RU2300086C1 - Heat meter and method of measurement of heat energy of heat transfer agent in open heat supply water systems - Google Patents

Abstract

FIELD: measuring technique.

SUBSTANCE: feeding and reverse pipelines in heat meter are provided with volumetric electromagnet flow meter, pressure converters, and temperature converters, units for computing density, enthalpy and weight of heat transfer agent. Four division units for dividing output signals from feeding and reverse pipelines are introduced into heat meter as well as two memory units, environmental temperature two conversion units and two temperature subtraction units. All outputs of introduced units are connected with indicator. Received relations of output signals of volumetric flow meters, pressure and temperature converters are chosen as test signal. During exploitation, the test signal is compared current meaning of volumetric masses and consumption of heat transfer agent during average time and corresponding corrections are received. From common signal, mixed with noises, rest voltage, heat noises and zero drift are selected. Coefficient of conversion of devices is determined at feeding and reverse pipelines and corresponding correction is introduced into volumetric consumption and mass of heat agent is intruded.

EFFECT: improved precision of measurement.

2 cl, 1 dwg

Description

The invention relates to experimental equipment and can be used in energy, water supply of public utilities, industrial facilities, oil and gas industry, etc.

Known heat meter for measuring thermal energy in water heat supply systems and flow rate. The design of the flow meter of this heat meter contains: two channels (metal pipe), two measuring thermocouples, two compensation thermocouples (film thermistors), included in the unbalanced DC bridges with amplifiers, a heater control unit and a computing unit. The heater control unit periodically turns on the heater, generating heat marks into the stream. When the heater is turned on, the command to start the time measurement is implemented in the computing unit and the counting time of the label transfer by the thermistors begins. Next, the label transfer time is determined by the control time section, and, consequently, the volumetric flow rate. The time difference is used to determine the density of the coolant and then the mass flow rate.

This solution allows you to determine the volumetric and mass flow rate of the coolant in an indirect way (Dynamic thermoconvective method for measuring the mass flow rate of binary liquid solutions “Commercial metering of energy carriers.” Materials of the 20th International Scientific and Practical Conference November 23-24, 2004, pp. 150-154. Authors : Sokolov G.A., Syagaev N.A., Tugushev K.R.).

The disadvantages of this heat meter: the error in determining the mass flow rate of 1.2-1.8%; it is difficult to control the density of the medium being measured, consisting of two or more components, it is difficult to measure the fluid velocity at different viscosities, and a long measurement time.

A known method for determining the volumetric flow rate of a coolant (liquid):

- through heat conduction and convection, the volumetric flow rate of the liquid is determined when implementing the labeling method for measuring the heat transfer process from the label source (heater) to the substance stream and from the stream to thermal converters;

- show that the label transfer time in the control section is uniquely related to the volumetric flow rate and does not depend on the properties and composition of the medium being measured;

- analytically determine the one-dimensional problems of the propagation of a thermal pulse in the fluid flow and reach a maximum mark in the registration zone.

This solution allows us to determine the volumetric flow rate of the liquid (Dynamic thermoconvective method for measuring the mass flow rate of binary liquid solutions "Commercial metering of energy carriers." Materials of the 20th International Scientific and Practical Conference, November 23-24, 2004, pp. 150-154. Authors: Sokolov G. A., Syagaev N.A., Tugushev K.R.).

The disadvantages of this method are that in the measurement process, the transfer time of the label by the flow consists of the duration of the conductive transfer of heat from the heater to the liquid flow and from the stream through the chamber wall (metal pipe) to the thermal converter, etc.

Heat meters are known for determining thermal energy and volumetric (mass) flow rate of a heat carrier (cold, hot water).

Electromagnetic heat meters are intended for measuring and commercial accounting of the amount of heat, volume and mass of heat carrier consumed by residential, public buildings, etc., in closed and open water heat supply systems for measuring and recording volumetric and mass flow rate and heat carrier parameters in both directions through primary flow converters, as well as for use in automated systems of accounting, control and regulation of the amount of heat. The heat meter includes a volume electromagnetic flowmeter (one for a closed, two for an open water heat supply system), temperature and pressure transducers.

The electronic unit is an industrial controller with software. Structurally, it is made in a dust and moisture protective housing located directly on a volume electromagnetic flowmeter. The heat meter kit includes one or two volumetric flow meters, two thermocouples, one thermocouple for measuring ambient temperature and two pressure transducers.

The electronic unit performs measurement, digitization and subsequent processing of the output signals of the transducers of volumetric electromagnetic flow meters (OER), temperature (PT) and coolant pressure (PD). The calculated coolant parameters can be transferred in units of the meter (t / h, kPa, ° C, etc.).

Such a heat meter allows you to determine thermal energy, volumetric and mass flow rate, temperature and pressure of the coolant in open and conditionally open water heat supply systems (Electromagnetic heat meters KM-5 "Operation manual. Part 1 ACP 42/8 2003" p. 3-4, p. .10, 14).

