The corrosion failure of the high-pressure heat exchanger in a petrochemical enterprise was simulated. A multiphase flow and heat and mass transfer simulation shows that the vortex core with a higher gas phase content and lower temperature is the region of easy crystallization, located on both sides of the center of the tube. The crystallization process occurs in the gas phase. As the reaction progresses, the crystallization range spreads from the tube wall to the center of the tube bundle, and the inner diameter of the tube bundle decreases continuously. In Fluent, a user-defined function, based on the ammonium chloride crystallization reaction, is loaded. The results show that crystallization first occurs in the tube bundles on both sides of the center of the tube and that the corrosion is aggravated by the erosion wall surface of crystal particles at the elbow, which is consistent with the actual corrosion failure location.