【 Abstract 】 By analyzing the influencing factors of air conditioning and ventilation system in shopping malls on indoor air quality, this paper puts forward effective measures to improve indoor air quality from various aspects.

[Paper Keywords] air conditioning and ventilation system indoor air quality countermeasures

Indoor air indicators include the oxygen content in the air, the concentrations of CO2 and CO, the contents of dust and planktonic microorganisms, the number of ions in the air and volatile organic compounds (VOC). The air quality in shopping malls usually depends on the dust content, bacteria content and the concentration of various harmful gases. Supermarkets, hypermarkets and other shopping malls are important places for people to shop, and the air quality of shopping malls is related to the health of customers and employees. Because most shopping malls are located in downtown areas of the city, there is a large flow of people in shopping malls, and all kinds of goods are stored centrally. The air quality in shopping malls depends largely on the ventilation and air conditioning system of shopping malls.

First, the main functions and characteristics of air conditioning and ventilation system in shopping malls

The air conditioning and ventilation system in shopping malls mainly dilutes and discharges harmful pollutants by continuously sending enough fresh air, and reduces the volume fraction of indoor pollutants such as CO2, thus changing the indoor air quality and solving the problems of air suffocation and pollution in shopping malls. On the other hand, the fresh air volume determines the energy consumption of the air conditioning system, and the air conditioning system generally uses return air to save energy. Due to the continuous circulation of return air, the indoor pollution gas concentration will increase. Therefore, the rational use of fresh air has played a very good role in maintaining indoor air quality and saving energy.

Second, the impact of air conditioning and ventilation system on the air quality of shopping malls

There are many factors that affect the air quality in shopping malls. Relevant research shows that air conditioning and ventilation system has an important impact on the air quality of shopping malls. Mainly in the following aspects:

1. Insufficient fresh air. In the process of system design and installation, in order to save energy and reduce investment, the load design parameters of air conditioning and ventilation system are too conservative, the equipment capacity is improperly selected, the necessary fresh air volume can not be guaranteed, and the indoor air quality is difficult to guarantee.

2. Improper purification of fresh air and return air. Because the filtration treatment of fresh air and return air can not meet the requirements, it pollutes other components in the air conditioning system, and can not purify harmful gases and odors in the return air, resulting in potential disease sources and odor sources, and finally pollutes indoor air.

3. Improper inhalation of fresh air. The air distribution in the air conditioning system is not good, and the fresh air distribution is uneven. Fresh air mixed with return air or sent into indoor polluted area first greatly reduces the "freshness" and even causes secondary pollution of indoor air.

4. Poor discharge of condensed water. Because the slope of the condensate pipe is not enough, or there is a big trap, or it is blocked by dust, the accumulated water provides a good temperature and humidity environment for the growth of bacteria during the system shutdown.

5. Improper operation and maintenance management. Due to the lack of regular cleaning and replacement of filters in operation management, the air supply bamboo duct and air handling unit are seriously polluted, which may make the system resistance too large, resulting in a significant decline in fresh air volume and total air supply volume, leading to indoor air pollution.

Third, improvement measures.

According to the characteristics of ventilation and air conditioning system in shopping malls, it is suggested to take measures from the following aspects to maximize the efficiency of ventilation and air conditioning system and ensure the indoor air quality in shopping malls.

1. Ensure the necessary fresh air volume. Calculate the demand for fresh air reasonably according to the flow of people in the mall, and consider excluding the fresh air required for indoor equipment, building decoration materials and storage items. China's Code for Design of Heating, Ventilation and Air Conditioning (GBJ 19-87) stipulates that the minimum fresh air volume of shopping malls is 8.0 m3/(h person).

2. Improve the purification level of fresh air and return air in air conditioning system. Because the concentration of atmospheric dust in China is much higher than that in developed countries, it is difficult to dilute only by the specified minimum fresh air volume, and effective air filtration treatment must be taken at the same time. Because bacteria in the air are attached to dust particles, the higher the dust content, the higher the bacteria content. Effectively filtering out the dust in the air can filter out most of the planktonic bacteria in the air, thus greatly reducing the probability of disease transmission. In order to ensure the indoor air quality, the air treatment in air conditioning in shopping malls must be equipped with coarse and medium-efficiency filtration, and sub-high-efficiency filtration can be used when necessary. The research shows that the concept of effective filtration means that the filtration efficiency of air filter for 3nm particles can not be lower than 60%. In addition, in order to eliminate various odors and VOC emitted by the decoration of some commercial buildings, it is also possible to consider installing an activated carbon filter on the air conditioning return duct.

3. Optimize the fresh air supply mode. It is suggested to adopt an independent fresh air handling and conveying system to shorten the path of fresh air entering the room, which can not only ensure the purification requirements of fresh air and avoid mixing with return air or polluted airflow to reduce the "freshness", but also ensure the necessary fresh air volume during the suspension of air conditioning system. When designing, we should also pay attention to the position of fresh air inlet not close to the sewage outlet and not far from the spray cooling tower. Foreign studies have proved that this kind of cooling tower is the easiest tool for Legionella to breed and spread.

4. Improve indoor air distribution. Displacement ventilation is used to send air to the lower part of the room at low speed. Fresh air first comes to the breathing area of people, and then carries pollutants from the upper part, so the ventilation efficiency is good.

5. Control indoor humidity to reduce the generation of indoor pollutants. Studies have shown that the relative humidity of air exceeds 60%, which is very beneficial to the reproduction of bacteria and other microorganisms. In order to minimize microbial pollution, the relative humidity of indoor air must be controlled below 60%. At the same time, different types of goods in shopping malls are stored and managed scientifically to reduce the indoor air pollution caused by different goods.

6. Improve the operation and management of ventilation and air conditioning system. The research shows that the air supply volume is much smaller than the designed air supply volume because the filter was not cleaned in time, and the air supply volume doubled after cleaning the filter. Therefore, it is of great significance to formulate strict and detailed operation management rules, regularly clean system equipment, timely clean or replace filters, and strengthen the operation management of air conditioners in shopping malls to ensure the indoor air quality in shopping malls.

References:

[1] Liu Zhonghua et al. Study on indoor air quality in shopping malls [J]. Journal of Harbin University of Commerce (Natural Science Edition), 2004, (3): 36 1 ~ 364.

[2] Fang Tu et al. Analysis of pollution control methods of air conditioning and ventilation system in shopping malls [J] .2006, (1): 60 ~ 62

[3] Hu Chuanshun et al. Thoughts on air quality in shopping malls [J]. Refrigeration and Air Conditioning, 2006, (2): 90 ~ 93

;