US20110114304A1

US20110114304A1 - Method for the hydraulic compensation and control of a heating or cooling system and compensation and control valve therefor

Info

Publication number: US20110114304A1
Application number: US13/003,211
Authority: US
Inventors: Urs Keller
Original assignee: Belimo Holding AG
Current assignee: Belimo Holding AG
Priority date: 2008-07-25
Filing date: 2009-07-21
Publication date: 2011-05-19
Also published as: EP2304325B1; WO2010010092A2; CN102216691A; EP2304325A2; CA2727779A1; CN102216691B; WO2010010092A3

Abstract

The invention relates to a method for the hydraulic compensation and control of a heating and cooling system. The system comprises at least one pump and a plurality of lines respectively comprising a compensation and control valve and a load. The method for compensation and control consists of the following steps: a control value for each of the compensation and control valves is determined for which the predetermined discharge values are reached in each line; a control range of each compensation and control valve is defined as the difference between the determined control value and the position when the compensation and control valve is closed; and the signal control range of one each of the compensation and control valves is represented in the newly defined control range.

Description

TECHNICAL FIELD

The present invention relates to a balancing and regulating valve for a heating or cooling system and to a method for the hydraulic balancing of such a balancing and regulating valve in a branch of a heating or cooling system.

PRIOR ART

The hydraulic balancing of a heating or cooling system is carried out before the system is transferred to the customer. The system must be fully installed and be in operation. The aim is to distribute, as required, the medium delivered from the central pump to the various zones of the system. Balancing is usually carried out only at one operating point, to be precise under full load. This means, for such a system, that all the regulating valves are opened to a maximum. In this state, then, the rotational speed of the pump and the position of balancing throttles or balancing valves, which precede or follow the actual regulating valves, are set such that the throughflow values stipulated by the planner are achieved in each branch. The rotational speed of the pump is in this case to be set as low as possible, but sufficiently high to achieve all the throughflows required.
A person therefore goes physically from valve to valve, measures the throughflow there and turns on the balancing throttle until the throughflow assumes the desired value. A differential pressure measuring instrument is often used for throughflow measurement. The pressure loss is measured across a known resistance, for example a measuring diaphragm or heat exchanger. Alternatively to differential pressure measurement, a mobile ultrasonic throughflow meter may also be used, which can be mounted on the pipework on the outside.
It is known from US 2004/182443 to improve this procedure to the effect that two valves, a balancing valve and a regulating valve, connected in series with a load in a branch are no longer provided but, instead, a combined balancing and regulating valve can be used. However, the valve described in this document is complicated and demands that the expert making the settings should use various inserts in order to achieve the aim of hydraulic balancing. Nor is it simple to regulate this combined balancing and regulating valve.
EP 0 301 568 discloses an autocalibration method for a regulating valve, in which the effective actuating travel of the valve is established and the regulating range is limited to this effective actuating travel. The effective actuating travel is in this case defined as the range of the total actuating travel between 5% and 95% of maximum throughflow. This document is not concerned with the set object of hydraulic balancing.

