The installation position of the cooling tower should consider the pressure requirements of the water system? What problems are likely to occur when multiple cooling towers are connected in parallel? This is a professional question about the cooling tower, and it also needs us to think about it carefully. Therefore, Xiaobian collected some information from the Internet, summarized and sorted out, and the answers are as follows.
There are two main forms of cooling water system: pump front type and pump back type. When determining, the bearing capacity of the water system should be considered. The largest bearing capacity of the water system is the water pump.
If the cooling tower is located on the roof of the main building of a high-rise building, the pressure generated is higher than the pressure bearing capacity of the unit, the cooling water pump should be located in the condenser outlet of the chiller to reduce the working pressure of the condenser. But the pump inlet negative pressure is too large, will produce cavitation. In fact, the height difference between the cooling tower and the water chiller is much greater than the resistance of the pipeline and the resistance of the condenser, and the water pump has a allowable vacuum suction height.
The cooling water system pump head calculation should be the system resistance (the sum of pipe, pipe fittings and condenser resistance), the height difference between the water level of the cooling tower water collecting tray and the cooling tower water distributor, the required pressure composition of the cooling tower water distributor, and the additional 5%-10% margin. The common mistake is to calculate the height difference of the system at the sight of the open system. Although the cooling tower is an open system, the cooling tower comes with a water collecting plate, which is equivalent to a water tank on the roof. The static pressure of the water and the static pressure required by the water supply pipe rise offset, so it only needs to be included in the height difference between the cooling tower chassis and the water pipe.
In the actual project, due to many reasons, the roof of the building is not allowed to place cooling tower, and the condenser is set in the high place. In this system, when the water pump stops running, the cooling water in the pipe returns to the tower to form a vacuum, resulting in siphon and backflow, and the water collection plate of the cooling tower will overflow all over the ground. The design generally takes certain measures, such as installing a vacuum destroy valve at the top of the cooling water pipe. Or a snorkel at the top.
When selecting the host, it is necessary to try to match the size so as to adapt to the change of load, but then the condenser, water pump and cooling tower are connected to be very troublesome. In engineering, when multiple cooling towers are running in parallel, there are generally 5 piping ways. Some engineering pipelines are the most complex, occupying a large space, but the flow distribution is reasonable and the operation reliability is high. While some of the pipeline layout is simple, but often appear overflow and water replenishment phenomenon, the main reasons are:
(1) When several cooling towers of different sizes are connected together, the water level in the tower is not the same high, and the tower with the lower water plate is bound to overflow.
(2) Generally, the inlet pipe of the tower is installed with an electric valve, while the outlet pipe is not installed. The inlet valve of the tower is closed without operation, but the outlet pipe is connected. When a single tower is operating, the water level in the cooling tower's tray rises, causing an overflow, while the other tower's tray is constantly replenished.
(3) The unbalanced distribution of water in each tower is mainly due to the layout of pipelines. Some towers have small resistance of inlet pipe and large resistance of outlet pipe. Too much water and too little water, resulting in overflow. Some towers do the opposite, constantly replenishing water.
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