THE INVESTIGATION OF DIFFERENT APPROACHES TO HEATING SYSTEM LOAD DETERMINATION

Abstract

This paper analyzes various approaches that might be used for heating load calculation for room. These approaches include calculations from national and European standards (EN 12831) and special software for building dynamic simulation EnergyPlus. The results of these calculations vary due to influence of thermal bridges on heat transfer through building envelope. Thermal bridges effect can increase heat load for the room by 10%. Ventilation thermal losses are almost the same in all three approaches. Also ground heat transfer is treated by different methods, for example, by dividing the floor into the thermal zones or by equivalent heat transfer coefficient. The results of heat transfer rate through the floor using European standard and Slab pre-processor in EnergyPlus program are very different due to the fact, that EnergyPlus uses monthly average ground temperatures. The influence of the intermittent heating on the room heating load was also explored for different set-back temperatures and reheat time. Heating-up capacity required to compensate for the effects of intermittent heating increases with the increase of temperature difference during occupied and unoccupied hours and with the decrease of reheat time. Therefore, using intermittent heating modes for public buildings on the one hand decreases energy consumption for heating, but on the other hand increases heating load and capital cost of heating system. Further investigation can be developed for searching the optimum between energy saving potential and capital cost increase for heat source and emission system in terms of set-back temperature and reheat time.