U.S. patent application number 16/896918 was filed with the patent office on 2020-12-17 for flow control module and method for controlling the flow in a hydronic system.
The applicant listed for this patent is GRUNDFOS HOLDING A/S. Invention is credited to Casper HILLERUP LYHNE, Agisilaos TSOUVALAS.
Application Number | 20200393160 16/896918 |
Document ID | / |
Family ID | 1000004938055 |
Filed Date | 2020-12-17 |
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United States Patent
Application |
20200393160 |
Kind Code |
A1 |
TSOUVALAS; Agisilaos ; et
al. |
December 17, 2020 |
FLOW CONTROL MODULE AND METHOD FOR CONTROLLING THE FLOW IN A
HYDRONIC SYSTEM
Abstract
A flow control module (39) controls one or more pumps in a
hydronic system that includes a primary side (3) with first and
second ports (21, 27), a source element (7) and a flow actuator
(9), and a secondary side (5) with third and fourth ports (31, 35),
a load element (11), and a flow actuator. An intermediary transfer
element (17) between the primary side and the secondary side. The
flow control module is configured to calibrate a measurement of a
first temperature differential (.DELTA.T.sub.c) between the first
port and the third port in a first situation when a primary side
flow (q.sub.1) exceeds the secondary side flow (q.sub.2), and to
calibrate a measurement of a second temperature differential
(.DELTA.T.sub.h) between a temperature at the fourth port and a
temperature at the second port in a second situation when the
secondary side flow exceeds the primary side flow.
Inventors: |
TSOUVALAS; Agisilaos;
(Silkeborg, DK) ; HILLERUP LYHNE; Casper;
(Aabyhoj, DK) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
GRUNDFOS HOLDING A/S |
Bjerringbro |
|
DK |
|
|
Family ID: |
1000004938055 |
Appl. No.: |
16/896918 |
Filed: |
June 9, 2020 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
F24F 11/76 20180101;
F24F 11/84 20180101; F24F 11/75 20180101 |
International
Class: |
F24F 11/84 20060101
F24F011/84; F24F 11/76 20060101 F24F011/76; F24F 11/75 20060101
F24F011/75 |
Foreign Application Data
Date |
Code |
Application Number |
Jun 13, 2019 |
EP |
19180068.9 |
Claims
1. A flow control module for controlling the flow in a hydronic
system, wherein the hydronic system comprises a primary side with a
first port in fluid connection with an output of at least one
source element, a second port in fluid connection with an input of
the at least one source element, and at least one controllable
primary side flow actuator for providing a primary side flow, a
secondary side with a third port in fluid connection with an input
of at least one load element, a fourth port in fluid connection
with an output of the at least one load element, and at least one
controllable secondary side flow actuator for providing a secondary
side flow, and an intermediary transfer element between the primary
side and the secondary side, wherein the intermediary transfer
element is in fluid connection with the first port, the second
port, the third port and the fourth port, wherein the flow control
module is configured: to calibrate a measurement of a first
temperature differential between a temperature at the first port
and a temperature at the third port in a first situation when the
primary side flow exceeds the secondary side flow; and to calibrate
a measurement of a second temperature differential between a
temperature at the fourth port and a temperature at the second port
in a second situation when the secondary side flow exceeds the
primary side flow.
2. The flow control module according to claim 1, wherein the flow
control module is configured to force the hydronic system, for
calibration purposes, into the first situation and/or second
situation by controlling the primary side flow actuator and/or the
secondary side flow actuator.
3. The flow control module according to claim 1, wherein the flow
control module is configured to identify the first situation and/or
the second situation by comparing the first temperature
differential with the second temperature differential.
4. The flow control module according to claim 1, wherein the flow
control module is configured to identify the first situation and/or
the second situation when a certain pre-defined threshold of an
absolute value of a signed deviation value, between the first
temperature differential and the second temperature differential,
is exceeded.
5. The flow control module according to claim 1, wherein the flow
control module is configured to adapt the thermal power transfer of
the intermediary transfer element by controlling the primary side
flow by means of the at least one controllable primary side flow
actuator and/or the secondary side flow by means of the at least
one controllable secondary side flow actuator in a continuously or
closed-loop regularly based on minimizing a signed deviation value
being correlated with the thermal power transfer of the
intermediary transfer element.
6. The flow control module according to claim 5, wherein the flow
control module is configured to maintain a current primary side
flow if the signed deviation value is between a negative reference
value and a positive reference value.
7. The flow control module according to claim 5, wherein the flow
control module is configured to increase the primary side flow if
the signed deviation value is below a negative reference value.
8. The flow control module according to claim 5, wherein the flow
control module is configured to maintain the primary side flow if
the signed deviation value is below a negative reference value and
the primary side flow is at or above a predetermined maximum
threshold.
9. The flow control module according to claim 5, wherein the flow
control module is configured to decrease the secondary side flow if
the signed deviation value is below a negative reference value and
the primary side flow cannot be increased.
10. The flow control module according to claim 5, wherein the flow
control module is configured to decrease the primary side flow if
the signed deviation value is above a positive reference value.
11. The flow control module according to claim 5, wherein the flow
control module is configured to maintain a current primary side
flow if the signed deviation value is above a positive reference
value and the primary side flow is at or below a predetermined
minimum threshold.
12. The flow control module according to claim 1, wherein the flow
control module is integrated in one of the at least one
controllable primary side flow actuator and/or one of the at least
one controllable secondary side flow actuator.
13. The flow control module according to claim 1, wherein the flow
control module is integrated in a cloud-based computer system
and/or a building management system.
14. A method for controlling the flow in a hydronic system, wherein
the hydronic system comprises a primary side with a first port in
fluid connection with an output of at least one source element, a
second port in fluid connection with an input of the at least one
source element, and at least one controllable primary side flow
actuator for providing a primary side flow, a secondary side with a
third port in fluid connection with an input of at least one load
element, a fourth port in fluid connection with an output of the at
least one load element, and at least one controllable secondary
side flow actuator for providing a secondary side flow, and an
intermediary transfer element between the primary side and the
secondary side, wherein the intermediary transfer element is in
fluid connection with the first port, the second port, the third
port and the fourth port, the method comprising: calibrating a
measurement of a first temperature differential between a
temperature at the first port and a temperature at the third port
in a first situation when the primary side flow exceeds the
secondary side flow; and calibrating a measurement of a second
temperature differential between a temperature at the fourth port
and a temperature at the second port in a second situation when the
secondary side flow exceeds the primary side flow.
15. The method according to claim 14, further comprising a step of
forcing the hydronic system into the first situation and/or second
situation by controlling the primary side flow actuator and/or the
secondary side flow actuator prior to the calibrating steps.
16. The method according to claim 14, further comprising a step of
identifying the first situation and/or the second situation by
comparing the first temperature differential with the second
temperature differential.
17. The method according to claim 16, wherein the first situation
and/or the second situation is identified when a certain
pre-defined threshold on the absolute value of a signed deviation
value between the first temperature differential and the second
temperature differential is exceeded.
18. The method according to claim 14, further comprising a step of
adapting the thermal power transfer of the intermediary transfer
element by controlling the primary side flow by means of the at
least one controllable primary side flow actuator and/or the
secondary side flow by means of the at least one controllable
secondary side flow actuator unit in a continuously or closed-loop
regularly, based on minimizing a signed deviation value being
correlated with the thermal power transfer of the intermediary
transfer element.
19. The method according to claim 18, wherein a current primary
side flow is maintained if the signed deviation value is between a
negative reference value and a positive reference value.
20. The method according to claim 18, wherein the primary side flow
is increased if the signed deviation value is below a negative
reference value.
21. The method according to claim 18, wherein the primary side flow
is maintained if the signed deviation value is below a negative
reference value and the primary side flow is at or above a
predetermined maximum threshold.
22. The method according to claim 18, wherein the secondary side
flow is decreased if the signed deviation value is below a negative
reference value and the primary side flow cannot be increased.
23. The method according to claim 18, wherein the primary side flow
is decreased if the signed deviation value is above a positive
reference value.
24. The method according to claim 18, wherein a current primary
side flow is maintained if the signed deviation value is above a
positive reference value and the primary side flow is at or below a
predetermined minimum threshold.
Description
CROSS REFERENCE TO RELATED APPLICATION
[0001] The application claims the benefit of priority under 35
U.S.C. .sctn. 119 of European Application 19 180 068.9, filed Jun.
13, 2019, the entire contents of which are incorporated herein by
reference.
TECHNICAL FIELD
[0002] The present disclosure is directed to a flow control module
and a method for controlling the flow in a hydronic system, in
particular for use in a heating, ventilating, and air-conditioning
(HVAC) system of a building.
