Final run: outlet crude temperature: 248°C, U = 291 W/m²·K, pressure drops shell/tube: 58/31 kPa, fouling resistance: 0.00035 m²·K/W. Within all limits.
Elena’s mentor, Old Man Callahan, who smelled of coffee and war stories, dropped a dog-eared manual on her desk. “Rule one, kid,” he said. “HTRI doesn’t forgive. It only calculates. Respect the baffles.”
But a new warning blinked red: Vibration potential. Bundle natural frequency close to vortex shedding frequency. htri heat exchanger design
She switched to instead of single. HTRI’s geometry builder rendered the new arrangement: two baffle windows per baffle, promoting more longitudinal flow. The pressure drop plummeted to 55 kPa, and U rose to 275 W/m²·K. Nearly there.
She opened the software. The input panel stared back: Tube layout, shell type, baffle cut, nozzle location. She chose a BEM shell (stationary tubesheet, floating head, pull-through bundle) because fouling was a nightmare with this crude. She set the tube pitch to 1.25 inches—square pitch, to allow mechanical cleaning. Final run: outlet crude temperature: 248°C, U =
“Ah, the killer,” Callahan murmured. “You don’t fix that, tubes will sing for a week, then snap like guitar strings.”
Elena reduced unsupported tube length by adding support plates. She increased tube wall thickness from 1.65 mm to 2.11 mm. HTRI’s vibration analysis tab recalculated: frequency ratio now 1.8 (safe above 1.2). Red warning turned yellow, then green. “Rule one, kid,” he said
Better. U climbed to 250. But pressure drop on the shell side spiked—from 40 kPa to 95 kPa, exceeding the 70 kPa limit. Trade-off city.
She clicked to the (shell-and-tube) module. The color-coded flow map showed dead zones near the shell’s center. The baffle spacing was too wide—fluid was meandering, not turbulent. She reduced baffle spacing from 500 mm to 300 mm. Re-ran.