The present invention concerns an air handling unit for cooling down an indoor
airflow to be blown into a room of a building, and a method for controlling such an air
handling unit.
5 Data centers are equipped with air conditioning equipment, which functions on a
permanent basis to cool Information Technology (IT) equipment installed in IT spaces. To
maximize the coefficient of performance (COP), free cooling is preferably used. Free
cooling efficiency is generally larger than mechanical cooling (with a refrigeration
apparatus). The COP of free cooling is about 15, while the COP of mechanical cooling is
10 only about 4 to 5.
Direct introduction of outside air to the IT space is not considered due to the potential
pollution of the outside air. Free cooling must be indirect. Indirect free cooling can be
performed with different types of heat transfer devices, for example: air/air heat exchanger,
enthalpy wheel, “Kyoto” heat exchanger, or hydronic loop.
15 For using outside air to indirectly cool an air stream, which is recirculated in the IT
space, outside air temperature needs to be colder than the fresh air to be blown in the IT
space. So that heat can be transferred between two air streams (indoor air and outside air) a
temperature gradient between the two streams is required. For instance, for direct air/air
heat exchange, minimum temperature gradient may be about 4-5°C. For an indoor
20 temperature request of 22°C, “free cooling effect” can therefore be applied if ambient air
temperature is lower than 18°C. If ambient temperature is above 18°C, free cooling must
be replaced by a different cooling technique (for example mechanical cooling using a
refrigeration apparatus).
For hydronic loop application, using air to water exchangers, this minimum
25 temperature gradient may be as high as 8 to 10°C (in traditional applications). For instance,
4°C temperature gradient may be needed to transfer the heat from the IT space to the
hydraulic loop. Water entering to “indoor” heat exchangers therefore needs to be at 18°C
or lower to obtain 22°C air required for IT space.
To produce 18°C water, 14°C ambient air is needed (if required temperature gradient
30 is 4°C). Ambient air temperature therefore needs to be 14°C or lower to produce 18°C
water.
There are generally much more operating hours with ambient air temperature below
18°C than below 14°C. Free cooling with hydronic loops must therefore be often replaced
3
by mechanical cooling. There is therefore a need for optimizing the efficiency of the air
handling units depending on the ambient air temperature.
The aim of the invention is to provide a new air handling unit which maximizes use
of free cooling to improve its efficiency no matter what the outside temperature conditions
5 are.
To this end, the invention concerns an air handling unit for cooling down an indoor
airflow to be blown into a room of a building, comprising at least one fan circulating
the indoor airflow inside the air handling unit, wherein the air handling unit
comprises a first and a second cooling subsystems comprising each:
10 - a refrigeration apparatus comprising an evaporator and a condenser,
- a first water circuit connected to the condenser and comprising at least one outside
heat exchanger exposed to outside air, in which the water releases heat to the outside
air under action of a fan,
- a second water circuit connected to the evaporator and comprising at least one
15 indoor heat exchanger exposed to the indoor airflow, in which the water draws heat
from the indoor air flow,
- water connections linking the first water circuit and the second water circuit,
- water connection means for selectively connecting :
- the first water circuit to the condenser and the second water circuit to the
20 evaporator and disabling the water connection, in a mechanical cooling mode where
the refrigeration apparatus is operating or
- the first water circuit to the second water circuit and disabling water circulation in
the evaporator and the condenser, in a free cooling mode where the refrigeration
apparatus is stopped;
25 wherein the at least one indoor air heat exchanger of the first cooling subsystem and
the at least one indoor air heat exchanger of the second cooling subsystem are placed
in series with respect to the indoor air flow,
and wherein the air handling unit comprises control means for operating the
mechanical cooling mode or the free cooling mode of the first cooling subsystem and
30 the mechanical cooling mode or the free cooling mode of the second cooling
subsystem depending on a temperature of the outside air.
