Currently in the field of real estate water ring heat pump air-conditioning system due to its high system efficiency (compared to air-cooled heat pump system), investment and living, easy independent billing and other characteristics of a wide range of applications, but also achieved some economic benefits. However, the system also exposed some problems during use. As part of the load conditions, how to reduce the pump power consumption? In the real estate project air conditioning system, the current use of sub-district independent household water ring heat pump unit, each district (households) use their own needs to determine the opening and closing time and the required temperature. Cooling water system set. Each district (household) charges their respective meters when they are charged, and the electricity charges of centralized pumps and cooling towers are apportioned by each user. This raises the question of how to reduce the pump's power consumption during the transitional season and when only a few users are staying. On this point we will naturally think of the pump to run with variable water. But the problem is that the conventional central air-conditioning system chilled water pump variable range of water is limited by the type of chiller evaporator, usually full liquid evaporator is not less than 70% of rated water, dry evaporator and lithium bromide unit evaporator Less than 50% of rated water. However, for the water ring heat pump system, its partial load may reach 10% or less. How to maintain the economic operation of the water system under such a small load? Water system in the design to take what measures? First: Each water ring heat pump unit cooling water into the goods are set two-way valve, the switch linkage with the unit, the unit open to open, the unit off it is also closed. Second: the unit side of the pump open and stop and two-way valve linkage, the system as long as there is a two-way valve is open, the unit side pump put into operation. Third: the unit side pumps according to the supply and return pressure for frequency control. Fourth: Pump in the system design process should consider the load characteristics with reasonable size. Fifth: cooling tower (boiler) side of the pump according to the system back to the temperature decided to open stop. (32 ℃ above or below 16 ℃) The above program in the implementation process mainly to solve two problems. The first is based on the load characteristics of how to configure the unit side of the pump. The second is the system uses what kind of control. For these two points we have to elaborate. 1 unit side of the pump configuration Water pump variable speed operation of the variable water system in the selection of the pump should pay attention to two points, first, to prevent the variable speed pump vibration frequency and vibration isolation device the same natural frequency resonance. Second, to prevent the water system due to the closure of two-way valve caused by changes in the characteristics of the pipeline, so that the pump operating point into the surge zone. (On this point in the pump selection by the manufacturer to check) Here we pass through a project example to illustrate the variable water pump system selection. A real estate project using water ring heat pump air conditioning system, the total cooling water 600t / h, the system may reach the minimum load of 5% of the design load. , Under normal circumstances configure the three pumps, each flow is 200t / h. Assuming the rated speed of the pump are 1450r / min. When the partial load of 5%, if the amount of circulating water decreases, then the pump speed will reach 218r / min (constant pressure pump flow and speed into a relationship). What happens then? We know a speed of 1450r / min pump vibration frequency is about 24HZ, when the pump speed reduced to 218r / min when the pump vibration frequency is about 3.6HZ. The natural frequency of the shock absorber is about 3 ~ 6HZ. This pump will slow down in the process of resonance. Therefore, in order to prevent resonance (also to control the pump vibration transmission rate), and general civil buildings in terms of pump vibration frequency and natural frequency of the shock absorber should be more than 2.5. In this example, it is assumed that the natural frequency of the shock absorber is 6HZ, then the vibration frequency of the pump should be above 15HZ and the minimum speed of the pump should not be less than 900r / min (at this moment the pump flow is about 120t / h). This speed corresponds to the system at 20% of the partial load. Therefore, in order to ensure that the pump can operate economically even when the system is under a lower load, we have another small pump in the water system design. Small pump configuration is based on the principle of a large pump running to its minimum speed, if the system load is still further decline, then the big pump down, turn on the small pump. That is, the maximum flow of a small pump for a large pump speed after the minimum flow. In this case the flow of a small pump should be 120t / h (its rated speed is still 1450r / min). When the speed of 900r / min, the flow rate of about 75t / h, this flow corresponds to about 12.5% ​​of the part load. This pump configuration can basically meet the economic operation of the water system. If you need to further reduce the water flow with the load drop, it can also be equipped with a smaller flow pump. The same principle. In this example, the nominal flow of this pump is 75t / h (rated speed 1450r / min). When the speed drops to 900r / min, the pump flow drops to 45t / h, which corresponds to 7.5% of the system load. This configuration can further reduce the pump at low load power consumption. 