RU2282792C2 - Method and device for control of water flow temperature - Google Patents

Abstract

FIELD: heating systems.

SUBSTANCE: method comprises control of temperature of at least one of secondary flows of fluid in the secondary circuit which outflows from heat exchanger (1) by means of the primary flow in the primary circuit with the use of control members (5) and (11) that control the primary flow under the action of control unit (7), determining the difference of enthalpies of the primary flow that enters heat exchanger (1) and primary flow that leaves heat exchanger (1), measuring the secondary flow, measuring the flow in the primary circuit, and sending the parameters determined to control unit (7) for control of control members (5) and (11). As a result, the primary flow is controlled by the secondary flow so that the power supplied to the heat exchanger with the primary flow is, in fact, equal to the sum of the power required for the heating of the secondary fluid from the initial current temperature up to the specified outlet temperature, power required for the compensation of energy stored in heat exchanger (1), and power losses from heat exchanger (1). The description of the device for control of water temperature is also presented.

EFFECT: enhanced reliability.

13 cl, 9 dwg

Description

The present invention relates to a method and apparatus for controlling the temperature of at least one secondary stream in a secondary circuit exiting the heat exchanger by means of a primary stream in the primary circuit, through a control element that can be exposed from the control unit, wherein the element controls the primary flow. The invention also relates to a method for measuring power output and amount of heat.

During the supply of hot tap water from the district heating installation, the primary stream of centrally heated water is supplied to the heat exchanger, while the secondary stream of hot tap water is heated in the heat exchanger to a constant consumption temperature. In the district heating installation, maintaining a constant temperature of consumption is ensured by automatic mechanical or electronic control devices that regulate the temperature by correcting the difference between the set and actual output temperatures on the secondary side using feedback on temperature measurement on the secondary side. When using electronic control devices, proportional-integral or proportional-integral differential regulators are usually used, which depending on the current output temperature on the secondary side regulate the flow on the primary side by closing or opening the valve on the primary side. Therefore, in order to obtain a predetermined outlet temperature of the hot tap water, the thermal effect is controlled on the primary side.

Both mechanical and electronic devices have drawbacks, because regulation is not as fast as we would like, as a result of which there may be a delay before the corrected temperature is reached on the secondary side. This entails a delay in reaching the correct temperature at the location of the taps on the secondary side and, in the worst case, the risk of scalding.

Another disadvantage is that fluctuations easily occur during regulation, since in practice it is impossible to optimize the regulating equipment for all available operating modes. The temperature of the pipelines and the pressure difference in the district heating system, that is, on the primary side, changes during the year and along the pipeline path of the district heating system.

Pressure fluctuations in the district heating system depend partly on the available distance from the heat source, and partly on the relative location of the district heating station in the system. The statically programmable characteristics of the regulators cannot be optimized for all encountered operating scenarios, which entails, among other things, fluctuations in the output temperature under certain operating conditions. For example, the following potential disadvantages are due to temperature fluctuations.

Low comfort at the locations of the cranes with a small smoothing effect of the pipeline system, which is especially noticeable in individual residential households.

Increased calcification of heat exchangers when the temperature reaches above 60 ° C. Increased cushioning of regulatory elements.

Harmful cooling of the district heating system, which can entail large production costs.

A system is already known from US Pat. No. 5,363,905, in which temperature feedback on the secondary side is used to act on the control valve on the primary side. In this solution, the pressure drop on the primary side is corrected, but the desired quick temperature correction is not provided when fluctuations in the flow of hot tap water on the secondary side. In this case, the measurement of both the pressure drop across the throttle in the primary circuit and the pressure measurement on the primary side, as well as the temperature measurement before and after the heat exchanger on the primary side are used. Such a system will be relatively expensive, since two pressure gauges are needed on the primary side, and it is not easy to quickly adjust the temperature on the secondary side with unexpected changes in the flow taken on the secondary side. No adjustment is carried out until the actual temperature drops on the secondary side, and typical fluctuations in the temperature of the hot tap water occur.

EP 0 526 884 discloses a control method for thermographic printers in which the recording head is maintained at a constant temperature, firstly, by regulating the electrical energy supplied to the printer head, and secondly, by means of an adjustable compensating flow of cooler. The temperature of the thermal head is measured by the first temperature sensor, and the temperature of the discharged coolant is measured by the second temperature sensor. When measuring and regulating the flow rate of the cooler, the device calculates the heat output in the flow of the cooler, and measures the temperature of the inlet as well as the outlet (heated) stream of the cooler.

