Experimental and numerical analysis of heat transfer in the cavities of hollow blocks

Given the importance of the assessment of the insulation performance of the building envelope in the context of energy certification of buildings, a detailed analysis of the reliability of the methods of evaluation of heat transfer in the air cavities of hollow blocks has been carried out. An experimental study was conducted in the laboratory. Heat transfer measurements on specimens with parallelepiped cavities were done, through a guarded hot plate device according to UNI EN 12664. A numerical analysis of the heat transfer in the specimens through the software ANSYS FLUENT was carried out. The analysis of the numerical and experimental results when compared with the predictions obtained from simplified models of technical standards, have called attention to the order of magnitude of the calculation accuracy obtainable with such procedures. For some geometric configurations and boundary conditions, the application of the standards can lead to large errors of evaluation of the thermal resistance of the cavity.