For cold water heater, the reduction of chilled water flow is quite dangerous. In the design of evaporator, a certain water flow (or a small range of fluctuations) is very important to ensure the uniformity of water flow in the evaporator tube. When the flow rate decreases, the flow rate is not uniform. In particular, in some conversion (such as head), the "shooter" with slow flow rate or no flow is more so in the process of continuous cooling of the evaporator due to the low temperature of the evaporator. Therefore, the energy flow of the cold water heater must be basically constant.

But on the other hand, from the perspective of terminal equipment requirements, users need to change the water system to change the amount of cooling (heat). The two constitute a pair of contradictions. The most common way to solve this contradiction is to install the differential pressure bypass valve on the water supply pipeline.

The working principle of the differential pressure bypass valve is that when the system is in the design state and all the equipment is in full load operation, the opening degree of the differential pressure bypass valve is 0 (no bypass flow), and the differential pressure at both ends of the differential pressure bypass valve (differential pressure of supply and return water at the user end) is P0. When the end load becomes smaller, the end two-way valve becomes smaller, and the water pressure difference P0 becomes higher, which exceeds the set value. Under the action of the differential pressure controller, the bypass valve opens automatically. Because the bypass valve is parallel to the water system on the user's side, with the increase of openness, the water pressure difference P0 will decrease, and it will not stop until it reaches P0. Part of the water flows from the bypass valve directly into the recovery pipe, and after mixing with the return water on the user's side, it will enter the water pump and the water chiller, so the water quantity passing through the water chiller will not change.

Finally, we talk about the selection of differential pressure bypass valve. Generally, we need to consider pressure, flow range, working pressure, interface form, temperature, medium and other factors in the selection. Now take the typical system as an example.

When selecting hznk differential pressure bypass valve, the following three points should be considered:

First of all, to compare the lift to determine whether its scope of work can include the largest lift circulating pump.

Secondly, in order to compare the flow rate, it is complex to study the flow curve of the differential pressure bypass valve to determine whether the flow will cover the flow of the pump. Not everything that covers this flow meets the requirements. Different caliber valves can meet this requirement, so it needs to be compared and confirmed according to the flow curve of pump and differential pressure valve.

Third, it is necessary to determine whether the working pressure, temperature and medium meet the requirements. The installation position of the differential pressure bypass valve must be between the inlet and circulation of the main pipeline. In other words, if there is no end, the differential pressure bypass valve can be directly connected to both ends of the main engine circulating pump.