From another document WO 96/17210, a control device for a district heating installation is already known, in which temperature measurements and flow measurements on the primary side are carried out in order to provide the desired regulation and to calculate the energy consumption for billing the consumer. In this case, the flow rate on the secondary side is also not measured, which means that fluctuations in the temperature of the outgoing water on the secondary side are likely to occur in the system.

DE U 129617756 discloses a system in which bypass regulation is performed on the primary side with feedback on the primary side, with the flow exiting the heat exchanger back to the incoming heat exchanger stream. In this case, the assumption is made that if the temperature of the flow on the primary side leaving the heat exchanger is kept constant, a constant temperature of hot tap water will be achieved on the secondary side. This assumption certainly entails the existence of temperature fluctuations on the secondary side, since the surfaces of the heat exchanger must first be cooled by hot tap water. In addition, the system does not respond quickly to sudden changes in the flow rate of hot tap water, since adjustment is not performed until the temperature on the primary side drops.

In the prior art, the need for a quick action was not considered when the heat consumption on the secondary side changes dramatically, that is, when the flow rate changes incrementally. This means that when there are fluctuations, the control systems often stop working because the temperature on the secondary side is taken into account. Despite the large number of individual solutions related to particular problems, there is no system with characteristics that ensure stable operation regardless of its location in the district heating system. In most of the systems in which it is necessary to precisely regulate the temperature on the secondary side, there are control loops with feedback on information regarding the current temperature value, whereby the deviation of the measured value of the output temperature from its predetermined value is counteracted. Therefore, the action of such a system depends on the deviation of the resulting output temperature. Before countermeasures can be taken, such a system should be on hold until a deviation can be detected, which entails a time delay when the actual set heat consumption changes.

The objective of the invention is to create equipment for fast and stable regulation in heat transfer plants, in which on the primary side there may be significant variations in inlet temperatures and pressure drops, in which the best temperature constancy of hot tap water on the consumer side, in fact, keeping the temperature constant, is achieved without the need feedback on the value of the actual temperature on the secondary side.

This problem is solved using the features indicated in the attached claims.

Using this invention, the risk of temperature fluctuations on the secondary side, which in the district heating installation corresponds to the hot tap water circuit, is eliminated. Often, a district heating installation also has heat exchange circuits for heating and ventilation systems, for which this invention is well suited. In systems of this type, the dynamics of load changes are often slower.

Regardless of the volume of consumption, the invention provides increased adaptability to the load. In addition, the risk of calcification in heat exchangers is significantly reduced, since faster control systems with higher accuracy can counteract temperature peaks above 60 ° C.

The constancy of the temperature of the hot tap water on the consumer side is based on finding the thermal power necessary to increase (alternatively, cooling to lower) the temperature of the secondary stream to a predetermined value. The invention is not based on the dynamic correction of the discrepancy between the set and actual temperatures of the outgoing secondary medium, which makes it possible to carry out regulation without feedback on the actual temperature on the secondary side.

In most district heating systems, the use of the invention also entails the possibility of installing a control system without adjusting the adjustment parameters, which significantly reduces the time required for installation and maintenance / fine tuning.

In another embodiment, the method and apparatus can be applied in the event of changes on the secondary side regarding fluctuations in the temperature of the incoming water to be heated in the heat exchanger. This embodiment is applicable when the temperature of the incoming cold water fluctuates. (In a normal situation, it is assumed that the water for the most part has a constant temperature.) With this embodiment, the same system can be applied in a larger number of geographical areas, and in the case of another area, correction, mainly of possible fluctuations in the temperature of incoming fresh water, can be to carry out by simple modifications.

In addition, the invention can be used to measure the transmitted power and the amount of heat, for example for billing purposes or to control energy consumption, and it is also applicable for cooling, for which only change the direction of heat transfer.

Below the invention will be described in the form of a number of embodiments with reference to the accompanying drawings, in which:

figa - connection diagram of a system according to the invention;

fig.1b-d are examples of embodiments of the system of figure 1;

figure 2 is an example of a variant of the system with hot tap water and with the circulation of hot industrial water;

figure 3 is an example of a connection diagram of a district heating installation, including the functions of regulating hot tap water and regulating water for heating, measuring the amount of heat, detecting a discrepancy, warning of danger, and with a means of communication with a dispatch system;

4 is a schematic view of an integrated hydraulic unit for controlling and measuring the primary flow according to the invention, including a valve element, a differential pressure gauge, a temperature sensor and a control element acting on the valve element, which can be integrated into the hydraulic unit or, alternatively, placed in him;

5 is a sectional view of an integrated hydraulic unit that performs several functions according to the invention for a heat exchange circuit; and

6 is a view of three heat exchangers, each connected to an integrated hydraulic unit interconnected for interconnecting the primary stream, and to three separate connections for secondary flows, and to a common control unit.

