EP3055571A1 - Method for operating a pump unit, pump unit and use thereof - Google Patents

Method for operating a pump unit, pump unit and use thereof

Info

Publication number
EP3055571A1
EP3055571A1 EP14786634.7A EP14786634A EP3055571A1 EP 3055571 A1 EP3055571 A1 EP 3055571A1 EP 14786634 A EP14786634 A EP 14786634A EP 3055571 A1 EP3055571 A1 EP 3055571A1
Authority
EP
European Patent Office
Prior art keywords
pump unit
accordance
flow rate
volumetric flow
differential pressure
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP14786634.7A
Other languages
German (de)
French (fr)
Inventor
Karsten Laing
Gabor Szabo
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Xylem IP Holdings LLC
Original Assignee
Xylem IP Holdings LLC
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Xylem IP Holdings LLC filed Critical Xylem IP Holdings LLC
Publication of EP3055571A1 publication Critical patent/EP3055571A1/en
Withdrawn legal-status Critical Current

Links

Classifications

    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
    • F04B—POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS
    • F04B49/00—Control, e.g. of pump delivery, or pump pressure of, or safety measures for, machines, pumps, or pumping installations, not otherwise provided for, or of interest apart from, groups F04B1/00 - F04B47/00
    • F04B49/06—Control using electricity
    • F04B49/065—Control using electricity and making use of computers
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
    • F04B—POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS
    • F04B49/00—Control, e.g. of pump delivery, or pump pressure of, or safety measures for, machines, pumps, or pumping installations, not otherwise provided for, or of interest apart from, groups F04B1/00 - F04B47/00
    • F04B49/20—Control, e.g. of pump delivery, or pump pressure of, or safety measures for, machines, pumps, or pumping installations, not otherwise provided for, or of interest apart from, groups F04B1/00 - F04B47/00 by changing the driving speed
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
    • F04B—POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS
    • F04B49/00—Control, e.g. of pump delivery, or pump pressure of, or safety measures for, machines, pumps, or pumping installations, not otherwise provided for, or of interest apart from, groups F04B1/00 - F04B47/00
    • F04B49/08—Regulating by delivery pressure
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
    • F04B—POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS
    • F04B49/00—Control, e.g. of pump delivery, or pump pressure of, or safety measures for, machines, pumps, or pumping installations, not otherwise provided for, or of interest apart from, groups F04B1/00 - F04B47/00
    • F04B49/10—Other safety measures
    • F04B49/106—Responsive to pumped volume