The disadvantages of this heat meter: low accuracy of measuring thermal energy from 4 to 5% due to the fact that the influence of thermal noise, permanent deformation, and aging of materials of the OER design with a long operating time are not taken into account. A known method of determining thermal energy and flow rate. Using heat meters modification KM-5-1 thermal energy is determined as follows:

- A matched pair of platinum thermal converters installed on the supply and return pipelines of the heat supply system is connected to the input of KM-5-1.

- Determine the thermal energy for a closed water heat supply system Q = V · ρ (h ₁ -h ₂ ), where V is the volume of coolant flowing through the supply (return) pipe during the observation; ρ is the density of the coolant (network water) corresponding to the temperature of the coolant in the supply (return) pipeline, according to GSSSD 188-99; h ₁ , h ₂ - specific enthalpy of the coolant (network water), respectively, in the supply and return pipelines according to GSSSD 188-99.

- Determine the volume of the measured medium V, passed through the volumetric flowmeter during the observation time, V = ∫G _V (τ) dτ, where G _V (τ) is the value of the volumetric flow rate at time τ.

- Determine the mass flow rate G _m (τ) at time τ G _m (τ) = ρ (t, P) · G _V (τ); and the mass M of the measured medium M = ∫ρ (t, P) · G _V (τ) dτ.

This solution allows you to determine the thermal energy, volumetric and mass flow rates of the coolant in the supply and return pipelines of open and conditionally open water supply systems (Electromagnetic heat meters KM-5 “Operation manual. Part 1 of the AKP 42/8 2003” p. 3-4, p. .10, 14).

The disadvantage of this method of determining the volumetric flow rate of the coolant is associated with the ambiguity of the measurement. This is because when determining the flow rate, its value depends on the design parameters of the volumetric flow meter. A change in these parameters, in particular magnetic induction, pipe dimensions, the influence of temperature and static pressure over time affect the measurement results.

Closest to the proposed invention, the technical solution is a heat meter that contains the supply, return, make-up pipelines. The supply and return pipelines, each, contains one OER, PT and PD. The make-up channel contains PT cold water. The supply and return pipelines are also equipped with units for calculating the enthalpy and density of the coolant. At the outlet of each pipeline, the flow rate, mass and volume of the coolant are determined. It is noted that the configuration with measuring components for different measurement equations may be different. For example, a heat meter can be equipped with a PD or pressure can be set by a contract constant.

This solution allows you to determine the thermal energy, volumetric and mass flow rate of the coolant in the heat supply systems (Commercial metering of energy carriers. Materials of the 22nd International Scientific and Practical Conference. St. Petersburg 2005, pp. 80-89. "On the issue of type tests of heat meters for water heat supply systems. ”Authors MN Burdunin, A.A. Vargin.).

The disadvantages of this heat meter are: low accuracy in determining the volumetric flow rate due to the neglect of the influence of residual deformation, thermal noise of the OER, PT and PD.

The closest technical solution is a method for determining the volumetric flow rates of the coolant in water heating systems.

The essence of the method for determining thermal energy and flow rate is as follows:

- In a given time interval Δτ determine the mass of the coolant in the supply and return pipelines M ₁ = ρ ₁ q ₁ Δτ and M ₂ = ρ ₂ q ₂ Δτ, where M ₁ , M ₂ - mass of the coolant in the supply and return pipelines; q ₁ , q ₂ -volume flow rate in each pipeline; ρ ₁ , ρ ₂ - density of the coolant in each pipeline.

- At the outlet of the heat meter determine the thermal energy of the coolant in open water heat supply systems

where ρ = ρ (Р, t) and h = h (Р, t),

P - overpressure,

t is the temperature

ρ is the density of the coolant, determined according to GSSSD 188-99.

- Moreover, the flow meters of the heat meter are graduated in a cold-water installation: q = k (q) f, where k (q) is the calibration coefficient as a function of flow rate; f is the output electrical signal (voltage).

This method allows you to determine thermal energy and heat carrier flow in water heat supply systems (Commercial metering of energy carriers. Materials of the 22nd International Scientific and Practical Conference. St. Petersburg 2005, pp. 80-89. "On the question of type tests of heat meters for water heat supply systems. ”Authors MN Burdunin, A.A. Vargin.).

The disadvantage of this method of determining thermal energy and coolant flow is the neglect and uncertainty of the effect of residual deformations on pressure and temperature, especially during prolonged use. The effects of changes in ambient temperature are not taken into account. OER graduated with cold water.

The objective of the present invention is to improve the accuracy of measuring the volumetric flow rates of the coolant in the heat supply system by unambiguously measuring the volumetric flow rates of the coolant and isolating noise, residual deformation (hysteresis) and external influences from the total flow rate signal of the coolant.