On figa shows the implementation of the invention in a district installation for heat supply to the consumer. The installation comprises a heat exchanger 1 having a primary circuit 3 and a secondary circuit 2. The primary stream 3i entering the primary circuit 3 is formed by hot water from the district heating system, while the outgoing primary stream 3u is formed by recycled water. The secondary stream 2i of the secondary circuit 2 is formed by incoming fresh water heated in the heat exchanger 1, while the diverted secondary stream 2u is formed by heated, hot tap water supplied to the taps of the end user or user. In the case when the temperature of the incoming secondary stream 2i cannot be taken known in any way (for example, due to the fact that it is constant and known well in advance), a temperature sensor (shown in dashed lines in the figures) is introduced into the incoming stream 2i.

In the secondary circuit 2i-2u, a flowmeter 4 is installed, it is preferable that it is on the input side, and signals from the flowmeter are supplied to the control unit 7. On the primary side in the inlet stream 3i, a first temperature sensor 8 is arranged, and in the return stream 3u a second temperature sensor 9 is arranged. The output signals from these sensors are transmitted to the control unit 7.

To regulate the flow 3 on the primary side, a control valve 5 is installed in the primary circuit, it is preferable to be in the return flow 3u, where the temperature is lower and cavitation loads on the valve are lower. The degree, a, of the opening of the valve is regulated by the control element 25, which, in turn, receives control signals from the control unit 7.

In the shown embodiment, a differential pressure gauge 6 is used to determine the flow rate in the primary circuit 3i-3u, and this pressure gauge is connected between the inlet and outlet ports of the control valve 5.

Fig. 1b shows an embodiment similar to that shown in Fig. 1a, but here the control element acting on the primary circuit is formed by a pump 11 with a predetermined dependence of the flow 3 in it on the speed and the pressure difference on the pump. The difference ΔP of pressure at the pump is measured by a differential pressure gauge 6. The control unit 7 controls the speed of the pump in order to obtain a given primary flow 3.

Another embodiment is shown in FIG. 1c, where the target flow is controlled by measuring the primary flow 3 by the flow meter 12 and by adjusting the degree of opening of the valve to obtain the desired primary flow (pay particular attention to the local control loop with feedback on the actual flow value )

The embodiment of FIG. 1d is a fourth embodiment in which the flow measurement is carried out by means of a fixed throttling element 13 and a pressure gauge 6 at its ends, designed to measure the pressure difference on the throttling element.

Figure 2 shows an embodiment where, on the primary side, the incoming fresh water 2i consists of a mixture of cold water and recycled water, the so-called circulating flow of hot industrial water. In this case, a change in the temperature of the incoming secondary stream 2 is achieved, and a temperature sensor 10 must be introduced to measure this temperature T _{second_in} .

Figure 3 shows an embodiment of the invention in a district heating installation, which is entrusted with a number of functions. Examples of these functions include regulation of hot tap water and regulation of water for heating, measuring the total amount of heat transferred in the corresponding circuit, as well as presenting this information via a communication line to an external dispatch system. It is assumed that the fault detection functions in the heat exchanger and in other components of the installation, implemented using the values measured in the installation, and communication with the control center via the communication line are part of the functions performed by the control unit 7. Sensors are provided for measuring the resulting temperatures of the outgoing secondary flows in order to carry out any control and / or warning signal in case of violation of the control function and / or to measure the amount of heat (at the same time, these sensor readings are not used for dynamic temperature stability).

The basic theory of regulation

The invention is based on the fact that the supplied / absorbed power in the primary circuit should be regulated relative to the current set, supplied / taken to / from the secondary medium in order to change the temperature from the current temperature of the incoming secondary stream to the set temperature of the outgoing secondary stream. This is done by controlling the flow rate in the primary circuit, depending on the difference between the temperature of the incoming and outgoing primary streams.

