Experimental and theoretical energy and comfort analyses on radiant systems

When dealing with emission systems, energy and comfort aspects should be considered simultaneously since the terminal units directly affect the indoor thermal environment. The present work focuses on radiant systems and presents both experimental and theoretical energy and comfort analyses. Simulations taking into account the dynamic behaviour of the building structures and the transient operation of water in the embedded pipes were carried out to analyse the seasonal emission efficiency of radiant systems in buildings with different levels of insulation and thermal mass and, with constant and variable supply water temperature. Their energy performance when supplied by a water to water heat pump and overheating risk were also investigated. A better performance of the radiant systems was found with a better quality of the envelope, the climatic control was confirmed to ensure a lower overall energy consumption and overheating effects were found to be not especially due to radiant system but happening in any case also with ideal convective systems. In the second activity field measurements in a building were carried out to compare the performance of a wet floor radiant system with a reduced thickness of the screed with the performance of a traditional floor radiant system. First air and surface temperature data along with water temperature and thermal power recorded by the energy meters were analyzed. Then simulations under the same boundary conditions were performed, in continuous and intermittent operation and limited and unlimited available thermal power. No significant difference was found in the thermal energy need neither comparing the two systems, nor comparing continuous and intermittent operation. As regards comfort, two activities involving test rooms are presented. Thermal global and local sensations were assessed by means of questionnaires during experimental investigations in a test room. The surface temperatures of the upper and lower parts of the room were progressively increased and decreased, while inlet air temperature was kept constant. Air stratification and vertical radiant asymmetry were analysed in the two kinds of tests, along with air velocity. No relevant asymmetry problem resulting in opposite sensations on head and feet at the same time was found in the analysis of the answers, while other factors played a significant role. For more comprehensive analyses on well-being of people, perception of the indoor environment and productivity, a novel test room equipped with radiant systems on all the surfaces and fresh air with controlled flow rate, supply temperature and relative humidity has been designed. The design and partial realisation are presented in the thesis as well as some hints on future research activity.