Definitions

  • the invention relates to a method for operating a pump unit comprising a pump and a drive motor for the latter, said pump unit being disposed in a fluid circuit that is to be filled with a liquid to be moved and in which the liquid to be moved is moved using the pump unit.
  • the invention relates to a pump unit comprising a pump and a drive motor for the latter for carrying out the method .
  • the invention relates to the use of a pump unit.
  • a pump unit of the above-mentioned kind in a fluid circuit of what is known as a "draindown" system of a solar thermal collector appliance.
  • the pump unit pumps the liquid to be moved into the initially empty fluid circuit.
  • the pump is required to deliver high power at initially low delivery volume (volumetric flow rate).
  • Typical power input values are of the order of magnitude of about 50 W to 100 W; therefore, the pump unit must be designed for high power.
  • the pump unit circulates the moved liquid through the filled fluid circuit, with the differential pressure between the pump unit's suction and discharge sides being considerably lower.
  • the pump unit is oversized for this mode of operation; therefore, energy is unnecessarily consumed when running in the circulation mode of operation.
  • this object is achieved in a method of the kind mentioned at the outset by determining the fill status of the fluid circuit and, with the use of a control unit, modifying the working point of the pump unit in operation thereof depending on the fill status of the fluid circuit.
  • the method in accordance with the invention provides the possibility of modifying the working point of the pump unit depending on the fill status of the fluid circuit.
  • this allows the pump unit, which is preferably powered by an inverter, to be operated in accordance with a hydraulic characteristic curve in which the delivery pressure and the volumetric flow rate of moved liquid are adjusted such that filling of the fluid circuit and operation in the circulation mode can be carried out and sustained while keeping the power input of the pump unit as low as possible.
  • the working point is modified for minimizing the power input of the pump unit in particular when the fluid circuit is in the filled state.
  • the volumetric flow rate is reduced compared to a method of the generic kind, thereby minimizing the amount of energy consumed by the pump unit.
  • an internal control unit of the pump unit can be used for determining the fill status of the fluid circuit and for modifying the working point of the pump unit.
  • the method can have a simple design.
  • it can be carried out using a pump unit powered by an inverter (inverter pump unit) in which a control unit can control the mode of operation of the drive motor for driving the pump.
  • inverter inverter pump unit
  • the need for an external control unit can be eliminated, thereby making the method also cost-effective to
  • internal operating parameters of the pump unit are used for determining the fill status, with it being particularly preferred that only internal operating parameters of the pump unit be used.
  • the need for external sensors which are arranged at the fluid circuit and generate external operating parameters can thereby be eliminated . This makes it possible for the method to be implemented in a cost-effective manner using a design that is simple in structure.
  • the fill status is preferably determined by determining the differential pressure of moved liquid applied at the pump and/or the volumetric flow rate of moved liquid.
  • the pump unit can have preset or presettable values of the differential pressure and/or the volumetric flow rate of moved liquid for the circulation mode of operation . This makes it possible, for example by
  • the power input of the drive motor, the rotational speed of the drive motor and/or characteristic values of hydraulic properties of the pump unit is advantageous for the power input of the drive motor, the rotational speed of the drive motor and/or characteristic values of hydraulic properties of the pump unit to be used, with said characteristic values being stored in a storage unit.
  • the values of power input as well as the rotational speed of the drive motor are known to the pump unit from the voltage applied at the drive motor and the current at the drive motor.
  • a preferably internal control unit of the pump unit is able to determine the differential pressure and/or the volumetric flow rate.
  • hydraulic properties can be used, in particular the hydraulic characteristic curve of the pump unit.
  • the control unit can read the pump-specific hydraulic properties from a storage unit. For example, in performing the determination, the control unit reads a table stored in the storage unit, said table having stored therein the differential pressure and/or the volumetric flow rate depending on the power input and/or the rotational speed .
  • the storage unit is for example integrated in the control unit.
  • the modification of the working point of the pump unit is advantageous for the modification of the working point of the pump unit to be realized by changing the power input and/or by changing the rotational speed of the drive motor.
  • this can be accomplished using a design that is simple in structure.
  • the modification of the working point leads to a change in the differential pressure and/or the volumetric flow rate of moved liquid, these values in turn being capable of being determined on the basis of the preferably internal operating parameters of the pump unit.
  • the power input and/or the rotational speed of the motor to be controlled depending on a differential pressure determined and/or a volumetric flow rate of moved liquid determined. Operation of the pump unit can thereby be successively controlled to an energy-saving operation in accordance with a hydraulic characteristic curve. Provision may be made for the working point not to be modified when the differential pressure determined differs from a preset or presettable
  • differential pressure by less than a threshold differential pressure and/or when the volumetric flow rate determined differs from a preset or presettable volumetric flow rate by less than a threshold volumetric flow rate.
  • the preset or presettable values for the differential pressure and/or volumetric flow rate are for example stored in a storage unit of the pump unit and are interpreted by the latter for identifying the circulation mode of operation.
  • control unit can regard this as an indication of reaching the circulation mode of operation if at the same time the volumetric flow rate is above a preset or presettable threshold.
  • the working point of the circulation mode of operation is set by presetting the differential pressure and/or the volumetric flow rate in circulation operation.
  • the pump unit may comprise a setting element, for example a potentiometer.
  • the processes of determining the fill status and modifying the working point are performed in real-time.
  • the above- mentioned control of the power input and/or the rotational speed takes place in the range of a few milliseconds.
  • the method is preferably used in filling the fluid circuit of a draindown system with liquid to be moved .
  • the fluid circuit need not be closed .
  • the fluid circuit may be what is known as an "open-loop" fluid circuit.
  • the invention further relates to a pump unit. It is an object to provide a pump unit for carrying out any one of the above- mentioned methods. In accordance with the invention, this object is accomplished in a pump unit comprising a pump and a drive motor for the latter, by the fill status of the fluid circuit in which the pump unit is connected for moving a liquid to be moved being determinable and by the working point of the pump unit being modifiable in operation thereof depending on the fill status of the fluid circuit.
  • a determination is capable of being made as to whether the fluid circuit has not yet been filled or whether it has been filled and the moved liquid is being circulated .
  • the working point is modifiable for minimizing the power input of the pump unit in particular when the fluid circuit is in the filled state.
  • the pump unit comprises an internal control unit by which, through the pump unit, the fill status of the fluid circuit is determinable and the working point of the pump unit is modifiable.
  • the fill status is determinable by the differential pressure of moved liquid applied at the pump being determinable and/or by the volumetric flow rate of moved liquid being determinable.
  • the power input of the drive motor, the rotational speed of the drive motor and/or characteristic values of hydraulic properties of the pump unit are usable, with said characteristic values being stored in a storage unit.
  • the pump unit comprises the storage unit.
  • the storage unit may for example be integrated in a control unit, in particular in a control unit of the pump unit.
  • the working point of the pump unit is variable by changing the power input and/or by changing the rotational speed of the drive motor.
  • the power input and/or the rotational speed of the drive motor is/are controllable depending on a differential pressure determined and/or a volumetric flow rate of moved liquid determined .
  • differential pressure by less than a threshold differential pressure and/or when the volumetric flow rate determined differs from a preset or presettable volumetric flow rate by less than a threshold volumetric flow rate.
  • the pump unit comprises a setting element by which the working point of the circulation mode of operation is adjustable by presetting the differential pressure and/or the volumetric flow rate in circulation operation.
