An experimental investigation of heat transfer in packed beds of low tube/particle diameter ratio is reported and the most widely-used two-dimensional homogeneous continuum models are thoroughly tested by statistical methods using the experimental data obtained. It is shown that the omission of axial dispersion effects leads to significant lack-of-fit in such models and to parameter estimates which vary systematically with bed depth. A model including axial dispersion is considered for each of two possible simplified downstream boundary conditions. This axially-dispersed model shows no lack-of-fit and yields depth-independent parameter estimates when the boundary condition is placed at infinity; when the alternative condition at bed exit is used this model shows little improvement over the model which omits axial dispersion. A new theory for predicting the axial and radial effective thermal conductivities and the apparent wall heat transfer coefficient is derived from a two-phase continuum model containing the essential underlying and independently measurable heat transfer processes. The theory gives good agreement with the results obtained in this work, in contrast with previously existing theory, explains much of the confused literature data, and pin-points the remaining major areas of uncertainty.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:649573 |
| Date | January 1978 |
| Creators | Dixon, Anthony George |
| Publisher | University of Edinburgh |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://hdl.handle.net/1842/13655 |
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