Heat and mass transfer in confined spaces.
Thesis DisciplineChemical Engineering
Degree GrantorUniversity of Canterbury
Degree NameDoctor of Philosophy
A novel experimental technique had been used to investigate the simultaneous transfer of heat and moisture in a simulated building cavity by natural convection. This technique employed two porous plastic plates as the two cavity walls and this arrangement allowed the imposition of a simultaneous moisture gradient on top of a temperature gradient and vice-versa. Both aiding and opposing-flow conditions were investigated for the vertical and horizontal cavity configuration. The aspect-ratio of the experimental cavity used was 7.0 and the fluid investigated was air. The experimental results were correlated in the form of Nusselt and/or Sherwood number versus an appropriately defined Rayleigh number which depended on the type of gradient causing the flow. The Nusselt and Sherwood numbers were found to agree well with the theoretical values of this work obtained from numerical calculation using a finite-difference technique. The temperature, concentration, stream-function and velocity fields from the numerical calculation also augmented the experimental results. As no previous results on the rate of moisture-transfer and s interaction with the rate of heat-transfer in an actual building cavity were available, the results of this work addresses this gap in the literature. Under the conditions investigated, which corresponded to the actual temperature and moisture gradients in a typical building cavity in New Zealand, the simultaneous temperature gradient had increased significantly the rate of moisture transfer while the presence of the simultaneous moisture gradient had not increased significantly the rate of heat transfer.