Impact of slab edge zones on slab-on-grade heat losses

The object of research is the slab-on-grade in a one-room apartment located on the first floor of an apartment building. The climate type is Dfa according to the Köppen classification. Method. Field thermal tests of the object were carried out by the "additional wall" method in the cold season. All control tests were performed within 14 days, recording parameters every 15 minutes, taking into account the high thermal mass of the soil. For greater coverage of measurement points, two 10-channel programmable modules were used. In total, 6 edge zones of the slab-on-grade in various configurations were studied. Results. Maximum fluctuations in heat flux were recorded in the edge zones of the slab-on-grade adjacent to the outer wall, which indicates the unsteady nature of the heat transfer process. It has been proven that the thermal resistance on the inner surface of the slab-on-grade is nearly to zero, therefore, when modeling the process of unsteady heat transfer via the slab-on-grade, Dirichlet boundary conditions can be used. The attenuation of temperature fluctuations in ground mass and their delay in time is caused by high thermal inertia of soil. For the first time, significant variations in the coefficient of thermal uniformity (CTU) were established in the edge zones of the slab-on-grade adjacent to the outer wall (from 0.16 to 0.97). A decrease in CTU indicates an increase in heat losses via the edge zones of the slab-on-grade compared to areas of the slab remote from the edge zones. To reduce the heat loss via the ground, it is necessary to isolate the edge zones of the slab. This solution meets the minimum requirements for thermal protection of buildings.