  • the processes of determining the fill status and modifying the working point are performable in real-time.
  • the invention further relates to the use of a pump unit.
  • a pump unit of the above-mentioned kind by which a method of the above-mentioned kind is capable of being carried out is used as the circulation pump unit in a draindown system of a solar thermal collector appliance.
  • FIG. 1 is a schematic representation of a solar thermal collector appliance comprising a draindown system, with the fluid circuit of the draindown system having connected therein a pump unit constructed in accordance with the invention for carrying out the method in accordance with the invention;
  • FIG. 2 is a schematic block diagram of the pump unit
  • Figure 3 is a schematic representation of hydraulic characteristic curves according to which the pump unit can be operated.
  • FIG 1 is a schematic representation of a solar thermal collector appliance, designated by the reference numeral 10, which comprises what is known as a "draindown" system.
  • the solar thermal collector appliance 10 comprises a collector 12 which is for example mounted on the roof of a house, said collector 12 having connected thereto a feed conduit 14 which on the flow side is connected to a tank 16.
  • the tank 16 stores a liquid to be moved, in particular water. Filling of the tank 16 is through a supply conduit 18 which is in particular connected to a water supply network.
  • a discharge conduit 20 which opens into the tank 16.
  • the tank 16 has connected thereto a consumer conduit 22 which feeds to a consumer water that was heated by use of the collector 12.
  • the feed conduit 14 has connected therein an
  • a pump unit 24 constructed in accordance with the invention which will be explained in more detail below.
  • the feed conduit 14 and the discharge conduit 20 have connected therein what is called a "draindown" valve 26, of a kind known per se.
  • a drain conduit 28 is connected to the valve 26.
  • an aeration and ventilation valve 30 Further connected to the discharge conduit 20, at a position near the collector 12, preferably at the highest point of the solar thermal collector appliance 10, is an aeration and ventilation valve 30.
  • an open fluid circuit 32 (“open loop") is formed that is filled with water which is supplied through the supply conduit 18 and is discharged through the consumer conduit 22. Circulation of the water is accomplished by use of the pump unit 24.
  • the fluid circuit 32 When the solar thermal collector appliance 10 is returned to service, the fluid circuit 32 has to be filled with water. To this end, the pump unit 24 pumps water from the tank 16 through the feed conduit 14 and into the collector 12, which is arranged at the highest point of the fluid circuit 32.
  • the pump unit 24 Because of the difference in height between the pump unit 24 and the collector 12 (which may be for example about 10 meters), the pump unit 24 has to supply a relatively large amount of initial pressure. The initial volumetric flow rate is small compared thereto.
  • FIG 3 On the basis of the volumetric flow rate-pressure diagram for the pump unit 24 depicted in Figure 3, there is schematically illustrated a working point A where the pump unit 24 has pumped water through the feed conduit 14 into the collector 12 up to the highest head (pressure p , volumetric flow rate V ⁇ ). Thereafter, the fluid circuit 32 starts to fill in the section of the discharge conduit 20.
  • the latter To allow initial filling of the fluid circuit 32 based on the difference in height between the collector 12 and the pump unit 24, the latter must be designed for a relatively high pumping power, for example approximately 50 W to 100 W.
  • the pressure that is required for continued filling and that is to be supplied by the pump unit 24 decreases because water flowing from the collector 12 through the discharge conduit 20 and into the tank 16 causes a reduction in the differential pressure between the suction and discharge sides of the pump unit 24. In this condition, no hydrostatic pressure need be overcome any longer, but instead only the flow losses need be compensated. Therefore, with the fluid circuit 32 completely filled, circulation can be maintained at a circulation pressure p ⁇ that is smaller when compared to the maximum pressure p .
  • a pump unit (not shown) that is capable of being operated in accordance with a further characteristic curve 36 so that a circulation pressure p z at a reduced volumetric flow rate V z can be provided at a circulation point Z.
  • volumetric flow rate V z is considerably smaller when compared to the volumetric flow rate V ⁇ ; therefore, the pump unit has a considerably smaller power input of the order of magnitude of a few watts, for example about 5 W to 10 W.
  • the further pump unit that is operated in accordance with the characteristic curve 36 cannot provide the pressure p needed to reach the maximum head.
  • the circulation pressure p z at working point Z is below the circulation pressure p ⁇ at working point E.
  • the working point Z is where the resistance characteristic curve 37 intersects the characteristic curve 36.
  • a method in accordance with the invention is possible with the pump unit 24 constructed in accordance with the invention and with the use thereof in accordance with the invention.
  • a determination can be made as to whether the fill phase or the circulation phase is being performed and depending on such determination the working point of the pump unit 24 can be modified for minimizing the power thereof.
  • the pump unit 24 comprises a pump 38 connected in the feed conduit 14 and a drive motor 40 therefor. Furthermore, the pump unit 24 has a control unit 42 in bidirectional communication with the drive motor 40. The control unit 42 can be used to adjust the operating mode of the drive motor 40, thereby influencing the operating mode of the pump 38.
  • control unit 42 can be used to read and evaluate operational parameters of the drive motor 40.
  • the pump unit 24 further comprises a storage unit 44 which in the present case is preferably integrated in the control unit 42.
  • the control unit 42 can determine the power input and the rotational speed of the drive motor 40. On the basis of the power input and the rotational speed, the control unit 42 is able to determine the differential pressure applied at the pump 38 and the volumetric flow rate of water delivered. In this process, the control unit 42 can use pump-specific characteristics, stored in the storage unit 44, for determining the differential pressure and the volumetric flow rate, with said pump-specific characteristics being given for example by the construction of the pump.
  • the above-mentioned determination process enables the control unit 42 to determine what the working point of the pump unit 24 is on the volumetric flow rate-pressure diagram in accordance with Figure 3. Said working point varies as the fill level of the fluid circuit 32 increases, whereby the control unit 42 can, on the basis of the values determined for the differential pressure and volumetric flow rate, make an assessment as to whether the fluid circuit 32 is filled . It is in particular possible to make an assessment as to whether the fill phase is still present or whether the circulation phase is already present.
  • the working point of the pump unit 24 can be modified by the control unit 42 by changing, and in particular reducing, the power input and the rotational speed of the drive motor 40 depending on the values
  • control unit 42 can then again and repeatedly determine the changed differential pressure and the changed volumetric flow rate in order for the pump unit to be operated in accordance with the characteristic curve 46.
  • this allows the power input and the rotational speed of the motor to be controlled depending on the differential pressure and volumetric flow rate determined.
  • the working point of the pump unit 24 can thereby be modified based solely on internal operating parameters, using the control unit 42, depending on the fill status of the fluid circuit 32. In particular, there is no need to make available sensors external to the pump unit 24 for providing operating parameters and/or to make available an external control unit.
  • the pump unit 24 can store therein preset information related to the
  • circulation pressure p z and the volumetric flow rate V z at circulation point Z to which circulation pressure and/or volumetric flow rate the pump unit 24 is controlled .
  • a setting element 48 for example a potentiometer, is provided which can be used by a user to set or preset the volumetric flow rate V z or the circulation pressure p z at circulation point Z. It is thereby possible for the pump unit 24 to be adapted to different solar thermal collector appliances, these differing for example in the number of collectors 12 they have.
  • control unit 42 can regard this as an indication of reaching the circulation mode of operation if at the same time the volumetric flow rate is above a presettable threshold.
  • control unit 42 can make a
  • Controlling the mode of functioning of the pump unit 24 to the hydraulic characteristic curve 46 can essentially be accomplished in real-time.
  • the control unit 42 determines the power input and the rotational speed of the drive motor 40 at short intervals, for example at intervals of a few milliseconds.
  • the power input and the rotational speed of the drive motor 40 can be adjusted at short intervals for modifying the working point.
  • the power input of the pump unit 24 is minimized . It is therefore possible, by use of the pump unit 24 and by carrying out the method, for the solar thermal collector appliance 10 to be operated in an energy-efficient circulation mode of operation.