Thanks to the invention, all free cooling, mixed mechanical and free cooling or all
mechanical cooling configurations can be performed to better adapt to the ambient air
4
temperature, with the particular advantage to have the possibility of using free cooling the
perform a primary air cooling using free cooling in the most frequent temperatures interval,
allowing a high annualized COP.
According to further aspects of the invention that are advantageous but not
5 compulsory, such an air handling unit may incorporate one or several of the following
features:
- the control means comprise a control unit controlling the water connection means
and the refrigeration apparatus of each off the first and second cooling subsystems,
and an outside air temperature detector.
10 - the control unit is configured to operate the air handling unit in at least three
operating configurations:
- if the outside air temperature is below a first threshold, both the first and
second cooling subsystems function in free cooling mode,
- if the outside air temperature is above the first threshold and below a second
15 threshold, the first cooling subsystem functions in free cooling mode while the
second cooling subsystem functions in mechanical cooling mode;
- if the outside air temperature is above the second threshold, both the first
cooling subsystem and the second cooling subsystem function in mechanical
cooling mode.
20 - the at least one outside heat exchanger of the first and second cooling subsystems
are provided in a modular outside air component comprising at least one fan forcing
outside air circulation through said outside heat exchangers,
- the refrigeration apparatuses of the first and second cooling subsystems are
provided in a modular chiller component,
25 - the at least one indoor heat exchanger of the first cooling subsystem is
provided in a modular inlet component comprising an air inlet,
- the at least one indoor heat exchanger of the second cooling subsystem is
provided in a modular outlet component comprising an air outlet,
- the at least one fan circulating the indoor airflow inside the air handling unit
30 is provided in a modular fan component.
- the modular chiller component is installed in a bottom rear side of the air handling
unit, and the modular outside air component is installed in a top rear side of the air
handling unit above the modular chiller component.
5
- the modular fan component is installed in a bottom front side of the air handling
unit, and the modular inlet component and the modular outlet component are installed
in a top front side of the air handling unit above the modular fan component, with the
air inlet and the air outlet facing a front side of the air handling unit.
5 - the modular fan component is installed in a bottom front side of the air handling
unit, the modular inlet component is installed in a bottom front side in front of the
modular fan component and the modular outlet component is installed in a top front
side of the air handling unit above the inlet component, with the air inlet and the air
outlet facing a front side of the air handling unit.
10 - the at least one indoor heat exchangers and the at least one outside heat exchangers
of the first and second cooling subsystems are formed by V-shaped exchangers.
The invention also concerns a method for controlling an air handling unit for cooling
down an indoor airflow to be blown into a room of a building, said air handling unit
comprising at least one fan circulating the indoor airflow inside the air handling unit,
15 and a first and a second cooling subsystems comprising each:
- a refrigeration apparatus comprising an evaporator and a condenser,
- a first water circuit connected to the condenser and comprising at least one outside
heat exchanger exposed to outside air, in which the water releases heat to the outside
air under action of a fan,
20 - a second water circuit connected to the evaporator and comprising at least one
indoor heat exchanger exposed to the indoor airflow, in which the water draws heat
from the indoor air flow,
- water connections linking the first water circuit and the second water circuit,
- water connection means for selectively connecting :
25 - the first water circuit to the condenser and the second water circuit to the
evaporator and disabling the water connection, in a mechanical cooling mode where
the refrigeration apparatus is operating or
- the first water circuit to the second water circuit and disabling water circulation in
the evaporator and the condenser, in a free cooling mode where the refrigeration
30 apparatus is stopped;
the at least one indoor air heat exchanger of the first cooling subsystem and the at
least one indoor air heat exchanger of the second cooling subsystem being placed in
series with respect to the indoor air flow,
6
wherein the method comprises steps consisting of:
- if an outside air temperature is below a first threshold, operating both the first and
second cooling subsystems in free cooling mode,
- if the outside air temperature is above the first threshold and below a second
5 threshold, operating the first cooling subsystem in free cooling mode while operating
the second cooling subsystem in mechanical cooling mode;
- if the outside air temperature is above the second threshold, operating both the first
cooling subsystem and the second cooling subsystem in mechanical cooling mode.