BACKGROUND
[0003] Typically, hydronic systems are designed to operate at a
design temperature differential (.DELTA.T ) between a primary loop
comprising thermal power source, e.g. a heater, a chiller, a heat
exchanger and/or a common line coupling, and a secondary loop
comprising a thermal power consuming load, e.g. a radiator and/or
an air handling unit (AHU). It is known that hydronic systems may
suffer from an undesirable effect known as the "low .DELTA.T
syndrome". For a variety of reasons such as dirty chiller coils or
system components not designed for the same temperature
differential, the actual temperature differential may fall below
the design temperature differential, which leads to a less
energy-efficient operation of the hydronic system.
[0004] U.S. Pat. No. 8,774,978 B2 describes a water cooling system
with a primary loop, a secondary loop and an intermediary decoupler
or bypass connecting the primary loop and the secondary loop.
Therein, the problems of the low .DELTA.T syndrome are tackled by a
demand flow device performing an event-based triggered
re-adjustment of the new temperature differential supply
setpoint.
SUMMARY
[0005] The flow control module according to the present disclosure
provides a more efficient and stable solution to the low .DELTA.T
syndrome. For instance, new switched-in components replacing or
supplementing other components of a hydronic system may result in a
new design temperature differential that is not known or difficult
to determine or estimate. The flow control module disclosed herein
allows an efficient and stable operation of a hydronic system with
an unknown, undefined or varying design temperature differential.
The flow control module disclosed herein enables a continuous or
regular adaptation of the current thermal power supply to the
current thermal power demand and vice versa without controlling a
temperature differential supply setpoint.
[0006] According to a first aspect of the present disclosure, a
flow control module for controlling the flow in a hydronic system
is provided, wherein the hydronic system comprises [0007] a primary
side with a first port in fluid connection with an output of at
least one source element, a second port in fluid connection with an
input of at least one source element, and at least one controllable
primary side flow actuator for providing a primary side flow,
[0008] a secondary side with a third port in fluid connection with
an input of at least one load element, a fourth port in fluid
connection with an output of at least one load element, and at
least one controllable secondary side flow actuator for providing a
secondary side flow, and [0009] an intermediary transfer element
between the primary side and the secondary side, wherein the
intermediary transfer element is in fluid connection with the first
port, the second port, the third port and the fourth port. Said
flow control module is configured to calibrate a measurement of a
first temperature differential between a temperature at the first
port and a temperature at the third port in a first situation when
the primary side flow exceeds the secondary side flow, and in that
the flow control module is configured to calibrate a measurement of
a second temperature differential between a temperature at the
fourth port and a temperature at the second port in a second
situation when the secondary side flow exceeds the primary side
flow.
[0010] The temperature measurement is thus automatically calibrated
"online" when the first and/or second situation arises. The term
"calibrate" herein shall mean herein that a non-zero value based on
a measurement in the first and/or second situation is used as an
offset value to correct further measurements. In the first and/or
second situation, the non-zero value must in fact be zero, so that
it can be assumed that any non-zero value in the first and/or
second situation is entirely based on sensor inaccuracies.
Therefore, the non-zero value is "set" to zero by subtracting the
non-zero value as an off-set value for further measurements.
Preferably, the calibration is automatically repeated every time
the first and/or second situation arises. Alternatively, the
calibration may be manually or automatically repeated periodically,
e.g. only once a day or once a week, when the first and/or second
situation arises.
[0011] Optionally, the flow control module may be configured to
force the hydronic system, for calibration purposes, into the first
situation and/or second situation by controlling the primary side
flow actuator and/or the secondary side flow actuator. For
instance, a primary side pump may be ramped up while the secondary
side pump may be ramped down in order to establish a significant
imbalance between the flow in the primary side compared to the
secondary side. Alternatively, or in addition, a secondary side
valve in the secondary side may be closed.
[0012] Optionally, the flow control module may be configured to
identify the first situation and/or the second situation by
comparing the first temperature differential with the second
temperature differential.
[0013] Optionally, the flow control module may be configured to
identify the first situation and/or the second situation when a
certain pre-defined threshold on the absolute value of a signed
deviation value between the first temperature differential and the
second temperature differential is exceeded.
[0014] Optionally, the flow control module may be configured to
adapt the thermal power transfer of the intermediary transfer
element by controlling the primary side flow by means of the at
least one controllable primary side flow actuator and/or the
secondary side flow by means of the at least one controllable
secondary side flow actuator in a continuous or regularly
closed-loop manner based on minimising a signed deviation value
being correlated with the thermal power transfer of the
intermediary transfer element.
[0015] The term "thermal power" Q may be defined herein as Q=pcqT,
wherein p is the fluid density, c is the heat capacity of the
fluid, q is the flow and the T is the temperature of the fluid. The
term "thermal power transfer" by fluid flowing from a port A to a
port B may be defined herein as a dimensionless variable QB/QA
ranging from 0 to 1, wherein QA is the thermal power at port A and
QB is the thermal power at port B.
[0016] Optionally, the thermal power transfer of the intermediary
transfer element from the first port to the second port and/or the
thermal power transfer of the intermediary transfer element from
the fourth port to the third port may be minimized by this
continuous or regularly closed-loop control of the flow(s).
Optionally, the thermal power transfer from the first port to the
third port and/or the thermal power transfer from the fourth port
to the second port may be maximized by this continuous or regularly
closed-loop control of the flow(s). The controllable
primary/secondary side flow actuator may for instance be a
speed-controllable pump or a combination of a fixed-speed pump with
a controllable valve. Controlling the primary/secondary side flow
may thus comprise controlling the speed of a primary/secondary side
pump and/or the opening degree of a primary/secondary side valve.
As alternatives to controlling a pump speed, the power consumption,
the stator flux and/or stator current of the pump's electric motor
may be controlled to control the flow(s). It should be understood
that the hydronic system may comprise a group of two or more
intermediary transfer elements.
[0017] The hydronic system may be a heating and/or cooling system.
The source element may be a heater, a chiller, a heat exchanger
and/or a common line coupling consuming chemical, thermal,
mechanical or electrical energy for providing thermal power to the
primary side of the hydronic system. The load element may be a fan
coil unit (FCU), an air handling unit (AHU), an anti-condensate
baffle (ACB), a ceiling cooling, a radiator, an underfloor heating,
or the like, consuming thermal power at the secondary side of the
hydronic system for providing it to a place or object in need for
thermal power, i.e. heating or cooling.
[0018] The intermediary transfer element may be a common line, also
known as "decoupler", decoupling the flow in the primary side from
the flow in the secondary side. For instance, when a load valve
(e.g. a radiator thermostat) in the secondary side may be closed
due to low demand for thermal power, a flow in the primary side may
continue through the common line. The com mon line may also be
denoted as "bypass" or "shunt", because the flow in the primary
side is able to bypass a load element in the secondary side via the
common line. Another name for the common line is "close Tees",
because the schematic representation of the common line may
resemble two letters "T" being connected with their legs. One end
of the common line may be a first T-connection connecting the first
and the third port, and the other end of the common line may be a
second T-connection connecting the fourth and the second port.
Optionally, the intermediary transfer element may be a heat
exchanger thermally coupling the primary side and the secondary
side in a parallel flow or counter flow configuration. Optionally,
the intermediary transfer element may be a hydraulic separator or a
tank. A hydraulic separator or a tank may be regarded as a wide
common line with heat exchanger functionality. In case of a common
line, a hydraulic separator or a tank, the pressure of the primary
side may be decoupled from the pressure in the secondary side by
means of pressure valves. In case of a heat exchanger, the primary
side and the secondary side may be fully decoupled in terms of
pressure without the need of decoupling pressure valves. As the
fluid in the primary side does not mix in the heat exchanger with
the fluid of the secondary side, different fluids may be used in
the primary side and in the secondary side. However, most
preferably, water is used as the fluid in both the primary side and
the secondary side.
[0019] The term "closed-loop control" shall mean that the signed
deviation value is used as a feedback value to be minimized by
adapting the flow(s). The signed deviation value is correlated with
the thermal power transfer of the intermediary transfer element and
influenced by the flow(s). The flow control module may thus be
denoted as a feedback controller. The signed deviation value may be
received and/or determined by the flow control module based on one
or more measured variables. The closed-loop control is not
event-triggered, but essentially continuous or regularly, which
means that, also during "stable" operation of the hydronic system,
the flow control module receives and/or determines essentially
continuously or regularly the signed deviation value and adapts
essentially continuously or regularly the flow(s) accordingly. The
flow(s) may stabilize when the signed deviation value is close to
or at a minimum.