The technical result is achieved by the fact that in a heat meter for open water heat supply systems containing supply, return, each supply and return pipelines are equipped with one volume electromagnetic flowmeter, pressure, temperature transducers, density calculation units, flow enthalpy, mass, cold water temperature transducer whose output through the unit for calculating the enthalpies of cold water is connected to the indicator, the outputs of the volumetric flow meters are connected to the inputs of the units the mass flow rate of the coolant, the outputs of the pressure and temperature transducers are connected to the inputs of the density and enthalpy blocks of the supply and return pipes, the output of the density blocks is connected to the input of the mass difference calculator, four division blocks, two memory blocks, and two ambient temperature transducers are additionally introduced media and two subtraction units, the outputs of volumetric electromagnetic flowmeters, pressure transducers, mass and enthalpy flow subtraction units and, respectively, the direct and return pipelines are connected to the inputs of the division blocks, the inputs of the memory blocks are connected to the corresponding outputs of the volumetric flow meters of the temperature and pressure transducers, the inputs of the two temperature subtraction units are respectively connected to the outputs of the temperature transducers in the supply and return pipelines and the environment, and the outputs of these two subtraction blocks are connected to the inputs of the memory blocks, calculating the density, enthalpy of the coolant, respectively, the supply and return pipes All outputs input blocks in heat meter connected to the indicator.

The technical result is also achieved by the fact that in the method for determining the thermal energy of the coolant in the supply and return pipes of open and conditionally open water heat supply systems, the density, temperature, enthalpy of the coolant and cold (make-up) water are determined, the equation for determining the flow rate, volume and mass difference of the coolant is used, volume electromagnetic flowmeters, pressure and temperature transducers are installed on direct sections of the supply and return pipelines, the distance between the flow by domestic and local resistances, choose at least the minimum allowable value determined in advance experimentally in the absence of coolant flow, overpressure and ambient temperature in the supply and return pipelines, determine the resting voltage and zero drift at the output of the volume electromagnetic flowmeter of temperature pressure transducers, register in blocks memory and in the indicator, then in the supply and return pipelines set the temperature drop to the permissible value of the drop temperature and record thermal noise at the output of volumetric electromagnetic flowmeters and temperature pressure transducers in the supply and return pipelines and the output signals of these devices are recorded in the indicator memory blocks, in the supply and return pipelines set discrete values of the coolant flow rate from zero in the forward direction to the permissible value, then inverse running from the permissible value to zero, while constantly maintaining excessive pressure and temperature and the output signals of volume electromagnets the flow meters, pressure and temperature transducers are recorded in the memory and indicator blocks, the total noise at the output of the volumetric electromagnetic flowmeter is determined and the pressure and temperature are converted and recorded in the indicator, then subtracted from the outputs of the volumetric electromagnetic flowmeters and pressure and temperature transducers mixed with noise, subtract total noise signals and receive signals without the influence of noise and register in the indicator, measure the signal from the outputs of both electromagnetic flowmeters, pre pressure generators, mass and enthalpy calculation units of the coolant by dividing the output signal from the outputs of the supply piping devices to the output signals of the return piping devices, receive the ratio of the two signals and select it as a test signal, and during operation, introduce the corresponding correction into the mass flow rate and the coolant volume, value thermal noise, resting voltage, zero drift and the ratio of output signals in the nominal modes of volumetric electromagnetic flow meters, temperature converters Temperature and pressure and the weight calculation block and coolant enthalpy is recorded in the data sheet of the heat meter.

The drawing shows a block diagram of a heat meter for determining thermal energy and mass of the coolant selected in open water heat supply systems. The flowchart shows the supply 1, return 2 pipelines. The supply pipe 1 is equipped with OER 3, PT 4 and PD 5, a temperature subtraction unit 6, density calculation units 7, enthalpy 8, heat carrier mass 9, memory 10, and environmental FET 21. Return pipe 2 contains OER 77, PD 12, and PT 13 , a second temperature subtraction unit 14, density calculation units 15, enthalpy 16, heat carrier mass 17, memory 18, and PT 22 of the environment. In addition, the heat meter is equipped with pressure dividing units 23, heat carrier mass 25, heat carrier volumetric flow rates 26 and indicator 27. The heat meter also contains a heat consumption unit, which includes pipelines for the selection of heat from hot water and hot water for hot water supply (see drawing). The outputs of the PD 5, 12, PT 4, 13, respectively, are connected to the inputs of the density calculation blocks 7, 75; enthalpies 8, 16. The outputs of the density calculation blocks 7, 15 and OER 3.11 are connected to the input of the mass calculation blocks of the coolant 9, 17. The return pipe 2 is also equipped with PT 19, the output of which is connected to the input of the cold water enthalpy calculation block 20, the output of the latter connected to the input of the display unit 27. The outputs of the PD 5, 12 are connected to the inputs of the division unit 23. The outputs of the temperature subtraction unit 6, PD 5, OER 3 are connected to the input of the memory unit 10. Similarly, the outputs of the PD 12 and the temperature subtraction unit 14, OER 77 are connected with inputs of the memory block 18. The outputs of the blocks subtract enthalpy sections 8, 16, OER 3, 11 and heat carrier mass 9, 17 are respectively connected to the inputs of the division blocks 24, 25, 26. The outputs of the blocks 23, 10, 24, 25, 26, 6, 14, 21, 22, 20 are connected with indicator input 27.