Exemplary embodiments according to the invention and including further
10 advantageous features of the invention are explained below, referring to the attached
drawings, in which:
- figure 1 is a synoptic drawing of an air handling unit according to a first
embodiment of the invention, running in all free cooling configuration;
- figure 2 is a synoptic drawing of the air handling unit of figure 1, running in a
15 mixed free cooling and mechanical cooling configuration;
- figure 3 is a synoptic drawing of the air handling unit of figure 1, running in an all
mechanical cooling configuration;
- figure 4 is a perspective view of an air handling unit according to a second
embodiment of the invention;
20 - figure 5 is a perspective view of an air handling unit according to a third
embodiment of the invention.
Figures 1 to 3 represent an air handling unit 1 for cooling down an indoor airflow A1
to be blown into a room of a building, for example an IT space in a datacenter. The air
handling unit 1 comprises at least one fan 3 circulating the indoor airflow A1 inside the air
25 handling unit 1.
The air handling unit 1 comprises a first cooling subsystem 5 and a second cooling
subsystem 15. Each of the cooling subsystems 5 and 15 have the same features, and only
the first cooling subsystem 5 will be described in detail, the second cooling subsystem 15
having the same components with the same references comprising the added digit “1”.
30 The first cooling subsystem 5 comprises a refrigeration apparatus 50 comprising an
evaporator 500, a compressor 502, a condenser 504, and an expansion valve 506. In
operation, the refrigeration apparatus 50 operates a closed-loop refrigerant circulation
shown by arrows R (figure 3).
7
The first cooling subsystem 5 also comprises a first water circuit 52, or “hydronic
loop”, which is connected to the condenser 504 and comprises at least one outside heat
exchanger 520. The first subsystem 5 comprises a fan 54, which forces an outside air flow
A5 through the outside heat exchanger 520. The outside heat exchanger 520 may not be
5 installed physically outside the air handling unit 1, but is exposed to outside air.
The water circuit 52 comprises a pump 522, which runs water circulation in the water
circuit 52 as shown by arrows W52. The heat exchanger 520 being exposed to outside air,
the water releases heat to the outside air under action of the fan 54 and its temperature is
reduced. During circulation of water in the condenser 504, the refrigerant releases heat to
10 the water, whose temperature increases.
The first cooling subsystem 5 also comprises a second water circuit 56 or “hydronic
loop” connected to the evaporator 500 and which comprising at least one indoor heat
exchanger 560 exposed to the indoor airflow A1. In the indoor heat exchanger 560, the
water draws heat from the indoor air flow A1, thus increasing its temperature and cooling
15 down the indoor air flow A1. In the evaporator 500, the water releases heat to the
refrigerant, thus lowering its temperature and increasing the temperature of the refrigerant,
which evaporates. The second water circuit 56 comprises a pump 562, which runs water
circulation in the second water circuit 56, as shown by arrows W56.
The first cooling subsystem 5 also comprises water connections linking the first
20 water circuit 52 and the second water circuit 56. These water connections are formed a
bypass line 58 which originates between the pump 522 and the condenser 504 and
terminates between the evaporator 500 and the indoor heat exchanger 560. The water
connections also comprise a bypass line 60 that originates from between the pump 562 and
the evaporator 500, and terminates between the condenser 504 and the outside heat
25 exchanger 520. The lines 58 and 60 are named “bypass” due to the fact that the condenser
504 and evaporator 500 are bypassed by the water circuit formed by the coupling of the
first and second water circuits 52 and 56 when water is circulated in the bypass lines 58
and 60.