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  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Computer Hardware Design (AREA)
  • Control Of Positive-Displacement Pumps (AREA)
  • Control Of Non-Positive-Displacement Pumps (AREA)

Abstract

The invention relates to a method for operating a pump unit comprising a pump and a drive motor for the latter, said pump unit being disposed in a fluid circuit that is to be filled with a liquid to be moved and in which the liquid to be moved is moved using the pump unit. In order to provide a method in which the pump unit can be operated in a more energy-efficient manner, it is proposed in accordance with the invention that the fill status of the fluid circuit be determined and, with the use of a control unit, the working point of the pump unit be modified in operation thereof depending on the fill status of the fluid circuit. Furthermore, the invention relates to a pump unit for carrying out the method and to the use of a pump unit.

Description

Method for Operating a Pump Unit, Pump Unit and Use Thereof
The invention relates to a method for operating a pump unit comprising a pump and a drive motor for the latter, said pump unit being disposed in a fluid circuit that is to be filled with a liquid to be moved and in which the liquid to be moved is moved using the pump unit.
Furthermore, the invention relates to a pump unit comprising a pump and a drive motor for the latter for carrying out the method .
Furthermore, the invention relates to the use of a pump unit.
It is known to use a pump unit of the above-mentioned kind in a fluid circuit of what is known as a "draindown" system of a solar thermal collector appliance. To fill the draindown system with liquid to be moved after an interim shutdown to prevent freezing damage, the pump unit pumps the liquid to be moved into the initially empty fluid circuit. Because of the differences in height between the pump unit and the solar thermal collector that occur in practical situations (and which may be for example about 10 m), the pump is required to deliver high power at initially low delivery volume (volumetric flow rate). Typical power input values are of the order of magnitude of about 50 W to 100 W; therefore, the pump unit must be designed for high power. During normal operation of the draindown system, the pump unit circulates the moved liquid through the filled fluid circuit, with the differential pressure between the pump unit's suction and discharge sides being considerably lower. However, the working point the pump unit adopts, as predetermined by the hydraulic characteristic curve adopted by the pump unit, leads to a high volumetric flow rate of moved liquid. The pump unit is oversized for this mode of operation; therefore, energy is unnecessarily consumed when running in the circulation mode of operation.
It is an object of the present invention to provide a method of the generic kind in which the pump unit can be operated in a more energy-efficient manner. In accordance with the invention, this object is achieved in a method of the kind mentioned at the outset by determining the fill status of the fluid circuit and, with the use of a control unit, modifying the working point of the pump unit in operation thereof depending on the fill status of the fluid circuit.
The method in accordance with the invention provides the possibility of modifying the working point of the pump unit depending on the fill status of the fluid circuit. In particular, this allows the pump unit, which is preferably powered by an inverter, to be operated in accordance with a hydraulic characteristic curve in which the delivery pressure and the volumetric flow rate of moved liquid are adjusted such that filling of the fluid circuit and operation in the circulation mode can be carried out and sustained while keeping the power input of the pump unit as low as possible.
Preferably, a determination is made as to whether the fluid circuit has not yet been filled or whether it has been filled and moved liquid is being circulated. It can be determined whether the pump unit is still performing the fill phase or whether it is performing the circulation phase, and the working point can be modified accordingly.
Preferably, therefore, the working point is modified for minimizing the power input of the pump unit in particular when the fluid circuit is in the filled state. This is in particular possible by the fact that by providing the relatively low differential pressure that is required for running in the circulation mode of operation, the volumetric flow rate is reduced compared to a method of the generic kind, thereby minimizing the amount of energy consumed by the pump unit.
It is advantageous for an internal control unit of the pump unit to be used for determining the fill status of the fluid circuit and for modifying the working point of the pump unit. In this way, the method can have a simple design. In particular, it can be carried out using a pump unit powered by an inverter (inverter pump unit) in which a control unit can control the mode of operation of the drive motor for driving the pump. The need for an external control unit can be eliminated, thereby making the method also cost-effective to
implement.
Preferably, internal operating parameters of the pump unit are used for determining the fill status, with it being particularly preferred that only internal operating parameters of the pump unit be used. The need for external sensors which are arranged at the fluid circuit and generate external operating parameters can thereby be eliminated . This makes it possible for the method to be implemented in a cost-effective manner using a design that is simple in structure.
The fill status is preferably determined by determining the differential pressure of moved liquid applied at the pump and/or the volumetric flow rate of moved liquid.
For example, the pump unit can have preset or presettable values of the differential pressure and/or the volumetric flow rate of moved liquid for the circulation mode of operation . This makes it possible, for example by
comparing the differential pressure determined and/or the volumetric flow rate determined with one or more preset or presettable values, to determine whether the system is running in the circulation mode of operation and, accordingly, whether the fluid circuit has completely, or substantially
completely, filled with liquid to be moved.
