Influence of Furniture on the Peak Load of an Intermittent Heating System -Analysis of Indoor Radiation Heat Transfer-

Room thermal analysis with furniture will generally result in differing heat load values and varying indoor temperatures compared to the same calculation without furniture. This is due to several factors concerning room configuration and its effect on the modes of heat exchange occurring within the indoor environment. The influence of furniture on indoor radiation heat transfer, specifically when computing the peak load of an intermittent heating system, was investigated in this study. The peak load value generally determines the required maximum output capacity of a heating system. Therefore, for reasons of economy and space, it is necessary to calculate an approximate figure. Computational analysis was done while explicitly computing the radiation heat exchange between all wall and furniture surfaces. A typical office space in Japan was simulated. Several cases with varying furniture configurations were investigated, and peak load values were compared to the case without furniture. During the heating start-up time, with the initial condition of almost uniform temperature everywhere, net radiation heat transfer becomes quite small. The computational results show that if walls and furniture surfaces have similar heat capacity and thermal conductivity, the increase in peak load in the case with furniture will be proportional to the increase in the total surface area on which convective heat transfer with room air occurs. Steady state heat load values in the cases with furniture were also compared and the influence of furniture position and configuration quantified. Computing the amount of net radiation heat transfer between wall and furniture surfaces requires complicated calculations for the geometrical configuration (shape) factor for each surface-to-surface relation. Another computational analysis was done wherein a partition wall between the interior and perimeter spaces was used to represent furniture in the room. Results from this extreme case show that it can approximate, to a good degree, the influence of furniture on the heat load analysis for an intermittent heating system.