Diffuse ceiling ventilation for buildings: A review of fundamental theories and research methodologies

Abstract Buildings consume more than 40% of global energy use and ventilation is one of the largest source of energy consumption. Sustainable design requires choosing energy efficient ventilation strategies. Diffuse ceiling ventilation (DCV) has a great energy saving potential due to the low pressure drop (∼2 Pa) through the ceiling panel. A DCV system has three components: plenum, suspended ceiling and ventilated room. Conditioned air is supplied to plenum, then diffuses into the ventilated room through the suspended ceiling made of porous materials. The system can be designed to handle high cooling loads without inducing thermal discomfort. This review references research articles on DCV published from 2008 to 2018 to highlight the research outcomes and to identify the research gaps. One major objective of this review paper is to document simplified theoretical modelling methods for proposing quick DCV system design tool. The flow in the plenum can be described as impingement jet over porous materials. A design procedure is proposed to determine the size and number of nozzles. The heat transfer in the porous ceiling is treated as two-phase energy transport. Buoyancy force generated by the heat sources in the room has been identified to drive the airflow circulation, which motivates the thoughtful review of fundamental theories of thermal plumes in a stratified environment. The major task on thermal plumes is to calculate the height and induced volume flow rate, which are summarized according to the type of heat sources, e.g., point or area sources. The principle behind heating efficiency of DCV might be explained by theories of turbulent fountains. The rising height of warm air coming out of diffuse ceiling is determined by the source Froude number. The popular research methods to study DCV system are full-scale experiments and CFD modelling. Full-scale experiments are often used to evaluate the performance of the DCV system based on thermal comfort, indoor air quality and energy efficiency. On the other hand, CFD modelling is used for parametric analysis to improve the design of the DCV system. Finally, future research on DCV is discussed.