PRESENTATION OF THE INVENTION

The invention is based on the recognition that said setting of the hydraulic balancing according to the prior art is carried out only when the regulating valves are open, in order to establish the minimum necessary pump delivery rate required under full load so as to achieve all the required throughflows in the individual branches. There is then the disadvantage that, in branches with an already throttled balancing valve (branch regulating valve), a relatively large part of the operating range of the regulating valve is lost. To be precise, if the balancing valve is partially closed, the overall characteristic curve (k_V—throughflow characteristic value) of the branch is flattened in the range of a relatively pronounced opening of the regulating valve, that is to say in its upper operating range. By contrast, where the regulating valve is opened to a lesser extent, that is to say is in its lower range, the overall characteristic curve is steeper. This deformation of the characteristic curve is detrimental to the regulating behavior for this line, because, on the one hand, resolution is poorer in the lower regulating range and, on the other hand, the overall circuit amplification is not constant over the operating range. Variable circuit amplification actually necessitates variable control parameters. This makes it difficult to tune the controller, especially since variable parameters are mostly not provided in the controllers used.
An object of the present invention, therefore, is to overcome this disadvantage of the prior art and to combine hydraulic balancing and regulating in a simple way adjustably in control terms. In particular, an object of the present invention is to configure the overall characteristic curve, that is to say the characteristic curve of the regulating valve with a folded characteristic curve of the connected load, for example a heat exchanger, so as to be improved for the purpose of simpler and better regulation.
According to the present invention, these aims are achieved, in particular, by means of the elements of the independent claims. Further advantageous embodiments are provided, moreover, in the dependent claims and the description.
Instead of throttling a balancing valve (branch regulating valve), the operating range of the actual regulating valve is restricted. In addition to this restriction, the valve control is also advised of this, so that the signal range can be mapped automatically onto the new operating range. In this way, a 100% dynamic range remains for the control.
A method for the hydraulic balancing of a balancing and regulating valve in a branch of a heating or cooling system can be employed when such a balancing and regulating valve and a load are provided. A medium flows through a branch of the heating or cooling system. A setpoint value for the balancing and regulating valve is determined, at which a predetermined throughflow value of the medium, which is lower than the maximum throughflow value, is reached in the branch. This setpoint value is defined and set as the “maximum setpoint value”. The operating range of the balancing and regulating valve is then defined as the range between the set “maximum setpoint value” and the position with the balancing and regulating valve closed. The original signal regulating range of the balancing and regulating valve is then mapped onto the newly defined operating range. This then gives rise to full dynamics with reduced maximum setpoint value.
Advantageously, the valve characteristic curve is an equal-percentage characteristic curve in order, in interaction with a connected heat exchanger, to generate a linear dependence. As a result of the restriction of the operating range, a valve characteristic curve which is equal-percentage in the case of 100% operating range and is also equal-percentage in the balanced state, that is to say with a smaller operating range, for example 60%. This applies over the widest range of the restricted operating range.
Furthermore, a predetermined lower regulating range may be configured linearly, in order to ensure better regulation of the small valve openings. This division of the regulating range in two via a continuously differentiable transition makes it possible to combine the advantageous equal-percentage valve characteristic curve in the large opening range, in order to avoid a flattening of the gradient in the case of high control deflections, with the linear flat characteristic curve in a predetermined lower regulating range.
The setting of the “maximum setpoint value”, which can be set, for example, in the form of a limit angle, may be carried out manually directly on the control unit or else electrically via the actuating signal which is also used in regulating mode.
The storage of the “maximum setpoint value”, that is to say of the determined and set position of the valve as a new maximum value, may be carried out by pressing a key directly on the drive or else electronically by sending a bus command. This command may be sent either by a service tool or from the building management system.

BRIEF DESCRIPTION OF THE DRAWINGS

An embodiment of the present invention is described below by the way of example. The exemplary embodiment is illustrated by the following accompanying figures:

FIG. 1 shows a graph which shows diagrammatically a characteristic curve of a conventional regulating valve, which is connected in series with a balancing valve, and a characteristic curve of a balancing and regulating valve according to the invention.

FIG. 2 shows a graph which shows diagrammatically a characteristic curve of a heat exchanger as the load, a characteristic curve of a balancing and regulating valve according to the invention and the overall characteristic curve of a branch.