In the general case, for the primary and secondary circuits of heat exchangers:

where Q 'corresponds to the power transmitted by the circuit to the heat exchanger, m corresponds to the mass flow rate in the circuit, h (T) corresponds to the enthalpy of the medium (energy per unit mass) at a temperature T, T _o corresponds to the temperature of the outgoing stream and T _I corresponds to the temperature of the incoming stream.

Alternatively, equation (A) can be written as:

where c _p is the heat capacity of the medium, and ΔT = T _out -T _in .

The set power -Q _{second_set} , supplied to the secondary medium to achieve the set temperature of the outgoing secondary stream, is determined by the equation:

where m _sec corresponds to the mass flow in the secondary circuit, h _sec (T) corresponds to the enthalpy of the secondary medium at a temperature T, T _{sec_output} corresponds to a predetermined temperature of the outgoing secondary flow and T _{sec_input} corresponds to the current temperature of the incoming secondary flow.

During heat transfer, there is an energy balance in which the sum of the capacities supplied to the heat exchanger through the primary side Q ' _first , through the secondary side Q' _second and due to any leakage Q ' _{leakage of the} heat exchanger is equal to the increase in energy stored in the heat exchanger per unit time, Q _vx , i.e:

The invention provides for the regulation of power supplied from the primary side, Q ' _first , so that

If the leakage action is negligible, the _leakage Q ' _is also assumed to be zero, which gives:

During load changes, it may be appropriate to take into account Q ' _vx , which determines the dynamic effect of changes in the energy stored in the heat exchanger. For example, the system can be controlled by a control valve with a relatively low adjustment speed. This will be, for example, in the case of a rapid decrease in load, which means a higher supply of energy to the primary circuit than that required until the control element reaches the desired position. The supplied "excess energy" is partially stored in the heat exchanger and will cause a temporary increase in the temperature of the outgoing secondary stream. This temperature increase can be minimized by regulation, which compensates for the excess energy in the heat exchanger by temporarily reducing the input primary power until the excess energy is withdrawn by the secondary stream.

In a stationary state, the energy stored in the heat exchanger does not change, that is, Q ' _vx = 0, and the introduction of this value into equation (B3) gives:

The introduction of equation (A) for the primary side and (A3) in equation (B4) gives:

_By extracting m _{first defined} from equation (C) we obtain the basic control principle according to the invention in the form:

This basic control principle can be evaluated in various ways and with varying degrees of approximate simplifications, some of which are shown below. Often, costs are defined as volumetric costs, and therefore it is necessary to recalculate equation (D) for volumetric costs. For mass flow, m:

where: q is the volumetric flow rate and ρ is the density.

Since ρ depends on temperature, it is often necessary to take into account the temperature at which the volumetric flow rate is determined. Assume that the volume q _second on the secondary side is determined at the input and that the given q _{first-defined} on the primary side is defined at the output. After introducing equation (E) into equation (D), the resulting equation can be solved with respect to q _{first_set} :

When setting the volumetric flow somewhere else, equation (E) should be applied at the temperature of the medium at the place of measurement of the volumetric flow. For the enthalpy h (T):

where: c _p is the heat capacity (energy per unit mass and one degree).

The introduction of equation (G) in equation (F) gives:

where: ΔT _{second_set} = T _{second_out_set} -T _{second_in} , and

ΔT _first = T _{first_in-} T _{first_out} .

When using the same medium in the primary and secondary circuits and neglecting the temperature dependence of ρ and with _p (ρ _second = ρ _first ; with _{p (second)} = with _{p (first)} ), equation (F2) can be converted to:

Therefore, the invention can be evaluated in several more or less approximate ways (for example, by adjusting according to equation D, F, F2 or F3). What is common to them is that they are based on an array of parameters, the characteristics of the difference (Δh) of the enthalpies of the primary stream (3i) entering the heat exchanger (1), and the secondary stream (3u) leaving the heat exchanger (1), for example, on a number points of the function h (T) for the primary medium in the temperature range typical of the field of application, and T _{first_out} , T _{first_in} . An example of an alternative characteristic array of parameters instead of the specified difference in enthalpies is the heat capacity formed with _{p of the} primary medium in the temperature range, which is related to the field of application, and the difference ΔT of the _first temperatures.

According to the invention likewise possible to use other characteristic parameter arrays instead of mass flow (m _sec) in the secondary circuit (2) and the mass flow (m _prim) in the primary circuit.

