Kevin J. Farrell, Principal Engineer, Computational Simulation & Validation
When heat exchangers perform ineffectively, engineers often turn to computational fluid dynamics (CFD) for insight. In fact, most companies use CFD in this reactive manner to validate and troubleshoot their operating exchangers.
But innovative companies use CFD proactively to explore designs and optimize them virtually before physical confirmation. Doing so also makes good business sense, because building and testing an initial CFD model takes the majority of the analyst’s effort. Additional runs on the validated model have a high benefit-to-cost ratio.
HTRI continues to apply CFD in expanding and more complex ways, both for our own research and for proprietary contracts with other companies. Our CFD simulations have particular value and relevancy because we can draw on
- our current experimental investigations in our Research & Technology Center
- our members’ extensive design and operational experience
- our world-class design software Xchanger Suite®, which captures more than 55 years of our research on process heat transfer
Combining empirically tuned correlations and robust CFD models lets us predict thermal behavior and achieve a more realistic view of hydraulic behavior. We’ve done this with kettle reboilers, E shells, X shells, J shells, NTIW baffles, and single- and double-segmental baffles, as well as for single-phase and two-phase flows. For example, Figure 1 clearly illustrates the deleterious effects of bypass streams in an underperforming gas heater. On top of the bundle, a portion of the inflow is not heated, resulting in a lower than expected exit temperature. By blocking this bypass stream, as shown in Figure 2, the exit temperature increases substantially.
What’s next for CFD at HTRI?
In the near future, we’re applying CFD to studies of plate heat exchangers and simulations of fired heaters, two geometries we haven’t yet studied this way. Extending our CFD work into these new areas allows us to refine our methods for port pressure distribution in Xphe® and to further validate the methods and data underlying our new software, Xfh Ultra®.
Farther in the future, a heat exchanger avatar from HTRI on our tablets, tuned with data from Industrial Internet of Things (IIoT) sensors, may predict performance for variable operating scenarios.
We’re dreaming of what could be. Are you?
Figure 1. Pathlines originating at the inlet and colored by temperature indicate a reduced exit temperature of this double-segmental E-shell gas heater because of bypassing along the top of the bundle
Figure 2. Similar pathlines indicate an increased exit temperature and reduced bypass stream due to the addition of "T" or “mushroom” central baffles and wing baffles with a bridge or inverted “U” baffles