[0020] The closed-loop control of the flow(s) on the basis of the
signed deviation value as feedback thus reduces or prevents the
negative effects of the low .DELTA.T syndrome very efficiently. No
event-based recalibration to a new design temperature differential
is needed. As the signed deviation value is correlated with the
thermal power transfer of the intermediary transfer element, the
closed-loop control quickly adapts the flow(s) so that a low
.DELTA.T syndrome does not establish in the first place. The flow
control module disclosed herein allows the design temperature
differential of the hydronic system to be unknown or undefined. For
instance, a new component configured for an unknown or other design
temperature differential than the hydronic system may be installed
in the hydronic system without causing a low .DELTA.T syndrome.
This gives far more flexibility for maintaining and/or extending
the hydronic system by replacing or adding components. Furthermore,
the current thermal power supply is adapted to the current thermal
power demand and vice versa with-out controlling a temperature
differential supply setpoint.
[0021] Optionally, the signed deviation value may be a difference
between a first differential and a second differential, wherein the
first differential is a differential between any two measured
variables of a group of four variables and the second differential
is a differential between the other two measured variables of said
group of four variables, wherein the group of four variables
comprises a first variable of fluid flowing through the first port,
a second variable of fluid flowing through the second port, a third
variable of fluid flowing through the third port, and a fourth
variable of fluid flowing through the fourth port. Optionally, the
first variable may be the temperature T.sub.1 and/or pressure
p.sub.1 of fluid flowing through the first port, the second
variable may be the temperature T.sub.2 and/or pressure p.sub.2 of
fluid flowing through the second port, the third variable may be
the temperature T.sub.3 and/or pressure p.sub.3 of fluid flowing
through the third port, and the fourth variable may be the
temperature T.sub.4 and/or pressure p.sub.4 of fluid flowing
through the fourth port.
[0022] The first differential may for instance be
.DELTA.T.sub.1=T.sub.1-T.sub.4 or .DELTA.T.sub.1=T.sub.1-T.sub.3 or
.DELTA.T.sub.1=T.sub.3-T.sub.4, and the second differential may for
instance be .DELTA.T.sub.2=T.sub.3-T.sub.2 or
.DELTA.T.sub.2=T.sub.2-T.sub.4 or .DELTA.T.sub.2=T.sub.1-T.sub.2,
respectively. Analogously, in case of a common line as the
intermediary transfer element, the first differential may for
instance be .DELTA.p.sub.1=p.sub.1-p.sub.4 or
.DELTA.p.sub.1=p.sub.1-p.sub.3 or .DELTA.p.sub.1=p.sub.3-p.sub.4,
and the second differential may for instance be
.DELTA.p.sub.2=p.sub.3-p.sub.2 or .DELTA.p.sub.2=p.sub.2-p.sub.4 or
.DELTA.p.sub.2=p.sub.1-p.sub.2, respectively. In case of a heat
exchanger as the inter-mediary transfer element, the primary side
pressure is fully decoupled from the secondary side pressure,
wherein the first differential may for instance be
.DELTA.p.sub.1=p.sub.1-p.sub.2 and the second differential may for
instance be .DELTA.p.sub.2=p.sub.3-p.sub.4. The signed deviation
value may be .DELTA..DELTA.T=.DELTA.T.sub.2-.DELTA.T.sub.1 or
.DELTA..DELTA.p=.DELTA.p.sub.2-.DELTA.p.sub.1.
[0023] The thermal transfer between the first port and the third
port and/or the thermal transfer between the fourth port and the
second port may be denoted as a thermal transfer "across" the
intermediary transfer element, whereas the thermal transfer between
the first port and the second/fourth port and/or the thermal
transfer between the fourth port and the first/third port may be
denoted as a thermal transfer "along" the intermediary transfer
element. By adapting the flow(s), the thermal transfer across the
intermediary transfer element may be maximized, whereas the thermal
transfer along the intermediary transfer element may be minimized.
The signed deviation value .DELTA..DELTA.T and/or .DELTA..DELTA.p
may be correlated with the thermal transfer along the inter-mediary
transfer element.
[0024] In case of a common line as the intermediary transfer
element, a negative deviation value .DELTA..DELTA.T and/or
.DELTA..DELTA.p may be representative for a flow along the common
line from the fourth port to the third port. Such a "negative" flow
is undesirable, because the "temperature lift" between the first
port and third port would be reduced, resulting in an aggravation
of a low .DELTA.T syndrome. Analogously, a positive deviation value
.DELTA..DELTA.T and/or .DELTA..DELTA.p may be representative for a
flow along the common line from the first port to the second port.
Such a "positive" flow is also undesirable, because the thermal
capacity of the primary side is not fully used.
[0025] In case of a very efficient heat exchanger as the
intermediary transfer element, a negative deviation value
.DELTA..DELTA.T and/or .DELTA..DELTA.p may be representative for a
lack of thermal transfer across the heat exchanger from the first
port to the third port. This is undesirable, because the
"temperature lift" between the first port and third port would be
reduced, resulting in an aggravation of a low .DELTA.T syndrome.
Analogously, a positive deviation value .DELTA..DELTA.T and/or
.DELTA..DELTA.p may be representative for an abundance of thermal
transfer along the heat exchanger from the first port to the second
port. Such a thermal transfer is also undesirable, because the
thermal capacity of the primary side is not fully used.
[0026] Optionally, the signed deviation value may be a difference
between a measured or determined flow q in a common line as the
intermediary transfer element and a pre-determined common line
reference flow, preferably a zero common line flow. For instance, a
flow meter in the common line may provide a measured flow variable
q. Alternatively or in addition, the flow in the common line may be
determined by a pressure differential along the common line. For
instance, a first pressure sensor may be placed between the first
port and the third port and a second pressure sensor may be placed
between the second port and the fourth port. After a calibration of
the pressure differential between the two pressure sensors for zero
flow, the pressure differential may be used as the signed deviation
value. The primary/secondary flow(s) may be adapted to keep the
flow in the common line to a minimum. There is no need for a check
valve preventing a negative flow q from the fourth port to the
third port.
[0027] Optionally, the signed deviation value may be a difference
between a flow differential in a heat exchanger as the intermediary
transfer element and a pre-determined reference heat exchanger
differential flow, preferably a zero heat exchanger differential
flow. For instance, a first flow meter in the primary side a may
provide a first measured flow variable q.sub.1 and a second flow
meter in the secondary side a may provide a second measured flow
variable q.sub.2, wherein the signed deviation value may be a flow
differential .DELTA.q=q1-q2. The primary/secondary flow(s) may be
adapted to keep the flow differential .DELTA.q to a minimum.
[0028] Optionally, the flow control module may be configured to
maintain a current primary side flow if the signed deviation value
is between a negative reference value and a positive reference
value, preferably essentially zero. The negative reference value
and a positive reference value may be predetermined low values
between which the thermal power transfer along the intermediary
transfer element is sufficiently small, i.e. the thermal power
transfer across the intermediary transfer element is sufficiently
large. This situation may be regarded as a stable operation with
the current primary side flow. The current secondary side flow may
also be maintained. However, other control schemes, such as a
building management system, a radiator thermostat or a manual AHU
switch may open/close one or more load valves indicating a
higher/lower demand for thermal power at a load element. Such other
control schemes may command a higher/lower secondary side flow. For
instance, an internal automatic pump controller of a secondary side
pump may establish a corresponding target pressure/flow by
increasing/decreasing the speed of the secondary side pump. Despite
of a high thermal power demand, the control module disclosed herein
may overrule such an underlying control scheme to decrease the
secondary side flow for a minimum of the signed deviation value.
However, as long as the signed deviation value is above the
negative reference value, the flow control module may allow an
internal automatic pump controller of a secondary side pump to
increase the speed of the secondary side pump in order to establish
a target pressure and flow in the secondary side to meet the
thermal power demand of the load element.
[0029] Optionally, the flow control module may be configured to
increase the primary side flow if the signed deviation value is
below a negative reference value. In case of a common line, this
undesirable "negative" flow spoiling the temperature lift across
the common line is tackled by a higher thermal power supply to the
intermediary transfer element via the first port. However, this
increase of thermal power supply may be limited a maximum primary
side pump speed, a maximum primary side valve opening and/or the
maximum capacity of the source element(s). Therefore, the flow
control module may be configured to maintain the primary side flow
if the signed deviation value is below a negative reference value
and the primary side flow is above a predetermined maximum
threshold. The predetermined maximum threshold may be defined by a
maximum primary side pump speed, a maximum primary side valve
opening or a maximum capacity of the source element(s).
[0030] In one embodiment of the flow control module disclosed
herein, only the primary side flow is controlled by the flow
control module. As long as the signed deviation value is above a
positive reference value, the flow control module decreases the
primary side flow until a minimum primary side flow is reached. A
minimum primary side flow may, for instance, be a predetermined
value defined by the source element(s) that may require a minimal
primary flow.