Control Valve Design

The design of the valve 5 may be different, while for a particular design should be known flow characteristics. Examples of valves include seat, spool, ball and poppet valves. When using a slide valve, which when opened / closed is actuated by an adjusting screw, the size of the valve opening is substantially proportional to the stroke.

Depending on the current pressure difference? P _{of the valve} on the valve, the flow q through the _valve and the valve opening degree of a valve for each type of valve can be determined characteristic k _v (a). Therefore, the flow rate through the valve is determined by the ratio:

from which can be found:

and

where: f _cv (x) is the inverse function of k _v (x).

Valve control function with differential pressure measurement

During use of the valve, the position of the valve is controlled to achieve a corrected flow rate. For each type of valve, the achieved flow rate can be empirically determined based on the current position of the valve and the pressure drop across the valve.

The position of the valve, a, necessary for regulation, can be expressed depending on the measured flow rate in the secondary circuit, the measured temperature difference on the primary side, the measured differential pressure on the control valve and the specified temperature difference in the secondary circuit.

For each given flow rate in the primary circuit, the valve position can be adjusted according to the equation:

on the basis of which, after introducing equation (F) into equation (J2), an expression is obtained for the control principle according to the invention:

or after the introduction of (F3) in (J2):

since the same heat carrier is used on the primary and secondary sides, and since the temperature dependence of ρ and c _p is negligible. For each valve, it is possible to empirically determine the current inverse flow characteristics f _cv (x) (and / or flow characteristics k _v (x)).

It is assumed that the determination of the differential pressure ΔP of the _valve can be performed in an arbitrary way, for example, by means of a differential pressure gauge connected upstream and downstream of the valve, or by means of a first absolute pressure gauge for measuring pressure P1 upstream of the valve and another absolute pressure gauge for measuring pressure P2 downstream of the valve.

Power and heat measurement

Based on equation (A), the input power and the amount of heat can be measured on the primary side and / or on the secondary side of the heat exchanger. After inserting into equation (A) equations (H) and (E) applied to the medium in the valve, we obtain:

where: T _{first_valve} is the temperature of the primary medium in the valve.

If the valve is placed in the primary stream (3u) exiting the heat exchanger, then T _{first_valve} ≅T _{first_ out} , and accordingly, if it is placed in the primary stream (3i) entering the heat exchanger, then T _{first_valve} ≅T _{first_in} .

After inserting equation (G) into equation (L), an alternative equation is obtained:

According to a preferred embodiment, the power supplied on the primary side is found in part by determining the temperatures T _{first_in} , T _{first_out} and the pressure drop ΔP of the _valve on the control valve placed downstream of the outlet of the primary side; and in part by means of information on the characteristics k _v (a) and the degree of valve opening a, and the density and enthalpy of the primary medium, the values of which are used to calculate Q ' _first in accordance with equation (L), as an alternative in accordance with (L2) .

By integrating the power supplied during the time interval t1-t2, we obtain the amount of heat supplied by the primary circuit during this interval:

Equation (L) inserted in equation (M) gives:

и соответствующих интервалов времени для образования среднего значения Δt_i:Integration can be carried out, for example, by determining and summing the partial energies one after the other, while the energies are defined as the products of periodic average power values

and corresponding time intervals for the formation of the average Δt _i :

According to a preferred embodiment of the invention, the power output and the amount of heat are also determined on the secondary side. In this case, the determination is based on the temperatures T _{sec_inv} and T _{sec_v out} (measured by the fourth temperature sensor) and the flow q q _sec (measured by the flow sensor or otherwise determined, for example, by the known characteristics of a variable speed pump) and equation (A).

Assuming a steady state and negligible heat leakage from the heat exchanger, the power output and the amount of heat on the primary side form the first indicator, and the power output and the amount of heat on the secondary side form the second power indicator Q 'and the amount of heat Q that are transferred to the heat exchanger. You can use one or the other of these two independently determined indicators of power output and amount of heat, for example, for billing or monitoring energy consumption.

By comparing these two independently determined indicators, system reliability can be improved. For example, excessive values of Q 'can be used to obtain a warning signal that the indicators are not reliable if these indicators differ from each other by more than an acceptable value, for example, ± 10% or preferably ± 2% of a higher value.

The second area of application can be switching the system to the backup mode by any method based on the definition of Q ', provided that the error of the measuring signal, which is included in the definition of Q' in accordance with another method, is found in another independent way. Example: if it is determined, for example, by checking for consistency that the temperature sensor on the primary side is damaged, then you can determine the backup value for the damaged sensor by using the value Q 'defined on the secondary side. Similarly, backup values can be calculated for any sensor whose error is detected independently.