To determine the differential pressure and/or the volumetric flow rate of moved liquid, it is advantageous for the power input of the drive motor, the rotational speed of the drive motor and/or characteristic values of hydraulic properties of the pump unit to be used, with said characteristic values being stored in a storage unit. The values of power input as well as the rotational speed of the drive motor are known to the pump unit from the voltage applied at the drive motor and the current at the drive motor. On the basis of these internal operating parameters, a preferably internal control unit of the pump unit is able to determine the differential pressure and/or the volumetric flow rate. In this process, hydraulic properties can be used, in particular the hydraulic characteristic curve of the pump unit. The control unit can read the pump-specific hydraulic properties from a storage unit. For example, in performing the determination, the control unit reads a table stored in the storage unit, said table having stored therein the differential pressure and/or the volumetric flow rate depending on the power input and/or the rotational speed .
It is advantageous for an internal storage unit of the pump unit to be used, whereby the need for an external storage unit can be eliminated. The storage unit is for example integrated in the control unit.
It is advantageous for the modification of the working point of the pump unit to be realized by changing the power input and/or by changing the rotational speed of the drive motor. In an inverter pump unit in particular, this can be accomplished using a design that is simple in structure. The modification of the working point leads to a change in the differential pressure and/or the volumetric flow rate of moved liquid, these values in turn being capable of being determined on the basis of the preferably internal operating parameters of the pump unit. By continuously modifying the working point by changing the power input and/or by changing the rotational speed of the drive motor, it is thereby possible for the hydraulic characteristic curve of the pump unit to be changed in order to adjust a working point for operation, especially for the circulation mode of operation, at as low a power input as possible.
Overall, it is advantageous for the power input and/or the rotational speed of the motor to be controlled depending on a differential pressure determined and/or a volumetric flow rate of moved liquid determined. Operation of the pump unit can thereby be successively controlled to an energy-saving operation in accordance with a hydraulic characteristic curve. Provision may be made for the working point not to be modified when the differential pressure determined differs from a preset or presettable
differential pressure by less than a threshold differential pressure and/or when the volumetric flow rate determined differs from a preset or presettable volumetric flow rate by less than a threshold volumetric flow rate. The preset or presettable values for the differential pressure and/or volumetric flow rate are for example stored in a storage unit of the pump unit and are interpreted by the latter for identifying the circulation mode of operation.
If the differential pressure determined is below a preset or presettable threshold, the control unit can regard this as an indication of reaching the circulation mode of operation if at the same time the volumetric flow rate is above a preset or presettable threshold.
Preferably, the working point of the circulation mode of operation is set by presetting the differential pressure and/or the volumetric flow rate in circulation operation. To this end, the pump unit may comprise a setting element, for example a potentiometer.
Advantageously, the processes of determining the fill status and modifying the working point are performed in real-time. By way of example, the above- mentioned control of the power input and/or the rotational speed takes place in the range of a few milliseconds.
The method is preferably used in filling the fluid circuit of a draindown system with liquid to be moved .
Especially in a draindown system, the fluid circuit need not be closed . The fluid circuit may be what is known as an "open-loop" fluid circuit.
As mentioned at the outset, the invention further relates to a pump unit. It is an object to provide a pump unit for carrying out any one of the above- mentioned methods. In accordance with the invention, this object is accomplished in a pump unit comprising a pump and a drive motor for the latter, by the fill status of the fluid circuit in which the pump unit is connected for moving a liquid to be moved being determinable and by the working point of the pump unit being modifiable in operation thereof depending on the fill status of the fluid circuit.
The advantages that can be achieved in conjunction with the method in accordance with the invention can be achieved using the pump unit and in this respect reference is made to explanations given above.
Correspondingly, with respect to the advantageous embodiments of the pump unit constructed in accordance with the invention as mentioned hereinafter, reference may be made to the explanations of advantageous exemplary embodiments of the method in accordance with the invention.
Preferably, a determination is capable of being made as to whether the fluid circuit has not yet been filled or whether it has been filled and the moved liquid is being circulated .
Advantageously, the working point is modifiable for minimizing the power input of the pump unit in particular when the fluid circuit is in the filled state.
Preferably, the pump unit comprises an internal control unit by which, through the pump unit, the fill status of the fluid circuit is determinable and the working point of the pump unit is modifiable.
It is advantageous for internal, and preferably only internal, operating parameters of the pump unit to be usable for determining the fill status.
Advantageously, the fill status is determinable by the differential pressure of moved liquid applied at the pump being determinable and/or by the volumetric flow rate of moved liquid being determinable. Preferably, for determining the differential pressure and/or the volumetric flow rate of moved liquid, the power input of the drive motor, the rotational speed of the drive motor and/or characteristic values of hydraulic properties of the pump unit are usable, with said characteristic values being stored in a storage unit.
Preferably, the pump unit comprises the storage unit. The storage unit may for example be integrated in a control unit, in particular in a control unit of the pump unit.
It is advantageous for the working point of the pump unit to be variable by changing the power input and/or by changing the rotational speed of the drive motor.
Advantageously, the power input and/or the rotational speed of the drive motor is/are controllable depending on a differential pressure determined and/or a volumetric flow rate of moved liquid determined .
Provision may be made for the working point not to be modified when the differential pressure determined differs from a preset or presettable
differential pressure by less than a threshold differential pressure and/or when the volumetric flow rate determined differs from a preset or presettable volumetric flow rate by less than a threshold volumetric flow rate.
