Multistage expanded bed
Staged beds and downcomers support counterflow contact within the double-shell concept.
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03 / Thermal system design
Direct Contact Heat Exchanger
Heat transfer. Thought through.
An ongoing graduation project exploring how a direct contact heat exchanger can transfer heat from hot particles to air—while making its containment more practical.
The decision
Separate high-temperature exposure from pressure containment using a cooled double shell.
The evidence
Original CAD and concept evaluation; air-only CFD scope, with full thermal validation still ahead.
KSU Solar Tower application
Two shells.
Different jobs.
A cooled outer path separates high-temperature exposure from pressure containment.
900–1,000°C Hot-particle inlet design range
Design conditions from the project brief.
Not measured prototype performance.
01 / The thermal challenge
Recover the heat.
Manage the exposure.
In a particle-based solar thermal system, hot particles carry energy that must be transferred into an air stream. The exchanger has to provide contact, guide both flows and accommodate demanding thermal conditions.
The report establishes a particle inlet design range of 900–1,000°C, an air inlet condition of 180°C and a 90% effectiveness target. These are design requirements, not achieved results.
The selected concept uses staged counterflow contact and a cooled double-shell arrangement. Its purpose is to reduce the need for the pressure-containing structure to experience the highest temperatures directly.
02 / Compare before committing
Three ways to bring
particles and air together.
Falling particle curtain
A different contact pattern, evaluated alongside the staged approach.
Moving packed bed
Another route to particle-to-air contact, with different flow and integration trade-offs.
Qualitative summary of the report’s concept evaluation. Numerical aggregate scores are omitted because the source table contains inconsistent totals.
03 / Follow the air
Down the outside.
Up through the heat.
- Enter the outer passage
The incoming air travels downward through the annular space, cooling the shell arrangement.
- Turn at the bottom
The lower region redirects the stream upward into the internal heat-transfer path.
- Meet the falling particles
Air rises through porous stages while particles descend through downcomers.
- Leave through the central outlet
The flow exits through the central pipe-in-pipe arrangement.
04 / Simulation, with boundaries
A useful model starts
with an honest scope.
The current CFD work is air-only analysis in ANSYS Fluent: airflow distribution, recirculation and pressure losses support design evaluation.
That does not validate the complete multiphase particle-to-air heat-transfer process. The supplied report documents the concept and CAD stage; it does not include the newer air-only simulation exports, so no pressure contours, velocity results or CFD performance numbers are reproduced here.
Still to establish
Full coupled heat-transfer performance, experimental validation, and a completed material-cost comparison. A material-cost reduction is a potential benefit, not treated as a verified outcome.
The takeaway
Separate the functions.
Then test the assumptions.
The double-shell concept turns one difficult material problem into distinct thermal and structural roles. The next challenge is to verify that the flow distribution, particle contact and practical construction support the intended benefit.