A third application may be self-calibration of the sensor or, for example, the use of the valve characteristics in the same way to calculate backup values in case of sensor failure.

Integral Valve Units

In order to simplify the manufacture and assembly of the systems according to the invention, in a preferred embodiment, several functions can be jointly implemented in an integral valve assembly, which can be manufactured as a semi-finished product for subsequent integration to form a complete system. 4 schematically shows an integrated hydraulic unit for controlling and measuring the primary flow according to the invention, including a valve element, a differential pressure gauge and a temperature sensor, as well as a control element acting on the valve element, which can be integrated into the hydraulic unit or as an option installed in it. This hydraulic unit can advantageously be used to control the primary flow and to measure the pressure drop across the valve elements and the temperature of the primary flow at the valve.

Several functions / components can be assigned to the hydraulic unit 40 shown in FIG. 5, comprising a first channel 56 between pipe couplings 41 and 42 for connecting to a district heating system and a heat exchanger, respectively, and branch pipes 43 and 44 to any adjacent pipes additional hydraulic units; see Fig.6.

In the channel 56, a valve member 53 is arranged, which is controlled by a control member 54. Pressure gauges 61 and 62 are mounted on either side of the valve member 53 to measure the pressure difference upstream and downstream of the valve member. Sensors 8 are also located in channel 56 for measuring the temperature of the medium in channel 56. In the hydraulic unit 40, a second channel 57 is made, and this channel can be connected through the pipe couplings 45 and 46 to the incoming medium of the district heat supply system and to the heat exchanger, respectively. The branch pipes 47, 48 from the second channel 57 can be used to connect to adjacent additional hydraulic units. In another channel 57, sensors 9 are also located for measuring the temperature of the medium in this channel. The third and fourth channels 58 and 59 with pipe couplings 49 and 51 for connecting to the heat / cold consumer, and pipe couplings 50 and 52 to the heat exchanger are also part of the hydraulic unit 40. To measure the temperature of the medium in channels 58 and 59, sensors 55 and 10 are located in the corresponding channels. To determine the flow rate of the medium in channel 59, a pressure gauge 70 is provided. Contact elements (not shown) are provided for connecting communication lines to and from the hydraulic unit 40, through which measurement data and / or control signals.

The integrated hydraulic unit of FIG. 4 can, with advantage, be manufactured in the form of a semi-finished product for subsequent integration with the formation of a complete system, for example, shown in FIG. 6. The use of hydraulic units provides potential benefits in addition to those already mentioned due to the significant simplification of the placement and connection of the primary and secondary circuits.

In most typical embodiments, the temperature of the secondary stream 2 leaving the heat exchanger 1 is constant, for example, 55 ° C. Of course, you can manually or automatically set the setpoint. For example, the setpoint can be set using the potentiometer in the control unit 7. Certain manual adjustments can be made depending on the wishes of consumers of hot water or carried out depending on the current season of the year. For example, warmer hot tap water may be required during the winter to compensate for heat loss between the heat exchanger and most remote users. Correction of the season-dependent outlet temperature on the secondary side can also be carried out automatically by the control unit in accordance with a predetermined compensation curve and / or signals from an external temperature sensor.

In one application of the invention in a system in which a heat exchanger heats the heating circuit, appropriate correction in most cases is necessary depending on the outdoor temperature, as well as a correction of the temperature of the incoming secondary stream. In this embodiment, there is no need for direct feedback on the temperature of the effluent on the primary side.

The control elements for the control valve can be of several different types, and a control signal corresponding to the control element used is supplied to each. For example, valves with a servo motor controlled by pulse width modulation (PWM), or with flow control in proportion to the control current or voltage, may be used.

The method in accordance with the invention can be advantageously combined with fault detection in the heat exchanger. In those embodiments in which the pressure drop across the valve is measured, initial clogging on the primary side (caused by deposits of calcium, dirt, etc.) can be detected by analyzing the pressure drop over time at a given degree of valve opening. During the initial blockage, the pressure drop across the control valve decreases at a constant flow rate, since a constantly increasing pressure drop will be damped by the heat exchanger. Fault detection can also be done by evaluating the heat transfer of the heat exchanger. For example, you can apply the following method: all measured signals (at least the temperature difference in the primary circuit, the primary stream, the secondary stream and the set temperature difference on the secondary side) are stored for a number of different load modes (transmitted power) and system modes (temperature and pressure incoming primary stream). If the heat exchanger becomes clogged, the heat transfer characteristics deteriorate, which entails the need to increase primary flows.

