Investigating wall-to-bed heat transfer in view of a continuous temperature swing adsorption process

- Calculated wall-to-bed heat transfer coefficients are compared to measured values.
- Heat transfer at single tubes and tube bundles of different geometry properties is investigated.
- Different models lead to diverse results, but are in mediocre agreement to the measured data.
- Measuring heat transfer is advised for best possible design of in-bed heat exchangers.

Heat transfer between bubbling fluidized beds and immersed heat exchanger surfaces is studied in view of continuously operated temperature swing adsorption processes for post-combustion CO2 capture. A novel heat transfer measurement test device was used to measure wall-to-bed heat transfer coefficients. The present work focuses on the comparison of experimentally obtained and calculated heat transfer coefficients. Heat transfer at horizontal single tubes and tube bundles immersed in fluidized particle beds of glass beads with 140 μm and 200 μm in Sauter mean diameter is investigated. It is shown that the experimental results for single tubes are in mediocre agreement to established mathematical models, such as the ones proposed by Natusch et al. (1975) and Molerus et al. (1995), and that heat transfer is significantly influenced by the tube diameter. The model by Petrie et al. (1968) was considered to take the effect of the tube diameter into account, which lead to promising results. Furthermore, measured heat transfer coefficients at tube bundles of different geometries are compared to predictions using the models by Natusch et al. (1975) and Lechner et al. (2013). Some of the tube bundle reduction factors predicted by the model by Lechner et al. (2013) are larger than one, which stands in contrast to the finding that the highest heat transfer coefficients occur at single tubes. However, both models lead to adequate results when calculating heat transfer coefficients for different tube bundle geometries.