Droplets generated in industrial buildings may do harm to the workers, the construction and the environment. Ventilation is often used to control this kind of air-borne contaminants. In order to provide a basis and reference for the efficient ventilation on droplets control, a numerical simulation method is adopted to reveal the evaporation and movement of fine water droplet populations released from a tank in industrial buildings. The variations of diameter and velocity of water droplets with identical initial diameter and velocity were studied. The results showed the evaporation and movement of the droplet populations presented obviously nonuniform distributions, due to vapor concentration and velocity distribution of the air around the droplets. When the droplets were closer to the centerline of the tank, they showed a lower evaporation rate, a larger velocity and a bigger velocity difference between droplets and its surrounding air. The effects of initial diameter and the relative humidity of the ambient air on droplet evaporation and movement were discussed. Compared to the relative humidity of the ambient air, the initial diameter had a more significant effect on the droplet evaporation and movement. The effects of the initial diameter variation (1 µm-50 µm) on the evaporation time variation and the terminal height variation were almost 17 times and 10 times larger than the effects by the relative humidity variation of the ambient air (20%-80%), respectively.

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Industrial buildings are playing an important role in national construction and economic development. The total constructed floor area of industrial buildings in China is over 500 million square metres per year since 2011. Up till now, the total area of existing industrial buildings is over 10 billion square metres. However, simultaneously, the areas of single industrial buildings have been expanding to occupy larger spaces. 1 The energy consumption of industrial building is the sum of the energy consumed during the entire lifetime of the building, rather than just the energy consumption for industrial production. 2 The consideration of energy consumption of industrial buildings mainly focuses on the heating, ventilation and air conditioning (HVAC) systems. This type of energy consumption accounts for rather a smaller proportion when compared to energy consumption for production. However, its absolute value cannot be overlooked. Therefore, how to effectively save the energy consumption of industrial buildings has become one of the most urgent problems in the field of built environment and energy efficiency. The differences in the energy efficiency design between industrial and civil buildingsThe indoor environment of industrial buildings should meet requirements of indoor operators, production, animal welfare, as well as safety and explosion protection. 3 Therefore, environmental control technology and energy efficiency design of industrial and civil buildings are oriented toward different foci, so as to solve different scientific problems using different methods. Due to the diversity of technological conditions in industrial production, the control requirements of industrial buildings' indoor environments differ with different types of industries, for example, industrial buildings with high pollution emissions and clean room. In addition, there are significant differences between industrial and civil buildings in architectural form. Compared with civil buildings, industrial buildings with smaller shape coefficient and window to wall ratio are simple and practical.Therefore, the energy efficiency designs of industrial and civil buildings are very different in both basic principles and technological strategies. Employing the energy efficiency methods of civil buildings directly to industrial buildings usually leads to unsatisfatory results. Thus, when we explore the energy efficiency design of industrial buildings, innovation should be further developed on the basis of existing technologies for civil buildings. Strictly speaking, principles and ideas of energy efficiency of civil buildings can be used for reference and learning, but a new energy efficiency design system should be formed, and novel contents should be added, centred on indoor sources (heat source and pollution source), enclosure structure and equipment system characteristics of industrial buildings.

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