The first cooling subsystem 5 further comprises water connection means for
30 selectively connecting:
- the first water circuit 52 to the condenser 504 and the second water circuit 56 to
the evaporator 500 and disabling the bypass lines 58 and 60, in a mechanical cooling mode
or “chiller” mode, where the refrigeration apparatus 50 is operating, or
8
- the first water circuit 52 to the second water circuit 56 and disabling water
circulation in the evaporator 500 and the condenser 504, in a free cooling mode, where the
refrigeration apparatus 50 is stopped.
The connection means comprise a first valve 62 provided in the first water circuit 52
5 between the condenser 504 and the bypass line 60. In a first position (figure 1), the valve
62 prevents water circulation between the condenser 504 and the water circuit 52. In a
second position (figure 3), the valve 62 allows water circulation from the condenser 504 to
the water circuit 52.
The water connection means comprise a second valve 64 provided in the second
10 water circuit 56 between the evaporator 500 and the bypass line 60. In a first position
(figure 1), the valve 64 prevents water circulation between the pump 562 and the
evaporator 500, thus directing the water of the second water circuit 56 towards the bypass
line 60. In a second position (figure 3), the valve 64 allows water circulation from the
pump 562 to the evaporator 500, thus preventing water from flowing towards the bypass
15 line 60.
When the valves 62 and 64 are in their first position, the first and second water
circuits 52 and 56 are joined in a single “hydronic loop” and the condenser 504 and the
evaporator 500 are bypassed (arrows W5). When the valves 62 and 64 are in their second
position, the first and second water circuits 52 and 56 each function in independent closed
20 loops.
The indoor air heat exchanger 560 of the first cooling subsystem 5 and the indoor air
heat exchanger 1560 of the second cooling subsystem 15 are placed in series with respect
to the indoor air flow A1. In other words, the indoor air flow A1 passes successively first
through the indoor air heat exchanger 560 then into the indoor air heat exchanger 1560.
25 The fan 3 may be placed downstream the indoor air heat exchanger 560 and upstream the
indoor air heat exchanger 1560.
The indoor air flow A1 is therefore subject to two successive cooling phases, which
firstly lower the air temperature from a high temperature T1 to an intermediary
temperature T2, then secondly from the intermediary temperature T2 to a low temperature
30 T3. The high temperature T1 is the temperature at which the indoor air flow A1 is
extracted from the IT space (for example 35°C). The low temperature T3 is the
temperature at which the indoor air flow A1 is blow into the IT space (for example 22°C).
9
The low temperature T3 is a request value calculated to allow proper functioning of the IT
equipment in the IT space.
The air handling unit 1 also comprises control means for operating the mechanical
cooling mode or the free cooling mode of the first cooling subsystem 5 and the mechanical
5 cooling mode or the free cooling mode of the second cooling subsystem 15 depending on a
temperature of the outside air.
Each of the first and second cooling subsystems 5 and 15 can therefore be run in a
different mode to optimize cooling depending on the outside temperature conditions.
The use of hydronic loops allows very easily to convert each subsystem from free
10 cooling mode to mechanical cooling mode. The outdoor heat exchangers 520 and 1520 can
be used for both purposes: in free cooling mode as a way to reject the heat from the
hydronic loops 52 and 152 respectively coupled with the hydronic loops 56 and 156, in
mechanical cooling mode as a way of rejecting the heat from the condensers 504 and 1504.
The control means may comprise a control unit 20 controlling the valves 62, 64, 162,
15 164 with non-shown signals and the refrigeration apparatuses 50 and 150 of each off the
first and second cooling subsystems 5 and 15, and an outside air temperature detector 22
sending outside temperature measurements to the control unit 20. To control the
refrigeration apparatuses 50 and 150, the control unit 20 may command the start or stop of
the compressors 502 and 1502 with non-shown signals.
