(74l) 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.