How to realize the variable flow regulation of the circulating water pump in the heating system

How to realize the variable flow regulation of the circulating water pump in the heating system

After heating metering and charging, the radiators are equipped with temperature control valves. Due to the regulating effect of the temperature control valve, the heating system changes from constant flow (that is, quality adjustment) operation to variable flow operation. But at this time, the change of system circulation flow is caused by the throttling effect of the temperature control valve (or electric control valve).

Observed from the working curve of the circulating water pump, its operating point will shift to the left, causing the pump lift to increase and the flow rate to decrease, while a large proportion of the power output by the motor is consumed on the throttle of the regulating valve, causing electrical energy Unnecessary waste.

　　 At present, in a considerable number of water systems with combined cooling and heating, a differential pressure regulator is used to adjust the variable flow rate. The specific method is to install the pressure difference regulator on the bypass pipe of the heat source or cold source. When the user needs to change the heat (cold) load, the regulating valve on the radiator (or fan coil) will adjust, which will cause the bypass pipe. When the upper pressure difference changes, the pressure difference regulator works to keep the pressure difference of the bypass pipe constant, so as to adjust the change of the user's system circulation flow.

　　 It should be said that this adjustment method is good for improving the working conditions of the user's control valve (such as temperature control valve, electric control valve), but from the perspective of power saving, there is no improvement.

　　 Starting from the goal of improving the energy efficiency of the system, in the design of the metered and charged heating system, the variable flow design of the system's circulating water pump should be synchronized. Minimize the energy loss caused by unnecessary throttling. In doing so, at least the following benefits can be brought:

　　 First of all, the system energy efficiency is improved. The circulating water pump realizes variable flow regulation, which can save electricity by at least 30%-50% during the entire operation period. The actual energy-saving potential of this technical measure is far more obvious than the current discussion about the effect that the head of the circulating water pump should not be too large.

　　Secondly, the working conditions of control valves (temperature control valves, electric control valves) have been improved. If the circulating water pump implements constant flow operation, when the load demand changes greatly, the opening of the regulating valve will vary within a large range, which will not only affect its service life, but also be prone to failure.

　　 When the circulating water pump realizes variable flow regulation, its flow rate is controlled in time with the change of load. In this way, the regulating valve is always in a state of fine-tuning, which not only improves the regulating function, but also greatly improves its working conditions. The superiority is obvious.

　　 Secondly, it can also effectively cooperate with the adjustment function of the self-operated balance valve. As for the self-operated balancing valve, it has gradually been widely used in China. For the self-operated balance valve, its superiority has been recognized by the majority of professionals in the constant flow system (such as the circulating water pump running at a constant speed, installing a three-way valve, etc.).

　　 But in a variable flow system, can a self-operated balancing valve be used? It has become a hot topic of concern among industry personnel. It should be admitted that in the variable flow system where the circulating water pump runs at a constant speed, the use of self-operated balancing valves is flawed.

　　People are familiar with: The function of the self-operated balance valve is to automatically limit the system flow to the set flow. When the system requires low flow conditions, the regulating valve (temperature control valve, electric regulating valve, etc.) will be closed. At this time, the self-operated balancing valve tries to maintain the original set flow, and its spool tends to open. This leads to the inconsistency of actions between the regulating valve and the self-operated balancing valve.

If we use circulating water pump variable flow regulation at this time, the total flow of the system will decrease in real time as the load decreases, which will cause the pressure difference between the front and rear of the self-operated balance valve to be less than the working pressure difference of its spring, and the self-operated balance valve will no longer open. , The discordance phenomenon can disappear.