DK202101237A1

DK202101237A1 - Pressure independent flow system with temperature regulation

Info

Publication number: DK202101237A1
Application number: DKPA202101237A
Authority: DK
Inventors: Bogar Siniša; Kongsgard Nielsen Claus; Muhič Miran
Original assignee: Danfoss As Intellectual Property
Priority date: 2021-12-21
Filing date: 2021-12-21
Publication date: 2023-06-27

Abstract

The present invention relates to a method to control a heating system (100) supply a heating fluid to a heat consuming device (2) by a supply line (8) with a supply temperature Ts and returned from the heat consuming device (2) by a return line (9) at a return temperature Tr, and a pressure regulation unit (3) adapted to maintain a substantially constant pressure of the heating fluid and a flow controller (4) to control the flow rate of the heating fluid, and an actuator (5) connected to adjust the flow controller (4) according to a flow rate setting, wherein the actuator (5) is adapted to regulate the flow controller (4) to be within a given range of flow rates.

Description

DK 2021 01237 A1 1

PRESSURE INDEPENDENT FLOW SYSTEM WITH TEMPERATURE

REGULATION

BACKGROUND

The present invention relate to a method of optimizing the operation of a heating system such as a distrtict heating system. The present invention more specificually realtes to conrtrolling a heat consuming device by an electrically- controlled pressure independent valve regulated by a controller based on temperature input.

In some situations the controller induces flow rate may not match some requirement, e.g. a consumer wanting a higher temperature than otherwise provided.

SUMMARY OF THE INVENTION

The problems are solved according to the features given in the claims. This includes introducing a method to control a heating system supplying a heating fluid to a heat consuming device by a supply line with a supply temperature Ts and returned from the heat consuming device by a return line at a return temperature Tr, and a pressure regulation unit adapted to maintain a substantially constant pressure of the heating fluid and a flow controller to control the flow rate of the heating fluid, and an actuator connected to adjust the flow controller according to a flow rate setting, wherein the actuator is adapted to regulate the flow controller to be within a given range of flow rates.

DK 2021 01237 A1 2

The flow controller may be regulated to change the flow rate of the heating fluid passing the heat consuming devices to keep the return temperature Tr above or below a given threshold Tt, or may control the return temperature Tr based on set return temperature Ts, or may control temperature difference between supply and return temperatures based on set dT temperature, or may maintain temperature difference between the supply and return temperatures, AT = Ts-

Tr, above, or below, a given threshold Tt.

The method including to control the flow controller according to a stored characteristic curve of the flow controller setting relative to the flow rate,

A controller may be positioned in data exchange communication with the actuator and control the heating system to a desired flow by changing the flow controller by communicating a flow rate setting signal to the actuator.

The characteristic curve may be stored in the memory of the actuator, and when the controller communicates flow rate setting signal related to a requested flow rate of the heating fluid, the actuator then adjusting the flow controller using the characteristic curve to find the correct flow controller setting.

The controller may be adapted to control the flow rate according to a minimum allowed controller given flow rate Fmin, but where the actuator is adapted to overrule the setting signal from the controller to change the minimum actuator allowed flow rate Fmin,actuator to a different value.

The change may selectable by a user among a plural of selectable different minimum actuator given allowed flow rates Fmin, actuator.

The controller may be positioned remote from the actuator.

The controller may be positioned as part of the actuator.

DK 2021 01237 A1 3

The flow controller may be positioned at the supply or return line.

The actuator may include a memory to store data like the characteristic curve of the flow controller and comprise a processer to perform calculations etc.

The pressure regulation unit may be positioned to ensure a constant differential pressure over the flow controller.

The pressure regulation unit and flow controller may be constructed as a single pressure independent valve unit, the pressure regulation unit connecting respectively to the inlet and outlet of the flow controller by pressure channels formed within the unit.

The present invention further relates to an actuator adapted to control the heating system according to the method of any of the preceding embodiments.