Preferably, the pump unit comprises a setting element by which the working point of the circulation mode of operation is adjustable by presetting the differential pressure and/or the volumetric flow rate in circulation operation.
Advantageously, the processes of determining the fill status and modifying the working point are performable in real-time.
As mentioned at the outset, the invention further relates to the use of a pump unit. Use in accordance with the invention is characterized in that a pump unit of the above-mentioned kind by which a method of the above-mentioned kind is capable of being carried out is used as the circulation pump unit in a draindown system of a solar thermal collector appliance.
The advantages of the use in accordance with the invention are apparent from the advantages of the method in accordance with the invention and
advantageous embodiments thereof as well as of the pump unit constructed in accordance with the invention and advantageous exemplary embodiments thereof; therefore, in this respect, reference may be made to explanations given above.
The following description of a preferred embodiment of the invention serves to explain the invention in greater detail in conjunction with the drawings. In the drawings:
Figure 1 is a schematic representation of a solar thermal collector appliance comprising a draindown system, with the fluid circuit of the draindown system having connected therein a pump unit constructed in accordance with the invention for carrying out the method in accordance with the invention;
Figure 2 is a schematic block diagram of the pump unit; and
Figure 3 is a schematic representation of hydraulic characteristic curves according to which the pump unit can be operated.
Figure 1 is a schematic representation of a solar thermal collector appliance, designated by the reference numeral 10, which comprises what is known as a "draindown" system. The solar thermal collector appliance 10 comprises a collector 12 which is for example mounted on the roof of a house, said collector 12 having connected thereto a feed conduit 14 which on the flow side is connected to a tank 16. The tank 16 stores a liquid to be moved, in particular water. Filling of the tank 16 is through a supply conduit 18 which is in particular connected to a water supply network.
Also connected to the collector 12 is a discharge conduit 20 which opens into the tank 16. On the discharge side, the tank 16 has connected thereto a consumer conduit 22 which feeds to a consumer water that was heated by use of the collector 12.
For moving the water, the feed conduit 14 has connected therein an
advantageous embodiment of a pump unit 24 constructed in accordance with the invention which will be explained in more detail below. Downstream of the pump unit 24, the feed conduit 14 and the discharge conduit 20 have connected therein what is called a "draindown" valve 26, of a kind known per se. A drain conduit 28 is connected to the valve 26.
Further connected to the discharge conduit 20, at a position near the collector 12, preferably at the highest point of the solar thermal collector appliance 10, is an aeration and ventilation valve 30.
During normal operation of the solar thermal collector appliance 10, an open fluid circuit 32 ("open loop") is formed that is filled with water which is supplied through the supply conduit 18 and is discharged through the consumer conduit 22. Circulation of the water is accomplished by use of the pump unit 24.
For freeze protection of the solar thermal collector appliance 10 it is known to interrupt the fluid communication of the feed conduit 14 and the discharge conduit 20, thereby isolating the collector 12 from the tank 16. Drainage of the fluid circuit 32 on the collector 12 side is accomplished through the drain conduit 28.
When the solar thermal collector appliance 10 is returned to service, the fluid circuit 32 has to be filled with water. To this end, the pump unit 24 pumps water from the tank 16 through the feed conduit 14 and into the collector 12, which is arranged at the highest point of the fluid circuit 32.
Because of the difference in height between the pump unit 24 and the collector 12 (which may be for example about 10 meters), the pump unit 24 has to supply a relatively large amount of initial pressure. The initial volumetric flow rate is small compared thereto. On the basis of the volumetric flow rate-pressure diagram for the pump unit 24 depicted in Figure 3, there is schematically illustrated a working point A where the pump unit 24 has pumped water through the feed conduit 14 into the collector 12 up to the highest head (pressure p , volumetric flow rate V^). Thereafter, the fluid circuit 32 starts to fill in the section of the discharge conduit 20.
To allow initial filling of the fluid circuit 32 based on the difference in height between the collector 12 and the pump unit 24, the latter must be designed for a relatively high pumping power, for example approximately 50 W to 100 W. As the fill level of the fluid circuit 32 increases, the pressure that is required for continued filling and that is to be supplied by the pump unit 24 decreases because water flowing from the collector 12 through the discharge conduit 20 and into the tank 16 causes a reduction in the differential pressure between the suction and discharge sides of the pump unit 24. In this condition, no hydrostatic pressure need be overcome any longer, but instead only the flow losses need be compensated. Therefore, with the fluid circuit 32 completely filled, circulation can be maintained at a circulation pressure p^ that is smaller when compared to the maximum pressure p .
If, as is conventional, the pump unit 24 is operated in accordance with a predetermined hydraulic characteristic curve 34, then at a point in time when the fluid circuit 32 is filled and end pressure p^ is reached, this leads to a volumetric flow rate at end point E (Figure 3). This proves disadvantageous because the volumetric flow rate associated with the end pressure p^ would not have had to be supplied per se, meaning that the pump unit 24 is oversized for the circulation mode of operation. Accordingly, when running in circulation mode at working point E, the pump unit 24 has a high power input that is not necessary per se.
For operation in the circulation mode, it would be sufficient for example to use a pump unit (not shown) that is capable of being operated in accordance with a further characteristic curve 36 so that a circulation pressure pz at a reduced volumetric flow rate Vz can be provided at a circulation point Z. The
volumetric flow rate Vz is considerably smaller when compared to the volumetric flow rate V^; therefore, the pump unit has a considerably smaller power input of the order of magnitude of a few watts, for example about 5 W to 10 W. However, the further pump unit that is operated in accordance with the characteristic curve 36 cannot provide the pressure p needed to reach the maximum head.
