Betancourt, Arturo

Shell-and-tube heat exchangers (STHXs) are a popular choice in the petroleum refining industry,
chemical industry, food processing industry and in power generation plants. This kind of heat
exchanger is made up of an array of baffles that redirects the working fluid to increase heat
transfer. The objective of this work is to understand the underlying physics of the heat transfer in a
shell-and-tube heat exchanger and its interconnection to the fluid structure associated with their
design. This research focuses on the steady state three dimensional analysis of the time averaged
turbulent flow and heat transfer characterization of the shell side of a small scale single segmented
baffle heat exchanger. The study is carried out using the computational fluid dynamics (CFD) software
package ANSYS: FLUENT 15.0 on a hybrid unstructured mesh. The CFD results are then compared
against experimental results. The Reynolds averaged-Navier-stokes (RANS) based turbulent model
realizable is used to model the turbulence inside the heat exchanger. The results obtained from CFD
and experiment from the shell side wall outlet temperature differ by 5 %. Based on the computational
results it is found that the regions of highest velocity at the inlet and in the core flow lead to a higher
local heat transfer enhancement. A better understanding of the complex flow and heat transfer regimes
inside a shell and tube heat exchanger given by this work would aid to further the development of more
cost efficient and effective heat exchanger designs.

A common technique to improve the performance of shell and tube heat
exchangers (STHE) is by redirecting the flow in the shell side with a series of baffles. A
key aspect in this technique is to understand the interaction of the fluid dynamics and
heat transfer. Computational fluid dynamics simulations and experiments were performed
to analysis the 3-dimensional flow and heat transfer on the shell side of an STHE with
and without baffles. Although, it was found that there was a small difference in the
average exit temperature between the two cases, the heat transfer coefficient was locally
enhanced in the baffled case due to flow structures. The flow in the unbaffled case was
highly streamed, while for the baffled case the flow was a highly complex flow with
vortex structures formed by the tip of the baffles, the tubes, and the interaction of flow
with the shell wall.