Transport Phenomena in Multi-phase Media: Slurries, Foams, Boiling Bubbly Media and Pulps
thesisposted on 24.10.2013 by Seongchul Jun
In order to distinguish essays and pre-prints from academic theses, we have a separate category. These are often much longer text based documents than a paper.
The aim of this work is to study experimentally and theoretically the transport phenomena of multi-phase materials: slurries, foams, boiling bubbly media and pulps. Foam is added to gypsum slurries to make lighter wallboards. To produce high quality low-cost wallboards, understanding of rheology of gypsum slurries with foam is important. Foam content in slurries could significantly affect the rheological behavior and the results of this work quantified these effects. A theoretical model of gravitational foam drainage was proposed. The general model was applied to foam drainage in a gravity settler. It was predicted that liquid drainage from foam in a gravity settler begins with a slow drainage stage. Next, a second stage with a faster drainage process sets in where the drainage rate doubles compared to the initial stage and the theory was verified by the experiments. The approach based on the ideas of the consolidation theory was applied to predict the evolution, stability and approach to a steady-state configuration of threads of Pantene foams. The experiments with threads of Pantene foams at different concentrations were conducted and compared to the theoretical predictions. Pool boiling on nano-textured surfaces was studied experimentally and theoretically for ethanol and water as working fluids. The results revealed that the heat flux and heat transfer coefficient in pool boiling on the nano-textured surfaces were about 3-8 times higher than those on the bare copper surfaces. On the other hand, the critical heat flux (CHF) on the nano-textured surfaces was found to be very close to its counterpart on the bare copper surfaces. Cracking of USG ceiling tile materials was studied experimentally and theoretically. To observe the cracking phenomena, three point bending tests were performed on vacuum drained materials with 83% water. From the bending test results, stress-strain relations were established along with corresponding mechanical properties such as Young’s modulus, the yield stress, and cracking stress and strain. Furthermore, a plausible physical mechanism was proposed and the corresponding theory was developed. The theory showed a fair agreement with the actual cracking position at the industrial conveyor belt.