FIGURES

Fig. 1 Example heating system where the present invention could be implemented

Fig. 2 Examples of different valve characteristic curves

Fig. 3 Example heating system where the present invention could be implemented, illustrating a valve actuator being adapted to communicate with other devices.

DK 2021 01237 A1 4

DETAILED DESCRIPTION OF THE INVENTION

The detailed description and specific examples, while indicating embodiments of the invention, are given by way of illustration only.

Fig. 1 illustrates an example heating system 100 to supply a heating fluid to a heat consuming device 2, such as e.g. a radiator, floor heating installation etc.

Heating fluid is supplied to the heat consuming device 2 by a supply line 8 with a supply temperature Ts and returned from the heat consuming device 2 by a return line 9 at a return temperature Tr.

Temperature sensors 10 may be positioned to measure the temperatures of the fluid passing the heat consuming devices 2 such as positioned to measure the supply temperature Ts return temperature Tr of the heating fluid.

The lines 8, 9 may be directly or indirectly connected to a heating plant of any kind, such as a district heating network, a geothermal heating system, solar heating system etc., or a combination thereof. By direct connection is referred to the heat consuming devices 2 being feed directly by the heating fluid supplied by the heating plant, and by indirect connection is referred to there being an intermediate heat exchanger transferring thermal energy from the heating fluid supplied from the heating plant to the heating fluid to be feed to the heat consuming devices 2.

As indicted the heat consuming devices 2 could be e.g. radiators or floor heating installations, and could thus be fluid to air heat exchangers.

The heating system 100 further comprises a pressure regulation unit 3 adapted to maintain a substantially constant pressure allowing a hydraulic balancing of the heating fluid.

DK 2021 01237 A1

The pressure regulation unit 3 may comprise a pressure regulation valve of any kind adapted to control the differential pressure of a part of the heating system 100 and may thus be in pressure communication to two positions at the heating system, the pressure difference between the two positions being the differential 5 pressure. The pressure regulation unit 3 controls the differential pressure to a setpoint differential pressure which may be adjustable. One such example pressure regulation valve is to be found in e.g. European Patent publication 3093729.

A flow controller 4 is positioned in relation to the supply line 8 (as illustrated) or the return line 9 controlling the fluid flow, such as the fluid flow passing the heat consuming device 2. An actuator 5 connects to the flow controller 4 and is adapted to change it to regulate to a new flow rate. The flow controller naturally could be a valve formed with a valve element and valve seat, where the position of the valve element relative to the valve seat defines the valve opening. A valve stem or spindle connects the valve element to the actuator 5 which changes the valve opening by changing the valve element position through the valve stem or spindle. This then changes the flow rate through the flow controller 4. The flow controller 4 may be connected to an actuator to adjust its valve opening, where the actuator may be remotely controlled, e.g. by the controller 5.

The control valve 4 may be operated according to a stored characteristic of the flow controller setting relative to a flow rate, such as giving a relation of valve flow in relation to valve opening. Different such characteristic 6 curves are seen in fig. 2 showing valve opening O relative to flow rate F, and could as illustrated e.g. be a linear, quick opening, square root, modified parabolic, equal percentage or a hyperbolic characteristic curve 6.

Due to the pressure regulation unit 3 the pressure of the heating fluid is substantially constant and known, this enabling the control according to the characteristic curve 6. By a fluctuating differential pressure of the flow controller

DK 2021 01237 A1 6 4, the pressures, or differential pressure, would be needed in the regulation of the flow controller 4, or a flow sensor 11 to ensure the correct flow rate.

The actuator 5 itself could include a memory to store data like the characteristic curve 6 of the flow controller 4 and may be in data exchange communication with devices like temperature sensors 10, flow sensors 11 and controllers 7.

The actuator 5 further could comprise a processer to perform calculations etc,

Pressure regulation unit 3 in the illustrated embodiment is positioned to ensure a constant differential pressure over the flow controller 4, the pressure regulation unit 3 thus being connected at a position upstream and downstream of the flow controller respectively, e.g. by pressure conducting pipes or capillaries connected to the supply line 8.

