DA-07-055 Impact of the Position of the Radiators on Energy Consumption and Thermal Comfort in a Mixed Radiant and Convective Heating System PDF

This paper studies the heating load and thermal comfort distribution in a typical office with a mixed radiant and convective heating system for two different locations of radiant heat sources for a typical heating condition. Accurately estimating the heating load in a mixed heating space requires careful consideration of the energy balance on each room surface and the comfort level in the space. A pure radiant heating system heats the room surfaces first; the warm surfaces then heat room air. The higher surface temperatures will increase the heat loss from the enclosure to the ambient environment for a fixed air temperature. On the other hand, a radiant heating system creates a higher mean radiant temperature in the space. By keeping the same operative temperature as used with a convective heating system, this system can have a lower room air temperature, which reduces the energy to heat infiltrating air or ventilation air and reduces the convective heat transfer between the room air and enclosure surfaces during the heating season. The reduced room air temperature has the potential to reduce the heat loss from the enclosure to the ambient environment. This paper compares the heating load and comfort level as measured by uniformity of operative temperature for two different layouts of radiators in the same geometric space. It is found that when radiators are close to the window and controlled to maintain the same operative temperature as with convective heating, they would increase heating consumption slightly (up to 3.6%) compared to 100% convective heating in an unoccupied space. In an occupied space, radiant heating would slightly reduce heating load (up to 7.7%) depending on the location of the radiator(s) and the outside air supply rate for the cases simulated. Comfort analysis shows that locating the radiator near the window can improve the comfort level in a space and the heating load can be slightly reduced compared with 100% convective heating. On the other hand, if the radiantly heated space is controlled to maintain the same air temperature as with convective heating, heat load with radiant heating will be at least 7% higher than for convective heating for the cases evaluated.

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