RU2325591C1 - Automatic regulation of heat flow in heating network for dual-flow heating system - Google Patents

Abstract

FIELD: heating systems.

SUBSTANCE: technique for automatic regulation of flow of heat in a heating system for a dual-flow heating system is based on provision of an optimum mode for the heating system through maintaining given ratios of pressure and temperature in direct and reverse network of pipes consisting of first contour with a heat source, main-line pump with output to a heat exchanger, which is connected to the second contour of the heating network with a circulator pump, and heating system with regulated parameters. The parameters are regulated using regulators in the network pipes directly in the stream of the heat carrier. Signals from the pressure and temperature sensors are passed on to microcontroller processors, and then to a computer for processing and storage. Change in the flow of the heat carrier and its regulation is achieved through pumping units with frequency converters, when signals are applied to the microprocessor, from pressure sensors at the pump input and output, as well as from sensors for active power expended by the motor of the pump. Heat input is calculated in the computer using a formula. There is programmed control of the heat input from the source and the resultant pressure in accordance with the program in the microprocessor controller of the first contour, with consideration of ambient temperature and losses in the network. Regulation of flow is done by a frequency converter through changing the frequency of rotation of the pump shaft. Heat from the first contour of the heating network reaches the heat exchanger on a given program, where it is passed to the second contour of the network. Using a circulator pump and a feed regulator, the given ratios of the pressure and temperature in the direct and reverse network pipes, are maintained. In this case the network operates in an optimum mode. The heat quantity from the source G_"hs" is equal to the quantity of heat released by the consumer G_"co" with nominal losses ΔG_"nl" in the network. If it is not possible to maintain the given drop in temperature in the direct and reverse pipelines of the second contour of the heating network, a command is passed to the main-line pump of the first contour, which lowers the flow until the given ratio between pressure and temperature in the direct and reverse pipelines appears in the second contour. If necessary, the main-line pump of the first contour is shut down for a defined time when the given ratio between pressure and temperature in the network is maintained, for which the heating system operates in the given mode.

EFFECT: increased effectiveness and economy in regulation of heat flow in a heating system.

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Description

The invention relates to heat supply systems of cities and other settlements and can be used for automatic metering and regulation of heat consumption in heat supply systems.

Modern heat supply systems are complex engineering structures, the peculiarity of which is that they are two-parameter, when the amount of released heat energy is determined both by the temperature of the coolant and the pressure drop in the network, therefore, they must be controlled by two interconnected systems, one to regulate the temperature regime and the other to regulate the hydraulic mode. The implementation of this task requires the knowledge of a large amount of primary information about the parameters of the heating network, obtained in real time, and, as a result, a large number of relevant equipment.

Known methods and devices for regulating, measuring and accounting for heat consumption, which are characterized by the following indicators: for measuring the flow rate, it is necessary to install primary sensors in the fluid flow, the operational reliability and efficiency of which does not meet the requirements of today, therefore they are not widely used; to regulate the flow, it is necessary to install flow controllers, which is economically disadvantageous; for a large change in flow rate, pumps of various capacities are used, which reduces the reliability of the system and leads to additional operating costs; the presence of several pumping units with different capacities leads to a large discreteness in the flow rate, which reduces the efficiency of regulation. / Automatic devices, regulators and computer systems: Reference manual. / Under. ed. V.D. Kasharsky. - L .: Engineering, 1976 / [1]. / Adjustment and operation of water heating networks: Reference book / V.I.Manyuk, Ya.I. Kaplinsky, E.B. Hizh et al. - 3rd ed., Rev. and add. - M .: Stroyizdat, 1988 .-- 432 p. [2]. / Accounting and control of energy and thermal energy consumption. Methods and devices / Kakhanovich V.S. [et al.], Ed. B.C. Kakhanovich. - M .: Energy, 1990 / [3].

In the proposed control methods, the flow measurement is performed without installing measuring instruments in the fluid flow, since the pump itself is a flow meter, which increases the reliability of the system and reduces the operating costs of its maintenance. Flow control is carried out by a frequency converter using only one pump unit.

There are also known methods for determining the flow rate of liquid and heat by the parameters of the pumping unit / Pat. 2119148 Russian Federation, IPC ⁶ G01F 1/34. A method of measuring the mass flow rate and density of a liquid supplied by a centrifugal electric pump / Krichke V.O., Groman A.O., Krichke V.V. - No. 96104446; declared 03/05/96; publ. 09/20/1998, Bull. No. 26 / [4].