In the supply, return and make-up pipelines of the heat meter, PT is used in most of the platinum with a nominal resistance of 100, 500 Ohms. The criterion for the selection of the converter is stability, accuracy and cost. The method of connecting a PT 100 Ohm with an amplifier through a 4-wire communication line, with two current and two potential conductors. For PT 500 Ohm, a two-wire line is used. In this case, the input impedance of the amplifier should be hundreds of megohms. PT 13 measures the temperature of the coolant, PT 19 measures the temperature of cold (make-up) water. Fri 21, 22 measure the temperature on the outer surface of the supply and return pipelines. If these pipelines are insulated from the medium by heat-insulating material, then measure the temperature on the surface of the insulating layer. The dependence of the output signal of platinum PTs on temperature is nonlinear. In reality, for example, the error of the PT comes from the limit of the permissible relative error of the set of the PT (matched pair) when measuring temperatures Δt,% δ _Δt = ± (0.5 + 3Δt _min / Δt), where Δt is the numerical value of the temperature difference, ° С ; Δt _min - the lower limit of the temperature difference range, is selected from a number of 1, 2, 3 ° C, depending on the class of the applied PT set. Known classes of thermocouples of the TS are classified by accuracy characteristics as A, B, C. The highest accuracy is class A, the lowest is C. Heat meters are classified as C, B, A.

Overpressure in the supply and return pipelines is controlled using the known PD 5, 12. Excessive static pressure controls the PD, their types are very diverse - tensometric, capacitive, piezoresistive, inductive, etc., domestic and foreign production. At the output of the PD, electronic matching and amplification units are arranged; they are mounted next to the flow converter. The accuracy of measuring overpressure is from - 0.01 to 0.5%. The principle of converting pressure into an electrical signal is that a change in pressure on the AR leads, for example, to strain gauge and capacitive PDs, respectively, to a change in resistance ΔR and capacitance ΔС, respectively, to a change in relative resistance ΔR / R and capacitance ΔС / С. The output signal will vary in proportion to the relative increment of the resistance or capacitance multiplied by the polarization voltage of the PD.

In heat meters, volumetric flow meters 3, 11 give an electrical signal proportional to the flow rate of the liquid. The volume is obtained by integrating the flow rate over time. The mass flow rate or the mass of water (coolant) is calculated as the product of the flow rate or volume and the density of the coolant. The density is calculated in blocks 7, 75. The values of the heat carrier density are defined in normative documents of heat supply, for example, MI 2412-97 or in the work “Density, enthalpy and viscosity of water”. GSSSD 188-99 "Specific volume and enthalpy of water at temperatures 0 ... 1000 ° C and pressures of 0.001 ... 1000 MPa." These sources determine ρ _i = ρ _i (P _i , t _i ) and mass flow rate m _i = ρ _i (Р _i , t _i ) q _i , where i = 1, 2 are the numbers of the supply and return pipelines, ρ _i - density, h _i is the coolant enthalpy as a function of the change in pressure P _i and temperature t _i . The density of deaerated water is significantly dependent on temperature. With a change in temperature from 0 to 150 ° C, the density varies from 0 to - 10%.

The dependence of the density change of deaerated water on absolute pressure is from 30 to 11 kgf / cm ² , the density varies from - 0.027 to - 0.013%.

In pipelines of the heat supply system, temperature and pressure are different, which means that the density and enthalpy of water are different. The density in the return pipe is higher because the temperature is lower here, and it follows that ideally the volumetric flow rate and volume in the return pipe, based on the mass balance, should be as much lower as the water density here compared to the feed pipe. If there is no selection of the coolant, then the ratio should be observed: V ₂ ρ ₂ = V ₁ ρ ₁ , where V ₁ , V ₂ is the volume of water in m ³ in the supply and return pipelines, in practice this does not happen. Often the volume imbalance is substantially less than the mass unbalance. This is explained by the fact that in reality water contains undissolved gases, air whose density is three orders of magnitude lower than deaerated water (Commercial metering of energy carriers. Materials of the 20th International Scientific and Practical Conference. November 23-24, 2004. Authors V.I. Lachkov, On the Unbalance of Mass Measurement Results in Pipelines of a Water Heat Supply System, pp. 44-49.).

OER of direct measurement of flow velocity with an induction system.

где q - средний расход жидкости, мл/с. Питание переменным напряжением устраняет электролитическую поляризацию расходомера, если частота достаточно высокая, а также позволяет использовать усилитель переменного тока для усиления выходного сигнала расходомера. Выходное напряжение ОЭР не зависит от характера потока - ламинарный или турбулентный, и от профиля скоростей потока. Однако значимая осевая несимметрия потока может влиять на выходной сигнал.The coolant flows through pipelines 1-2, located in a magnetic field, the induction of which is equal to B, and are electrically isolated from the pipe. If the fluid flows through the pipeline with an average velocity v, then an electric charge is induced and a potential difference is formed e = vBd, where d is the internal diameter of the pipeline. This expression can be represented as

where q is the average fluid flow rate, ml / s. AC voltage eliminates the electrolytic polarization of the flow meter if the frequency is high enough, and also allows the use of an AC amplifier to amplify the output signal of the flow meter. The output voltage of the OER does not depend on the nature of the flow — laminar or turbulent, and on the flow velocity profile. However, significant axial flow asymmetry can affect the output signal.