With the assumption of a square resistance characteristic curve 37 of the fluid circuit 32, the circulation pressure pz at working point Z is below the circulation pressure p^ at working point E. The working point Z is where the resistance characteristic curve 37 intersects the characteristic curve 36.
For avoiding the use of two pump units and for saving energy, a method in accordance with the invention is possible with the pump unit 24 constructed in accordance with the invention and with the use thereof in accordance with the invention. The possibility exists for determining the fill status of the fluid circuit 32 and for modifying the working point of the pump unit 24 depending on the fill status such that as a result, the power input of the pump unit 24 is minimized and operation of the pump unit 24 at circulation point Z, at low circulation pressure pz and low volumetric flow rate Vz, is possible.
Accordingly, a determination can be made as to whether the fill phase or the circulation phase is being performed and depending on such determination the working point of the pump unit 24 can be modified for minimizing the power thereof.
It is in particular possible to determine the fill status and modify the working point by only using the pump unit 24 itself and changing it in its mode of operation.
To this end, the pump unit 24 comprises a pump 38 connected in the feed conduit 14 and a drive motor 40 therefor. Furthermore, the pump unit 24 has a control unit 42 in bidirectional communication with the drive motor 40. The control unit 42 can be used to adjust the operating mode of the drive motor 40, thereby influencing the operating mode of the pump 38.
Conversely, the control unit 42 can be used to read and evaluate operational parameters of the drive motor 40.
The pump unit 24 further comprises a storage unit 44 which in the present case is preferably integrated in the control unit 42.
In operation of the pump unit 24, when filling the fluid circuit 32, the control unit 42 can determine the power input and the rotational speed of the drive motor 40. On the basis of the power input and the rotational speed, the control unit 42 is able to determine the differential pressure applied at the pump 38 and the volumetric flow rate of water delivered. In this process, the control unit 42 can use pump-specific characteristics, stored in the storage unit 44, for determining the differential pressure and the volumetric flow rate, with said pump-specific characteristics being given for example by the construction of the pump.
The above-mentioned determination process enables the control unit 42 to determine what the working point of the pump unit 24 is on the volumetric flow rate-pressure diagram in accordance with Figure 3. Said working point varies as the fill level of the fluid circuit 32 increases, whereby the control unit 42 can, on the basis of the values determined for the differential pressure and volumetric flow rate, make an assessment as to whether the fluid circuit 32 is filled . It is in particular possible to make an assessment as to whether the fill phase is still present or whether the circulation phase is already present.
There is the possibility of controlling the working point of the pump unit 24 to a hydraulic characteristic curve 46 in order to go from working point A, where the maximum head is reached, to circulation point Z, where the pump unit 24 can be operated at circulation pressure pz and reduced volumetric flow rate Vz, thus saving energy.
To this end, the working point of the pump unit 24 can be modified by the control unit 42 by changing, and in particular reducing, the power input and the rotational speed of the drive motor 40 depending on the values
determined for the differential pressure and the volumetric flow rate. On the basis of the changed operating parameters of power input and rotational speed, the control unit 42 can then again and repeatedly determine the changed differential pressure and the changed volumetric flow rate in order for the pump unit to be operated in accordance with the characteristic curve 46.
As a result, this allows the power input and the rotational speed of the motor to be controlled depending on the differential pressure and volumetric flow rate determined. The working point of the pump unit 24 can thereby be modified based solely on internal operating parameters, using the control unit 42, depending on the fill status of the fluid circuit 32. In particular, there is no need to make available sensors external to the pump unit 24 for providing operating parameters and/or to make available an external control unit.
The pump unit 24 can store therein preset information related to the
circulation pressure pz and the volumetric flow rate Vz at circulation point Z, to which circulation pressure and/or volumetric flow rate the pump unit 24 is controlled . In particular when it is not known in what kind of solar thermal collector appliance the pump unit is to be used, provision may be made for the circulation pressure pz or the volumetric flow rate Vz to be presettable. By way of example, a setting element 48, for example a potentiometer, is provided which can be used by a user to set or preset the volumetric flow rate Vz or the circulation pressure pz at circulation point Z. It is thereby possible for the pump unit 24 to be adapted to different solar thermal collector appliances, these differing for example in the number of collectors 12 they have.
If the differential pressure determined is below the presettable differential pressure pz, the control unit 42 can regard this as an indication of reaching the circulation mode of operation if at the same time the volumetric flow rate is above a presettable threshold.
In performing the control procedure, the control unit 42 can make a
determination as to whether the differential pressure determined and the volumetric flow rate determined differ from the circulation pressure pz and from the reduced volumetric flow rate Vz by less than a preset or presettable threshold . If this is the case, then the circulation point Z can be maintained without changing the power input and the rotational speed of the drive motor 40.
Controlling the mode of functioning of the pump unit 24 to the hydraulic characteristic curve 46 can essentially be accomplished in real-time. By way of example, the control unit 42 determines the power input and the rotational speed of the drive motor 40 at short intervals, for example at intervals of a few milliseconds. Correspondingly, the power input and the rotational speed of the drive motor 40 can be adjusted at short intervals for modifying the working point. At circulation point Z, the power input of the pump unit 24 is minimized . It is therefore possible, by use of the pump unit 24 and by carrying out the method, for the solar thermal collector appliance 10 to be operated in an energy-efficient circulation mode of operation.