Known automated system for measuring and accounting for flow of heat carrier and heat in heating systems / Pat. 2144162 Russian Federation, IPC 7 F24D 19/10. Automated system for measuring and accounting the flow of heat carrier and heat in heat supply systems / Krichke V.O., Groman A.O., Krichke V.V. - No. 96114663 declared. 07/16/96; publ. 01/10/2000 Bull. No. 1 / [5]. The disadvantages of these methods is that the measurement of the flow rate of the coolant is carried out directly by the pump units, however, they do not consider dual-circuit heating systems and the use of frequency converters to control the flow of the coolant.

The essence of the invention is to ensure the heat balance in the heat network, when the amount of heat supplied for a certain time by the heat source is equal to the amount of heat energy consumed by the heat consumer, taking into account its losses in the network with high reliability and efficiency of the technical means used.

The technical result of the invention is to increase the efficiency and economy in the regulation of heat consumption in the heating network.

The specified technical result in the implementation of the invention is achieved by the fact that in the known method of automatically controlling the heat consumption in the heating network with a dual-circuit heating system, which consists in ensuring the optimal mode of the heating network by maintaining the specified ratios between pressures and temperatures in the forward and return pipelines of the network containing the primary circuit with a heat source, a network pump with access to a heat exchanger, to which a second circuit of the heating network with a circulation pump is connected heating system with regulating the network parameters using the regulators installed in the network pipelines directly in the coolant flow, a feature is that the signals from the pressure and temperature sensors are fed to microprocessor controllers, from which they are fed to computers for processing and storage, and the coolant flow rate is changed and its regulation is carried out by pumping units with frequency converters according to the method when from pressure sensors located at the inlet and outlet of the pump, as well as from the sensor active power consumed by the pump drive electric motor, signals are sent to the microprocessor controller, and then to the computer, where the heat supplied is calculated using the formulas:

G = Q (T _p -T _o ) s, Gcal / s,

where Q = A (1-e- ^{M / m} ), m ³ / s

or G = A (1-e- ^{M / m} ) (T _p -T _o ) s, Gcal / s,

where Q is the coolant flow rate, m ³ / s; A and m are the calculated coefficients; C is the heat capacity of the pumped liquid; T _p - temperature in the supply pipe, ° C; T _about - temperature in the return pipe, ° C; M is the consumption coefficient, which is equal to

,

,

where the operational coefficient η _eq is

,

,

the coefficient of convergence K is equal to

K = M _n / [(N / p) η _ek - (N _o / p _o )],

where N · N _o · r-r _o is the power on the pump shaft N kW and the pressure developed by the pump p MPa during the measurement period and the power on the pump shaft N _o kW and the pressure created by the pump r _o MPa when the pump is operating on a closed valve, taken from the passport characteristics of the pump or obtained experimentally in advance, while providing programmed control of the supplied heat from the source and the generated pressure in accordance with the program embedded in the microprocessor controller of the primary circuit taking into account the external temperature and network losses, at Volume control of the flow is carried out by a frequency converter by changing the rotation frequency of the pump shaft, the heat from the first circuit of the heating network enters the heat exchanger according to a predetermined program, where it is transferred to the second circuit of the network, in which the specified relations between pressure and temperature are maintained using a circulation pump and a charge controller in the forward and return network which provide optimum operation of the network when the amount of heat applied from the heat source G _um, pa but the amount of heat which is released to the consumer

G _with with nominal losses ΔG _PL in the network

G _um -ΔG _mp = G _co, Gcal / h;

if it is not possible to maintain the specified temperature difference in the forward and return pipelines of the second circuit of the heating network, a command is sent to the main pump of the primary circuit, which reduces the flow rate until the specified ratio between the pressures and temperatures in the forward and return pipelines occurs in the second circuit, and when If necessary, the primary pump of the primary circuit stops for a certain time, while the secondary ratio maintains a predetermined ratio between the pressures and temperatures in the network at which the system The heating theme works in the set mode.

The proof of the essential features of the proposed method for regulating heat consumption in the heating network with a dual-circuit heating system was carried out only in comparison with the above.

