Abstract

Introduction

Modern life is unthinkable without pumps. Effective and safe for the environment pumps move any liquids - hot or cold, clean and pollution — providing comfortable living conditions to everyone.

In life support systems of buildings used by a lot of pumps. They perform a variety of functions.

Most famous of them— circulating pump for heating systems. In addition to the circulating pumps systems used:

• pumping stations to increase the pressure needed to serve of water to the building with insufficient pressure in the city water system;

• pumps for hot water systems that provide hot water supply at any time in any crane;

• pumps for drainage and drainage of sewage and dirty water;

• pumps for fountains and aquariums;

• pumps for fire fighting applications;

• pumps for cold water and cooling systems;

• heat pumps;

• many others.

Very often the owners of private homes are confronted not only by the lack of hot water, but also with the task domestic heating. Gas or electric flow heaters, as well as electrode boilers (electric boilers) require maintaining a certain pressure in the system. Here, the pipeline must be necessarily connected to the apparatus maintaining a stable pressure — circulation pump.

Apply circulation pumps: a radiator and geothermal heating systems, «warm floors» as well as for hot water supply of houses and apartments. They had a great serve, don't occupy much space and almost noiseless. Because they don't need much heat the coolant, in contrast to schemes with natural circulation, don't use circulator pump. To the desired parameter in the heating circuit was maintained automatically require special thermostat responsive to the outside temperature. It will be useful circulating pumps with built-in auto-adjusting — they alter the frequency of the rotor, depending on the needs of the system. Thus, almost double the costs are reduced energy and cost! In addition, a stable regime of water supply and extend the life of heating appliances.

Topical issue

Water systems (WS) are among the most demanding technological facilities in the communal agriculture and industry. The biggest component is the resource-consumption. Ukraine belongs to energy deficient countries. Therefore, energy savings as an important avenue of energy policy in Ukraine and relevant is the scientific and technical problem of reducing energy intensity of the technological process water. Decision of this problem can be achieved through the use of improved technology and electrical equipment or the development of automation of pumping stations (PS) to improve management processes technological equipment and improvements at the expense of the economic performance of WS.

Objective

Aim of this study is to improve the economic efficiency of water supply systems by applying methods of energy saving operating modes of the pumping stations with pumps having a wet rotor.

Object of study

Object of study— automated management of pumping stations of water supply systems.

Subject studies

Subject studies — automation of decision-making procedures and processes of governance modes pumping stations to reduce the energy intensity of processes of water supply.

Methods

Methods based on regulations and methods of the theory of hydraulic networks theory of automated electric, optimization techniques, linear and nonlinear programming using a computer.

Main section

The energy consumption of centrifugal pumps

Motor drives the pump shaft rotation that has the impeller.

The pump creates high pressure and fluid moves through it, which is the result convert electrical energy into hydraulic. The energy required engine, called the energy consumed by the pump P1 [1].

Output characteristics of pumps

In an experiment using two pumps Wilo-TOP-S received the output characteristics of centrifugal pumps, which are shown in figure 1: vertical axis, the ordinate, mean energy consumption P1 pump in watts [W]. The horizontal axis or abscissa shows the pump flow Q in cubic meters per hour [m3 / h]. In catalogs characteristics of pressure and power are often combined to demonstrate relationship. Output characteristic demonstrates the following relationship: motor consumes minimum energy at a low pitch.

With increasing feed consumption also increases.

Figure 1— Characteristics Wilo-TOP-S

Effect speed motor

When you change the rotation frequency of the pump and the other conditions of constant power consumption P varies in proportion to the value of the frequency n in the cube.

Based on these considerations, changing the speed of the pump can be adapted to the required pump heat load of the consumer. With increasing speed doubled, increasing supply in the same proportion. Pressure grows to four times. Therefore, the energy consumed by the drive is obtained by multiplying by approximately eight. By reducing the frequency, flow, pressure in the pipeline and energy consumption are reduced in the same proportion.

Сonstant rotational speed, due to the design

Distinguishing characteristic of the centrifugal pump is that the pressure depends on the motor and its speed. Pumps with a frequency of n > 1500 rpm called high-speed pumps, and those with frequency n <1500 rpm called slow.

Motors slow pumps have a more complex structure, which means they are more expensive. However, in cases where the use of low-speed pump can even be due to the characteristics of the heating circuit, the use of high-speed pump can lead to unnecessarily high energy consumption. Thus, the high price of low-speed pump offset by substantial savings of energy consumed by the drive. This facilitates rapid return initial investment.

Providing a controlled reduction of speed while reducing the heating load, the device stepless speed control contributes to significant savings.

