Buoyancy-driven convection in cavities with particular application to the development of a low cost solar water heating system.
The overall aim of the research reported here was the development of a simple,
low-cost passive solar heating system for operation in the Portuguese climate. The
performance of this device is critically dependent on the rate of convective heat
exchange across the cavity behind the heater plate. Both computational and
experimental studies of the heat transfer characteristics of this new storage device,
have been conducted.
An experimental installation in full scale was designed and constructed to enable
the measurement of local heat transfer rates. Computer simulations of the laminar
flow under solar-driven conditions were made using an existing steady, threedimensional
computational fluid dynamics (CFD) code based on the finite-volume
method (PHOENICS Code shareware version 1.S). A boundary-fitted co-ordinate
system was developed to fit the non-rectangular geometry of the cavity, that
represented the water store, which provided the computational grid for the CFD
The experimental data from the test rig was used to validate the CFD model. A solar
water heating system was built to test the design under realistic weather conditions.
The experimental thermal performance was evaluated in 48% while the theoretical
was estimated in 51 %.