Errors in measuring the OER of the coolant can occur due to stray voltage between the electrodes of the flow meter. These voltages appear due to galvanic potentials between the electrodes and other metal parts, as well as when the flowmeter is polarized with DC voltage. The magnitude of random noise arising in the flow meter, and the influence of external electromagnetic fields increase with increasing resistance of the coolant.

The flow meters used in the heat meter are standard, for example, type KM-5.

The principle of operation of the flow meter is based on the phenomenon of electromagnetic induction during the passage of an electrically conductive liquid through the supply 1 and return 2 pipelines, respectively containing volumetric electromagnetic flowmeters 3, 11. A fluid passing at an average speed through magnetic field B induces an EMF in it. The signal taken from the output of the volume electromagnetic flowmeter is proportional to the magnitude of the induction B and the polarization voltage.

According to the guidance document OKP 4218, the indicator contains interface converters; peripheral adapter AP-5 of various modifications; modem; network integrator. The indicator provides information in the following form: thermal energy Q [Gcal] and [MW · h] for one or two thermal systems; volume V, [m ³ ] and mass M, [t] coolant in the supply and / or return pipelines; thermal power; temperature, temperature difference; operating time of the heat meter; pressure in pipelines, etc.

The output electrical signal allows you to get information about the calendar time, operating hours, thermal energy, temperature, etc. Operating modes: “main” (“WINTER” SUMMER-1, SUMMER-2 and SUMMER-3), are set manually from the heat meter menu. The determination of thermal energy, mass and volume of the coolant is carried out according to the instructions. All matching and amplifying units are placed in a hermetically sealed enclosure of OER, PD and PT. This design of the transducers protects them from any external influences. Additionally, blocks have been introduced in the heat meter, i.e. four division blocks, two subtractions and two memories, known in electronic and computer technology, are standard. These blocks can be placed in the indicator or in the design of the corresponding blocks, i.e. blocks OER, PD and PT.

The method of determining thermal energy and mass of the coolant open or conditionally open water heating systems is as follows.

Stage 1. OER, PD and PT are installed on the direct sections of the supply and return pipelines. Distances between flowmeters and local resistances are chosen not less than the minimum permissible value determined in advance experimentally.

2 stage. In the calculation blocks 9, 17, the mass is calculated as for a time interval, the flow rate is averaged: M1 = q ₁ · ρ ₁ Δτ and M2 = q ₂ · ρ ₂ Δτ. The memory blocks 10, 18 respectively store the values of t ₁ , P ₁ , q ₁ and t ₁ , P ₂ , q ₂ . In the division blocks 23, 25, 24, 26, respectively, the measurement results in the supply pipe are divided by the measurement results of the return pipe, i.e. P ₁ / P ₂ , M ₁ / M ₂ , q ₁ / q ₂ and h ₁ / h ₂ . Heat energy is calculated using the heat carrier equation in an open water heat supply system by indicator 27 according to the measurement equation

3 stage. The coolant with a volumetric flow rate q ₁ with a certain temperature t ₁ and gauge pressure P _{1 is} supplied to the supply pipe. The coolant passes through the return pipe and the OER with a flow rate of passing water q ₂ with a certain temperature t ₂ and overpressure P ₂ . In reality, these parameters are not equal to each other q ₁ ≠ q ₂ , t ₁ > t ₂ and P ₁ > P ₂ . When the coolant passes through both pipelines in the OER, PT and PD, electrical voltages U _1q , U _2q , U _t1 , U _t2 , U _p1 , U _p2 , U _thv , U _t01 and U _{t02 arise simultaneously} , where indices 1, 2 are the supply, return pipelines, signals U _1q and U _2q from the outputs of the OER 3, 11 are fed to the inputs of the mass calculation units 9, 17 and division 26. Signals PD 5, 12 U _P1 , U _P2 PT 4, 13 are fed to the inputs of the density calculation blocks 7, 75, enthalpies 8, 16. The signals from the outputs of blocks 7, 15 are fed to the inputs of blocks 9, 17. The signals from the outputs of blocks 8, 16 are fed to the inputs of the division unit 24. The output signal of blocks 9, 17 is received to the inputs of the division unit 25.

Moreover, the signals from the outputs of blocks 4, 13 are fed through subtraction blocks 6, 14 to the inputs of blocks 7, 8, 15, 16. The signals from the outputs of the transducers of ambient temperature 21, 22 are fed to the inputs of blocks 6, 14. The output signal of block 19 is fed to block input 20. All output signals of these blocks are input to indicator 27. Through the indicator, all blocks are controlled, i.e. water supply, maintenance of temperature and pressure of the set levels.

4th stage. The enthalpy of the coolant in the supply and return pipelines and cold (make-up) water of the heat meter in blocks 8, 16, 20 is determined as a function of the corresponding pressure and temperature as: h ₁ = f (P ₁ , t ₁ ), h ₂ = f (P ₂ , t ₂ ), h _XB = f (P _XB , t _XB ), kJ / kg. A typical algorithm for calculating the density and enthalpy of network water at an average temperature is determined as using linear interpolation of the data of the GSSSS 188-99 tables, wired programs ρ _icp = [ρ _- + (ρ ₊ -ρ _- ) · (t _cr -t _- ) / ( t ₊ -t _- )] / 100, where ρ _cf is the density of network water at an average temperature, kg / m ³ ; ρ _- , ρ ₊ , t ₊ , t _- - data from the GSSSD table 188-99. h _icp = [(h _- + h ₊ -h ₁ ) · (t _cr -t _- ) / (t ₊ -t _- )] / 4190, where h _icp is the enthalpy of network water at an average temperature, Gcal / t, t _- , t ₊ - data from the GSSSD 188-99 table (“Heat accounting is almost simple”, Osipov Yu.N., Kolmogorov AN St. Petersburg, 2001, p. 73).

