In this thesis it is demonstrated how mass transfer can be induced within a network of reticulated channels through turbulent mixing, and how this mechanism can be applied as an integrated functional structure in a building envelope. The research is based on suggestions in literature that there are transient modes of mass transfer which are active in termite mounds of the species Macrotermes michaelseni and which do not rely on steady or cross flows: is the interaction of transient air flows, induced or natural, and the geometry found in the mounds – a complex reticulated network of tunnels with variable dimensions – conducive to controlled mass transfer? My original contribution is to show that such mass transfer is possible, to demonstrate the ways which geometry and input flow interact to create turbulent mixing, and to demonstrate how these parameters may be useful to control the flow within and across building elements. The research method is structured around a series of experiments where various geometries, based on the egress complex of termite mounds, are exposed to transient fluid flows, either a controlled, low amplitude oscillation or external turbulent flow. The resulting mass transfer is measured using tracer gas measurements and visualisations using planar laser and/or fluorescent dye. It is found that the oscillations in certain conditions, which involve a combination of geometry and oscillation properties, lead to the emergence of large scale turbulent convection which can increase the mass transfer rates with up to two orders of magnitude over an unperturbed system. It is concluded that such mechanisms are potentially useful to control the flows of heat and moisture within buildings and across building envelopes. The particular properties of the described flows can complement conventional steady flows and expands the repertoire available to the building designer, enabling new types of boundaries and functional integration in the building envelope.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:706293 |
| Date | January 2016 |
| Creators | Andreen, D. N. |
| Publisher | University College London (University of London) |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
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