In another embodiment the pressure regulation unit 3 and flow controller 4 is constructed as a single pressure independent valve unit, the pressure regulation unit 3 connecting respectively to the inlet and outlet of the flow controller 4 by pressure channels formed within the unit.

A controller 7 may be positioned in data exchange communication with the actuator 5, where the data exchange communication could be of any kind such as wireless, wired, digital, analogue etc. The controller 7 may be adapted to control the heating system 100 to a desired flow by changing the flow controller 4 by communicating a the flow rate setting signal to the actuator 4.The controller 7 could be a. Building Management System (BMS) and could be positioned remote from the actuator 5.

The controller 7 may in general be adapted to control and regulate the operation of the heating system 100, such as the flows, pressures and temperatures of the fluids entering and leaving the heat consuming device 2. The controller 7 may include a processor and operate as e.g. as a Pl or PID controller, this part being referred to as a PI or PID controller. The controller 7 could further include

DK 2021 01237 A1 7 a memory storing required parameters, such as data regarding operating point, operational data and nominal data or settings.

A flow sensor 11 may be connected to register the flow rate, possible only operating at regular times periods to calibrate the characteristic curve 6.

The flow controller 4 is regulated to change the flow rate of the heating fluid passing the heat consuming devices 2 to meet changing requirements and is controlled to keep the return temperature Tr above a given threshold Tt, or to maintain temperature difference between the supply and return temperatures,

AT = Ts-Tr, above, or below, a given threshold Tt.

As the heat delivery of the heat consuming devices 2 changes at least the return temperature Tr, and the temperature difference AT changes too.

In one embodiment the controller 7 is in data exchange communication to the temperature sensors 10 and the optional flow sensor 11 and communicates a signal to the actuator 5 to adjust the flow rate.

The characteristic curve 6 in one embodiment is stored in the memory of the actuator 5, the controller 7 giving a signal in the form of a requested flow rate, the actuator 5 then adjusting the flow controller 4 using the characteristic curve 6 to find the correct flow controller 4 setting.

In another, or additional embodiment, the characteristic curve 6 is stored in the memory the controller 7 (the characteristic curve 6 possible in this embodiment being stored in the actuator 5 too), this thus directly giving a signal in the form of a requested setting of the flow controller 4.

A design flow rate is defined by an operational setting of the heating system 100 of the flow rate, the controller 7 adapted to operate the actual flow rate of the heating fluid as a relation of the design flow rate.

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In one embodiment the controller 7 is adapted to control the flow rate according to a minimum allowed flow rate Fmin, for example 10% of the design flow rate, or 5% or 15% or some other value. When for example the temperature difference AT gets low this may indicate too much thermal energy is supplied to the heat consuming device 2 leading to a loss of thermal energy. The controller 7 therefore reacts by lowering the flow rate. However, it is an advantage that the heating fluid flow rate does not become too low, hence the controller 7 includes the minimum allowed flow rate Fmin.

The actuator 5 in the present invention includes a temperature management function, being the actuator 5 being adapted to overrule the setting signal from the controller 7 to change the minimum allowed flow rate Fmin,actuator to a different value.

This could be a consumer selection among a plural of different such actuator 5 set minimum allowed flow rates Fmin,actuator, and could include values both higher and lower than the minimum allowed flow rate Fmin of the controller 7.

For example, if the minimum allowed flow rate Fmin is 10% of the design flow rate, the selectable actuator 5 set minimum allowed flow rates Fmin,actuator could include 5%, 8%, 15% and 20%, or any other values. In some embodiment the actuator 5 has the possible of a selectable PID setting if additional control is required or desired.

The selection of the selectable actuator 5 set minimum allowed flow rates

Fmin,actuator could e.g. be by a selection function on the actuator 5 itself, or could be remotely set e.g. using a cell phone, computer or other devices.

