Apparatus and method for controlling a supply air flow in an air treatment system

Abstract

An air treatment device (1) comprising a controller (15), a chilled beam (2) having outlets (7) and covers (9), wherein each cover (7) is associated with a cover (9) and wherein each cover (9) is movable by an actuator unit (12), wherein the controller (15) is arranged to determine a K-factor corresponding to a control signal, determine a current airflow (Vac) based on the k-factor and wherein the air treatment device (1) is characterized in that the controller (15) is further configured to determine the K-factor based on the K-factor coefficient when the indication of a current position (Uac) of the actuator unit (12) falls above a lower limit (L-Limit) and determine the K-factor based on a leakage k-factor (K0) when the indication of a current position (Uac) of the actuator unit (12) falls below the lower limit (L-Limit).

Description

[0001] APPARATUS AND METHOD FOR CONTROLLING A SUPPLY AIR FLOW IN AN

[0002] AIR TREATMENT SYSTEM

[0003] TECHNICAL FIELD

[0004] The teachings herein relate to an apparatus and method for controlling the supply air flow to a room and conditioning the room air, by means of an air treatment device - more speci fically a so-called chilled beam .

[0005] BACKGROUND

[0006] The Swedish patent published as SE 537 916 C2 discloses (with reference to figure 1A, showing original figure 3 of SE 537 916 C2 ) a method for and an air treatment device 1 for regulating supply air flow Vac . The air treatment device 1 comprises a chilled beam ( or cooling baf fle ) 2 and the air treatment device 1 will sometimes be referred to interchangeably as the chilled beam 2 , where technically the chilled beam is the actual baf fle while the air treatment device 1 comprises additional components , that could be understood to be part of the chilled beam by a technician, depending on the design and implementation of the air treatment device 1 . The air treatment device 1 is connected to an air treatment system (not shown in figure 1A, but referenced 4 in figure IB ) .

[0007] The chilled beam 2 includes a pressure box 5 with inlet 6 and several outlets 7 . The outlets 7 have a changeable configuration where a cover part 9 is movable in relation to the outlets 7 . The pressure box 5 includes a pressure sensor 13 in a pressure measurement outlet ( also referred to as 13 ) , which registers static pressure Ps in a pressure line through the pressure box 5 . Furthermore , the air treatment device 1 includes an actuator unit 12 for regulating the supply air flow Vac .

[0008] The air treatment device ( 1 ) includes at least one room sensor 14 , arranged to register the conditions of a room A and communicate this to the air treatment device ( 1 ) . The air treatment device 1 is characteri zed by the fact that it registers the static pressure Ps in the pressure box 5 and the position of the actuator unit 12 and on the basis of these , the actual supply air flow Vac in the chilled beam 2 is calculated . The actuator unit 12 is arranged to change the configuration of the outlets 7 in order to change the supply air flow Vac by linear movement of the cover part 9 i f necessary . In particular, the cover part 9 of SE 537 916 C2 is proposed to be of a rectangular shape in order to provide a linear change as the cover part is moved linearly .

[0009] As air treatment devices in general , and also the air treatment device 1 of SE 537 916 C2 , are arranged to operate for extensive periods of time , they inevitably have high power consumption, which both af fects the environment as well as individuals ' economy .

[0010] There is thus a constant need for improving such air treatment devices .

[0011] And, as will be discussed, the inventors have reali zed - through inventive reasoning and insight - manners in which the air treatment device 1 of SE 537 916 C2 can be further improved and such improvements will be discussed in detail further down .

[0012] SUMMARY

[0013] The inventors have inventively reali zed that even i f the outlets 7 and the covers 9 are arranged with a rectangular shape , and even i f the covers 9 are moved in a linear movement , this may not provide a linear change in airflow . For example , i f a rectangular cover is set to rotate ( around a center axis or a side axis ) in a linear fashion between a fully open and a fully closed position ( covering the outlet 7 ) , the change in coverage may not be linear, but rather be proportional to a sine function . Furthermore , rectangular shapes are not always practical , nor are rectangular covers . For example , an outlet may provide a more laminar flow of air i f arranged in a non-rectangular shape . Same applies to the covers which may also be arranged to operate or act as guides for the air, for example to provide a cooling factor in a speci fic direction .