[0031] Optionally, the flow control module may be configured to
maintain a current primary side flow if the signed deviation value
is above a positive reference value and the flow in the primary
side is below a predetermined minimum threshold. Such a situation
may be denoted as a stable "low demand operation", wherein the
thermal transfer along the intermediary transfer element between
the first port and the second port is minimized.
[0032] In another embodiment of the flow control module disclosed
herein, only secondary side flow is controlled by the flow control
module. In yet another embodiment of the flow control module
disclosed herein, both the primary and secondary side flows are
controlled by the flow control module. If the secondary side flow
is controllable by the flow control module, the flow control module
may be configured to decrease the secondary side flow if the signed
deviation value is below a negative reference value and the primary
side flow cannot be increased. The increase of the primary side
flow may be limited by a primary side pump already running at
maximum speed, a primary side valve being already fully opened, or
a maximum capacity of the source element(s). Another reason could
be that the primary side flow may not be controllable by the flow
control module in the first place. Such a decrease of the secondary
side flow may be conflicting with an underlying internal automatic
pump controller of a secondary side pump aiming for a target
pressure and flow, because the secondary side flow is reduced when
the thermal power demand of the load element(s) is not met by the
thermal power supply of the source element(s). However, reducing
the secondary side flow increases in this case the thermal power
transfer across the intermediary transfer element from the first
port to the third port. Thus, the load element(s) are provided with
the maximum available thermal power by a reduced secondary side
flow. Despite of a high thermal power demand in the secondary side,
the flow control module overrules any underlying control scheme in
order to decrease the secondary side flow for a minimum of the
signed deviation value. However, as long as the signed deviation
value is above the negative reference value, the flow control
module may allow an internal automatic pump controller of a
secondary side pump to increase the speed of the secondary side
pump in order to establish a target pressure and flow in the
secondary side to meet the thermal power demand of the load
element.
[0033] Optionally, the flow control module may be integrated in one
of the at least one controllable primary side flow actuator and/or
one of the at least one controllable secondary side flow actuator.
Alternatively, or in addition, the flow control module may be
integrated in a cloud-based computer system and/or a building
management system (BMS).
[0034] According to a second aspect of the present disclosure, a
hydronic system is provided comprising [0035] a primary side
comprising at least one source element, a first port in fluid
connection with an output of the at least one source element, a
second port in fluid connection with an input of the at least one
source element, and at least one controllable primary side flow
actuator for providing a primary side flow, [0036] a secondary side
comprising at least one load element, a third port in fluid
connection with an input of the at least one load element, a fourth
port in fluid connection with an output of the at least one load
element, and at least one controllable secondary side flow actuator
for providing a secondary side flow, [0037] an intermediary
transfer element between the primary side and the secondary side,
wherein the intermediary transfer element is in fluid connection
with the first port, the second port, the third port and the fourth
port, and [0038] a flow control module as disclosed herein.
[0039] Optionally, the hydronic system may further comprise a group
of four sensors with a first sensor being arranged and configured
to determine a first variable of fluid flowing through the first
port, a second sensor being arranged and configured to determine a
second variable of fluid flowing through the second port, a third
sensor being arranged and configured to determine a third variable
of fluid flowing through the third port, and a fourth sensor being
arranged and configured to determine a fourth variable of fluid
flowing through the fourth port. For instance, the group of sensors
may be four temperature sensors or four pressure sensors preferably
being installed at the four ports.
[0040] Optionally, the intermediary transfer element is a common
line or a heat exchanger. In case of a common line being the
intermediary transfer element, the hydronic system may further
comprise a flow meter in the common line. In case of a heat
exchanger being the intermediary transfer element, the hydronic
system may further comprise a first flow meter in the primary side
and a second flow meter in the secondary side.
[0041] Alternatively, or in addition, the at least one controllable
primary side flow actuator and/or the at least one controllable
secondary side flow actuator may be at least one primary/secondary
side pump which is speed-controllable by means of the flow control
module. Alternatively, the at least one controllable primary side
flow actuator and/or the at least one controllable secondary side
flow actuator may be at least one combination of a fixed-speed pump
and a primary/secondary side valve, wherein the opening degree of
the primary/secondary side valve is controllable by means of the
flow control module.
[0042] According to a third aspect of the present disclosure, a
method for controlling the flow in a hydronic system is provided,
wherein the hydronic system comprises [0043] a primary side having
a first port in fluid connection with an output of at least one
source element, a second port in fluid connection with an input of
at least one source element, and at least one controllable primary
side flow actuator for providing a primary side flow, [0044] a
secondary side having a third port in fluid connection with an
input output of at least one load element, a fourth port in fluid
connection with an output of at least one load element, and at
least one controllable secondary side flow actuator for providing a
secondary side flow, and [0045] an intermediary transfer element
for transferring heat between the primary side and the secondary
side, wherein the intermediary transfer element is in fluid
connection with the first port, the second port, the third port and
the fourth port, the method comprising calibrating a measurement of
a first temperature differential between a temperature at the first
port and a temperature at the third port in a first situation when
the primary side flow exceeds the secondary side flow, and
calibrating a measurement of a second temperature differential
between a temperature at the fourth port and a temperature at the
second port in a second situation when the secondary side flow
exceeds the primary side flow.
[0046] Optionally, the method may further comprise a step of
forcing the hydronic system into the first situation and/or second
situation by controlling the primary side flow actuator and/or the
secondary side flow actuator prior to the calibrating steps.
[0047] Optionally, the method may further comprise a step of
identifying the first situation and/or the second situation by
comparing the first temperature differential with the second
temperature differential.
[0048] Optionally, the first situation and/or the second situation
may be identified when a certain pre-defined threshold on the
absolute value of a signed deviation value between the first
temperature differential and the second temperature differential is
exceeded.
[0049] Optionally, the method may further comprise a step of
adapting the thermal power transfer of the intermediary transfer
element by controlling the primary side flow by means of the at
least one controllable primary side flow actuator and/or the
secondary side flow by means of the at least one controllable
secondary side flow actuator unit in a continuous or regularly
closed-loop manner based on minimising a signed deviation value
being correlated with the thermal power transfer of the
intermediary transfer element.
[0050] Optionally, the signed deviation value may be a difference
between a first differential and a second differential, wherein the
first differential is a differential between any two measured
variables of a group of four variables and the second differential
is a differential between the other two measured variables of said
group of four variables, wherein the group of four variables
comprises a first variable of fluid flowing through the first port,
a second variable of fluid flowing through the second port, a third
variable of fluid flowing through the third port, and a fourth
variable of fluid flowing through the fourth port.
[0051] Optionally, the first variable may be the temperature and/or
pressure of fluid flowing through the first port, the second
variable is the temperature and/or pressure of fluid flowing
through the second port, the third variable is the temperature
and/or pressure of fluid flowing through the third port, and the
fourth variable is the temperature and/or pressure of fluid flowing
through the fourth port.
[0052] Optionally, the signed deviation value may be a difference
between a measured flow in a common line as the intermediary
transfer element and a pre-determined common line reference flow,
preferably a zero common line flow. Alternatively, a flow in a
common line may be determined by a pressure differential along the
intermediary transfer element between a first pressure sensor
placed between the first port and the third port and a second
pressure sensor placed between the second port and fourth port.
Such a pressure differential may be calibrated for zero flow and
then be used as the signed deviation value.
[0053] Optionally, the signed deviation value may be a difference
between a flow differential in a heat exchanger as the intermediary
transfer element and a pre-determined reference heat exchanger
differential flow, preferably a zero heat exchanger differential
flow. The flow differential being used as the signed deviation
value may be the difference between the primary side flow and the
secondary side flow.
[0054] Optionally, a current primary side flow may be maintained if
the signed deviation value is between a negative reference value
and a positive reference value, preferably essentially zero.
[0055] Optionally, the primary side flow may be increased if the
signed deviation value is below a negative reference value.
[0056] Optionally, the primary side flow may be maintained if the
signed deviation value is below a negative reference value and the
primary side flow is above a predetermined maximum threshold.
[0057] Optionally, the secondary side flow may be decreased if the
signed deviation value is below a negative reference value and the
primary side flow cannot be increased.
[0058] Optionally, the primary side flow may be decreased if the
signed deviation value is above a positive reference value.
[0059] Optionally, a current primary side flow may be maintained if
the signed deviation value is above a positive reference value and
the flow in the primary side is below a predetermined minimum
threshold.
[0060] The method disclosed herein may be implemented in form of
compiled or uncompiled software code that is stored on a computer
readable medium with instructions for executing the method.
Alternatively, or in addition, the method may be executed by
software in a cloud-based system and/or a building management
system (BMS), e.g. in the flow control module disclosed herein.
