Causes of failure of air-conditioning circulating water pump

Causes of failure of air-conditioning circulating water pump

The capacity and number of air-conditioning circulating water pumps, the selection of the best working point of the water pumps, and the technical and economic analysis will discuss how to choose water pumps to ensure that the air-conditioning system operates well and reduce power consumption.

　　 1. Reasons for the failure of the circulating water pump of the air conditioner:

　　 Excessive capacity of circulating water pump is a common problem in our country, and its capacity often reaches 2-4 times the actual need, causing serious waste of project investment and operating costs. The main reasons are as follows:

　　 1. The design cooling load is too large:

　　The design cooling load is the main basis for selecting equipment, so it is very important to calculate the building cooling load correctly for the design of the entire air conditioning system. At present, the air conditioning load calculation methods provided in textbooks and design manuals, whether calculating the wall load of the envelope structure, or the load of doors and windows, are calculated for a specific room. However, the equipment capacity of the air conditioning system is determined based on the cooling load of the entire building. Due to the different factors such as the orientation, location, use function and heat source of each room in the building, the time when the maximum cooling load appears in each room is often different. Therefore, the maximum building cooling load should be the maximum value of the hourly load superimposed on each room. According to the survey, some designers in my country simply superimpose the maximum cooling load of each room when calculating the cooling load of a building, resulting in the calculation result being much larger than the actual demand load. So we must pay enough attention to this to make the determination of the design load more reasonable and correct.

　　 2. The system circulation resistance is too large:

When calculating the cyclic resistance of the system, due to the lack of experience of the designer, some calculation parameters are too conservative, which causes the calculated value of the cyclic resistance to be too large. What is more, the estimation method is used to determine the cyclic resistance during the construction drawing design stage, resulting in the calculation cycle The resistance is more than double the actual value. The air-conditioning system can only operate when it is filled with water, and the inlet and outlet of the water pump bear the same hydrostatic pressure. Therefore, the head of the selected water pump can only overcome the resistance of the pipeline system. However, some designers include the hydrostatic pressure in the circulation resistance, which of course will increase the capacity of the circulating water pump a lot.

　　 3. System static pressure problem:

　　The air-conditioning system can only be operated when it is filled with water, and the inlet and outlet of the water pump bear the same hydrostatic pressure. Therefore, the head of the selected water pump can only overcome the resistance of the pipeline system. However, some designers include the hydrostatic pressure in the circulation resistance, which of course will increase the capacity of the circulating water pump a lot.

　　4. System hydraulic balance problem:

　　 Because the hydraulic balance calculation of the system is not carefully carried out during the design, and the comprehensive commissioning is not carried out as required after the completion of the project, the system is often hydraulically imbalanced and the system is unevenly cooled and heated. Some technicians mistakenly believe that the reason for this phenomenon is that the capacity of the circulating water pump is too small. As a result, it can be solved simply by increasing the water pump, which naturally increases the capacity of the water pump. Flange ball valve

　　 2. The reason why the design pump operating point shifts to the right along the pump characteristic curve:

When the working point of the water pump shifts to the right, the head produced by the circulating water pump decreases, which is extremely unfavorable to the normal operation of the system, especially the most unfavorable loop in the system, which will further reduce the flow of the loop and affect the normal Use function. There are two main reasons for the right shift of the working point:

　　 1. First, the hydraulic calculation in the design adopts an excessive safety factor and an impractical pressure drop calculation method.

　　2. Secondly, the designed system has not carried out serious hydraulic balance calculation, and has not carried out strict system debugging after construction. Therefore, in order to make the system operate according to the design conditions, in addition to careful calculations, the working point of the pump should be selected at an appropriate position on the left side of the best working point when selecting the pump to prevent the actual working point of the pump. Exceeding a certain range is in uneconomical operating conditions, affecting the normal operation of the system.