[0014] The inventors have thus inventively reali zed several situations where it would be beneficial to allow for nonlinear control of an air treatment device , such as when the covers and / or the outlets are not of a shape that allows for a linear change in cover by a linear movement of the cover relative the outlets , and also when a linear movement of the cover does not provide a linear change in coverage .

[0015] The advantages of the proposed solutions may seem to be small but taken over time they accumulate to be quite signi ficant . The teachings herein provide for a solution . The solution is provided through an air treatment device ( 1 ) as per the appended claims, wherein the air treatment device (1) comprising a controller (15) , a chilled beam (2) having outlets (7) and covers (9) , wherein each outlet (7) is associated with a cover (9) and wherein the cover (9) is controlled by an actuator unit (12) , wherein the controller (15) is arranged to receive an indication of a current position (Uac) of the actuator unit (12) , receive a pressure measurement of a pressure (Pa) in the chilled beam (2) from a pressure sensor (13) , receive a desired setting for the airflow (Vset) , and in response thereto determine a K-factor corresponding to the control signal, wherein the K-factor is indicative of the flow through the outlet (7) at a given position of the cover (9) and for a pressure of the chilled beam (2) , and wherein the k-factor is determined linearly based on a K-factor coefficient (K100) and the indication of the current position of the actuator (Uac) , determine a current airflow (Vac) based on the k-factor and determine a control signal (Uset) for the actuator unit (12) based on the current airflow (Vac) and the desired airflow setting (Vset) , wherein the air treatment device (1) is characterized in that the controller (15) is further configured to determine the K- factor coefficient (K100) based on a series of approximations of operating characteristics of the chilled beam (2) , wherein the series of approximations gives a K-factor coefficient (K100-U1, K100-U2, K100) for a range of the current position of the actuator (Uac) , wherein a first K-factor coefficient (K100-U1, K100) for a first range (Ul) is different from a second K-factor coefficient (K100-U2, K100) for a second range (U2) .

[0016] A solution is also provided through a method as per the appended claims wherein the method is for use in an air treatment device (1) comprising a chilled beam (2) having outlets (7) and covers (9) , wherein each outlet (7) is associated with a cover (9) and wherein the cover (9) is controlled by an actuator unit (12) , wherein the method comprises receiving an indication of a current position (Uac) of the actuator unit (12) , receiving a pressure measurement of a pressure (Pa) in the chilled beam (2) from a pressure sensor (13) , receiving a desired setting for the airflow (Vset) , and in response thereto determining a K-factor corresponding to the control signal, wherein the K-factor is indicative of the flow through the outlet (7) at a given position of the cover (9) and for a pressure of the chilled beam (2) , and wherein the k-factor is determined linearly based on a K-factor coefficient (K100) and the indication of the current position of the actuator (Uac) , determining a current airflow (Vac) based on the k-factor and determining a control signal (Uset) for the actuator unit (12) based on the current airflow (Vac) and the desired airflow setting (Vset) , wherein the method is characterized in that the method further comprises determining the K-factor coefficient (K100, K100-U1, K100-U2) based on a series of approximations of operating characteristics of the chilled beam (2) , wherein the series of approximations gives a K-factor coefficient (K100-U1, K100-U2, K100) for a range of the current position of the actuator (Uac) , and wherein a first K-factor coefficient (K100-U1, K100) for a first range (Ul) is different from a second K- factor coefficient (K100-U2, K100) for a second range (U2) .

[0017] The inventors have also inventively realized that even when fully closed the covers may not fully cover the outlets and there may be a leakage of air. Furthermore, such a leakage of air may also be present in other parts of the chilled beam. The chilled beam is composed of many mechanical parts that have been assembled together. Even if the installer strives to make everything sealed and airtight, this is a very difficult task to complete to perfection, and air leakage may be present despite good intentions and efforts.

[0018] To reiterate, as air treatment devices are run for long periods of time, even a small saving in power consumption leads to a great benefit over time as the saving accumulates. The inventors have therefore inventively realized an improved control of a chilled beam that accounts for leakage.