As you can see, heat meters use high-precision pressure and temperature transducers (0.1-0.5%). The most expensive and complex is the measurement of volumetric flow rates in water heating systems. From experience in operating domestic and foreign water heat supply systems, it was found that there are limits of the relative error of the flow meters ± 1% in the measurement range of the volumetric flow rate of the coolant 1: 100. The cost of foreign volume electromagnetic flowmeters is 2-3 more than domestic.

в соответствующих блоках согласно чертежу. В блоках памяти 9, 18 хранят

и

и регистрируют в индикаторе 27.5 stage. In the heat meter, in the absence of a coolant q ₁ = 0, an overpressure P ₁ = 0 and ambient temperature, with a polarized state, the OER and PD supply and record the resting voltage (zero level) from the outputs of blocks 3, 4, 5, 11, 12, 13 , 19, 21, 22,

in the respective blocks according to the drawing. In the memory blocks 9, 18 are stored

and

and register in indicator 27.

but. When at the output of the OER and PD constant voltage, then register

b. When at the output of the flowmeter an alternating voltage is recorded

at. Determine the zero drift (zero drift) of the output signals depending on time in the absence of coolant, pressure and temperature. Determining the zero _{drift of the} output signals U _0q1 , U _0g2 , U _0t1 , U _0t2 , U _0P1 , U _0P2 , etc. carried out by appropriate selection of a sequence of points in time.

Depending on the nature of the output signals and on the duration of the heat meter, choose the appropriate step, the uniformity of which may not be the same in time.

в зависимости от температуры в соответствующих блоках (см. чертеж), на входах индикатора. Устанавливают, что с повышением температуры магнитная проницаемость в слабых полях возрастает, а проницаемость в сильных полях, приближаясь к насыщению, падает. С ростом температуры регистрируют уменьшение коэрцитивной силы и остаточной индукции. Влияние температуры на величину магнитной проницаемости определяют формулой μ_d=μ_d20(1+TKμ_d·Δt), где μ_d20 и μ_d - соответственно величины дифференциальной магнитной проницаемости при +20°С и температуре, равной Δt+20°C.6 stage. From the analysis of the operating conditions of the OER, PD and PT, it follows that the influence of temperature is dominant not only in steady-state conditions, but also when the temperature changes sharply, it is more than the permissible value (thermal shock). Therefore, in such cases, in the falling and return pipelines, a stepwise temperature change is set with a step of 10 ° C from an ambient value to an acceptable 90 ° C and the output signal from the outputs of blocks 3, 4, 5, 11, 12, 13, 19, 21, is measured 22 -

depending on the temperature in the respective blocks (see drawing), at the indicator inputs. It is established that with increasing temperature, the magnetic permeability in weak fields increases, and the permeability in strong fields, approaching saturation, decreases. With increasing temperature, a decrease in coercive force and residual induction is recorded. The influence of temperature on the value of magnetic permeability is determined by the formula μ _d = μ _d20 (1 + TKμ _d · Δt), where μ _d20 and μ _d are the values of differential magnetic permeability at + 20 ° С and a temperature equal to Δt + 20 ° C, respectively.

где К - постоянная Больцмана, (1,38·10^-23 Дж/К); t - температура; f - полоса пропускания, Гц; R - сопротивление преобразователя давления, Ом.Thermal noise at the output of the pressure transducers is determined from the well-known expression as:

where K is the Boltzmann constant, (1.38 · 10 ^-23 J / K); t is the temperature; f is the passband, Hz; R is the resistance of the pressure transducer, Ohm.

7th stage. In the supply and return pipelines set the nominal coolant level q ₁ = q _nom q ₂ = q _nom and set the necessary overpressure P ₁ = const, P ₂ = const and the operating temperature t ₁ = t _1max ; t ₂ = t _2max . Under these conditions, the hysteresis (variation) of the output voltage of the OER and PD is determined depending on the change in the flow rate of the coolant from q = 0 to the maximum value q ₁ = q _max .

8 stage. When calibrating heat meter flow meters, it was found that when the coolant passes through the OER insulating tube on the second or third day, due to moisture penetration into the OER design, dielectric losses and permeability, leakage currents, insulation resistance decreases, etc. Therefore, these shortcomings affect the output signals of the OER, which carry information about the volumetric flow rates of the coolant. Therefore, it is proposed to carry out accelerated aging of OER heat meters in operation at elevated temperatures of 80-90 ° C.

The duration of the experiment is not less than two months, during which the output voltage from the output of the OER is measured depending on the time with a step of discreteness of 8 hours, i.e. build a daily schedule depending on the volumetric flow rate of the coolant and heat energy from time to time. The results of the experimental study are stored in the corresponding memory blocks.

