Design for Mechanical Integrity in Thermal Mixing Points

Design for mechanical integrity in thermal mixing points

Authors:         Santhosh K Shankar^*, Gonghyun Jung^{^}, Karl Anderson^*, Greg Bethke^*

Thermal fatigue can occur near mixing points where fluids of different temperatures comingle to reach a desired temperature for downstream processing requirements or in hydro-processing units where hydrogen is injected to treat a hydrocarbon stream at a different temperature. Failures due to thermal fatigue may lead to loss of primary containment, resulting in fire, health hazards and production deferment resulting from unplanned unit shut-downs and are hence associated with problems of high business impact. Thermal sleeves, quills and/or spray nozzles may be used in mix points to protect the walls of the piping against fatigue. The primary challenge towards design of thermal sleeve is- understanding the process of thermal mixing near and downstream of the mixing point under different flow regimes. Identification of the appropriate dimensional and non-dimensional quantities on which the thermal mixing process depends is hence critical. The present work showcases an attempt to identify key universal parameters that govern the thermal mixing process.

Towards this objective, a parametric study was conducted using computational fluid dynamic (CFD) simulation at varying process conditions to understand the thermal behavior of the flow. Temperature statistics are probed along the wall at downstream and azimuthal locations of the pipe to map trends in the thermal behavior of the flow.

Figure: Temperature fluctuations along the pipe walls encountered in a mixing point from mixing of hot (red) and cold (blue) fluids.