Baffle Cut Effect in a Shell and Tube Heat Exchanger

Description: Shell and tube heat exchangers are a workhorse of the chemical process industry, and this project investigates how baffle cut geometry affects thermal performance within them. Baffles redirect shell-side flow to improve heat distribution, but adding more of them also raises pressure drop, so this simulation examines that tradeoff by treating the baffles and fluid together as a conjugated heat transfer problem, with the metal baffles modeled as solid domains actively participating in the heat exchange.

Methodology: The geometry, built in Design Modeler, features a shell 600 mm long and 90 mm in diameter, containing six 4 mm-thick baffles spaced 86 mm apart with a 36% baffle cut, and seven tubes of 20 mm outer diameter arranged in a triangular pattern with 30 mm spacing. The domain is meshed in ANSYS Meshing as an unstructured grid of 1,953,754 elements with a 30 mm element size and a boundary layer mesh near the walls to satisfy Y-Plus requirements. Cool water enters the shell at 300 K and 0.7 m/s while the tube walls are held at a constant 450 K, with water properties defined as piecewise-linear functions of temperature for improved accuracy; the case is solved as steady-state using the pressure-based solver, realizable k-ε turbulence model with standard wall functions, SIMPLE pressure-velocity coupling, and first-order upwind discretization for the transport equations, with the shell wall treated as adiabatic and the outlet set to 0 Pa gauge pressure.

Analysis: Results show the shell-side water heating from 300 K at the inlet to roughly 360 K at the outlet as it passes the hot tubes, with the heat transfer coefficient and total heat transfer rate converging steadily as the solution progresses. The conjugated modeling approach shows that the baffles noticeably accelerate temperature diffusion throughout the shell, raising the average fluid temperature and improving the heat transfer coefficient, while the mid-plane pressure contour reveals a pressure drop of around 1 kPa, giving a clear picture of the tradeoff between improved thermal performance and the added flow resistance the baffles introduce.