ceiling

This study is to validate a CFD model of displacement ventilation combined with chilled ceiling and determine if this combination may create draught risk or influence badly indoor air quality.

A CFD code was used to study an office equipped with a radiant cooled ceiling and a wind-induced cross-ventilation system. Calculations covered several heights of the ceiling.

Flow and heat transfer calculations have been operated in a typical office room equipped with a displacement ventilation and a chilled ceiling system. Results show quasi-periodic flow when the values of internal thermal loads are high. They also show lateral oscillations of the plumes above heat sources which create after impact on the cold ceiling recirculating flows in the room.

The subject of this study is the design of cooled ceiling and displacement ventilation systems in buildings. States that good design of CC/DV systems can lead to better indoor air quality and thermal comfort in comparison to widely used VAV mixing systems. A key design parameter is the cooling load removed by the displacement ventilation. Due to a small vertical temperature gradient, a low DV has a positive effect on thermal comfort, but also has a negative effect on indoor air quality because of the increased mixing of room air.

In modern buildings, smoke control systems are integrated into the air supply systems. It is possible that the design of the smoke control system will dominate the design process of the air supply system. Smoke reservoir size is one of the design parameters for the smoke control system. The reservoir size has been limited to 2000-3000 m2 in both Hong Kong and UK. However, this study revealed that the smoke reservoir size should be considered in connection with the slab ceiling height of the smoke zone. The higher the slab ceiling, the larger the smoke reservoir could be.

The role of metallic surfaces is not only to save energy in winter and in summer by separating the inside and the outside. New and inexpensive ways of collecting solar energy for internal heating, new ways of ventilating, heating and cooling through the fabric elements are described. Two very significant prospects are : radiative cooling by metallic surfaces and enhancement of indirect daylighting by optimised ceilings. The subject of the European CURES program is to promote these new technologies by simulating and testing them.

Current model building codes require attic ventilation in all U.S. climates. Originally, these requirements were strictly based on concerns for condensation in attics during winter in cold climates, and they were based on limited technical information. Nevertheless, attic ventilation has become the uncontested strategy to minimize condensation and ice dams during winter and extreme attic temperatures during summer. However, other strategies exist that address each of these problems as well as or better than attic ventilation.

Dynamic simulation of a seawater-cooled chilling system is performed by using the dynamic models of centrifugal chillers, heat exchangers, seawater and chilled water networks, cooling coil, actuator, sensor, variable-speed pump and DDC controller ofBEMS. The on-line control strategies for the central chilling system are tested and evaluated by using them to control the living chilling system under different AHU dynamic loads in four seasons.