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Abstract
The drying of coffee is a critical aspect of the post-harvest process and plays a crucial
role in achieving high-quality coffee. The drying process requires significant energy to remove
moisture from the harvested beans, emphasizing the importance of using efficient equipment and
sustainable sources. The capstone project focuses on designing a heat exchanger for a
mechanical coffee drying system that uses biomass combustion. This report briefly covers coffee
processing, heat exchangers, and computational fluid dynamics. The project compared various
heat exchangers and deemed that a shell and tube heat exchanger could meet the requirements of
drying 1000 kg of coffee. The project deliverables include a validation study for SolidWorks
Flow Simulation 2023, a 3D model of the heat exchanger, and heat and flow simulations. Due to
time constraints, there was no constructed physical prototype. Kern’s method was used to
produce a thermal-hydraulic design for the first iteration of the shell and tube heat exchanger,
and SolidWorks was used to adjust key geometric parameters until the drying goals were met. A
validation study of conjugate heat transfer involving laminar and turbulent, incompressible flow
in SolidWorks Flow Simulation 2023 was conducted with a max deviation of 3.8% from
analytical results. The final heat exchanger design consisted of 19 (44 mm x 50 mm) tubes of
321 stainless steel alloy, one baffle cut 75%, and the tube bundle was 3.25 meters long with a
325.7 mm inner shell diameter. The weight of the tube bundle was 232 kg. The simulated air
outlet temperature value reached 51.5°C, producing a pressure drop of 2890 Pascals. The power
requirement to overcome pressure drop was calculated to be 4.9 kW, and the effectiveness of the
simulated heat exchanger was 72.9%. A mesh convergence study was conducted to confirm the
robustness of the simulation at 1.4 million cells.