Principle of Hydraulic Maladjustment Optimization

Date:2018-12-13 08:04:00 click:86

The balancing valve is equivalent to the adjustable resistance on the power grid. It is used to balance the resistance on the loop by setting the resistance value during system debugging. That is, when many loops are in parallel, in order to solve the problem that the current (water amount) of the distal loop reaches the rated current (flow rate), the loop near the power source (cold/heat source) must increase the resistance (that is, increase the resistance and set the balancing valve) to prevent the current (water amount) from increasing. There are two reasons for the unbalance of loop resistance. On the one hand, the system design is insufficient to provide the resistance value of balanced branch pipeline for some loops and equipment. On the other hand, during the construction process, due to the limitation of on-site construction conditions, the construction cannot be carried out in accordance with the design drawings, which increases or reduces part of the additional resistance, resulting in the destruction of the original design balance. To solve the unbalance problem caused by these two reasons, it is necessary to set static balancing valve in the proper position of the system for resistance distribution and flow distribution.

When the water supply and return temperature, temperature difference and water supply and return pressure difference of each building or unit need to be allocated are determined, the circulating water amount of each building corresponds to the building area, the circulating water amount per unit area can be calculated according to the load index of energy-saving buildings and the temperature difference between supply and return water. The flow rate of branch risers in each region can be adjusted according to this circulating flow index to make the area correspond to the circulating water flow rate of heating.

It is worth noting that, due to the temperature attenuation of pipeline extension, load infiltration or the change of the temperature of supply and return water, the circulating flow rate of buildings or units of the same area is also different to some extent. Therefore, it is necessary to conduct the flow rate of debugging unit according to the temperature difference between supply and return water of household units.

The realization of hydraulic balance must have several important characteristics:

1) The valve opening can be directly displayed, that is, the size of the valve opening can be determined by the position scale of the stem;

2) The valve body must have an interface for flow measurement, and the water flow of branch pipe segments can be measured in real time through the flow test instrument, so as to ensure that the water volume of the riser can reach the designed water volume;

3) The opening position of the adjusted valve can be locked to ensure that the hydraulic balance is not damaged by human after debugging. Therefore, the locking function is particularly important for the later operation management;

4) The measurement channel of the balancing valve can detect the water temperature and water supply pressure, so as to check whether the circulating water temperature of heating meets the design standard, and at the same time, it can judge whether the filter of the household unit is dirty and blocked, or whether the supply and return water pipeline is connected to the wrong position in the early stage of system installation (the pressure difference between the front and back of the valve is detected by flow measurement instrument;

In conclusion, after cleaning in the early stage of heating operation, the system adjusts the circulating water amount of each unit according to the occupancy condition of system users, so as to achieve accurate control of the circulating water amount of each unit.

The benefit to the system after the pipe network is balanced:

(1) Solve the uneven distribution of circulating water flow in the heating system (equivalent to the phenomenon that some floors or rooms in central heating are always too hot or too cold, and some rooms are never hot or cold);

(2) Solution in the operation of the system because of the time difference, the part of the heating system of circulating water flow high and low, lead to room temperature and high or low, poor comfort (equivalent to central heating, use less during the day, heating room temperature on the high side for a long time, night users increase, the room heating low temperature), can never achieve stable and comfortable environment;Especially at low and medium loads, although terminal devices have sophisticated controllers;

(3) To solve the fluctuation of the number of users in the operation of the system, the frequency of repeated start and stop of the heat exchanger unit increases, the energy consumption of the system increases, and the service life of the main engine is affected;

(4) Solve the problem that some rooms will never reach the required design temperature, especially when the load changes;

(5) Although the rated power of the production equipment is sufficient, the designed power cannot be transmitted, especially during startup after weekend or night reset;

(6) The most important thing is: after installing the balancing valve and debugging the heating system, the system circulation system can effectively control the temperature difference between supply and return water, and reduce the time required to reach the system design temperature difference, so as to reduce the energy consumption of the circulating water pump when the system is running.