[0061] Embodiments of the present disclosure will now be described
by way of example with reference to the following figures. The
various features of novelty which characterize the invention are
pointed out with particularity in the claims annexed to and forming
a part of this disclosure. For a better understanding of the
invention, its operating advantages and specific objects attained
by its uses, reference is made to the accompanying drawings and
descriptive matter in which preferred embodiments of the invention
are illustrated.
[0062] BREIF DESCRIPTION OF THE DRAWINGS
[0063] In the drawings:
[0064] FIG. 1 is a schematic view of an example of an embodiment of
a hydronic system according to the present disclosure;
[0065] FIG. 1a is a schematic view of an embodiment with a
controllable primary side flow actuator and/or a controllable
secondary side flow actuator 13 that are speed-controllable
pump(s);
[0066] FIG. 1b is a schematic view of an alternative embodiment
wherein the controllable primary side flow actuator and/or the
controllable secondary side flow actuator are fixed-speed pump(s)
in combination with controllable valve(s);
[0067] FIG. 2 is a schematic view of an example of another
embodiment of a hydronic system according to the present
disclosure;
[0068] FIG. 3 is a schematic view of an example of yet another
embodiment of a hydronic system according to the present
disclosure;
[0069] FIG. 4 is a schematic view of an example of yet another
embodiment of a hydronic system according to the present
disclosure;
[0070] FIG. 5 is a schematic view of an example of yet another
embodiment of a hydronic system according to the present
disclosure;
[0071] FIG. 6 is a schematic view of an example of yet another
embodiment of a hydronic system according to the present
disclosure;
[0072] FIG. 7 is a schematic view of an example of yet another
embodiment of a hydronic system according to the present
disclosure;
[0073] FIG. 8 is a schematic view of an example of yet another
embodiment of a hydronic system according to the present
disclosure;
[0074] FIG. 9 is a schematic view of an example of yet another
embodiment of a hydronic system according to the present
disclosure;
[0075] FIG. 10 is a schematic view of an example of an embodiment
of an intermediary transfer element hydronic system according to
the present disclosure;
[0076] FIG. 11 is a schematic view of an example of an embodiment
of a hydronic system according to the present disclosure; and
[0077] FIG. 12 is a schematic view of an example of the method for
controlling the flow in a hydronic system according to the present
disclosure.
DETAILED DESCRIPTION
[0078] FIG. 1 shows a hydronic system 1 having a primary side 3 and
a secondary side 5. The hydronic system 1 can be a heating or
cooling system. The pri mary side 3 comprises a source element 7,
which may for instance be a heater, chiller, a heat exchanger or a
common line coupling. The source element 7 provides thermal power
by heating up or chilling down a fluid circulating in the primary
side 3. The fluid may be water or a coolant with high thermal
capacity. The fluid is driven through the primary side 3 by a
controllable primary side flow actuator 9 for providing a primary
side flow q.sub.1. The secondary side 5 comprises a load element
11, which may for instance be a radiator or an air handling unit
(AHU). The load element 11 consumes thermal power provided by the
fluid circulating in the secondary side 5 and provides it to a
place or object in need for thermal power. The fluid is driven
through the secondary side 5 by a controllable secondary side flow
actuator 13 for providing a secondary side flow q.sub.2. The
secondary side 5 comprises a load valve 15, which may be a
motorized valve, a balancing valve, a check valve, a thermostat or
another valve to limit the flow in the secondary side 5. FIG. 1a
shows an embodiment wherein the controllable primary side flow
actuator 9 and/or the controllable secondary side flow actuator 13
are speed-controllable pump(s). FIG. 1b shows an alternative
embodiment wherein the controllable primary side flow actuator 9
and/or the controllable secondary side flow actuator 13 are
fixed-speed pump(s) in combination with controllable valve(s).
[0079] The hydronic system 1 further comprises an intermediary
transfer element 17 in form of a common line (or hydraulic
separator or tank) between the primary side 3 and the secondary
side 5. A first T-end 19 of the intermediary transfer element 17 is
connected to a first port 21 of the primary side 3, the first port
21 being in fluid connection with an output 23 of the source
element 7. A second T-end 25 of the intermediary transfer element
17 is connected to a second port 27 of the primary side 3, the
second port 27 being in fluid connection with an input 29 of the
source element 7. The first T-end 19 of the intermediary transfer
element 17 connects the first port 21 of the primary side 3 with a
third port 31 of the secondary side 5, the third port 31 being in
fluid connection with an input 33 of the load element 11. The
second T-end 25 of the intermediary transfer element 17 connects
the second port 21 of the primary side 3 with a fourth port 35 of
the secondary side 5, the fourth port 35 being in fluid connection
with an output 37 of the load element 11.
[0080] In principle, the intermediary transfer element 17 in form
of a common line allows for a fluid flow (downward in FIGS. 1, 4
and 5) from the first port 21 of the primary side 3 to the second
port 27 of the primary side 3. Such a "positive" primary side flow
downward along the common line may for instance be required when
the thermal power demand of the load element 11 is low and the load
valve 15 is closed. Likewise, the intermediary transfer element 17
also allows for a fluid flow (upward in FIGS. 1, 4 and 5) from the
fourth port 35 of the secondary side 5 to the third port 31 of the
secondary side 5. Such a "negative" secondary side flow upward
along the common line may for instance be required when the thermal
power supply by the primary side 3 is exceeded by a high thermal
power demand of the load element 11 with the load valve 15 being
fully opened. However, despite the principle possibility for a
positive and negative flow through the common line, a flow through
the common line is not desirable, because a negative flow
aggravates a low .DELTA.T syndrome and a positive flow does not
efficiently use the thermal power capacity of the source element
7.
[0081] Therefore, in order to minimize the flow in the common line,
the hydronic system 1 comprises a flow control module 39 for
controlling the primary side flow q.sub.1 and/or the secondary side
flow q.sub.2. The flow control module 39 may be integrated in the
controllable primary side flow actuator 9 and/or the controllable
secondary side flow actuator 13. Alternatively, or in addition, the
flow control module 39 may be integrated in a cloud-based computer
system and/or a building management system (BMS). The flow control
module 39 may control the primary/secondary side flow q.sub.1,2 by
means of controlling the speed of a speed-controllable
primary/secondary side pump (see FIG. 1a) and/or by controlling the
opening degree of a controllable primary/secondary side valve in
combination with a fixed-speed primary/secondary side pump (see
FIG. 1b).
[0082] The flow control module 39 may have a wired or wireless
first signal connection 41 with the controllable primary side flow
actuator 9 and/or a wired or wireless second signal connection 43
with the controllable secondary side flow actuator 13. If the
secondary side flow q.sub.2 is not controllable by the flow control
module 39, the second signal connection 43 is not needed (in FIGS.
1 to 6). Likewise, if the primary side flow q.sub.1 is not
controllable by the flow control module 39, the first signal
connection 41 is not needed (in FIGS. 1 to 6). For instance, either
the controllable primary side flow actuator 9 or the controllable
secondary side flow actuator 13 may comprise a fixed-speed pump
without a controllable primary/secondary side valve. However, in
the examples shown in FIGS. 1 to 6, both the primary side flow
q.sub.1 and the secondary side flow q.sub.2 are controllable by
means of the flow control module 39.
[0083] The hydronic system 1as shown in FIG. 1 further comprises a
group of four sensors 45a-d with a first temperature or pressure
sensor 45a being arranged and configured to determine the
temperature T.sub.1 or pressure p.sub.1 of the fluid flowing
through the first port 21, a second temperature or pressure sensor
45b being arranged and configured to determine the temperature
T.sub.2 or pressure p.sub.2 of the fluid flowing through the second
port 27, a third temperature or pressure sensor 45c being arranged
and configured to determine the temperature T.sub.3 or pressure
p.sub.3 of the fluid flowing through the third port 31, and a
fourth temperature or pressure sensor 45d being arranged and
configured to determine the temperature T.sub.4 or pressure p.sub.4
of the fluid flowing through the fourth port 35. Each of the
sensors 45a-d has a wired or wireless signal connection 47a-d with
the flow control module 39. The flow control module 39 receives the
respective measured temperatures or pressures via the signal
connections 47a-d. The sensors 45a-d may alternatively be signal
connected with the flow control module 39 via a data bus.
