NUMERICAL EVALUATION OF THE INFLUENCE OF SIZE AND POSITION OF RADIANT AND CONVECTIVE HEAT EMISSION SYSTEM ON THE MAIN INDOOR COMFORT PARAMETERS

Radiant heating is increasingly used and the interest in these systems is still increasing because of their low initial cost and capability in providing ideal comfort conditions coupled with low energy consumptions. In this system, thermal radiation covers more than 50% of the total heat exchanged and it becomes important to study in which way the position and the size of the radiant heater within a room influences the indoor comfort. By using conventional dynamic simulation codes in which the room energy balance is solved with a simplified approach, detailed information about the optimal position and geometry of the radiant heaters cannot be obtained. In fact, for the optimization of radiant heating systems it becomes mandatory to introduce a more detailed approach for the analysis of the heat transferred by radiation among the different surfaces in which radiation physics is correctly reproduced and this is out of the scope of the commercial dynamic software. In this work a model for the prediction of the radiant heat flux among the surfaces of a room having different temperatures is described. The radiation exchange was modelled by means of the net radiation approach. The calculation of the view factors among the surfaces is obtained by using Matlab. In the paper the effects obtained by adopting different sizes and positions of radiant and convective heaters in a room on the indoor comfort parameters are analyzed. In addition, it is shown in which way different envelopes with different thermal insulation levels can influence the distribution of the operative temperature in the room, the local comfort and the energy demand.