J.J. ROBERTS, A.N. FRIED, D.L. LAW and D.P. AVIRAM Kingston University
The paper presents the results of an optimisation of a Guarded Hot Box based upon a computational method and experimental data obtained during testing of a masonry block wall, A computational fluid dynamics (CFD) program was used to obtain solutions for air velocities and temperatures from the buoyancy driven laminar and turbulent flow and heat transfer equations with the domain of a Guarded Hot Box (GHB). The computational predictions of the flow regime within the original design of the GHB had indicated that a stratification of temperature fields and low flow velocities within the guard space was causing an uneven distribution of temperatures along the face of the test wall as well as an unsteady flow field which in turn prolonged the time it took for the box to reach steady state. It was, therefore, concluded that the guard area could benefit from a system of internal baffles that would allow for a better circulation of air within the guard cavity of the Hot Box, Following the computational analysis, a system of baffles was installed within the Guard Box and computerised temperature control and data logging capability incorporated in order to facilitate a fast and efficient data dissemination. Several tests were then conducted with a test wall made of Celcon Solar blocks on which an array of thermocouples had been installed. Experimental results indicate that flow within the guard area had indeed followed the trend of the computational predictions and steady state had been achieved within four hours of operation. Temperature stratification, although still present, had been reduced and corresponded well with the computed results.