FEA of Heat Exchanger (UHX 13.4 Approach)

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INTRODUCTION

Tube & Shell types of heat exchangers have their design procedure defined in ASME & TEMA Standards. Though the equipment is designed as per standards, it is not possible to decide the most severe condition for the design just by observation. Hence a set of anticipated condition is provided in UHX 13.4 of ASME Sec. VIII Div. 1. FEA is performed for all this conditions & behavior of the equipment is evaluated.

Process equipment manufacturer from India & Abroad approached ANALYZER to seek assistance in evaluating the design of their newly developed heat exchangers for a particular application to multiple loading conditions using simulation techniques & provide the solution in case of any observed failure either stress failure or tube to tubesheet weld failure.

FEA WORKFLOW

  • Design parameters & material properties extraction for Heat exchanger geometry
  • Preparing FEA Model for heat exchanger with complete structured Hexahedral Mesh.
  • Solving the FEA Model & Result extraction
  • Performing the weld qualification calculations for tube to tubesheet welds.
  • Preparing an easy to understand report for the performed FEA.

CHALLENGES

  • Preparing complete structural hexahedral mesh without losing small geometrical details.
  • Optimizing the mesh count in case of bigger heat exchangers
  • Modelling the weld between tube & tubesheet

THE SOLUTION

The heat exchanger was analyzed for different loading conditions as per UHX 13.4 using Finite Element Analysis in ANSYS APDL Solver. Stress Linearization has been carried out at various locations. The tube to tubesheet weld qualifications were performed for the weld. The results showed that the induced stresses were well within the acceptable limits as per guidelines. Also the load at the weld junction is found to be much below the allowable limit. Hence, the structure’s design was predicted to behave safe during operation without premature failure.

BENEFITS

  • Actual behavior of heat exchanger for the anticipated conditions is evaluated.
  • Reduced manufacturing time
  • The most critical component of heat exchanger tubesheet is also evaluated for its strength.