WAYS OF IMPLEMENTING THE INVENTION

FIG. 1 shows diagrammatically a characteristic curve 10 of a conventional regulating valve which is connected in series with a balancing valve, and a characteristic curve 20 of a balancing and regulating valve according to the invention.
It can be seen that the gradient 11 of the characteristic curve 10 of the conventional regulating valve is very much steeper in the lower regulating range, that is to say at values of, for example, 10 to 20%, than the gradient 21 of the characteristic curve 20 of a balancing and regulating valve according to the invention in the range of between 0% and 30%. This allows more accurate regulation in the lower regulating range and thus prevents more pronounced hunting. Mostly, in the valves according to the prior art and in the balancing and regulating valve described here, the gradient 11 or 21 is also associated with a range 13 without a gradient, also called a dead angle or dead zone, here at 0% to 10%.
Furthermore, it can be seen that the gradient 12 of the characteristic curve 10 of the conventional regulating valve flattens greatly in the upper regulating range, here from 80% of the operating range, and, for example here, approaches a percentage k_Vvalue of 25% which is predetermined as the maximum value by the preceding or following balancing valve. By contrast, there is still a rising and therefore sufficient gradient 22 of the characteristic curve 20 of the balancing and regulating valve according to the invention, so that the k_Vvalue of the branch is reached only when the regulating range of 100% is fully utilized.
Advantageously, the characteristic curve 20 of a balancing and regulating valve for this method and device is equal-percentage. In the case of an equal-percentage characteristic curve, identical input variable changes cause identical percentage output variable changes over the entire regulating range. An equal-percentage characteristic curve with an equal-percentage factor of above 4, for example, 4.5, is especially advantageous.
The advantage arising from this can be seen from FIG. 2 which shows a graph showing diagrammatically a characteristic curve of a heat exchanger 30 as the load, a characteristic curve 20 of a balancing and regulating valve according to the invention and the overall characteristic curve 40 of a branch. With the equal-percentage characteristic curve of the balancing and regulating valve, the exactly oppositely configured characteristic curve 30 of a heat exchanger connected as the load can be compensated, thus resulting in an overall characteristic curve 40 which is essentially linear.
Since both the characteristic curve 20 of the valve and the characteristic curve of the load 30 are essentially scaled in the case of a lower pre-setting, the resulting control characteristic curve 40 of a branch remains essentially linear or can be considered as such by a control unit.
In an even more advantageous refinement, the equal-percentage characteristic curve 20 referred to here is modified.
${k_{V} \rangle}_{\frac{α}{α_{100}} \leq \frac{1}{n_{gl}}} = k_{V 100} \cdot \frac{α}{α} \cdot n_{gl} \cdot e^{1 - n_{gl}}$ ${k_{V} \rangle}_{\frac{α}{α_{100}} \geq \frac{1}{n_{gl}}} = k_{V 100} \cdot e^{n_{gl} \cdot (\frac{α}{α_{100}} - 1)}$
Here, the expression
$(\frac{α}{α_{100}})$
is the quotient of the opening angle α and the set maximum opening angle α₁₀₀, that is to say the value which is plotted in FIG. 1 on the abscissa as a position signal; and k_V100is the throughflow value in the case of a completely open maximum opening angle. The desired characteristic curve is then described in an upper opening range 22 by an exponential function. The parameter n_gl(often called n_ep) is a measure of how sharply the characteristic curve is curved. Since exponential functions never cross the zero point, this definition of the characteristic curve is replaced in the lower range 21 by linear. The transition from the linear to the exponential part is continuously differentiable and is predetermined by the reciprocal value of n_gl. The overall characteristic curve is called “equal-percentage” (sometimes “modified equal-percentage”). In an exemplary embodiment described here, n_gl=4.5. The greater curvature, as compared with n_gl=2 to 4 of the prior art, is advantageous for the balancing function by means of an equal-percentage valve. Equal-percentage valves with a value of n_glof 4.5 to 6 or 7 are advantageous. Consequently, the region of transition of the curve into the linear part is likewise shifted toward lower
$(\frac{α}{α_{100}})$
values. In other words, with a restriction of the maximum operating range in the case of a predetermined valve, a flatter gradient is obtained in the linear range than in the prior art, thus making more accurate regulatability possible.
The function of hydraulic balancing of a heating or cooling system is then based, as follows, on the components of the system. Such a heating or cooling system comprises at least one pump and a multiplicity of branches which each have a balancing and regulating valve and a load, the valve and load being connected one behind the other in series. The load is usually a heat exchanger.
A maximum setpoint value is then set for each of the balancing and regulating valves, so that predetermined throughflow values are reached in each branch. After this setting step, the operating range of each balancing and regulating valve is defined as the range between the set maximum setpoint value and the position when the balancing and regulating valve is closed. The signal regulating range of each balancing and regulating valve is then mapped onto the newly defined operating range in the control circuit of the heating or cooling system, so that the full signal regulating width of 100% is available again and is applied to a reduced operating range. In other words, by virtue of the advantageously linear initial range and the subsequent exponential characteristic curve, the mapping of the signal regulating range of each balancing and regulating valve onto the newly defined operating range makes it possible to ensure that there is a reasonably regulatable range for low manipulated variables, since the gradient of the linear range remains flat and, because the curve for high operating ranges then rises exponentially toward the maximum, no control saturation occurs.
Advantageously, the maximum setpoint values of the individual balancing and regulating valves can be stored in said electronic control unit and can then, after being stored in this way, be transmitted as setting signals to the balancing and regulating valve in order to fix the maximum value of the valve opening.
The design of the heating or cooling system advantageously makes use of balancing and regulating valves and elements acting as the load, which in each case have a specific characteristic curve, so that the overall characteristic curve of a branch which arises from the load and from the balancing and regulating valve is essentially linear. Since the load characteristic curve mostly has a form like that of the characteristic curve 30 in FIG. 2, it is advantageous to use in each case balancing and regulating valves which have an equal-percentage valve characteristic curve and, even more preferably, a characteristic curve with an n_glof 4.5.
In addition to the balancing of a heating or cooling system having a plurality of branches, according to an exemplary embodiment of the invention, the balancing and regulating valve can also expediently be used on its own. A maximum setpoint value is then still set for this balancing and regulating valve, this setting being carried out by means of a setting knob, for example potentiometrically. It is advantageous that the maximum setpoint value is not just a limit stop, but a maximum settable angle or other manipulated variable of the valve, so that a predetermined maximum throughflow value in the branch of this valve is achieved. This maximum value can also be stored, for example, in a nonvolatile memory of an activation and control circuit of the valve. After this setting step, the operating range is defined in this activation and control circuit as the range between the set maximum setpoint value and the position when the balancing and regulating valve is closed. The signal regulating range of this balancing and regulating valve can then continue to be addressed over the full signal regulating width of 100% in the control circuit of the heating or cooling system, whereas this range is then actually applied to an operating range reduced in the valve. Mapping onto the newly defined operating range can thus take place solely in the balancing and regulating valve, thus making it possible to replace individual valve combinations of a branch valve and regulating valve in an older heating or cooling system with a balancing and regulating valve according to the invention, if the response of the control circuit is compatible. In this context, the signal regulating range is to be understood as meaning the range of input signals (digital or analog) for the balancing and regulating valve, with which a control unit can address this valve to maximum, this usually corresponding to values between 0% and a 100% maximum opening of the valve. In the invention, this maximum signal regulating range, exactly scaled, can address the full reduced operating range of the balancing and regulating valve, and no interval in the signal regulating range is lost.
Such a balancing and regulating valve can operate independently in a branch if it is subjected by a conventional control unit of a heating or cooling system to an activation signal of between 0 and 100%. According to another exemplary embodiment of the invention, however, it can also operate with a control unit of a heating or cooling system in which the balancing and regulating valve does not itself know or store a maximum threshold value, but instead, these maximum setpoint values are stored in this control unit and then the activation signal for a balancing and regulating valve does not have a signal value of between 0 and 100%, but covers only a range predetermined by the maximum setpoint value, then, however, with a signal value resolution of 100%.
An example is depicted in FIG. 1. In the case of a valve characteristic curve 20, the maximum setpoint value is fixed at 75% in a branch, for which purpose the reference symbol S₇₅has been used. An activation signal of 60% generated by a control unit then does not cause the valve to open according to the characteristic curve at the position A_60/100, but instead, the k_Vvalue is obtained just at the position A_60/75which is 60% of an activation range predetermined by the maximum setpoint value of 75%, that is to say at the position signal of 45% (=60%*75%).