20 The control unit 20 is configured to operate the air handling unit 1 in at least three
operating configurations:
- If the outside air temperature is below a first threshold Tinf, both the first and
second cooling subsystems 5 and 15 function in free cooling mode (figure 1),
- If the outside air temperature is above the first threshold Tinf and below a second
25 threshold Tmax, the first cooling subsystem 5 functions in free cooling mode while the
second cooling subsystem 15 functions in mechanical cooling mode (figure 2);
- If the outside air temperature is above the second threshold Tmax, both the first
cooling subsystem 5 and the second cooling subsystem 15 function in mechanical cooling
mode.
30 Such configuration allow maximizing the use of free cooling. Rather than cooling
directly the indoor air flow A1 with one cooling device from the high temperature T1 to
the low temperature T3, which would require a 14°C ambient air temperature to operate in
free cooling mode, the indoor air flow A1 is to cooled from the high temperature T1 to the
10
intermediary temperature T2 by the first cooling subsystem 5 and from the intermediary
temperature T2 to the low temperature T3 by the second cooling subsystem 15. For
example, the intermediary temperature T2 can be set to 27°C. The cooling subsystem that
has the target of 27°C will be able to operate in free cooling mode with an ambient air
5 temperature of 19°C or below. This means that for ambient air temperature below the frist
threshold Tinf, for example 14°C, the air handling unit 1 can function 100 % in free
cooling. For an ambient air temperature ranging from Tinf to the second threshold Tmax,
for example 19°C, the first cooling subsystem 5 uses free cooling mode. The air handling
unit 1 benefits from the efficiency of free cooling in half of its capacity. For ambient air
10 temperatures above the second threshold Tmax, the air handling unit 1 will operate 100%
in mechanical cooling, however such a situation is marginal in view of the quantity of time
in a year during which such a situation occurs. For example, for the annual temperature
conditions of Paris, the mean temperature is mainly between 14°C and 19°C. The concept
of the invention gives very high annualized performance (a COP superior to 12 for Paris
15 type ambient conditions). Overall efficiency will still be much better that operating with
mechanical cooling.
More precisely, in figure 1, both compressors 502 and 1502 are stopped to disable the
refrigeration apparatuses 50 and 150. The valves 62, 64, 162, 164 are commanded in their
first position, each cooling subsystem 5 and 15 forming a water loop through the bypass
20 lines 58, 60, 158, 160 (arrows W5 and W15). The indoor air flow A1 is cooled down to the
intermediary temperature T2 by the indoor heat exchanger 560 then to the low temperature
T3 by the indoor heat exchanger 1560. Water circulation in the first and second cooling
subsystems 5 and 15 induces release of heat acquired by the water through the indoor heat
exchangers 560 and 1560 to the ambient air via the outdoor heat exchangers 520 and 1520.
25 In figure 2, the compressor 502 is stopped, the valves 62 and 64 are in their first
position. The compressor 1502 is started prompting activation of the refrigeration cycle
(arrows R) of the refrigeration apparatus 150. The valves 162 and 164 are in their second
position, directing the water of the water loops 152 and 156 through the condenser 1504
and the evaporator 1500. The indoor air flow A1 is cooled to the intermediary temperature
30 T2 by free cooling, then to the low temperature T3 by mechanical cooling.
On figure 3, each of the refrigeration apparatuses 50 and 150 are running (arrows R),
and the valves 62, 64, 162, 164 are in their second position. The indoor air flow A1 is
cooled by two successive mechanical coolings.
11
Other embodiments of the invention are represented on figures 4 and 5. In these
embodiments, elements similar to the first embodiment have the same references and work
in the same way. Only the differences are detailed here after.
A second embodiment is represented on figure 4. In this embodiment, the outside
5 heat exchangers 520 and 1520 are provided in a modular outside air component 24 which
comprises the fans 54 and 154 forcing outside air circulation A5 and A15 through the
outside heat exchangers 520 and 1520. The term “modular component” means that the
component comprises a frame structure 240 in which the outside heat exchangers 520 and
1520 and the fans 54 and 154 are fixed, so that the component 24 can be transported as a
10 whole and installed in the air handling unit 1 with ease, and with readily available water
and control connections with the other parts of the air handling unit 1. Each of the first and
second cooling subsystems 5 and 15 may comprise several outside fans 54 and 154 and
several outside heat exchangers 520 and 1520.
