Performance Evaluation and Application of Stratum Ventilation to Hong Kong Buildings

Description

To reduce energy use in buildings, significantly higher room temperatures are recommended by several governments in East Asia in recent years. To maintaining thermal comfort under this warm condition becomes an imminent challenge. This project will provide a solution for small and medium rooms under warm conditions. Stratum ventilation supplies air from outlets installed in walls at the head level. By supplying air directly at the most important body part - head, stratum ventilation allows the ambience to be warm while maintaining thermal comfort. It also improves air quality since the supply air is directly delivered to the breathing zone. Besides the locations of air supplies, the equipment of stratum ventilation is almost the same as conventional systems, except that cavity partitions, instead of the ceiling/underfloor voids, are most likely to house the air duct and/or plenums. The installation is therefore safer and cheaper without the need for scaffold. The space occupied by the system is less because the needed cooling capacity is smaller due to better energy performance. The initial cost of stratum ventilation is therefore expected to be lower also. Studies since 2005, including laboratory measurements, human subject tests and numerical simulations, show that stratum ventilation improves air quality and energy efficiency while providing thermal comfort in a warm environment. These results have been reported in 15 SCI refereed journal articles. In the summary of the Ventilation 2009 Conference, stratum ventilation was regarded as one of two significant innovative ideas. Nevertheless, for practical application of stratum ventilation, further studies are needed to characterize the velocity and temperature profiles, to conduct human subject tests for their perceptions of comfort, and to improve the novel methodology coupling CFD and human thermoregulation modeling for optimizing the designs.The proposed tests will be carried out in our unique environmental chamber which conveniently allows (1) different ventilation methods to be switched; and (2) the configurations of office, classroom and retail shop to be realized. Objective experiments and computer simulations on thermal and flow conditions and on thermal comfort will be conducted. Human subjective responses on the thermal sensation and comfort of the whole body and of different body segments under different configurations will also be investigated. A novel simple evaluation tool to predict the thermal comfort condition of stratum ventilation will be developed for the use of practicing engineers. Finally, a set of design guidelines for the application of stratum ventilation in Hong Kong will be developed. To sum up, the advantages of the novel ventilation method demonstrates on the following aspects:Better thermal comfort ─ reverse and modest temperature gradient in the occupied zone;Better indoor air quality ─ horizontal air supply at the head level;Better energy efficiency ─ 20% to 40% less energy consumption compared with conventional methods;More environment-friendly ─ less carbon footprint throughout the life cycle (manufacture, installation, operation, recycling and demolition) due to smaller capacity of the system; andSafer installation ─ no scaffold is needed to set up ducts and air terminals.