LIST OF REFERENCE SYMBOLS

10 Characteristic curve of a known regulating valve
11 Gradient in the lower regulating range in the known regulating valve
12 Gradient in the upper regulating range in the known regulating valve
13 Gradient in a lowermost regulating range in the known regulating valve
20 Characteristic curve of a balancing and regulating valve for a system according to the invention
21 Gradient in the lower regulating range in the exemplary embodiment
22 Gradient in the upper regulating range in the exemplary embodiment
30 Characteristic curve of a heat exchanger for a system according to the invention
40 Overall characteristic curve of a system according to the invention

Claims

1. A method for the hydraulic balancing of a branch of a heating or cooling system, wherein the branch comprises a balancing and regulating valve and a load, the balancing and regulating valve being adapted to receive regulating signals within a signal regulating range, the method comprising:

(a) causing a medium to flow through the branch;

(b) determining a maximum setpoint value for the balancing and regulating valve, at which a predetermined throughflow value is reached in the branch, wherein the predetermined throughflow value is lower than a maximum possible throughflow value through the branch;

(c) restricting the operating range of the balancing and regulating valve to the range between the determined maximum setpoint value and a position in which the balancing and regulating valve is closed; and

(d) mapping the signal regulating range of the balancing and regulating valve onto the thus restricted operating range.

2. The method as claimed in claim 1, wherein the balancing and regulating valve has an equal-percentage valve characteristic curve.

3. The method as claimed in claim 1, wherein the balancing and regulating valve has a valve characteristic curve which has an at least approximately linear profile in a first, lower operating range and which has an equal-percentage profile in a second, upper range.

