Abstract
The heat balance equation at a wall surface is composed of the following terms; (1) heat conduction, (2) convective heat transfer, (3) short-wave radiation, (4) long-wave radiation and (5) mass transfer. This equation is very important in determining boundary conditions of a wall heat conduction problem. When mass transfer is negligible, the sensible heat balance at a roof surface can be measured by making use of instruments such as pyranometers, improved polyethylene-shielded pyrradiometers, heat flow meter panels and copper-constantan thermo-couples. The method of measurement and its accuracy are discussed in section 4, covering (1) atmospheric radiation, (2) total net radiation, (3) the absorptance of the surface for solar radiation, (4) the emittance of the surface, (5) convective heat transfer coefficient α_c and so on. By using several kinds of sol-air temperatures obtained from field experimental data, the thermal response of a roof slab is simulated by the successive calculation method which was already proposed in the previous paper. When the film coefficient α is regarded as a time variable parameter, i.e. α_n, based on the experimental data, then, for the temperature and the heat flow rate at the outside surface, the standard deviation of the calculated values from the experimental ones reduces to half respectively, as compared with the case of its time dependence neglected. Although this result is no more than an example, it is said that the accuracy of the analysis can be apparently improved by regarding α as a time variable parameter. Then the value of α_<c, n> may be smaller as the surface becomes larger.