2 variable water volume control system Variable water volume system uses DDC control, the advantages of this control method is (1) the entire system is reliable, energy-saving. (2) cheaper prices, low installation costs, save space. (3) easy to use, easy to upgrade, strong security. (4) Have technical support. (5) Can realize the soft start of the pump, make the startup process have little influence on the power grid. The entire control system is in each floor or a certain air-conditioning area set a site controller, when a water ring heat pump unit is put into use corresponding to the two-way valve that is open (unit and two-way valve control by the unit itself Supporting controller). Two-way valve account opening signal to the scene controller, and then by the scene controller signal to the central building of the central controller, and finally by the central controller will signal to the pump, control the pump start. When all the water ring heat pump units in the system stop working, all two-way valves are closed, no signal is sent to the scene controller at this time, and there is no signal input from the centralized controller. In this case, the water pump is turned off. After the central controller sends the signal to the pump (group), the pump starts. According to the example above 75t / h flow of small pumps first start. The speed of the pump after start-up by the side of the supply and return water pressure control, with the system put into operation more units, was opened two-way valve also will increase, the system for the return water pressure gradually decreased, the water pump The speed gradually increased. When the speed of the small pump reaches its rated speed, the pressure difference between the supply and return water will decrease if it decreases again. The small water pump stops running. The pump with the flow rate of 120t / h is put into operation. If the open two-way valve in the system continues to increase , The system supply and return water pressure continues to decrease, the pump speed continues to increase, when the pump reaches its rated speed, if the supply and return water pressure drop then the pump stops running, a 200t / h flow pump started . The speed of this pump is still gradually increased by the differential pressure of the supply and return water. When the rated speed is reached, the second 200 t / h pump is put into operation if the differential pressure between supply and return drops again. At this time the first 200t / h flow pump deceleration, the two pumps at the same time by the supply and return water pressure control to maintain synchronous speed. When both pumps reach their rated speed, the third 200 t / h pump continues to operate if the pressure differential continues to drop. At this point the original speed reaches the rated speed of two pumps decelerate, three pumps with the same supply and return water pressure control to maintain synchronous speed until the system reaches full capacity of three pumps have reached the rated speed. For the cooling tower (boiler) side of the pump its open stop by the unit side of the pump backwater temperature control, fixed water volume operation mode. When the return water temperature exceeds 32 ℃, the pump is turned on and the cooling tower is put into operation. When the backwater temperature is lower than 16 ℃, the pump is on and the boiler is put into operation. 3 Economic Analysis of Variable Water Running How is the energy-saving effect after using the variable water volume operating mode on the side water pump of the unit? We still make an analysis according to the previous engineering examples. The real estate project is a comprehensive project, which includes office, shopping malls, residential and other parts. Its annual air-conditioning running time is 250 days. (Ie 6000 hours) The distribution of air-conditioning load throughout the year in the whole building is shown in Table 1. Load rate% 5 10 20 30 40 50 Time frequency h 300 400 400 500 750 800 Load ratio% 60 70 80 90 100 Time frequency h 1000 800 700 300 50 Several models of pumps rated power respectively: (1) flow 200t / h pump, rated power of 22kw. (2) flow 120t / h pump, rated power of 11kw. (3) Flow 75t / h pump, rated power of 7.5kw. According to the constant pressure system pump flow and input power showed a one-way relationship, we can calculate the variable water pump system at different air conditioning load factor of the input power. See Table II. Load factor% 5 10 20 30 40 50 Input power kw 4.5 6 11 19.8 27.2 33 Power consumption kwh 1350 2400 4400 9900 20400 26400 Load factor% 60 70 80 90 100 Input power kw 39.6 46.2 52.8 59.4 66 Power consumption kwh 39600 36960 36960 17820 3300 Accumulated 199490 If the project pump is not configured with two other small pumps, only three large pumps for speed control. So in the partial load conditions the annual pump power consumption will happen? See Table III. Load rate% 5 10 20 30