In the central air-conditioning system, the cooling tower, as a terminal cooling device, has very important functions. The configuration is effective, convenient and usable, economical, safe and reliable. If the configuration is not scientific, it may cause a lot of consumption, and even more serious, affect the normal operation of the refrigeration unit, and have obvious adverse effects on manufacturing and daily life. Like a single tower, compared to a multi-tower system, if the process design is unscientific, it can also produce huge consumption and affect manufacturing. This article is talking about the multi-tower system of subway stations. Because of the small size of the cooling tower balance pipe, the system is out of control, which affects the production and manufacturing. According to scientific research, analysis and estimation, this problem is solved.
Take a subway station in Shenzhen as an example today to prove its deficiencies.
A subway station in Shenzhen is a large station that integrates railway station, bus, minibus, taxi, border control, and central park. It has complete functions and is divided into landscape layer (ground layer) and traffic layer (underground layer). , Metro station hall floor (basement level two), subway station entrance level (basement level three). The area of the hall floor is about 5700m2, there are several entrances and exits, and the design temperature is 30℃. The area of the station entrance is 2641m2, the design temperature is 27℃, the design temperature of the air-conditioned equipment room is 25℃, and the equipment configuration of the subway station air-conditioning system is as follows:
As far as the equipment configuration is concerned, there is a one-to-one start-up, that is, one main engine matches one cooling water pump, one chilled water pump, and one cooling tower. When two main engines are turned on, it matches two chilled water pumps and two cooling towers. Two cooling water pumps and two cooling towers. There are two control modes of the system: automatic and manual. The control boxes of refrigeration pumps, cooling pumps, and cooling towers (the electric valve is on the cooling tower control box) have automatic, stop, and manual changeover switches. The fan of the cooling tower is controlled by the exhaust pipe pressure of the main engine and the temperature of the cooling water. The exhaust pipe pressure is higher than 1310KPa, and the first fan starts. When the exhaust pipe pressure is less than 1170KPa, the first fan stops. The second/third fans (parallel with the first fan) start and stop controlled by the cooling water temperature. When the cooling water temperature is higher than 30℃, the second fan starts; when the water temperature is less than 28℃, the second fan stops. When the switch is in the manual position, the machinery and equipment can be selectively turned on according to needs, such as: 1# refrigeration pump → 2# electric butterfly valve → 2# cooling pump → 2# host. But at this time, the temperature of the cooling water cannot control the stopping of the fan. In terms of the specific operation of the system, when two refrigeration units were opened, the system was normal; but when one refrigeration unit was opened, the cooling tower was abnormal: the operating tower was overflowing, and the stopped tower was making up water. The same problem occurs in other subway stations. Try to deal with the following methods:
1. Change the water replenishment float valve. When the water level line is low, and some leaks out of the return pipe, the return water sucks in the air, the cooling effect declines, and the exhaust pipe pressure rises until the high pressure alarm trips;
2. Turn off the water make-up float valve of the stop-use tower. As a result, the water level of the tower will be very low, so that the return water will suck in the air, and the cooling effect will decline. Once the main engine is replaced, the cooling tower needs to be replaced, so that the other tower is replenishing water.
3. Turn off all the water replenishment float valves. In the summer of Shenzhen, if water is not replenished for one hour, the cooling tower will be short of water and the main engine will trip.
4. Open the bypass valve of the tower electric valve that stops using the tower. The opening happens to be no need to make up water. This temporarily solves this problem (in fact, part of the cooling water is not cooled by the fan). Finally, the tower does not leak water, the host does not jump, and can operate normally. However, these methods are only used in the short-lived seasons of spring, autumn and winter in Shenzhen. In the long summer, it would be useless to start it like that, and the main engine would frequently trip at high temperature, which affected the normal operation of the passenger station.
5. Turn on the bypass valves of the two towers, place the cooling tower manually, and turn on the fan motor. That's okay, and it can save a lot of electricity. But at night, due to the subway outage, there are no passengers, and the temperature is uncertain. , Tripping often occurs. When the cooling tower is placed fully automatic, part of the cooling water is not cooled by the fan, resulting in high condensing temperature and large host current (about 6% in actual measurement), resulting in large consumption, and frequent high temperature trips, providing large Trouble.
After the renewal and transformation, I carried out a specific test. The specific test of the water level drop is 50mm, the standard deviation is 45.6mm, and the error is 4.4mm, which is basically the same as the theory; the cooling water is all cooled by a fan and becomes controllable. That way, during normal startup, the tower is not easy to seep water, the fan is controlled by the temperature and pressure of the cooling water, and the chiller is not easy to alarm and shut down. The actual operation and control are simple, easy to use, basically no maintenance, and the original standard is achieved. Therefore, this time the renovation was successful.
Guangdong Trlon Energy-saving Air Conditioning Equipment Co., Ltd.
Company Address： 1916A, Block A, David Donglong Business Building, Longhua, Longhua District, Shenzhen