[0084] The flow control module 39 is configured to continuously or
regularly monitor the measured temperatures T.sub.1-4 or pressures
p.sub.1-4 in order to control the flow(s) q.sub.1, q.sub.2 in a
continuous or regularly closed-loop manner based on minimising a
signed deviation value .DELTA..DELTA.T or .DELTA..DELTA.P being
correlated with the thermal power transfer of the intermediary
transfer element 17. The signed deviation value .DELTA..DELTA.T or
.DELTA..DELTA.P may be determined by the flow control module 39 and
may be a difference between a first differential .DELTA.T.sub.1 or
.DELTA.p.sub.1 and a second differential .DELTA.T.sub.2 or
.DELTA.p.sub.2. In case of sensors 45a-d being temperature sensors,
the first differential may for instance be
.DELTA.T.sub.1=T.sub.1-T.sub.4 or .DELTA.T.sub.1=T.sub.1-T.sub.3 or
.DELTA.T.sub.1=T.sub.3-T.sub.4, and the second differential may for
instance be .DELTA.T.sub.2=T.sub.3-T.sub.2 or
.DELTA.T.sub.2=T.sub.2-T.sub.4 or .DELTA.T.sub.2=T.sub.1-T.sub.2,
respectively. Analogously, in case of a common line being the
intermediary transfer element 17 (see FIGS. 1, 4 and 5) and the
sensors 45a-d being pressure sensors, the first differential may
for instance be .DELTA.p.sub.1=p.sub.1-p.sub.4 or
.DELTA.p.sub.1=p.sub.1-p.sub.3 or .DELTA.p.sub.1=p.sub.3-p.sub.4,
and the second differential may for instance be
.DELTA.p.sub.2=p.sub.3-p.sub.2 or .DELTA.p.sub.2=p.sub.2-p.sub.4 or
.DELTA.p.sub.2=p.sub.1-p.sub.2, respectively. In case of a heat
exchanger being the intermediary transfer element 17 (see FIGS. 2,
3 and 6) and the sensors 45a-d being pressure sensors, the primary
side pressure is fully decoupled from the secondary side pressure,
wherein the first differential may for instance be
.DELTA.p.sub.1=p.sub.1-p.sub.2 and the second differential may for
instance be .DELTA.p.sub.2=p.sub.3-p.sub.4. The signed deviation
value may be .DELTA..DELTA.T=.DELTA.T.sub.2-.DELTA.T.sub.1 or
.DELTA..DELTA.p=.DELTA.p.sub.2-.DELTA.p.sub.1.
[0085] The current primary side flow q.sub.1 is maintained by the
flow control module 39 if the signed deviation value
.DELTA..DELTA.T or .DELTA..DELTA.P is between a negative reference
value and a positive reference value, preferably essentially zero.
The negative reference value and a positive reference value may
define a band around zero, within which a fluid flow q through the
common line is sufficiently low. In other words, the thermal power
transfer along the intermediary transfer element 17 (upward between
the fourth port 35 and the third port 31 or downward between the
first port 21 and the second port 27) is minimal, whereas the
thermal power transfer across the intermediary transfer element 17
(from the first port 21 to the third port 31 and from the fourth
port 35 to the second port 27) is maximal. This is a stable and
desirable operation of the hydronic system 1.
[0086] Once the signed deviation value .DELTA..DELTA.T or
.DELTA..DELTA.P falls below the negative reference value, however,
a negative flow q upward along the common line is indicated. If the
flow control module 39 is able to control the primary side flow
q.sub.1, the flow control module 39 immediately reacts to such a
feedback in a closed-loop manner by increasing the primary side
flow q.sub.1. As a consequence, the negative deviation value
.DELTA..DELTA.T or .DELTA..DELTA.P should rise above the negative
reference value, i.e. the negative flow q upward along the common
line should reduce or stop. A stable and desirable operation at a
higher primary side flow q.sub.1 may thus be established.
[0087] If the negative deviation value .DELTA..DELTA.T or
.DELTA..DELTA.P does not rise above the negative reference value,
the primary side flow q.sub.1 is increased until it cannot be
increased anymore, e. g. when a maximum primary side pump speed or
maximum primary side valve opening is reached, or until the primary
side flow q.sub.1 has reached a predetermined maximum threshold
q.sub.max. In this situation and in case the primary side flow
q.sub.1 is not controllable by the flow control module 39 in the
first place, the secondary side flow q.sub.2 is decreased. It
should be noted that such a decrease may seem counter-intuitive,
because the load element 11 demands more thermal power than it gets
through the fully opened load valve 15. Normally, an internal
automatic secondary side pump controller would react with an
increase of speed to an opening of the load valve 15 in order to
establish a target pressure and flow in the secondary side 5.
However, the flow control module 39 may overrule such an internal
automatic secondary side pump controller and may command a decrease
of the secondary side flow q.sub.2 in case of a negative common
line flow q in order to maximize the available thermal power
transfer across the intermediary transfer element 17. In this
situation, the supply of thermal power by the primary side 3 is
either at its maximum or uncontrollable by the flow control module
39. As long as the signed deviation value .DELTA..DELTA.T or
.DELTA..DELTA.P is above the negative reference value, the flow
control module 39 may allow an internal automatic secondary side
pump controller to increase the secondary side flow q.sub.2 in
order to establish a target pressure and flow in the secondary side
5 to meet the thermal power demand of the load element 11 indicated
by the opened load valve 15.
[0088] In case the load element 11 has a low demand for thermal
power and the load valve 15 is at least partly closed, for
instance, the situation may occur that the signed deviation value
.DELTA..DELTA.T or .DELTA..DELTA.P rises above the positive
reference value, which indicates a positive flow q downward along
the common line. If the flow control module 39 is able to control
the primary side flow q.sub.1, the flow control module 39
immediately reacts to such a feedback in a closed-loop manner by
decreasing the primary side flow q.sub.1. As a consequence, the
positive deviation value .DELTA..DELTA.T or .DELTA..DELTA.P should
fall below the positive reference value, i.e. the positive flow q
downward along the common line should reduce or stop. A stable and
desirable operation at a lower primary side flow q.sub.1 may thus
be established.
[0089] If the positive deviation value .DELTA..DELTA.T or
.DELTA..DELTA.P does not fall below the positive reference value,
the primary side flow q.sub.1 is decreased until it cannot be
decreased anymore, e.g. when a minimum primary side pump speed or
mini mum primary side valve opening is reached, or until the
primary side flow q.sub.1 has reached a predetermined minimum
threshold g.sub.min. Once a minimum primary side flow
q.sub.1=q.sub.min is reached, the primary side flow q.sub.1 is
maintained and a stable low demand operation is established with a
minimal acceptable positive flow q downward along the common
line.
[0090] FIG. 2 shows an embodiment with the intermediary transfer
element 17 being a counter-flow heat exchanger. The primary side 3
and the secondary side 5 are completely decoupled in terms of
pressure. There may even be different fluids running through the
primary side 3 and the secondary side 5, because there is no mixing
between the primary side 3 and the secondary side 5. The
controlling of the flow actuator(s) 9, 13 is identical to FIG. 1.
The flow control module 39 may not even be able to distinguish
whether the intermediary transfer element 17 is a common line or a
very efficient heat exchanger.
[0091] FIG. 3 shows an embodiment with the intermediary transfer
element 17 being a parallel-flow heat exchanger. The only
difference is the direction of the secondary side flow q.sub.2, so
the position of the third port 31 and the third sensor 45c is
swapped with the position of the fourth port 35 and the fourth
sensor 45d. The controlling of the flow actuator(s) 9, 13 is
identical to FIGS. 1 and 2.
[0092] FIG. 4 shows an embodiment with the intermediary transfer
element 17 again being a common line or a hydraulic separator or a
tank. However, instead of the group of four temperature or pressure
sensors 45a-d, just one bidirectional flow meter 49 is installed in
the common line for measuring the flow q along the common line. The
flow control module 39 is signal connected to the flow meter 49 via
a wired or wireless signal connection 51 for receiving the measured
common line flow. The common line flow q is then used as the signed
deviation value to be minimized. With the measured common line flow
q being the signed deviation value, the controlling of the flow(s)
q.sub.1, q.sub.2 is identical to FIGS. 1 to 3.
[0093] FIG. 5 shows an embodiment similar to FIG. 4, wherein the
common line flow q is not measured by a flow meter, but determined
from a pressure differential along the common line. Therefore, a
first pressure sensor 50a is located at the first T-end 19 of the
intermediary transfer element 17 between the first port 21 of the
primary side 3 and the third port 31 of the secondary side 5. The
flow control module 39 is signal connected to the first pressure
sensor 50a via a wired or wireless signal connection 52a for
receiving a first pressure value p.sub.1. A second pressure sensor
50b is located at the second T-end 25 of the intermediary transfer
element 17 between the second port 27 of the primary side 3 and the
fourth port 35 of the secondary side 5. The flow control module 39
is signal connected to the second pressure sensor 50b via a wired
or wireless signal connection 52b for receiving a second pressure
value p.sub.2. Once the pressure differential
.DELTA.p=p.sub.1-p.sub.2 is determined by the flow control module
39 and calibrated for zero flow q, it can be used as the signed
deviation value. With the pressure differential Ap being the signed
deviation value, the controlling of the flow(s) q.sub.1, q.sub.2 is
identical to FIGS. 1 to 4.
