The corresponding transformation of energy through the circulating pump of central air conditioning analysis. And through on the central air conditioning circulating pump power supply frequency conversion processing and general condition, circulating water pump through years of frequency conversion control can be more than 45% of the energy-saving. The central air-conditioning circulating water pump power supply frequency conversion, energy saving effect is obvious, worthy of promotion.

General equipment for a wide range of large, more power consumption. The circulating water pump is an important auxiliary equipment of central air conditioning. Mainly divided into cold (warm) cold water pump, central air conditioning is widely used in enterprises and other places. Cooling water pump. Conservative circulating pump control is full rated operation, circulating pump provides fixed water, heat exchange. And actual production and life. With the change of external temperature and other indicators and need to flow control and adjustment, the most commonly used method is by regulating valve or damper opening degree to adjust the controlled object, thus making quite a lot of energy to valves, baffles and interception loss loss consumed many central air conditioning circulating pump operating efficiency is only 45% - 50% thus, improve the pump efficiency is very conducive to the economic operation of central air conditioning.

Energy consumption analysis of circulating water pump in central air conditioning system

In China, a large number of field survey data from the National Institute of refrigeration display. Especially in the Pearl River Delta region, the annual air conditioning boot time is about 10 months.

Space circulating pump energy-saving central air conditioning so great. From above we can see 100%70% load in 789 in; 70%40% load presented in 5610. Below 40% load presented in 341112; visible in a system load rate accounted for more than 50% of the overall running time in more than 50% of the time.

Energy saving analysis of circulating water pump

Variable frequency variable speed pump has great potential for energy saving. According to the analysis of the following diagram of pump power curve characteristics.

Operation analysis of 1 air conditioning system water pump

Increase the 5%10% of excess circulating pump output must be at the maximum flow rate and resistance of the water cycle system based on rated power. Because of the circulating water pump is adopted mostly running speed, central air conditioner circulating pump is set out from the angle of the safe operation in accordance with the maximum load in a year were selected. It convenient to load regulation are generally taken by the regulation of baffle or valve opening to control the flow and pressure, resulting in large throttle loss, waste a lot of energy.

2 variable frequency variable speed regulation method

If the speed change, the pump characteristic curve provided by the manufacturer. Pump performance changes, so that the operating point changes. Variable speed (slow down) by adjusting the pump operating point, does not produce additional friction loss, so higher efficiency, adjustment to adapt to a wider range.

3 pump adopts frequency speed after the analysis of energy saving

1 non peak flow regulation

For example, in the air conditioning system: flow Q'=0.8Q that n'/n=0.8

Then: N'=n'/n3N=0.8*0.8*0.8N=0.512N

Type: QHN represent the pump speed for n when the flow rate, head and shaft power.

From the above formula by variable speed pump can save electricity 49.8% when the flow is reduced to 0.8 times the original.

The "York YS450" two sets of screw chillers, taking a project as an example. 45kW cooling water pump 3 units (of which 1 for spare) 37kW cooling water pump 3 units (of which 1 for spare) 250m3/h cooling tower 2. Chillers chilled water flow of the maximum and minimum values were 356m3/h and 163m3/h chilled water system flow of the maximum and minimum values were 712m3/h and 163m3/h adjustable range of chilled water flow 22.9%~100%

Under the condition of chilled water flow 80% saving electricity (45kW2+37kW249.8%=81.67kW day according to the 10 hour operation to save electricity 81.6710=816.7kWh electricity, the air conditioning system 2 sets of chilled water pump, 2 sets of cooling water pump through calculation of the most conservative. Every year is calculated according to 8 months of operation, save power 816.7308=196008kWh power, thereby reducing the cost of air conditioning operation greatly.

Not only can save electricity, water pump using frequency modulation scheme. But you can also get such in the following aspects.

2 circulating water pump motor start

To overcome the large current impact of motor start and stop pump water hammer, water pump motor soft start. Reduce the impact on the grid at the same time, but also reduce the power consumption of reactive power and prolong the service life of equipment.

3 chilled water pipe network regulation

And the constant pressure difference a number of closed loop adjust the pump speed and decided to put into the pump due to the freezing water pipe network water is vary with the load of chiller and water quantity, types of input is randomly occurring between so load content, cold water unit of water pump running water quantity three are very difficult to match. Can scientifically, more than three of the balance, and save a lot of water pump power.

Electrical implementation system

To achieve the purpose of saving energy to ultimately improve the means of electrical control, frequency speed adjustment of water circulating pump in air conditioning water system. Can achieve the following key points in the design of electrical control.

The differential pressure sensor to provide the working content of the condenser, 1. Chiller condenser, water outlet pipe device differential pressure sensing transmitter. In order to limit the flow of dynamic water flow working set, the maintenance of value.

The differential pressure sensor to provide the working content of the evaporator, 2. Water chiller evaporator inlet, outlet device differential pressure sensing transmitter. In order to limit the flow in variable flow work setting, the maintenance of value.

Cold signal sensor transmitter provides the unit opened number. Cold quantity transmitter also provides critical flow of cold water (less than minimum flow rate of a water chiller) open the differential pressure signal of the bypass valve. 3 cold water chiller refrigeration device sensor transmitter.

4 chillers chilled water and cooling water pipe device for temperature sensing transmitter.

5 frozen water chiller water and cooling water pipe pressure sensor device.

Inverter based on the total, measuring the return pipe of the pressure difference and the set pressure is, 6. The chilled water system, cooling water system respectively, the device a frequency converter. Variable frequency speed regulation and according to inputs or the withdrawal of water pump units (input process of the implementation of soft start, variable frequency operation, frequency operation) in a comprehensive way, closed-loop control of a constant total, return pipe of pressure difference.

There is a certain economic benefit and society benefit, central air-conditioning circulating water pump and application of inverter. And also it is feasible in technology of circulating water pump equipment with variable frequency speed control technology is an ideal speed control mode, not only with the significant energy-saving effect, and is convenient for operation, improve the efficiency of the equipment, reducing equipment maintenance, maintenance costs, better meet the requirements of the production process, the economic benefit is very obvious.