|dc.description.abstract||This thesis presents an investigation into the performance of a Membrane Distillation
(MD) system used for seawater desalination. The research is focused on the effects of
intermittent use of the MD module when powered with a solar energy collector. The
aim is to assess the feasibility of directly powering an MD unit with a
from a solar collector.
An investigation into the effect of temperature on the microstructure of the
membrane was carried out. In a series of experiments, samples of PTFE membrane
were imaged while heated from 17 C to temperatures between 60 C and 80 C. It was
found that the membrane pore size increased with increases in temperature. When
heated to 80 C the pore diameter increased by 44%.
Intermittent use of the system would cause the temperature of the MD module
fluctuate, therefore altering the membrane microstructure. An investigation was
carried out to determine the in
fluence of intermittent MD operation on the
conductivity of the distillate. The system was tested after overnight shutdown periods
and was also tested with short term `on/off' periods of between 5 and 20 minutes,
simulating the intermittent output from a concentrated solar collector.
It was found that as the module was heated, the distillate
flux produced increased,
while the distillate conductivity decreased. Conversely, when the module cooled, the
flux decreased and the quality of the distillate worsened. This was the result of the
dependancy of membrane pore size on temperature.||en_US