Figure 1 is a diagram of a dual-circuit heating system.

Figure 2 shows the conditional temperature graphs of the coolant supply over time: a - in the first control loop and b - in the second control loop.

In Fig. 3, for example, the operating characteristics of the centrifugal electric pump SE 1250-14-11 are given together with the flow characteristic M-Q.

Figure 1 shows a dual-circuit heating system in a heating network, which consists of: a boiler installation 1, a combustion process control unit in a boiler 2, a network pump 3, a heating network of the first circuit 4, a heat exchanger 5 at the heat consumer, a circulation pump 6 of the second circuit, heating network 7 of the second circuit, heating system 8, make-up regulators 9 - the first circuit and 10 - the second circuit.

The regulation task is to provide such a mode of operation of the heating network in which the amount of heat G _it supplied by the boiler unit 1, taking into account losses in the line ΔG _pl, was equal to the amount of heat G _co consumed in the heating system 8.

To ensure regulation, the system provides for the installation of the following devices and equipment. For temperature measurement - temperature sensors with electrical output TT1, TT2, TT3, TT4, TT5 and TT6. For pressure measurement - pressure sensors with electrical output RT7, PT8, PT9, PT10, PT11, PT12, PT13 and RT14. To measure the active power consumed by the electric motors of the pumping unit drive - power sensors or active energy meters PW15, PW16. To regulate the rotational speed of the rotors of the electric motors of the drives, and consequently, the pump shafts, in order to regulate their performance, there is an emergency frequency converter. The signals from all sensors are fed for processing to microprocessor controllers K1, K2 and K3, the outputs of which are fed to a computer, which is located at the control room. The start-up of the pumps is controlled by the starters SA1 and SA2 with buttons SB1 and SB2, and the boiler is controlled through the control unit by the SBM button SB3. To maintain the given pressures, make-up regulators are used in the first circuit of PC17 and in the second circuit of PC18.

The regulation task is to provide such a mode of operation of the heating network in which the amount of heat G _it was equal to the amount of heat G _co consumed in the heating system 8

G _it -ΔG _PL = G _co , Gcal / h

This ensures a ratio in which the amount of heat supplied by the boiler installation must be in strict accordance with the heat that returns back to the boiler installation. This ensures minimal heat loss during its transportation from the source to the consumer. The amount of heat supplied according to a given program is regulated depending on the outdoor temperature. On figa is a graph of the programmable temperature T _{1 of the} coolant coming from the heat source G _it with a nominal demand of T ₂ taking into account its loss ΔT = T ₁ -T ₂ in the network and a graph of fig.2b programmatic changes in temperature T ₂ when heat G _from the heat exchanger in the secondary circuit. Moreover, the losses ΔG in the network are

ΔG = G _it -G _co , Gcal / h

The graph of the programmed change in temperature T ₂ in the second circuit in its nature of change converges with the graph of the temperature T ₁ in the first circuit.

The regulation of pressure and temperature in the network is as follows. In the microprocessor controller K1, a program has been preliminarily laid down to maintain the preset values of pressure and temperature of the supplied coolant. The pressure value in the loop network alone is measured in the supply pipe by the PT11 pressure sensor, and in the return pipe by the PT12 pressure sensor, the signals from which are fed to the microprocessor controller K1, which compares them with the set values in the program and controls the pressure ratios for the supply and return pipelines network. If the pressure deviates from the given ratios, the controller generates a signal that is supplied to the frequency converter PE. The latter changes the frequency of rotation of the pump motor, which leads to a change in the flow and pressure created by the pump, and this is done until the values of the measured pressures are equal to the set ones. In the event of a coolant leak in the primary circuit, its compensation is carried out using the make-up regulator PC 17 with liquid coming from the reagent tank. The signals from the temperature sensors TT1 - the supplied coolant and TT2 - the outside air temperature are also supplied to the microprocessor controller K1, which compares them with the set temperature values stored in the controller program, and if these values deviate from the set values, then the microprocessor controller K1 gives a signal to the node control 2 of the combustion process in the UUK boiler to change the temperature of the supplied coolant until these values are equal to the set ones. At the same time, using the network pump 3, the heat consumption in the network is measured when the pump is simultaneously a flow meter [1].

