Experimental Study And Finite Element Numerical Analysis Of Hydraulically Expanded Tube-To-Tubesheet Joints For Shell-And-Tube Heat Exchangers

Heat exchangers are widely used in many industrial fields, like oil refining industry, chemical industry, nuclear power and so on. Tube and shell heat exchanger is one of the most commonly used heat exchangers. The performance of tube-to-tubesheet joint plays key roles to ensure reliable operation of shell-and-tube heat exchangers. The methods for joining the tube-to-tubesheet are weld, expansion and both of them. Among them, hydraulic expansion method is much more commonly used for its easier fabricating and controlling. Academically, the performance of the joints is usually characterized by the residual contact pressure between the tube outer surface and the inner surface of the tubesheet hole. However, in engineering practice, the tube-to-tubesheet joint is measured by the tube expanding rate which reflects the connecting strength of the joints.In this paper, the performance of hydraulically expanded tube-to-tubesheet joints is experimentally studied with the concentration on the tube expanding rate, pull-out force, push-out force and expansion pressure under 10# and 16Mn carbon steel,304 stainless steel,321 stainless tube-and-tubesheet materials. A three-dimensional Finite Element Method (FEM) is also applied to modeling the experimentation. The following results are presented.(1)The experimental results show the range of tube expanding rate when expansion pressure is 160MPa-180MPa for carbon steel joint material, and 180MPa-300MPa for 304 and 321 stainless steel joint material. Also, the relationship between pull-out (push-out) force and expansion pressure is presented. Further, The fitting formulas of tube expanding rate and expansion pressure, pull-out (push-out) force and expansion pressure, pull-out (push-out) force and tube expanding rate are presented. Based on GB151, the range of expansion pressure for three different combinations of tube-and-tubesheet joint materials is proposed in order to meeting the tube expanding rate and strength requirements.(2)The experimental results show that, with the increasing tube expanding rate, pull-out force increases first, then decreases. The oversize tube expanding rate may result in "overexpansion" and decrease the pull-out strength of joints.(3)The experimental results show that, with the increasing tube expanding rate, push-out force increases. Push-out force is greater than pull-out force when expansion pressures are the same.(4)The FEA results show that, expansion location has no obvious influence on tube expanding rate. As expansion location more and more close to tube pass of tubesheet, push-out force increases.(5)The FEA results show that, with the increasing initial clearance between tube and tubesheet holes, tube expanding rate increases and pull-out or push-out force decrease.(6)The FEA results show that, expansion length has no obvious influence on tube expanding rate, and pull-out force decreases with the increasing expansion length.