The obtained values of volumetric flow rates and thermal energy under operating conditions of heat meters at the facility are compared with the results of measurements in the calibration stage. The obtained operating results are corrected and the true value of the volumetric flow rates of the coolant and thermal energy is obtained.

выходных сигналов, смешанных с шумами помех, регистрируют в блоках памяти и в индикаторе. Определяют вариацию как абсолютную величину разности между значениями меньшего

и большего Δδ. Значение

вычисляют как среднее из значений погрешности в точке х_i диапазона измерений при медленном неоднократном изменении q₁. Значение Δδ определяют аналогично при плавном изменении q₁ со стороны больших значений х_i и окончательно определяют, что

. Затем определяютThe variation in the coolant flow rate is set from q ₁ = 0 (first point) of the forward stroke to q _max (last point) in 11 sections, then slowly from 11 sections return to q ₁ = 0 in the reverse direction and complete the cycle. Such cycles are performed by at least 8. Verification Results

output signals mixed with interference noise are recorded in the memory blocks and in the indicator. Variation is defined as the absolute value of the difference between the values of less

and larger Δδ. Value

calculated as the average of the error values at point x _{i of} the measurement range with a slow repeated change of q ₁ . The value of Δδ is determined similarly with a smooth change of q ₁ from the side of large values of x _i and finally determine that

. Then determine

where Δ _Mi and Δδ _i - j is the implementation of the error of the OER or PD.

9th stage. When the voltage at the outputs of the OER, PD, and PT is alternating, zero goes off (due to hysteresis or variation of the resting voltage), thermal noise arises independently and is not connected with each other. This confirms that the noise voltages in the heat meter are not correlated and they are summed up on the basis of the power addition rule and determine the total noise voltage at the output of the volumetric flow meter

respectively determine the noise at the output of the pressure transducer

and temperature

where indices 1, 2 are the falling and return pipelines. Then, noise signals are extracted from the common signal and the true value of the output voltages at the output of the OER is obtained

respectively determine the useful signal at the output

and

подают в блоки памяти, деления и индикатор. Эти сигналы в качестве тестовых сигналов хранятся в индикаторе. Затем определяют коэффициенты преобразования ОЭРThe resulting true value of the output signals

served in memory blocks, divisions and indicator. These signals are stored as test signals in the indicator. Then determine the coefficients of the conversion of OER

When the output of the OER, PD, PT constant voltage, the true value of the output voltage is determined as:

где, U^T означает текущее значение выходного напряжения на выходе ОЭР, ПД, ПТ.

where, U ^T means the current value of the output voltage at the output of the OER, PD, PT.

10 stage. The density ρ _1,2 = ρ _1,2 (P _1,2 , Δt _1,2 ) and the enthalpy h _1,2 = h _1,2 (P _1,2 , Δt _1,2 ) of the heat carrier are determined as a function of the overpressure P _1.2 and the temperature difference Δt ₁ , ₂ . The difference Δt _{1,2 is} determined by subtracting from the supply temperature t ₁ , return t ₂ pipelines the ambient temperature t ₀₁ and t _{02 of the} corresponding pipelines in the subtraction blocks 6, 14; those. Δt ₁ = t ₁ -t ₀₁ ; Δt ₂ = t ₂ -t ₀₂ . The values of Δt ₁ and Δt ₂ are served in the respective blocks and on the indicator.

Then, the mass of the coolant in the supply and return pipelines is determined, respectively, as: M ₁ = q ₁ · ρ ₁ · Δτ, M ₂ = q ₂ · ρ ₂ · Δτ, for Δτ - the time interval of averaging the measured flow values, which is chosen constant.

11 stage. In the division blocks 23, 24, 25, 26, the output signals are divided from the 3 U _q1 block to the 11 U _q2 block, from the 5 U _P1 block to - 12 U _P2 , from the 9 U _M1 block to - 17 U _M2 and from block 8 U _h1 at - 24 U _h2 , i.e. at the output of these blocks get

где q₁=const задают, и определяют расход в обратном трубопроводе как: 1,2q₂=q₁. Аналогичным образом поступают с другими сигналами. Полученные истинные значения отношений сигналов

принимают за основу как тестовый, хранят в индикаторе для дальнейшего использования в процессе эксплуатации теплосчетчиков. Далее сравнивают с результатами эксплуатации, вводят соответствующую коррекцию в массу и объем теплоносителя. Все процессы и действия (деление, вычитание, умножение и т.д.) осуществляют от индикатора. В формуляре или паспорте теплосчетчика заполняют эти относительные величины.In these formulas, identical terms are abbreviated and, due to this, a single output voltage is measured. In all formulas, the ratio of the left side is always greater than unity. Using the experimental tests listed above, it is determined with high accuracy (for example) that

where q ₁ = const is set, and the flow rate in the return pipe is determined as: 1,2q ₂ = q ₁ . Do the same with other signals. Received true signal relationship values

taken as a test basis, stored in an indicator for future use in the operation of heat meters. Next, they compare with the results of operation, introduce the corresponding correction in the mass and volume of the coolant. All processes and actions (division, subtraction, multiplication, etc.) are carried out from the indicator. These relative values are filled in the form or passport of the heat meter.