The refrigeration apparatuses 50 and 150 are provided in a modular chiller
15 component 26, which comprises a frame structure 260, and in which are fixed and
connected the various elements of the refrigeration apparatuses 50 and 150.
In the embodiment of figure 4, the indoor heat exchanger 560 of the first cooling
subsystem 5 is provided in a modular inlet component 28 comprising an air inlet 280.
The indoor heat exchanger 1560 of the second cooling subsystem 15 is provided in a
20 modular outlet component 30 comprising an air outlet 30.
The fan 3 that runs circulation of the indoor airflow A1 inside the air handling unit 1
is provided in a modular fan component 32. The modular fan component 32 may comprise
more than one fan 3.
The modular components 24, 26, 28, 30 and 32 are all interconnected with non25 shown water lines and electric control lines configured to operate the water circuits and
operation configuration described in relation with figures 1 to 3.
The air handling unit 1 is therefore modular, in other words built from several blocks
of components having different functions and that can be combined in various ways
depending on the cooling needs, resulting in ease of installation and possibility of use of
30 standard components. Application of standard components reduces the cost of the modular
components and provides adaptability to various scales of cooling applications (depending
for example on the size of the IT space).
12
The outside heat exchangers 520 and 1520, and the indoor heat exchangers 560 and
1560 are preferably V-shaped heat exchangers, formed by two water-air heat exchangers
forming an angle. Application of V-shaped heat exchangers for both indoor and outside
heat exchangers make the air handling unit 1 very compact compared to traditional flat
5 water-air heat exchanger architectures. Thanks to this configuration, the thermal exchange
surface area of the heat exchangers is very large, thus reducing the required temperature
gradient between air and water. The V-shaped heat exchangers can therefore operate in
free cooling mode with relatively high ambient air temperature.
As represented on figure 4, the modular chiller component 26 may be installed in a
10 bottom rear side of the air handling unit 1, while the modular component 24 may be
installed in a top rear side of the air handling unit 1 above the modular chiller component
26. The modular fan component 32 may be installed in a bottom front side of the air
handling unit 1, and the modular inlet component 28 and the modular outlet component 30
be installed in a top front side of the air handling unit 1 above the modular fan component
15 32, with the air inlet 280 and the air outlet 300 facing a front side of the air handling unit 1.
A third embodiment is represented on figure 5. This embodiment differs from the
embodiment of figure 4 in that the modular fan component 32 is installed in a bottom front
side of the air handling unit 1, the modular inlet component 28 is installed in the bottom
front side in front of the modular fan component 32, and the modular outlet component 30
20 is installed in a top front side of the air handling unit 1 above the inlet component 28. The
air inlet 280 and the air outlet 300 face a front side of the air handling unit 1.
According to non-shown variants, the indoor heat exchangers 560 and 1560 may be
formed by V-shaped exchangers arranged in the inlet and outlet components along a
vertical or horizontal direction, the “V” formed by the exchangers being either vertical or
25 horizontal.
According to a non-shown variant, the air handling unit 1 may comprises two
modular fan components 32 are installed in a front upper side, the inlet component 28
being installed in a front bottom side, and the outlet component 30 being installed in the
front upper side between the modular fan components 32 disposed laterally.
30 According to another non-shown variant, the modular fan components 32 may be
installed in a front bottom side, the inlet component 28 being installed in a front upper side
and the outlet component 30 being installed in the front bottom side between the modular
13
fan components 32 disposed laterally, in a configuration inverted relative to the
configuration described in the previous paragraph.