4. The method as claimed in claim 3, wherein, if the expression

(\frac{α}{α_{100}})

indicates the quotient of an arbitrary setpoint value α and the maximum setpoint value α₁₀₀and n_glindicates the characteristic equal-percentage number, the valve characteristic curve, in a first range of

(\frac{α}{α_{100}})

lower than the reciprocal value of n_glis a linear characteristic curve and, in the remaining second range of

(\frac{α}{α_{100}})

higher than the reciprocal value of n_gl, is an exponential characteristic curve:

{k_{V} \rangle}_{\frac{α}{α_{100}} \leq \frac{1}{n_{gl}}} = k_{V 100} \cdot \frac{α}{α_{100}} \cdot n_{gl} \cdot e^{1 - n_{gl}}

{k_{V} \rangle}_{\frac{α}{α_{100}} \geq \frac{1}{n_{gl}}} = k_{V 100} \cdot e^{n_{gl} \cdot (\frac{α}{α_{100}} - 1)}

5. The method as claimed in claim 4, wherein n_glis higher than 4.5.

6. A method for hydraulic balancing of a heating or cooling system comprising at least one pump and a plurality of branches, the method comprising:

causing a medium to flow through the heating or cooling system at a predetermined pump capacity; and

carrying out the method as claimed in claim 1 for each of the branches.

7. The method as claimed in claim 6, wherein an electronic control unit is provided, in which the maximum setpoint values of the individual balancing and regulating valves are stored, and by means of which, after said values have been stored, setting signals are transmitted to the balancing and regulating valves in order to transmit a maximum value of the valve opening.

8. A balancing and regulating valve for a heating or cooling system, adapted to be mounted as a balancing and regulating valve in a branch in series with a load, the balancing and regulating valve being configured such that a maximum setpoint value can be set so that a predetermined throughflow value in the branch is achieved,

the valve being configured such that the maximum setpoint value of the valve can be set as a part value with respect to a complete opening of the valve,

wherein the operating range of the valve can be set as the range between the set maximum setpoint value and the position when the valve is closed, and

wherein the valve has a signal regulating range adapted to be mapped onto the thus defined operating range.

9. The balancing and regulating valve as claimed in claim 8, comprising a control unit in which the maximum setpoint value can be input manually or electrically/electronically for defining the operating range of the balancing and regulating valve as arranged between the set maximum setpoint value and the position when the balancing and regulating valve is closed, and wherein the control unit is designed for mapping the signal regulating range of the balancing and regulating valve onto the thus defined operating range.

10. A device for the hydraulic balancing of a heating or cooling system, comprising at least one pump and a multiplicity of branches, wherein at least one branch has a balancing and regulating valve as claimed in claim 8 and a load,

the device comprising a control unit in which the maximum setpoint values, delivered manually or electrically/electronically by said balancing and regulating valves, can be input for defining the operating range of each of these balancing and regulating valves as the range between the set maximum setpoint value and the position when the balancing and regulating valve is closed, wherein the control unit is designed, further, for mapping the signal regulating range of each balancing and regulating valve onto the thus defined operating range.

11. The device as claimed in claim 10, wherein each of these balancing and regulating valves has a valve characteristic curve so that the overall characteristic curve of such a branch which arises from the load and from the balancing and regulating valve is linear.

12. The device as claimed in claim 10, wherein at least one such balancing and regulating valve has an equal-percentage valve characteristic curve.

13. The device as claimed in claim 10, wherein at least one such balancing and regulating valve has a valve characteristic curve which has an at least approximately linear profile in a first, lower operating range and which has an equal-percentage profile in a second, upper range.

14. The device as claimed in claim 13, wherein, if the expression

(\frac{α}{α_{100}})

indicates the quotient of the setpoint value α and the set maximum setpoint value α₁₀₀and n_glindicates the characteristic equal-percentage number, the valve characteristic curve of said balancing and regulating valve, in a first range of

(\frac{α}{α_{100}})

lower than the reciprocal value of n_gl, is a linear characteristic curve and, in the remaining second range of

(\frac{α}{α_{100}})

{k_{V} \rangle}_{\frac{α}{α_{100}} \leq \frac{1}{n_{gl}}} = k_{V 100} \cdot \frac{α}{α_{100}} \cdot n_{gl} \cdot e^{1 - n_{gl}}

{k_{V} \rangle}_{\frac{α}{α_{100}} \geq \frac{1}{n_{gl}}} = k_{V 100} \cdot e^{n_{gl} \cdot (\frac{α}{α_{100}} - 1)} .

15. The device as claimed in claim 14, wherein the value of the balancing and regulating valve n_glis higher than 4.5.

16. The method as claimed in claim 15, wherein ngl is higher than 5.

17. The method as claimed in claim 5, wherein ngl is higher than 5.