The technical and economic effect of the proposed invention is achieved by using the temperature difference in determining the flow rate, mass, volume, enthalpy of the coolant, isolating thermal noise signals from the common signal, resting voltage, zero drift and normalizing the output signals by dividing the output signals of mass, pressure, temperature, enthalpies of the supply pipe, respectively, to the output signals of mass, enthalpy, pressure and temperature of the return pipe, which compares favorably with the selected analog and prot type.

OOO TBN Energoservice checked the OER, PD and PT at the calibration stand of heat meters. The resting voltage of the OER at an ambient temperature of 20 ° C is 2-3 mV of a semiconductor overpressure converter of 1.0-1.5 mV, also after amplification. Thermal noise at a temperature of 80-90 ° C exceeded from the initial value by 2-2.5 times. The polarization voltage of the flowmeter and PD is 6 V. The type of OER and the diameter of the nominal bore are: a flowmeter as part of an electromagnetic heat meter KM-5 Du = 15 mm, pressure 5-6 at. The coolant flow rate for the considered period of time was maintained at 6 m ³ / h.

Температура в подающем трубопроводе 90°С, в обратном 40°С. Для упрощения расчетов температура холодной (подпиточной) воды полагалась 0°С.Variation (hysteresis) of the output voltage of the OER of 0.1-0.15%; semiconductor PD 0.05%. Calibration characteristics when changing the flow rate of the coolant from 0 to a nominal value of 30 m ³ linear. Relationship values

The temperature in the supply pipe is 90 ° C, in the return 40 ° C. To simplify the calculations, the temperature of cold (make-up) water was set at 0 ° С.

Claims (2)

1. A heat meter for determining thermal energy of a heat carrier in open water heat supply systems, comprising supply and return pipelines, each of which is equipped with a volume electromagnetic flow meter, pressure, temperature transducers, a unit for calculating density, enthalpy, heat carrier mass, and a cold water temperature transducer, output which through the unit for calculating the enthalpy of cold water is connected to the indicator, the outputs of the volume electromagnetic flowmeters are connected to the inputs of the units the mass of the coolant, the outputs of the pressure and temperature converters are connected to the inputs of the density and enthalpy of the coolant of the supply and return pipelines, the outputs of the density blocks are connected to the inputs of the blocks of calculating the mass difference of the coolant, characterized in that four fission units, two memory units, two are additionally introduced an ambient temperature transducer and two subtraction units, the outputs of volumetric electromagnetic flow meters, pressure transducers, and math calculation units the circuits and enthalpies of the supply and return pipelines are connected to the inputs of the respective division blocks, the inputs of the memory blocks are connected to the outputs of the volume electromagnetic flow meters, temperature and pressure transducers, the inputs of the two subtraction units are connected to the outputs of the temperature transducers in the supply and return pipelines and the environment, and the outputs of two subtraction blocks are connected to the inputs of the memory blocks, calculating the density, enthalpy of the coolant of the supply and return pipelines, all outputs of the input block connected to the indicator. 2. The method of determining the thermal energy of the coolant in open water heat supply systems, which consists in the fact that in the straight sections of the supply and return pipelines install volumetric electromagnetic flow meters, pressure and temperature transducers of the heat meter, measure the volumetric flow q ₁ , q _{2 of the} coolant by measuring the signals from the outputs electromagnetic flowmeters, pressure transducers measure the signals (P _{1, 2)} and the temperature (t _{1, 2)} to determine the density, mass and enthalpy of the coolant in the feed return pipelines, calculate the thermal energy of the coolant according to the equation connecting the enthalpy and the mass of the coolant in the supply and return pipelines, characterized in that in the absence and supply pipelines of the coolant flow, overpressure and at ambient temperature, the resting voltage and zero at the volumetric outputs are determined electromagnetic flow meters, pressure and temperature transducers and the output signals of these devices are recorded in the memory blocks and in the indicator, then in the supply and fraternal pipelines set the temperature difference to the permissible value of the temperature difference and record thermal noise at the outputs of the volume electromagnetic flowmeters and pressure transducers, temperatures, the output signals of these devices are recorded in the memory and indicator, in the supply and return pipelines set the discrete values of the coolant flow from zero to permissible values, then from the permissible value to zero, while maintaining a constant overpressure and temperature, the output signals of many electromagnetic flowmeters, pressure and temperature transducers are recorded in the memory blocks and the heat meter indicator, the total noise signals are determined at the outputs of the volume electromagnetic flow meters and pressure and temperature transducers and recorded in the indicator, then from the signals from the outputs of the volume electromagnetic flow meters and pressure and temperature transducers mixed with noise, subtract the total noise signals, receive signals without the influence of noise U _q1,2 , U _p1,2 , U _t1,2 , by dividing the output signals devices of the supply pipe to the output signals of the devices of the return pipe receive the ratio of the two signals and select it as a test signal, during operation determine the conversion coefficient of the devices in the supply and return pipelines

and introduce the appropriate correction in the volumetric flow rate and mass of the coolant.