[0094] FIG. 6 shows an embodiment with the intermediary transfer
element 17 again being a counter-flow heat exchanger. However,
instead of the group of four temperature or pressure sensors 45a-d,
a first flow meter 53a is installed in the primary side 3 for
measuring the primary side flow q.sub.1 and a second flow meter 53b
is installed in the secondary side 5 for measuring the secondary
side flow q.sub.2. The flow control module 39 is signal connected
to the flow meters 53a,b via wired or wireless signal connections
55a,b, respectively, for receiving the measured flows q.sub.1,
q.sub.2. The flow control module 39 determines a flow differential
.DELTA.q=q.sub.1-q.sub.2 and uses the flow differential Aq as the
signed deviation value to be minimized. With the flow differential
.DELTA.q being the signed deviation value, the controlling of the
flow(s) q.sub.1, q.sub.2 is identical to FIGS. 1 to 5.
[0095] In FIGS. 7 to 9, the control module 39, the signal
connections 45a-d, 51, 52a,b, 55a,b and the sensors 45a-d, 49,
50a,b, 53a,b are not shown and the intermediary transfer element 17
is only shown as a common line for simplicity. It should be
understood that any of the embodiments shown in FIGS. 1 to 6 are
applicable to any hydronic system topology shown in FIGS. 7 to 9.
The topology of the hydronic system 1 shown in FIG. 7 shows a
plurality of two load elements 11a,b in parallel in the secondary
side 5. Here, just one controllable secondary side flow actuator 13
drives the secondary side flow through both load elements 11. At
least one valve 15a,b is associated with each load element 11a,b
for restricting the secondary side flow through the respective load
element 11a,b.
[0096] The system topology shown in FIG. 8 comprises a plurality of
two parallel controllable secondary side flow actuators 13a,b, each
of which is associated with a load element 11a,b. There are several
options for controlling the respective secondary side flows through
the load elements 11a,b. A first option would be controlling the
primary side flow q.sub.1 only as described above for FIGS. 1 to 6.
If the primary side flow q.sub.1 is uncontrollable by the flow
control module 39 or if it has reached a maximum, the secondary
side flows through the load elements 11a,b may be decreased to
avoid a negative upward common line flow. The adaptation of the
secondary side flows through the respective load elements 11a,b may
be performed in different ways. One option would be a simultaneous
decrease by the same absolute amount or the same relative amount
with respect to the current secondary side flow. Another option
would be to reduce only a highest of the secondary side flows, for
instance only the fastest running half of speed-controllable
secondary side pumps.
[0097] The system topology shown in FIG. 9 comprises a plurality of
two parallel controllable primary side flow actuators 9a,b, each of
which is associated with a source element 7a,b. There are again
several options for controlling the primary side flows. A first
option would be controlling the secondary side flow q.sub.2 only as
described above for FIGS. 1 to 6. If the secondary side flow
q.sub.2 is uncontrollable by the flow control module 39 or if it
has reached a minimum or if the signed deviation value is above the
positive reference value indicating a positive downward common line
flow, the primary side flows may be decreased to reduce the
positive downward common line flow to a minimum. In case of a
signed deviation value being below the negative reference value
indicating a negative upward common line flow, the primary side
flows may be increased to avoid or reduce the negative upward
common line flow. The adaptation of the respective primary side
flows through the source elements 7a,b may be performed in
different ways. One option would be a simultaneous adaptation by
the same absolute amount or the same relative amount with respect
to the current primary side flow. Another option would be to
operate as many of the controllable primary side flow actuators
9a,b with a minimum in terms of energy consumption of the
associated source element 7a,b, and to adapt only as few as
possible primary side flows provided by the controllable primary
side flow actuators 9a,b.
[0098] FIG. 10 explains schematically the relations between the
temperatures at the four ports 21, 27, 31, 35 to the intermediary
transfer element 17. The intermediary transfer element 17 may be a
common line, a hydraulic separator, a tank or a counter-flow heat
exchanger. The hydronic system 1 is here a heating system. The
temperature T.sub.1 at the first port 21 is denoted as T.sub.h,l in
the sense of hot feed input into the intermediary transfer element
17. The temperature T.sub.2 at the second port 27 is denoted as
T.sub.c,o in the sense of cold return output of the intermediary
transfer element 17. The temperature T.sub.3 at the third port 31
is denoted as T.sub.h,o, as hot feed output of the intermediary
transfer element 17. The temperature T.sub.4 at the fourth port 35
is denoted as T.sub.c,i in the sense of cold return input into the
intermediary transfer element 17. The following relations
apply:
.DELTA.T.sub.h=T.sub.h,i-T.sub.h,o
.DELTA.T.sub.c=T.sub.c,o-T.sub.c,i
.DELTA.T.sub.i=T.sub.h,i-T.sub.c,i
.DELTA.T.sub.o=T.sub.h,o-T.sub.c,o
.DELTA.T.sub.a=T.sub.h,i-T.sub.c,o
.DELTA.T.sub.b=T.sub.h,o-T.sub.c,i
.DELTA.T.sub.a-T.sub.i+.DELTA.T.sub.b-.DELTA.T.sub.0=0
.DELTA.T.sub.a=T.sub.h-.DELTA.T.sub.b+.DELTA.T.sub.c=0
.DELTA..DELTA.T=.DELTA.T.sub.o-.DELTA.T.sub.s=.DELTA.T.sub.c-.DELTA.T.su-
b.h=.DELTA.T.sub.a-.DELTA.T.sub.b,
wherein .DELTA..DELTA.T=.DELTA.T.sub.2-.DELTA.T.sub.1 may be the
signed deviation value to be minimized. It shows that the first
temperature differential .DELTA.T.sub.1 may be .DELTA.T.sub.i,
.DELTA.T.sub.h or .DELTA.T.sub.b and the second temperature
differential may be .DELTA.T.sub.o, .DELTA.T.sub.c or
.DELTA.T.sub.a.
[0099] In FIG. 11, the measurement by the temperature sensors 45a-d
(not shown in FIG. 11) is calibrated in specific flow situations to
achieve a more accurate and more reliable flow control. The source
element 7 is here a chiller or heat sink that takes away heat -P
from the primary side 3, whereas the load element 11 consumes
cooling power by adding heat P to the secondary side 5.
Accordingly, the temperature T.sub.1 at the first port 21 is
denoted as .DELTA.T.sub.c,l in the sense of cool feed input into
the intermediary transfer element 17. In FIG. 11, the temperature
T.sub.1 at the first port 21 is denoted as .DELTA.T.sub.c,l in the
sense of cool feed input into the intermediary transfer element 17.
The temperature T.sub.2 at the second port 27 is denoted as
T.sub.h,o in the sense of hot return output of the intermediary
transfer element 17. The temperature T.sub.3 at the third port 31
is denoted as T.sub.c,o, as cold feed output of the intermediary
transfer element 17. The temperature T.sub.4 at the fourth port 35
is denoted as T.sub.h,i in the sense of hot return input into the
intermediary transfer element 17. In hydronic systems as shown in
FIGS. 1 to 11, it is energetically efficient to minimize a heat
transfer flow along the intermediary transfer device 17 in either
direction upward or downward. However, the desirable situation of
no upward or downward heat transfer flow along the intermediary
transfer device 17 has the effect, in particular in case of a
cooling system, that quite low temperature differentials
.DELTA.T.sub.c=T.sub.c,i-T.sub.c,o and
.DELTA.T.sub.h=T.sub.h,i-T.sub.h,o prevail.
[0100] Low temperature differentials .DELTA.T.sub.c and
.DELTA.T.sub.h pose a challenge for the controlling process,
because inaccurate temperature measurements may account for a large
fraction of the measured temperature differentials. So, the
controlling action may be mostly triggered by measurement errors
rather than actual temperature differentials. If the control tries
to minimize the upward or downward heat transfer flow along the
intermediary transfer device 17 based on inaccurately measured
temperature differentials, the flow is in fact not minimized.
[0101] It is therefore preferable to accurately measure the
temperature differentials. This can, of course, be achieved by
using very accurate and pre-calibrated sensors. However, this
approach is expensive, dependent on sensor quality, and does not
guarantee good performance over time as the quality of the sensors
may degrade over time. As a solution to this, the measurements by
the temperature sensors 45a-d are here repetitively calibrated
"online" during their use in specific situations.
