I am working on a project to recover waste heat for industrial processes and use it to heat up sand to 250 degrees Celsius. I am an electrical engineering student with not much knowledge about heat transfer and heat exchangers, but I am learning very fast about them. If there's anyone working in the thermal energy space and with heat exchangers knowledge, please assist me.
Design a low-cost and efficient heat exchanger for waste heat recovery to charge sand up to 250°C by:
Using a compact, spiral-wound or plate-type heat exchanger design
Selecting materials with high thermal conductivity, such as copper or steel
Implementing a counter-flow or cross-flow configuration for optimal heat transfer
Utilizing waste heat sources like exhaust gases or hot water to achieve the desired temperature.
In my opinion, the simplest and most reliable way would be to blow the sand up using hot air flow while keeping the sand flying in the hot air long enough to make the sand hot. Long enough means to let the Fourier number to become much bigger than 1. Fourier number equals the sand material's thermal diffusivity "a" times time "t" divided by the square of the sand's piece diameter "d": Fo = at/(d^2)
I.e. flying time t>>(d^2)/a
In this case every piece of the sand will become hot.
See Fourier number - Wikipedia
Fourier number - Wikipedia
I would highly recommended checking the book Heat Transfer
Book by Yunus A Çengel. - Chapter 13 in particular.
This should give you the necessary theoretical background.
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