Рarameter control of pumps depending on HEAT LOADS

Switching speed pump

Pump manufacturers offer pumps with wet rotor with a manual speed control. As mentioned in previous sections, with the decrease in speed is reduced and the volume consumption (supply) — depending on the capacity and thermostatic control valves. Thanks to these properties, the circulation pump can be switched to a lower rotational speed, when need to reduce the temperature in the room, and vice versa.

Figure 2 — Characteristics of Wilo-TOP-S

To rotational speed of motors can be varied in their design used multisection coil. If the pipelines of the heating system is a small amount of water, the resistance inside the pipe is low, so the pump can operate in the minimum speed. At the same time significantly reduced consumption electrical power.

Meanwhile, it designed a large number of control devices [2], for smooth stepless control of circulation pumps of heating systems. These devices control the frequency change speed automatically depending on the following parameters:

• time

• water temperature

• differential pressure

• other factors affecting system performance.

Infinitely variable speed control

Possibility stepless speed control of pumps with dry rotor equipped high-power motors, depending on the heating load appeared in the first half of the 80-ies. For this purpose the electronic frequency converters.

To understand this technology can recall that in a normal mains AC current has a frequency of 50 Hz. With a frequency proportional to the rotor rotates in the pump motor.

With electronic devices can increase or decrease the frequency of alternating current, i.e. continuously regulate the frequency, for example, between 100 Hz and 0 Hz.

However, in connection with the design of the motors, the frequency of current in the heating systems can not be less than 20 Hz or 40% of the maximum speed. Since the maximum heat is calculated for the coldest days, the need to use motors with a maximum frequency of rotation can occur only in exceptional cases. Manufacturers of pumps offer pumps with wet rotor with a manual speed control[3]. As mentioned in previous sections, with the decrease in speed is reduced and the volumetric flow rate (flow) — in Depending on the capacity and thermostatic control valves. Thanks to these properties circulation pump can be switched to a lower rotational speed, when you need to reduce the temperature in the room, and vice versa.

20 years ago had to use huge transformer units, frequency converters are now so small that they can easily fit in the terminal boxes directly on the pump body, such as a pump Wilo-Stratos[5].

Integrated stepless speed control ensures the maintenance of established pressure at a constant level irrespective of what should be the feed, determined by weather conditions and features operation.

In 2001 took another step forward in developing pumps with wet rotor[9]. The advantage of the latest generation of these pumps, also called high-efficiency pumps, is essential power savings through the latest technology ECM (engine with electronic communication, or motor with permanent magnet) in combination with high efficiency.

Сontrol methods

Presented on the market today pumps with electronic controls allow you to choose different ways of regulating and operating modes with electronic control unit.

This should make a distinction between the ways of regulation[4] in which the pump is regulated automatically, and operating modes in which the pump is not automatically adjusted, and adjusted to a operating point by using the commands.

Below is an overview of the most frequently used methods of management and operating modes of the pump. With the additional controls and regulation can be manipulated, and transmitted as a series other information.

Possible control methods:

Δpc - Permanent pressure drop Electronics supports the generated pump pressure drop within the permissible range at the level of the adjusted set point differential pressure HS to achieve maximal performance.

Figure 3 — Permanent Pressure Drop: Δpc

Δpv - Variable pressure drop Electronics serves a given change in pressure drop, which should be supported by a pump For example, linear in the range from HS to 1/2HS. The nominal value of pressure differential (H) decreases or increases depending on the feed (Q).

Figure 4 — Pressure differential: Δpv

Δp-cv — Variable/ permanent pressure drop In this method of control electronics maintains a pressure differential created by pump at set point differential pressure to achieve a certain feed (HS 100%). With a further decrease in supply electronics linearly changing pressure drop, which should supported by the pump in the range of HS 100 HS% to 75%.

Figure 5 — AC / DC differential pressure: Δp-cv

Δpt - Regulation of the pressure drop of temperature In this method of control electronics change the set value of pressure differential, which should be supported by a pump, depending on the measured temperature of the medium.

Figure 6 — Regulation of the pressure drop of the temperature: Δpt

Conclusion

Thus, the results in their totality, can reduce energy supply systems automation. Algorithms and software ensuring decision-making procedures for optimal selection of the working technology scheme, the formation of technological tasks for the National Assembly, coordination modes controlled pumping units to maximize the current value of efficiency NA as well as the functional structure of the automated control system of technological equipment NA can be the basis for design development of automation systems of the National Assembly.

At the time of writing the summary master's work was not completed. The final work can be obtained from the author or scientific adviser after December 2010.

Literature

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9. http://www.arista.com.ua/inform/1377/1379

   Описание экономическое значение насосов WILO

10. http://nasos.guitarsoul.ru/ustrojjstvo_nasosa.html

    Представлено устройство центробежного насоса.