dangerous path is located at the fillet of tube unit side of tubesheet. Due to different thermal characteristics of materials, high stress exists in the welding position which connects tubesheet and shell. The thermal stress is very high in a very thin surface layer where is close to the shell unit of tubesheet owning to the great temperature gradient there. The stress of heat exchanger mainly depends on thermal stress, shell pressure plays a positive role in enhancing stress and tube pressure is in the opposite way.In addition, influence of stress for different fillet of tubesheet was analyzed. It shows that increasing the fillet radius can effectively decrease the stress in this region and relieve the stress concentration of heat exchanger and improve the reliability of equipment.