The fan exhausts and cools down, that is, the fan is used to reduce the temperature. The products include electric fans, fans, axial fans, centrifugal fans, etc. The characteristics are cheap, easy to install, but the effect is not good. When the temperature is high, the effect of ventilation can only be achieved, and the cooling effect is very small. Compression refrigeration cooling uses refrigerant vapor compression method to reduce temperature. The products are central air conditioner, purification air conditioner and split air conditioner, such as central air conditioner. The cooling effect , but high investment costs, high operating costs, less fresh air volume, and poor air quality, such plant cooling equipment generally requires ## personnel to maintain, not suitable for large-scale production workshops Ventilation and cooling problems.

Negative pressure water curtain cooling and ventilation system is a kind of ventilation and cooling method adopted by service factories in recent years. It is widely used in the Pearl River Delta region. Its basic working principle is that moisture evaporates to take away heat and achieve a cooling effect. A louver exhaust fan is installed on one side of the closed room, and a cooling water curtain and a water circulation system are installed on the other side. The louver exhaust fan changes the indoor air for one minute . Under the action of the louver exhaust fan, the outside air is washed and filtered by the water curtain to reduce the temperature of the air, and the evaporation of water takes away the heat in the room to achieve cooling. Negative pressure circulation ventilation is formed in the room, so that the indoor air is kept fresh, clean, and comfortable, and the indoor dust and odor are reduced, which effectively prevents the occurrence of occupational diseases and the spread of infectious diseases. The negative pressure water curtain cooling ventilation system is not an air conditioner, but the effect is better than the air conditioner. The characteristics of this type of product are low investment, the purchase cost requires only 1/4 of the air conditioner, the operating cost is low, and only 1/8 of the air conditioner is required. At the same time, it is simple to install and maintain. After installation, its indoor temperature can generally fall within 4-13 ° C.

Water curtain is the main component of the negative pressure water curtain cooling and ventilation system. It is a multilayer corrugated fiber laminate. It is characterized by good hydrophilicity and ventilation performance. The actual evaporation heat transfer area is its surface area. 100 times; strong texture, water immersion resistance, corrosion resistance, non-deformation, normal service life 5 ~ 8 years. The evaporative filter has a good filtering function for the dust in the air. When the hot air passes, it will form a clean and fresh air after the heat and mass exchange with the water on the filter.