According to further non-shown variants of the invention:
- Each of the first and second cooling subsystems 5 and 15 may comprise several
5 indoor heat exchangers 560 and 1560 and several outside heat exchangers 520
and 1520;
- The high, intermediate and low temperatures T1, T2 and T3 may be different
depending on the needs for cooling of the IT spaces.
The technical features of the embodiments and variants described here above may be
10 combined to form new embodiments within the scope of the claims.

We Claim:
1.- An air handling unit (1) for cooling down an indoor airflow (A1) to be blown into
a room of a building, comprising at least one fan (3) circulating the indoor airflow
5 (A1) inside the air handling unit (1), wherein the air handling unit (1) comprises a
first and a second cooling subsystems (5, 15) comprising each:
- a refrigeration apparatus (50, 150) comprising an evaporator (500, 1500) and a
condenser (504, 1504),
- a first water circuit (52, 152) connected to the condenser (504, 1504) and
10 comprising at least one outside heat exchanger (520, 1520) exposed to outside air
(A5, A15), in which the water releases heat to the outside air (A5, A15) under action
of a fan (54, 154),
- a second water circuit (56, 156) connected to the evaporator (500, 1500) and
comprising at least one indoor heat exchanger (560, 1560) exposed to the indoor
15 airflow (A1), in which the water draws heat from the indoor air flow (A1),
- water connections (58, 60, 158, 160) linking the first water circuit (52, 152) and the
second water circuit (56, 156),
- water connection means (62, 64, 162, 164) for selectively connecting :
- the first water circuit (52, 152) to the condenser (504, 1504) and the second water
20 circuit (56, 156) to the evaporator (500, 1500) and disabling the water connection
(58, 60, 158, 160), in a mechanical cooling mode where the refrigeration apparatus
(50, 150) is operating or
- the first water circuit (52, 152) to the second water circuit (56, 156) and disabling
water circulation in the evaporator (500, 1500) and the condenser (504, 1504), in a
25 free cooling mode where the refrigeration apparatus (50, 150) is stopped;
wherein the at least one indoor air heat exchanger (560) of the first cooling
subsystem (5) and the at least one indoor air heat exchanger (1560) of the second
cooling subsystem (15) are placed in series with respect to the indoor air flow (A1),
and wherein the air handling unit (1) comprises control means for operating the
30 mechanical cooling mode or the free cooling mode of the first cooling subsystem (5)
and the mechanical cooling mode or the free cooling mode of the second cooling
subsystem (15) depending on a temperature of the outside air.
15
2. An air handling unit according to claim 1, wherein the control means comprise a
control unit (20) controlling the water connection means (62, 64, 162, 164) and the
refrigeration apparatus (50, 150) of each off the first and second cooling subsystems
(5, 15), and an outside air temperature detector (22).
5
3. An air handling unit according to claim 2, wherein the control unit (20) is
configured to operate the air handling unit (1) in at least three operating
configurations:
- if the outside air temperature is below a first threshold (Tinf), both the first and
10 second cooling subsystems (5, 15) function in free cooling mode,
- if the outside air temperature is above the first threshold (Tinf) and below a second
threshold (Tmax), the first cooling subsystem (5) functions in free cooling mode
while the second cooling subsystem (15) functions in mechanical cooling mode;
- if the outside air temperature is above the second threshold (Tmax), both the first
15 cooling subsystem (5) and the second cooling subsystem (15) function in mechanical
cooling mode.
4. An air handling unit according to any preceding claim, wherein:
- the at least one outside heat exchanger (520, 1520) of the first and second cooling
20 subsystems (5, 15) are provided in a modular outside air component (24) comprising
at least one fan (54, 154) forcing outside air circulation through said outside heat
exchangers,
- the refrigeration apparatuses (50, 150) of the first and second cooling subsystems
(5, 15) are provided in a modular chiller component (26),
25 - the at least one indoor heat exchanger (560) of the first cooling subsystem (5) is
provided in a modular inlet component (28) comprising an air inlet (280),
- the at least one indoor heat exchanger (1560) of the second cooling subsystem (15)
is provided in a modular outlet component (30) comprising an air outlet (300),
- the at least one fan (3) circulating the indoor airflow (A1) inside the air handling
30 unit (1) is provided in a modular fan component (32).
