Abstract
Buildings contain the environment in which almost all human activities take place, and therefore, nowadays, they represent a great sink of energy. Establishing thermal comfort conditions within these buildings is responsible for a large portion of their energy demand. This paper aims at providing a theoretical framework of the performance and the trends in research and implementation of night air conditioning by outside air ventilation. The bibliographic search was conducted in the academic directory Scopus, and the information extracted was processed in the VOSviewer software, through which text mining, map of terms and networks of investigative action were carried out. The literature showed that direct ventilation has a more significant cooling potential in regions characterized by a high difference between day and night air temperatures. The effectiveness of night cooling and the reliable prediction of thermal behavior are strongly related to the model adopted for the convection algorithm. A reliable prediction of heat transfer by convection requires an approach based on computational simulations of fluid dynamics, which are much more demanding in terms of computational power, compared to simulations of the variation of energy flows as a function of time. Most studies showed that the position of the thermal mass is not significant, while the amount of ventilation air is of great importance. In particular, the energy demand for cooling a building decreases sharply if the air flow rates increase.
Highlights
Air conditioning or air handling processes aimed at providing thermal comfort to people performing various activities in a space defined by buildings is called indoor air conditioning [1, 2]
From an economic and technological perspective, nations see in night air conditioning by ventilation with outside air a timely and effective energy strategy to respond to the energetic demands of buildings
Goethals et al [18] focused on the convective heat transfer coefficients inside the buildings. They indicated that both the effectiveness of night cooling and the reliable prediction of thermal behavior are strongly related to the model adopted for the convection algorithm
Summary
Air conditioning or air handling processes aimed at providing thermal comfort to people performing various activities in a space defined by buildings is called indoor air conditioning [1, 2]. Night ventilation is a bioclimatic strategy that allows the passive cooling of buildings decreasing the energy demand due to air conditioning. Using outside air to cool off rooms at night is a millennial process. This process is combined with modern and complex processes of active air conditioning of interior spaces (Fig. 1). Given the cooling potential of nocturnal ventilation, two effects are considered based on the observation of the physical phenomenon: First, the direct convective cooling due to the fresh outdoor air that improves the thermal conditions of the building’s interior environment and its occupants. The heat exchange between the supplied external air and the interior surfaces of the building envelope, which discharge the thermal mass of the building by the effect of sensible heat removal [6-8]
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