[0102] The main idea is to either force or identify a first or
second situation where there is definitely more flow in one side
than in the other side. For instance, in the first situation, the
primary side 3 may have a higher flow q.sub.1 than the secondary
side 5, or vice versa in the second situation. If the primary flow
q.sub.1 is higher than the secondary flow q.sub.2 in the first
situation, the flow coming from the primary side 3 splits at the
first port 21 into the secondary side 5 and the intermediary
transfer element 17. This means that the flow entering from the
primary side 3 into the secondary side 5 at the third port 31 has
not been mixed with water of another temperature. Therefore, it
must have the same temperature as the water leaving the primary
side 3 at the first port 21 assuming the heat loss to the ambient
environment is negligible. In this first situation, any measured
temperature differential .DELTA.T.sub.c can be assumed to be fully
due to sensor inaccuracy and stored as systematic error in form of
an offset.
[0103] Such an offset can then simply be subtracted from all
subsequent measurements of .DELTA.T.sub.c, which means that the
measurements by the temperature sensors 45a and 45c are calibrated
for the purpose of the flow control. In the second situation, when
the secondary side 5 has more flow than the primary side 3, i.e.
q.sub.2>q.sub.1, a similar situation arises in view of the
temperature differential .DELTA.T.sub.h between the fourth port 35
and the second port 27. It should be zero, but the temperature
sensors 45b and 45d may indicate a temperature differential
.DELTA.T.sub.h based on sensor accuracy. In this second situation,
any measured temperature differential .DELTA.T.sub.h can be assumed
to be fully due to sensor inaccuracy and stored as systematic error
in form of an offset. Such an offset can then simply be subtracted
from all subsequent measurements of .DELTA.T.sub.h, which means
that the measurements by the temperature sensors 45b and 45d are
calibrated for the purpose of the flow control.
[0104] These first or second situations, in which
q.sub.2>q.sub.1 or q.sub.2<q.sub.1, may arise naturally
during a normal operation of cooling cycles during the day in most
hydronic systems. Therefore, there may not be a need to force the
hydronic system into such situations, but merely to identify them.
These situations can be identified by comparing the temperature
differentials .DELTA.T.sub.c and .DELTA.T.sub.h with each other. If
one temperature differential is much higher than the other, then
the lower temperature differential can be assumed to be actually
zero, even if it shows a non-zero value due to sensor inaccuracy.
The measurement by the corresponding sensor pair can then be
calibrated. For instance, if a certain pre-defined threshold on the
signed deviation value
.DELTA..DELTA.T=|.DELTA.T.sub.c--.DELTA.T.sub.h| is exceeded, a
calibration situation is indicated.
[0105] In some hydronic systems, however, the flow imbalance is
almost always to the same side, and hence one of the temperature
differentials is always relatively high due to mixing from the
intermediary element 17. Then, either the first or the second
situation does not arise naturally in which the measurements by the
corresponding temperature sensors could be calibrated. If a
measurement of a pair of temperature sensors has not had the chance
to be calibrated for a certain time, then it is preferable to force
the hydronic system into that one of the first and second
situation, which allows the needed calibration. This can be
achieved by controlling the primary side flow actuator 9 and/or the
secondary side flow actuator 13. For instance, the speed of pumps
as primary/secondary side flow actuators 9, 11 may be adjusted to
imbalance the primary/secondary flows for calibration purposes.
[0106] FIG. 12 shows a schematic figure of an example of the method
for controlling the flow in the hydronic system 1, wherein both the
controllable primary side flow actuator 9 and the controllable
secondary side flow actuator 13 are controllable by the flow
control module 39. The hydronic system 1 may start up by ramping up
(step 1101) the primary side flow q.sub.1 and the secondary side
flow q.sub.2 to initial flows by means of a variable speed drive
(VSD) or a motorized valve. Once the hydronic system 1 is started,
a signed deviation value .DELTA..DELTA.v is continuously or
regularly determined and monitored by the flow control module 39 to
check (step 1103) whether it is approximately zero, i.e. in a small
band between a negative reference value and a positive reference
value. As previously described, the signed deviation value
.DELTA..DELTA.v may be a temperature differential .DELTA..DELTA.T,
a pressure differential .DELTA..DELTA.p, a flow differential
.DELTA.q, a pressure differential .DELTA.p or a measured common
line flow q.
[0107] If the signed deviation value .DELTA..DELTA.v is
approximately zero, the flow control module 39 maintains (step
1105) the primary side flow q.sub.1 and the secondary side flow
q.sub.2. It should be noted that the primary side flow q.sub.1
and/or the secondary side flow q.sub.2 may change due to other
control schemes. For instance, an opening of a load valve 15 in the
secondary side 5 indicating a higher thermal power demand of the
load element(s) 11 in the secondary side 5 may trigger an automatic
internal secondary side pump controller to increase the pump speed.
However, the continuously or regularly determined and monitored
signed deviation value .DELTA..DELTA.v may be affected by this,
whereby the flow control module 39 may be caused to adapt the
primary side flow q.sub.1 and/or the secondary side flow q.sub.2
accordingly.
[0108] If the signed deviation value .DELTA..DELTA.v is not
approximately zero (step 1103), it is checked (step 1107) whether
it is negative, i.e. below a negative reference value. If this is
the case, it is checked (step 1109) if the primary side flow
q.sub.1 is below a predetermined maximal threshold q.sub.max. The
maximal threshold q.sub.max may, for instance, be determined by the
maximum speed of a speed-controlled primary side pump, a maximal
opening of a primary side valve or a maximal flow requirement of
the source element 7. The primary side flow q.sub.1 may be measured
by a flow meter 53a or be deduced from the current speed or the
current power consumption of a primary side pump. If a further
increase of the primary side flow q.sub.1 is possible and allowed,
the primary side flow q.sub.1 is increased (step 1111). The effect
of this adaptation on the signed deviation value .DELTA..DELTA.v is
again continuously or regularly determined and monitored by the
flow control module 39 (step 1103). If a further increase of the
primary side flow q.sub.1 is not possible or not allowed, the
secondary side flow q.sub.2 is decreased (step 1113). Again, the
effect of this adaptation on the signed deviation value
.DELTA..DELTA.v is continuously or regularly determined and
monitored by the flow control module 39 (step 1103).
[0109] If the signed deviation value .DELTA..DELTA.v is not
approximately zero (step 1103) and positive, i.e. above a positive
reference value (step 1107), it is checked (step 1115) if the
primary side flow q.sub.1 is above a predetermined minimal
threshold g.sub.min. The minimal threshold g.sub.min may, for
instance, be determined by the minimum speed of a primary side
pump, a minimal opening of a primary side valve or a minimal flow
requirement of the source element 7. If a further decrease of the
primary side flow q.sub.1 is possible and allowed, the primary side
flow q.sub.1 is decreased (step 1117). The effect of this
adaptation on the signed deviation value .DELTA..DELTA.v is again
continuously or regularly determined and monitored by the flow
control module 39 (step 1103).
[0110] Where, in the foregoing description, integers or elements
are mentioned which have known, obvious or foreseeable equivalents,
then such equivalents are herein incorporated as if individually
set forth. Reference should be made to the claims for determining
the true scope of the present disclosure, which should be construed
so as to encompass any such equivalents. It will also be
appreciated by the reader that integers or features of the
disclosure that are described as optional, preferable,
advantageous, convenient or the like are optional and do not limit
the scope of the independent claims.
[0111] The above embodiments are to be understood as illustrative
examples of the disclosure. It is to be understood that any feature
described in relation to any one embodiment may be used alone, or
in combination with other features described, and may also be used
in combination with one or more features of any other of the
embodiments, or any combination of any other of the embodiments.
While at least one exemplary embodiment has been shown and
described, it should be understood that other modifications,
substitutions and alternatives are apparent to one of ordinary
skill in the art and may be changed without departing from the
scope of the subject matter described herein, and this application
is intended to cover any adaptations or variations of the specific
embodiments discussed herein.
[0112] In addition, "comprising" does not exclude other elements or
steps, and "a" or "one" does not exclude a plural number.
Furthermore, characteristics or steps which have been described
with reference to one of the above exemplary embodiments may also
be used in combination with other characteristics or steps of other
exemplary embodiments described above. Method steps may be applied
in any order or in parallel or may constitute a part or a more
detailed version of another method step. It should be understood
that there should be embodied within the scope of the patent
warranted hereon all such modifications as reasonably and properly
come within the scope of the contribution to the art. Such
modifications, substitutions and alternatives can be made without
departing from the spirit and scope of the disclosure, which should
be determined from the appended claims and their legal
equivalents.
[0113] While specific embodiments of the invention have been shown
and described in detail to illustrate the application of the
principles of the invention, it will be understood that the
invention may be embodied otherwise without departing from such
principles.
* * * * *