[0019] The solution is provided through an air treatment device (1) as per the appended claims, the air treatment device (1) comprising a controller (15) , a chilled beam (2) having outlets (7) and covers (9) , wherein each cover (7) is associated with a cover (9) and wherein each cover (9) is movable by an actuator unit (12) , wherein the controller (15) is arranged to receive an indication of a current position (Uac) of the actuator unit (12) , receive a pressure measurement of a pressure (Pa) in the chilled beam (2) from a pressure sensor (13) , receive a desired setting for the airflow (Vset) , and in response thereto determine a K-factor corresponding to the control signal, wherein the K-factor is indicative of the flow through the outlet (7) at a given position of the cover (9) and for a pressure of the chilled beam (2) , and wherein the k-factor is determined linearly based on a K-factor coefficient (K100) and the indication of the current position of the actuator (Uac) , determine a current airflow (Vac) based on the k-factor and determine a control signal (Uset) for the actuator unit (12) based on the current airflow (Vac) and the desired airflow setting (Vset) , wherein the air treatment device (1) is characterized in that the controller (15) is further configured to determine the K- factor based on the K-factor coefficient when the indication of a current position (Uac) of the actuator unit (12) falls above a lower limit (L-Limit) and determine the K-factor based on a leakage k-factor (KO) when the indication of a current position (Uac) of the actuator unit (12) falls below the lower limit (L-Limit) .

[0020] The solution is also or alternatively provided through a method as per the appended claims, the method being for use in an air treatment device (1) comprising a chilled beam (2) having outlets (7) and covers (9) , wherein each outlet (7) is associated with a cover (9) and wherein the cover (9) is controlled by an actuator unit (12) , wherein the method comprises receiving an indication of a current position (Uac) of the actuator unit (12) , receiving a pressure measurement of a pressure (Pa) in the chilled beam (2) from a pressure sensor (13) , receiving a desired setting for the airflow (Vset) , and in response thereto determining a K-factor corresponding to the control signal, wherein the K-factor is indicative of the flow through the outlet (7) at a given position of the cover (9) and for a pressure of the chilled beam (2) , and wherein the k- factor is determined linearly based on a K-factor coefficient (K100) and the indication of the current position of the actuator (Uac) , determining a current airflow (Vac) based on the k-factor and determining a control signal (Uset) for the actuator unit (12) based on the current airflow (Vac) and the desired airflow setting (Vset) , wherein the method is characterized in that the method further comprises determining the K-factor coefficient (K100) based on a series of approximations of operating characteristics of the chilled beam (2) when the indication of a current position (Uac) of the actuator unit (12) falls above a lower limit (L-Limit) and determining the K-factor based on a leakage k-factor (KO) when the indication of a current position (Uac) of the actuator unit (12) falls below the lower limit (L-Limit) , wherein the series of approximations gives a K-factor coefficient (K100- Ul, K100-U2) for a range of the current position of the actuator (Uac) , and wherein a first K-factor coefficient (K100-U1) for a first range (Ul) is different from a second K- factor coefficient (K100-U2) for a second range (U2) .

[0021] A combined solution is provided through an air treatment device as per the appended claims, wherein the air treatment device (1) comprising a controller (15) , a chilled beam (2) having outlets (7) and covers (9) , wherein each outlet (7) is associated with a cover (9) and wherein the cover (9) is controlled by an actuator unit (12) , wherein the controller (15) is arranged to receive an indication of a current position (Uac) of the actuator unit (12) , receive a pressure measurement of a pressure (Pa) in the chilled beam (2) from a pressure sensor (13) , receive a desired setting for the airflow (Vset) , and in response thereto determine a K-factor corresponding to the control signal, wherein the K-factor is indicative of the flow through the outlet (7) at a given position of the cover (9) and for a pressure of the chilled beam (2) , and wherein the k-factor is determined linearly based on a K-factor coefficient (K100) and the indication of the current position of the actuator (Uac) , determine a current airflow (Vac) based on the k-factor and determine a control signal (Uset) for the actuator unit (12) based on the current airflow (Vac) and the desired airflow setting (Vset) , wherein the air treatment device (1) is characterized in that the controller (15) is further configured to determine the K- factor coefficient (K100) based on a series of approximations of operating characteristics of the chilled beam (2) , wherein the series of approximations gives a K-factor coefficient (K100-U1, K100-U2, K100) for a range of the current position of the actuator (Uac) , wherein a first K-factor coefficient (K100-U1, K100) for a first range (Ul) is different from a second K-factor coefficient (K100-U2, K100) for a second range (U2) , and wherein the controller (15) is further configured to determine the K-factor coefficient (K100) based on the series of approximations when the indication of a current position (Uac) of the actuator unit (12) falls above a lower limit (L- Limit) and to determine the K-factor based on a leakage k- factor (KO) when the indication of a current position (Uac) of the actuator unit (12) falls below the lower limit (L-Limit) .

