How to calculate the ventilation rate of the ventilation system in the production workshop?

How to calculate the ventilation rate of the ventilation system in the production workshop?

In the chemical production process, the air quality in the workshop is directly related to the health of employees and production safety. In order to ensure the safety and comfort of the workshop environment, a reasonable ventilation system design is essential. Among them, the ventilation rate is one of the core indicators in the design of ventilation system. This article will explain in detail the calculation method of the number of ventilation, and analyze its influencing factors.

What is the number of ventilation?

The number of air changes refers to the number of times the indoor air is completely replaced per unit time. For example, the number of air changes is 5 times/hour, which means that the air in the workshop will be completely changed 5 times per hour. The higher the air exchange rate, the faster the air renewal rate, but the energy consumption also increases accordingly. Therefore, the reasonable design of ventilation frequency is the key to balance ventilation efficiency and energy consumption.

ventilation rate calculation method

The calculation of the number of air changes is usually based on the following factors: the volume of the workshop, the concentration of harmful gases, the health needs of employees, and the special requirements of the production process. The following are common calculations:

1. 
   according to national or industry norms China's "building design fire protection code" and "industrial building ventilation design code" and other standards for different types of production workshop put forward the requirements of the number of ventilation. For example:

• Ordinary production plant: 5-10 times/hour
• Clean workshop: 10-20 times/hour
• workshop with harmful gas emission: 10-15 times/hour These specifications provide a basic basis for the calculation of the number of air changes.

1. Calculated according to workshop volume The formula for the number of air changes is: [ Number of air changes = \frac{\text {air volume }}{\ text {workshop volume}} ] Wherein, the air volume can be calculated by the following formula: [ Air volume = \text {area} \times \text {height} \times \text {air change rate} ] In the specific calculation, it is necessary to determine the area and height of the workshop first, and then calculate the required air volume according to the number of air changes. This calculation method is often used for preliminary estimation when designing ventilation systems.

2. According to the harmful gas concentration For workshops with harmful gases or dust, the number of air changes should be determined according to the concentration of harmful substances. For example, assuming that the allowable concentration of a harmful gas in the workshop is 0.1 mg/m, and the actual detected concentration is 1.0 mg/m, the number of air changes required is 10 times/hour. This calculation is suitable for scenarios where precise control of air quality is required.

Ventilation rate influencing factors

1. Nature of Production The production properties of chemical workshops are quite different, some require high temperature and high pressure environment, and some require constant temperature and humidity conditions. Different production conditions have different requirements for ventilation times.

2. Type and concentration of harmful gas or dust The presence of harmful gases or dust is the core basis for the design of ventilation times. The number of air changes needs to ensure that the concentration of harmful substances in the workshop is always lower than the national occupational health standards.

3. Number of people in workshop and working intensity Personnel density and work intensity directly affect the ventilation demand. A more crowded workshop usually requires a higher number of air changes.

4. Equipment calorific value and humidity The heat and humidity of the production equipment will affect the temperature and humidity environment in the workshop, thus affecting the design of the number of air changes.

Summary and recommendations

The calculation of ventilation rate is a key link in the design of ventilation system in chemical workshop, which directly affects the safety and comfort of workshop environment. In the actual design, the production nature of the workshop, the concentration of harmful substances, personnel density and other factors should be comprehensively considered, and the calculation and design should be carried out in strict accordance with the relevant specifications.

For chemical companies, it is recommended to hire a professional ventilation design team when designing the ventilation system to ensure the rationality of the ventilation rate and the efficiency of the ventilation system. Regularly maintain and test the ventilation system to ensure its long-term stable operation.