The required difference ΔT of the _first temperature can be calculated on the basis of T _{first_input} and T _{first_out} or by directly measuring the temperature difference, for example, with a thermocouple.

Since both the flow rate and the temperature difference are measured in the system, it is easy to calculate the consumed amount of heat to bill the end user.

In addition, the system is well suited for taking readings (calculating heat transfer), detecting malfunctions (clogging), climate control (with centralized setting of setpoints) and possible termination of operation. Only one interface is required for a communication line, and this interface is connected to a control or regulation unit.

The invention is not limited to use in district heating plants; it can be used in all areas where heat exchangers are an integral part, for example, in the petrochemical industry or in other types of heating control systems.

Claims (13)

1. The method of controlling the temperature of at least one outgoing secondary stream (2u) in the secondary circuit from the heat exchanger (1), through the primary stream (3) in the primary circuit, while the control unit (7) controls the control element (5, 11), which regulates the primary flow, and the temperature T _{sec. the} outgoing secondary stream is known or to be measured, characterized in that a) determine the array of parameters, the characteristic of the difference (Δh) of the enthalpies of the incoming primary stream (3i) to the heat exchanger (1) and the outgoing primary stream (3u) from the heat exchanger (1), b) determine the array of parameters, the characteristic mass flow rate (m _sec ) in the secondary circuit (2), c) determine the array of parameters, the characteristic of the mass flow (m _first ) in the primary circuit (3), d) and the fact that the parameters defined in paragraphs a) to c) are transmitted to the control unit (7) for controlling the control element (5, 11), as a result of which the primary stream (3) is regulated depending on the secondary stream ( 2) so that the power transmitted to the heat exchanger by the primary stream (3) essentially corresponds to the sum of: 1) the power required to increase the temperature of the secondary medium from the current input temperature T _{sec. input} to a given output Temperature T _{sec. out given} and 2) the estimated power required to compensate for the stored energy in the heat exchanger (1), and 3) the estimated leakage rate from the heat exchanger. 2. The method according to claim 1, characterized in that the control element is controlled by coordinating the costs of the primary stream (3) against the secondary stream (2) so that the energy balance between the primary stream (3) and the secondary stream is maintained, while power consumption in the corresponding circuit with the flow has the form: Q = ρ · s _p · q · ΔT, from which the energy balance is obtained, and this flow q of the _first on the primary side is achieved by controlling the control element so that:

ρ _{second / first} - a predetermined density of the medium, respectively, in the secondary and primary circuit, with _{p (sec / primary)} - a predetermined specific heat of the medium, respectively, in the secondary and primary circuit, Q _first - flow in the primary circuit, obtained as a result of the action of the control element, q _sec - the actual measured flow rate in the secondary circuit, ΔT _first - the actual measured temperature difference between the incoming and outgoing media on the primary side, and ΔT _sec - the desired temperature difference between the inlet and outlet media of the secondary side, while only the temperature on the output side of the secondary circuit is a predetermined value, as a result of which the control element is controlled without direct feedback on the temperature on the output side of the secondary circuit. 3. The method according to claim 1 or 2, characterized in that the control element (5) is represented by a control valve with a known flow characteristic and pressure difference (pressure drop) on the control valve, as measured by a differential pressure gauge (6). 4. The method according to claim 3, characterized in that the degree (a) of opening the valve is a function of preferably empirically determined inverse flow characteristics of the valve f _{cv (x)} in accordance with:

where ΔР of the _valve is the measured pressure drop across the control valve, q _{first. preset} is the flow rate through the valve and a is the degree of valve opening. 5. The method according to claim 1 or 2, characterized in that the control element is represented by a pump (11) with a predetermined relationship between the flow through it as a function of speed and the pressure drop across the pump, as a result of which the control unit (7) controls the speed pump. 6. The method according to claim 1, characterized in that the temperature (T _{second. In} ) of the incoming secondary stream (2i) to the heat exchanger (1) is measured, and this measured value is used to calculate q _{first. given} . 7. A device for controlling the temperature of at least one outgoing secondary stream (2) from the heat exchanger (1) in the secondary circuit by means of the primary stream (3) in the primary circuit passing through the heat exchanger, while the control unit (7) controls the control element (5 , 11) installed to control the primary flow, characterized in that they install temperature sensors (8, 9) for measuring the temperature of the primary flows entering (3i) and leaving (3u) of the heat exchanger (1) to determine the difference in the enthalpies of these flows, install a flow meter (4) to measure the flow rate (q _sec ) of the secondary medium (2), set differential pressure gauges (6) to measure the pressure difference (ΔР) in the primary medium (3i) on the control element (5), and / or that sets the flowmeter (12) to measure the flow (q _prim) of the primary medium (3), and in that organizes the transmission of output signals from said sensors (4, 8, 9, 12) to the unit (7) for controlling the regulating member (5, 11), as a result of which it is possible to control the primary flow (3) depending flow from the secondary stream (2), so that the power transmitted between the heat exchanger and the primary stream (3) essentially corresponds to the sum: 1) the power required to increase the temperature of the secondary medium from the current input temperature T _{sec. in} to the specified output temperature T _{sec. out given} and 2) the estimated power required to compensate for the stored energy in the heat exchanger (1), and 3) the estimated leakage rate from the heat exchanger. 8. The device according to claim 7, characterized in that the control element (5) is represented by a control valve with known flow characteristics, a differential pressure gauge (6) installed to measure the pressure difference across the valve, and known flow characteristics for the valve (5) stored in the storage device of the control unit (7). 9. The device according to claim 7, characterized in that the control element is represented by a pump (11) with a predetermined relationship between the flow through it as a function of speed and the pressure drop across the pump, as a result of which the control unit (7) provides for adjusting the speed of the pump . 10. The device according to claim 7, characterized in that the valve (5) is integrated into the hydraulic unit (20), comprising a valve element (24) with a control element (25) acting on it, couplings (22, 23) for pipes, connected to the valve (5), a device (6) for determining the pressure drop across the valve element, which is connected upstream and downstream of the valve element (24), a temperature sensor (8) that determines the temperature of the flow through the valve. 11. An apparatus according to any of claims 7-10, characterized in that the unit (7) comprises at least one storage device (30) for storing the degree of (a) opening the valve (5) as a function of the flow q _sec of the secondary circuit ( 2), the difference ΔT _second temperature in the secondary circuit (2), the difference ΔT _first temperature in the primary circuit (3) and the difference ΔP of _the pressure valve on the valve (5). 12. The device according to claim 7, characterized in that the channels (56-59) for the conductive medium (3i, 3u, 2i, 2u) into and from the heat exchanger (1) are made in the hydraulic unit, in that these channels are provided at the ends couplings (41, 42, 45, 46, 49, 50, 51, 52) for pipes for connection with the primary and secondary flows (3, 2), so that the transverse channels (43, 44, 47, 48) are separated from at least some of these channels, while the transverse channels at the ends are likewise provided with pipe couplings for connecting the connecting pipes between several connected hydraulic units, and that in the hydraulic unit there are sections of channels for sensors (8, 9, 10, 55, 61, 62) of flow, differential pressure and temperature, in communication with the channels and at least one control valve. 13. A method for improving the reliability of a heat exchanger system (1) containing at least one secondary stream (2) in the secondary circuit and a primary stream (3), wherein the control unit (7) controls a control element (5, 11) that controls the primary flow (3), which determines the difference (Δh) of the enthalpies of the primary stream entering (3i) and leaving (3u) of the heat exchanger (1), determine the pressure difference (ΔР of the _{control element} ) by and the temperature (T of the _medium ) in the control element (5, 11) with known flow characteristics stored in ominayuschem block unit (7) controls preserve the density of the primary medium in the memory unit (7) control register difference (Δh) enthalpies, the pressure differential (.DELTA.P _{regulating member),} the temperature (T _medium) and the degree (a) opening regulating member, and these parameters, together with the flow characteristics and density, are stored in the memory of the control unit, provide a measure of the power and amount of heat supplied by the primary circuit, characterized in that the obtained measuring the power and amount of heat supplied by the primary circuit, with the true values of the power and amount of heat absorbed by the secondary circuit, which are calculated on the basis of the difference indices (Δh _sec ) of the enthalpies of the incoming and outgoing secondary flows and the secondary flow rate m _sec , which are stored or determined in the unit control, as a result of which an alarm signal is issued to the environment by means of communication if the values of power and amount of heat supplied and absorbed respectively primary and secondary circuits, deviate from each other more than a predetermined allowable value.

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