Claims

PATENT CLAIMS
1. Method for operating a pump unit comprising a pump and a drive motor for the latter, said pump unit being disposed in a fluid circuit that is to be filled with a liquid to be moved and in which the liquid to be moved is moved using the pump unit, characterized in that the fill status of the fluid circuit is determined and, with the use of a control unit, the working point of the pump unit is modified in operation thereof depending on the fill status of the fluid circuit.
2. Method in accordance with claim 1, characterized in that a
determination is made as to whether the fluid circuit has not yet been filled or whether it has been filled and moved liquid is being circulated.
3. Method in accordance with claim 1 or 2, characterized in that the
working point is modified for minimizing the power input of the pump unit in particular when the fluid circuit is in the filled state.
4. Method in accordance with any one of the preceding claims,
characterized in that an internal control unit of the pump unit is used for determining the fill status of the fluid circuit and for modifying the working point of the pump unit.
5. Method in accordance with any one of the preceding claims,
characterized in that internal operating parameters of the pump unit are used for determining the fill status.
6. Method in accordance with any one of the preceding claims,
characterized in that the fill status is determined by determining the differential pressure of moved liquid applied at the pump and/or the volumetric flow rate of moved liquid .
7. Method in accordance with claim 6, characterized in that for determining the differential pressure and/or the volumetric flow rate of moved liquid, the power input of the drive motor, the rotational speed of the drive motor and/or characteristic values of hydraulic properties of the pump unit are used, with said characteristic values being stored in a storage unit.
8. Method in accordance with any one of the preceding claims,
characterized in that the working point of the pump unit is modified by changing the power input and/or by changing the rotational speed of the drive motor.
9. Method in accordance with claim 8, characterized in that the power
input and/or the rotational speed of the motor are/is controlled depending on a differential pressure and/or a volumetric flow rate of moved liquid determined.
10. Method in accordance with claim 8 or 9, characterized in that the
working point is not modified when the differential pressure determined differs from a preset or presettable differential pressure by less than a threshold differential pressure and/or when the volumetric flow rate determined differs from a preset or presettable volumetric flow rate by less than a threshold volumetric flow rate.
11. Method in accordance with any one of the preceding claims,
characterized in that the working point of the circulation mode of operation is set by presetting the differential pressure and/or the volumetric flow rate in circulation operation.
12. Method in accordance with any one of the preceding claims,
characterized in that the determination of the fill status and the modification of the working point are performed in real-time.
13. Method in accordance with any one of the preceding claims,
characterized in that the method is used in filling with fluid to be moved the fluid circuit of a draindown system of a solar thermal collector appliance.
14. Pump unit for carrying out the method in accordance with any one of the preceding claims, said pump unit comprising a pump (38) and a drive motor (40) for the latter, characterized in that the fill status of the fluid circuit (32) in which the pump unit (24) is connected for moving a liquid to be moved is determinable and in that the working point of the pump unit (24) is modifiable in operation thereof depending on the fill status of the fluid circuit (32).
15. Pump unit in accordance with claim 14, characterized in that a
determination is capable of being made as to whether the fluid circuit (32) has not yet been filled or whether it has been filled and moved liquid is being circulated.
16. Pump unit in accordance with claim 14 or 15, characterized in that the working point is modifiable for minimizing the power input of the pump unit (24) in particular when the fluid circuit (32) is in the filled state.
17. Pump unit in accordance with any one of claims 14 to 16, characterized in that the pump unit (24) comprises an internal control unit (42) by which, through the pump unit (24), the fill status of the fluid circuit (32) is determinable and the working point is modifiable.
18. Pump unit in accordance with any one of claims 14 to 17, characterized in that internal operating parameters of the pump unit (24) are usable for determining the fill status.
Pump unit in accordance with any one of claims 14 to 18, characterized in that the fill status is determinable by the differential pressure of moved liquid applied at the pump (38) and/or the volumetric flow rate of moved liquid being determinable.
20. Pump unit in accordance with claim 19, characterized in that for
determining the differential pressure and/or the volumetric flow rate of moved liquid, the power input of the drive motor (40), the rotational speed of the drive motor (40) and/or characteristic values of hydraulic properties of the pump unit (24) are usable, with said characteristic values being stored in a storage unit (44).
21. Pump unit in accordance with any one of claims 14 to 20, characterized in that the working point of the pump unit (24) is variable by changing the power input and/or by changing the rotational speed of the drive motor (40).
22. Pump unit in accordance with claim 21, characterized in that the power input and/or the rotational speed of the drive motor (40) are controlled depending on a differential pressure and/or a volumetric flow rate of moved liquid determined.
23. Pump unit in accordance with claim 21 or 22, characterized in that the working point is not modified when the differential pressure determined differs from a preset or presettable differential pressure by less than a threshold differential pressure and/or when the volumetric flow rate determined differs from a preset or presettable volumetric flow rate by less than a threshold volumetric flow rate.
24. Pump unit in accordance with any one of the preceding claims,
characterized in that the pump unit (24) comprises a setting
element (48) by which the working point of the circulation mode of operation is adjustable by presetting the differential pressure and/or the volumetric flow rate in circulation operation.
25. Pump unit in accordance with any one of claims 14 to 24, characterized in that the determination of the fill status and the modification of the working point are performable in real-time.
26. Use of a pump unit in accordance with any one of claims 14 to 25 as a circulation pump unit (24) in a draindown system of a solar thermal collector appliance (10).
EP14786634.7A 2013-10-09 2014-10-06 Method for operating a pump unit, pump unit and use thereof Withdrawn EP3055571A1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
DE102013111185.8A DE102013111185A1 (en) 2013-10-09 2013-10-09 Method for operating a pump unit, pump unit and its use
PCT/EP2014/071349 WO2015052136A1 (en) 2013-10-09 2014-10-06 Method for operating a pump unit, pump unit and use thereof

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EP3055571A1 true EP3055571A1 (en) 2016-08-17

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EP (1) EP3055571A1 (en)
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CN107726642B (en) * 2017-11-01 2019-04-30 安徽春升新能源科技有限公司 A kind of flat plate solar water heater and application method

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WO2015052136A1 (en) 2015-04-16
DE102013111185A1 (en) 2015-04-09

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