5. An air handling unit according to claim 4, wherein the modular chiller component
(26) is installed in a bottom rear side of the air handling unit (1), and the modular
16
outside air component (24) is installed in a top rear side of the air handling unit (1)
above the modular chiller component (26).
6. An air handling unit according to claim 5, wherein the modular fan component
5 (32) is installed in a bottom front side of the air handling unit (1), and the modular
inlet component (28) and the modular outlet component (30) are installed in a top
front side of the air handling unit (1) above the modular fan component (32), with the
air inlet (280) and the air outlet (300) facing a front side of the air handling unit (1).
10 7. An air handling unit according to claim 5, wherein the modular fan component
(32) is installed in a bottom front side of the air handling unit (1), the modular inlet
component (28) is installed in a bottom front side in front of the modular fan
component (32) and the modular outlet component (30) is installed in a top front side
of the air handling unit (1) above the inlet component (28), with the air inlet (280)
15 and the air outlet (300) facing a front side of the air handling unit (1).
8. An air handling unit according to any preceding claim, wherein the at least one
indoor heat exchangers (560, 1560) and the at least one outside heat exchangers (520,
1520) of the first and second cooling subsystems (5, 15) are formed by V-shaped
20 exchangers.
9. Method for controlling an air handling unit (1) for cooling down an indoor airflow
(A1) to be blown into a room of a building, said air handling unit comprising at least
one fan (3) circulating the indoor airflow (A1) inside the air handling unit (1), and a
25 first and a second cooling subsystems (5, 15) comprising each:
- a refrigeration apparatus (50, 150) comprising an evaporator (500, 1500) and a
condenser (504, 1504),
- a first water circuit (52, 152) connected to the condenser (504, 1504) and
comprising at least one outside heat exchanger (520, 1520) exposed to outside air
30 (A5, A15), in which the water releases heat to the outside air under action of a fan
(54, 154),
17
- a second water circuit (56, 156) connected to the evaporator (500, 1500) and
comprising at least one indoor heat exchanger (560, 1560) exposed to the indoor
airflow (A1), in which the water draws heat from the indoor air flow (A1),
- water connections (58, 60, 158, 160) linking the first water circuit (52, 152) and the
5 second water circuit (56, 156),
- water connection means (62, 64, 162, 164) for selectively connecting :
- the first water circuit (52, 152) to the condenser (504, 1504) and the second water
circuit (56, 156) to the evaporator (500, 1500) and disabling the water connection
(58, 60, 158, 160), in a mechanical cooling mode where the refrigeration apparatus
10 (50, 150) is operating or
- the first water circuit (52, 152) to the second water circuit (56, 156) and disabling
water circulation in the evaporator (500, 1500) and the condenser (504, 1504), in a
free cooling mode where the refrigeration apparatus (50, 150) is stopped;
the at least one indoor air heat exchanger (560) of the first cooling subsystem (5) and
15 the at least one indoor air heat exchanger (1560) of the second cooling subsystem
(15) being placed in series with respect to the indoor air flow (A1),
wherein the method comprises steps consisting of:
- if an outside air temperature is below a first threshold (Tinf), operating both the first
and second cooling subsystems (5, 15) in free cooling mode,
20 - if the outside air temperature is above the first threshold (Tinf) and below a second
threshold (Tmax), operating the first cooling subsystem (5) in free cooling mode
while operating the second cooling subsystem (15) in mechanical cooling mode;
- if the outside air temperature is above the second threshold (Tmax), operating both
the first cooling subsystem (5) and the second cooling subsystem in mechanical
25 cooling mode.