In this case, the pressure sensor PT7 at the inlet to the pump, the pressure sensor PT8 at the outlet of the pump and the power sensor PW 15, which measures the active power consumed by the pump drive electric motor, sends signals to the microprocessor controller K3, which according to these data determines the heat consumption G by the formula:

G = Q (T _p -T _o ) s, Gcal / s,

where Q = A (1-e- ^{M / m} ), m ³ / s

or G = A (1-e- ^{M / m} ) (T _p -T _o ) s, Gcal / s,

where Q is the coolant flow rate, m ³ / s; A and m are the calculated coefficients; C is the heat capacity of the pumped liquid; T _p - temperature in the supply pipe, ° C; T _about - temperature in the return pipe, ° C;

M - expenditure coefficient, which is equal to

,

,

where the operational coefficient η _eq is

,

,

the coefficient of convergence K is equal to

K = M _n / [(N / p) η _ek - (N _o / p _o )],

where N · N _o · r-p _o is the power on the pump shaft N kW and the pressure developed by the pump p _o MPa during the measurement period and the power on the pump shaft N _o kW and the pressure created by the pump r _o MPa when the pump is operating on a closed valve, taken from the passport characteristics of the pump or obtained in advance experimentally. The flow rate is found from the basic flow characteristic of the M-Q pump, which is given in FIG. 3, by the above formula, or directly by the characteristic. To do this, according to the calculated value of the flow coefficient M, there is point A on the graph, then on the flow characteristic MQ point B, and on it the flow Q point C. Thus, in the first circuit of the heating network, according to a given program (Fig. 2a), a given temperature schedule is maintained in network and the corresponding pressure drop across the heat exchanger 5. In the second circuit of the heat network through the heat exchanger 5, the temperature enters according to the schedule laid down in the microprocessor controller K1 of the first circuit. The heat from the first circuit of the heat network is supplied according to a predetermined program laid down in the controller K1 to the heat exchanger 5, where it is transferred to the second circuit of the heat network, in which, with the help of the circulation pump 6 of the second circuit and the make-up regulator of the second circuit 10, the specified relations between pressures and temperatures are maintained in the forward and reverse pipelines of the network, this ensures the optimal mode of operation of the network, in which the amount of heat supplied from the heat source G _it is equal to the amount of heat released to heating G _with nominal heat loss ΔG _PL in the network, and is equal to

G _um -ΔG _{with mp} = G, Gcal / h.

If it is not possible to maintain the specified temperature differences in the forward and reverse pipelines of the second circuit, a command is sent to the mains primary pump, which reduces the flow rate until the specified ratio between the pressures and temperatures in the forward and return pipelines occurs in the second circuit. If necessary, the primary pump of the primary circuit can be stopped for a certain time, while in the second circuit a predetermined relationship between pressure and temperature is maintained at which the heating system operates in a predetermined mode. The task of regulation in the second circuit is to maintain the ratio of temperatures and pressures in the forward and return pipelines using a K2 microprocessor controller, in which signals from the temperature sensors TT5 and TT6 and pressure sensors PT13 and PT14, respectively, give signals about the values of temperatures and pressures in the supply and return pipes of the second contours that are compared by the microprocessor controller K2 with the set values, and if they are not equal to the set values, then the microprocessor controller K2 issues a command to regulate Drains Yator PC 18 to maintain a predetermined pressure ratio in the feed and return pipes of the second circuit and the controller command K1 that changes the network speed of the pump shaft 3 so far and in a direction that these pressures are equal specify. At the same time, signals from the PT9 and PT10 pressure sensors and the PW16 power sensor are also sent to the microprocessor controller K2, which calculates the heat consumption from the heating system 8. If the programmed relations between the temperatures TT5 and TT6 in the supply and return pipelines are not implementable, then the microprocessor the controller K2 instructs the microprocessor controller K 1 to change the operating mode of the primary circuit by adjusting the flow rate of the mains pump 3 by the frequency converter with an emergency frequency. This is done until the network parameters with respect to the pressure PT11 and PT12 and the temperature TT3 and TT4 are equal to the set ones. Under certain conditions, the operation of the heating network, the network pump 3 can be stopped for a certain time until the specified mode of heating is ensured in the second circuit according to the ratio of pressures PT9 and PT12 and temperatures TT5 (130 ^-70 ° C) and TT6 (95 -70 ° C) on the supply and return pipelines. As a result of such regulation, optimal thermal comfort is ensured among consumers with minimal economic costs.

