Calculation Method For Summer Cooling With Radiant Panels Francesco Causone, Stefano Paolo Corgnati and Marco Filippi Politecnico di Torino, Torino, Italy Corresponding email: francesco.causone@polito.it SUMMARY Radiant panels achieved a growing success in the last years as a cooling system, because they guarantee improvement in comfort and energy saving. The aim of the present work is to propose a method to evaluate the thermal behavior of radiant panels used for summer cooling. Experimental observations lead to notice that part of the radiant load hitting panels surface is directly removed by the refrigerating fluid (Direct Water Load), never becoming a room load. In order to evaluate the role of this fraction of load on thermal balance, it has been developed a specific procedure deriving from the Room transfer functions method. Through a lighting analysis tool it has been furthermore evaluated the Direct Water Load due to solar radiation, the most important radiative load for typical office rooms, in function of geometrical configuration and surfaces reflection factors (α, ρ). The right understanding of the role played by Direct Water Load on thermal behavior of radiant panels may lead to a better design of this kind of cooling systems. INTRODUCTION The use of radiant panels as a cooling system is quite new in a lot of countries, but it is developing extremely fast, conquering each year relevant market slices. The success of this kind of HVAC system is bound to design, comfort and energetic reasons. The use of radiant panels leads to have more free usable net floor space, to reduce draft risk, typical of cooling air systems, to achieve quite uniform temperatures into the rooms, to obtain significant energy saving. For comfort reasons, anyway, the surface temperature of panels must not be lower than 19°C and in order to avoid moist condensation it must not be lower than the dew point temperature of the room. Since cooling panels can control only sensible loads and not control air humidity and quality, they are always coupled with primary air, which can provide any air control. Sometimes primary air may even help the radiative system to balance peak loads, if they grow up beyond panels thermal efficiency. Radiative systems use wide exchange surfaces, and since human body exchanges heat through radiation approximately for the 50% of the whole balance (in cooling period), it is clear that panels temperature can be quite near to project air temperature maintaining optimal comfort condition. At the same time, since the most of heat exchanged between the body and the cooling system is through radiation, air temperature can have little higher values, without creating comfort problems, since operative temperature doesn’t change so much, so the thermal sensation of people remain the same. Higher values of air temperature bring anyway to a reduction of the cooling load, for the reduction of heat dispersions through walls and air infiltration. Proceedings of Clima 2007 WellBeing Indoors