Shock Wave Evaluation in Shell and Tube Heat Exchanger Tube Rupture Scenario

Abstract

Shell and Tube Heat Exchangers (STHEs) are commonly used in oil and gas plants to cool or heat process fluids. A possible issue when designing such systems is represented by the tube rupture scenario, when the internal HP (high-pressure) fluid is suddenly discharged to the LP (low-pressure) fluid in the shell. Since, usually, the tube and shell sides have different design pressures, this scenario must be analyzed to assess if the safety measures are fit to protect the weakest part of the system. The time evolution of this event is characterized by different phases; in the first one, a shock wave is generated and propagated very rapidly in the system, with a time scale in the order of a few ms. The phenomenon is so rapid that pressure relief devices are not effective. This kind of wave is normally not evaluated in the majority of available publications; however, it is deemed that it is of particular relevance for large-size SHTEs, due to their significant investment cost, and hence, a methodology has been developed in this work for the purpose. The main impact of such waves is expected in the LP piping connected to the exchanger. The amplitude of the shock wave at the source location, i.e., at the ruptured tube, is calculated based on the theory of the Riemann problem, with reference to different types of HP and LP fluids. Then, the relevant propagation up to the piping entrance is studied to estimate the wave damping and the effective wave amplitude impacting it. Both validation calculations and calculations referred to new design applications and existing installations are presented, and possible mitigation measures are proposed, if any.