The heating system is composed of heat exchange station, secondary network and indoor heating equipment. The pipe circulating pump is the key machine and equipment for transporting cooling water system to customers, and is the machine equipment in the core area connecting the heat exchange station, heating network and the heating system in the room, and also the key power consumption machine equipment in the heating system.
In specific work, the main parameters of the circulating pump are relatively wide, some of which are even more than twice the original main parameters. If the total flow rate and pump head of the circulating pump are too large, the electromagnetic energy will be consumed seriously. Therefore, it is important to select and install the circulating pump effectively.
The reason for the selection of circulating pump is a little larger
1. the design scheme does not carefully calculate the heat consumption and system software friction resistance, especially the friction resistance in the external network address and heat exchange station, and the estimation method is adopted. For insurance, the estimate is too high to increase the total flow and head of the selected circulating pump.
2. the system software did not carry out the initial adjustment with great effort after operation, and the system software had hydropower imbalance. In order to deal with the problem of non cold end customers, the circulating water pump with high power was removed and replaced.
3. The definition of pump power of circulating system is unclear. When designing the scheme, the ratio of software height to width is recorded in the pump head, which makes the pump head of circulating pump greatly increase and the energy consumption of circulating pump is also increased.
4. when selecting circulating water pump, it is difficult to select the centrifugal pump with the total flow and the pump head completely consistent due to the limitation of the specifications and models of centrifugal pump, and generally, it is difficult to select the larger one. This improves the operation of centrifugal pump power consumption, increased the operation cost of heating.
Selection of circulating pump
1. selection criteria
Circulating pump is often occupied in heating system, whether it is volume or total number of machine and equipment, there are many problems in operation. Therefore, it is very important to select, use and manage methods properly to ensure all normal heating and improve economic benefits. The following criteria should be taken into account in the selection:
① The selected circulating water pump shall reach the large total flow and pump head that is often required in the system software. In addition, the better working condition point of the circulating pump shall be close to the specific working point of the system software as far as possible, and it can operate in the high efficiency area for a long time to improve the rationality of the long-term operation of the circulating pump.
② It is necessary to select the circulating water pump with simple structure, small size, light weight and high efficiency.
③ It is expected that it can be reliable, stable, vibration small, low noise and good cavitation resistance.
④ The centrifugal pump with large total flow change and small head change is selected, that is, the centrifugal pump with a flat g-h characteristic curve.
2. Select many aspects to pay attention to
(1) Determination of total flow of circulating pump
The total flow of the circulating pump is determined by the sum of the customers' heat load under the outdoor temperature of heating, while the time for outdoor temperature calculation is very short in all heating time, which makes the total flow of the centrifugal pump larger in most of the time. Before the selection of circulating pump, the adjustment method of heating pipe network system software should be clear, and then the total flow of circulating pump should be clear according to the adjustment method of system software.
For the new heat exchange station, centrifugal pumps with different total flow can be installed. One 100% total flow and two 50% total flow circulating pumps are installed. The centrifugal pumps are adjusted according to the number of users and outdoor temperature. In addition, DC frequency conversion is selected to make the centrifugal pumps soft start, reduce the operating current and improve the service life of the centrifugal pumps, At the same time, it can adjust the total flow according to the change of temperature and the heating curve of different time periods at any time, so as to save electromagnetic energy and reach the water flow regulation of different stages of the circulating system, so as to achieve the actual effect of environmental protection and energy saving.
(2) Friction resistance of heat exchanger
The internal friction resistance of the heat exchange station is mainly the friction resistance of the heat exchanger. The import and export trade pipes of the heat exchanger should be consistent with the pressure test capacity between the heat transfer plates. If necessary, the total number of heat transfer plates can be moderately increased to reduce the gas pressure of the import and export trade. If necessary, the bypass valve pipe can be used to assist in many aspects, so as to prevent the total flow of the heat supply network customers from being insufficient.
3. How to choose
At present, the sales market has a complete range of pumps, suitable for heating system, such as single pole single suction or single pole double suction vertical pipe pump, single pole single suction horizontal centrifugal pump, direct single pole single suction horizontal centrifugal pump, shaft open single pole double suction horizontal centrifugal pump and single pole double suction middle open vortex shell centrifugal pump. Be able to select according to the following process:
(1) The original calculation of the total flow and pump head can not be carried out extra.
(2) Find the pump of a certain model and specification in the determined centrifugal pump series product table, and the total flow and pump head searched are consistent with the symbolic total flow and pump head listed in the "centrifugal pump characteristics table" (generally in the middle row). If there are two types of pumps of the above model and specification can meet the requirements, it needs to be measured and analyzed, Generally, the pump with higher specific speed (NS), small structure and light weight should be selected.
(3) After selecting the model and specification of the pump, it is necessary to check the operation of the pump in the system software, observe its total flow and pump head change scope, and check whether it is working in the high efficiency area. If the operating point is far away from the high efficiency area, it indicates that the rationality of the pump in the system software is poor, so it is necessary to select the pump again.
In a word, for the selection of circulating pump, we should use different methods to adjust the pipeline network of heat exchange station, calculate the system software load and friction resistance in detail, select the suitable centrifugal pump, and calculate whether its power consumption and heat transfer ratio meet the requirements. In addition, the pressure of centrifugal pump should be indicated, so it is not necessary to mistake the pump power as its pressure. In order to increase the power of waterproof pump, the electromagnetic energy is consumed.
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