Information sources

1. Automatic devices, regulators and computer systems: Reference manual / Under. ed. V.D. Kasharsky. - L .: Engineering, 1976.

2. Adjustment and operation of water heating networks: Handbook / V.I.Manyuk, Ya.I. Kaplinsky, E.B. Hizh et al. - 3rd ed. reslave. and add. - M .: Stroyizdat, 1988 .-- 432 p.

3. Accounting and control of energy and heat energy consumption. Methods and devices / Kakhanovich B.C. et al. Ed. B.C. Kakhanovich. - M .: Energy, 1990.

4. Pat. 2119148 Russian Federation, IPC ⁶ G01F 1/34. A method of measuring the mass flow rate and density of a liquid supplied by a centrifugal electric pump / Krichke V.O., Groman A.O., Krichke V.V. - No. 96104446; declared 03/05/96; publ. 09/20. 1998, Bull. No. 26.

5. Pat. 2144162 Russian Federation, IPC 7 F24D 19/10. Automated system for measuring and accounting the flow of heat carrier and heat in heat supply systems / Krichke V.O., Groman A.O., Krichke V.V. - No. 96114663; declared 07/16/96; publ. 10.01. 2000, Bull. No. 1.

Claims (1)

A method for automatically controlling the heat consumption in a heating network with a dual-circuit heating system, which consists in ensuring the optimal mode of the heating network by maintaining the specified ratios between pressures and temperatures in the direct and return pipelines of a network containing a primary circuit with a heat source, a network pump with access to the heat exchanger, which is connected to the second circuit of the heating network with a circulation pump and heating system with regulation of the network parameters using regulators installed in the pipes network wires directly in the coolant flow, characterized in that the signals from the pressure and temperature sensors are fed to microprocessor controllers, from which they are fed to computers for processing and storage, and the coolant flow rate is changed and regulated by pumping units with frequency converters according to the method when signals from the pressure sensors at the inlet and outlet of the pump, as well as from the sensor of active power consumed by the pump drive motor, are sent to the microprocessor MODULES, and then - to the computer, where it is calculated according to formulas supplied heat G = Q (T _p -T _o ) s, Gcal / s, where Q = A (1-e- ^{M / m} ), m ³ / s, or G = A (1-e- ^{M / m} ) (T _p -T _o ) s, Gcal / s, where Q is the coolant flow rate, m ³ / s; A and m are the calculated coefficients; C is the heat capacity of the pumped liquid; T _p - temperature in the supply pipe, ° C; T _about - temperature in the return pipe, ° C; M - expenditure coefficient, which is equal to

where the operational coefficient η _eq is

the coefficient of convergence K is equal to K = M _n / [(N / p) η _ek - (N _o / p _o )], where N · N _o · pp _o is the power on the pump shaft N, kW, and the pressure developed by the pump p, MPa, during the measurement period and the power on the pump shaft N _o , kW, and the pressure created by the pump, p _o , MPa during operation pump for a closed valve, taken from the pump nameplate or obtained in advance experimentally, while providing programmed control of the heat supplied from the source and the generated pressure in accordance with the program embedded in the microprocessor controller of the primary circuit taking into account the outdoor temperature and network losses, p In this case, the flow rate is controlled by the frequency converter by changing the rotation frequency of the pump shaft, the heat from the first circuit of the heating network enters the heat exchanger according to a predetermined program, where it is transferred to the second circuit of the network, in which the specified relations between the pressures and temperatures in the forward and return network which provide optimum operation of the network when the amount of heat applied from the heat source, G _m is equal to the amount of heat which is released to the consumer, G _w, with nominal losses ΔG _mp network G _um -ΔG _{with mp} = G, Gcal / h if it is not possible to maintain the specified temperature difference in the forward and return pipelines of the second circuit of the heating network, a command is sent to the main pump of the primary circuit, which reduces the flow rate until the specified ratio between the pressures and temperatures in the forward and return pipelines occurs in the second circuit, and when If necessary, the primary pump of the primary circuit stops for a certain time, while the secondary ratio maintains a predetermined ratio between the pressures and temperatures in the network at which the system The heating theme works in the set mode.

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