The change could be initiated by the consumer, or perhaps some other administrator, based on the criticality of the heat consuming device 2. If not critical, the actuator 5 selectable minimum allowed flow rates Fmin,actuator e.g.

DK 2021 01237 A1 9 being allowed to a lower value than the minimum allowed flow rate Fmin when the delivery of sufficient thermal energy to the heat consuming devices 2 is not critical, and to a higher value when it is critical, to ensure sufficient delivery.

Fig. 3 illustrates the same heating system as fig. 1, where the actuator 5 is adapted to be in data exchange communication to other device, such as flow controlling devices 12 like pressure independent valves, pressure control valves, flow control valves etc. The flow controlling devices 12 could be connected to other positions or branches of the heating system 1, or to other heating systems 1.

In another embodiment, the controller 7 forms part of the actuator 5.

Claims

DK 2021 01237 A1 1 CLAIMS

1. Method to control a heating system (100) supply a heating fluid to a heat consuming device (2) by a supply line (8) with a supply temperature Ts and returned from the heat consuming device (2) by a return line (9) at a return temperature Tr, and a pressure regulation unit (3) adapted to maintain a substantially constant pressure of the heating fluid and a flow controller (4) to control the flow rate of the heating fluid, and an actuator (5) connected to adjust the flow controller (4) according to a flow rate setting, wherein the actuator (5) is adapted to regulate the flow controller (4) to be within a given range of flow rates.

2. Method according to claim 1, wherein the flow controller (4) is regulated to change the flow rate of the heating fluid passing the heat consuming devices (2) to keep the return temperature Tr above or below a given threshold Tt - or to control the return temperature Tr based on set return temperature Ts or to control temperature difference between supply and return temperatures based on set dT temperature or to maintain temperature difference between the supply and return temperatures, AT = Ts-Tr, above, or below, a given threshold Tt.

3. Method according to claim 1 or 2, the method including to control the flow controller (4) according to a stored characteristic curve (6) of the flow controller setting relative to the flow rate,

4. Method according to claim 1, 2 or 3, wherein a controller (7) is positioned in data exchange communication with the actuator (5) and to control the heating system (100) to a desired flow by changing the flow controller (4) by communicating a flow rate setting signal to the actuator (5).

5. Method according to claim 4, wherein the characteristic curve (6) s stored in the memory of the actuator 5, and when the controller (7)

DK 2021 01237 A1 2 communicates flow rate setting signal related to a requested flow rate of the heating fluid, the actuator (5) then adjusting the flow controller (4) using the characteristic curve (6) to find the correct flow controller (4) setting.

6. Method according to 5, wherein the controller (7) is adapted to control the flow rate according to a minimum allowed controller given flow rate Fmin, but where the actuator (5) is adapted to overrule the setting signal from the controller (7) to change the minimum actuator allowed flow rate Fmin,actuator to a different value.

7. Method according to claim 6, wherein the change is selectable by a user among a plural of selectable different minimum actuator given allowed flow rates Fmin, actuator.

8. Method according to any of claims 4-7, wherein the controller (7) is positioned remote from the actuator (5).

9. Method according to any of claims 4-7, wherein the controller (7) is positioned as part of the actuator (5).

10 Method according to any of the preceding claims, wherein the flow controller 4 is positioned at the supply (8) or return (9) line.

11. Method according to claim 10, wherein the actuator (5) includes a memory to store data like the characteristic curve (6) of the flow controller (4) and comprise a processer to perform calculations etc.

12. Method according to any of the preceding claims, wherein the pressure regulation unit (3) is positioned to ensure a constant differential pressure over the flow controller (4).

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13. Method according to claim 12, wherein the pressure regulation unit (3) and flow controller (4) is constructed as a single pressure independent valve unit, the pressure regulation unit (3) connecting respectively to the inlet and outlet of the flow controller (4) by pressure channels formed within the unit.

14. Actuator (5) adapted to control the heating system (100) according to the method of any of the preceding claims.