Experimental and numerical investigations on stratified air distribution systems with special configuration: Thermal comfort and energy saving

• Experimental study for a STRAD system with innovative configurations was conducted.
• Extra energy saving potentials for STRAD systems was demonstrated.
• Energy saving for the cooling coil could be up to 21.0% of the space cooling load.
• Effects of locations of return grilles on thermal comfort and energy saving were illustrated.
• Recommends for the design of STRAD systems were presented.

In this paper, using a newly defined cooling coil load calculation method for stratified air distribution (STRAD) systems, the effects of separate location of the return and exhaust grilles on thermal comfort and energy saving are experimentally investigated. The results clearly demonstrated the extra energy saving potentials for STRAD systems with separate locations of return and exhaust grilles. After using the experimental results to validate our CFD method, numerical investigation is carried out for an office setting. Decreasing the height of return grille will increase exhaust air temperature and significantly reduce the cooling coil load. However, the risk of poor thermal comfort caused by too large temperature difference between the head and foot levels also increased, when the return inlet is located close to the floor level. Locating the exhaust grilles at ceiling level and close to external wall while locating the return grilles at the upper boundary of the occupied zone are recommended in practice. It is demonstrated that the purpose to simultaneously achieve satisfied thermal comfort and prominent energy saving can be attained with a STRAD system via deliberate locations of supply outlets and return and exhaust grilles in relation to the heat source locations.