[0022] Further embodiments and benefits of the present teachings will be apparent from the following description.

[0023] BRIEF DESCRIPTION OF THE FIGURES The solution will be disclosed with simultaneous reference to Figure 1A showing an air treatment device, Figure IB showing a simplified sketch of the principle of an air treatment system comprising an air treatment unit, supply and exhaust air ducts and the air treatment device connected to the supply air duct and which air treatment device supplies a room with supply air,

[0024] Figure 10 showing a simplified sketch of one side of a chilled beam of an air treatment device according to some embodiments herein, Figure 2 showing a schematic view of a control algorithm of some embodiments of the teachings herein,

[0025] Figure 3 showing a schematic plot of measurements of some embodiments of the teachings herein,

[0026] Figure 4 showing a schematic view of a control algorithm of some embodiments of the teachings herein,

[0027] Figure 5 showing a flow chart for a general method for some embodiments of the teachings herein,

[0028] Figure 6 showing a schematic plot of measurements of some embodiments of the teachings herein,

[0029] Figure 7 showing a schematic plot of measurements of some embodiments of the teachings herein,

[0030] Figure 8 showing a schematic view of a control algorithm of some embodiments of the teachings herein,

[0031] Figure 9 showing a flow chart for a general method for some embodiments of the teachings herein,

[0032] Figure 10 showing a schematic view of a control algorithm of some embodiments of the teachings herein, and

[0033] Figure 11 showing a flow chart for a general method for some embodiments of the teachings herein .

[0034] DETAILED DESCRIPTION

[0035] The teachings herein will be disclosed with simultaneous reference to figures 1A to 11 .

[0036] Figure IB shows an air treatment system 4 as per original figure 1 of the Swedish patent published as SE 537 916 C2 for use with an air treatment device 1 as shown in in figure 1A, and Figure 1C shows a sideview of a cross section of an air treatment system 4 as per original figure 2b of the Swedish patent published as SE 537 916 C2 . The air treatment system 4 comprises a conventional air handling unit 21 of a VAV system . The air treatment unit 21 is connected to a supply air duct 3 and an exhaust air duct 20 and it is symbolically shown that there are usually a number of branch ducts 24 connected to the system . Furthermore , an air treatment device 1 is connected to one end of the supply air duct 3 and this air treatment device 1 provides a room A with supply air, which is symbolically shown in Figure IB . In room A, a room sensor 14 and a presence sensor 17 are arranged for recording the current state of the room in terms of presence or non-presence , room temperature and / or carbon dioxide content . Depending on how the system is intended to be controlled, the room sensor 14 may be in the form of a temperature sensor 18 and / or a carbon dioxide sensor 19 . There are many alternatives available for such a system, and in various embodiments the air treatment system 4 comprises presence sensors 17 , temperature sensors 18 and carbon dioxide 19 .

[0037] The air treatment device 1 comprises a chilled beam 2 and a linear actuator unit 12 , which is arranged on the chilled beam 2 . As mentioned above , the air treatment device 1 will sometimes be referred to interchangeably as the chilled beam 2 . The chilled beam 2 is connected to the supply air duct 3 and the supply air enters the pressure box 5 of the chilled beam 2 through an inlet 6 , preferably at one end of the pressure box 5 . The outlet 7 is normally provided as punched holes in one or more of the wall portions 26 of the pressure box 5 .

[0038] In the pressure box 5 , a static pressure is built up depending on the air flow and the total open area of the outlets 7 . In contrast to the prior art , the outlets 7 can have any form and be arranged at regular or irregular intervals along basically the entire length of the pressure box 5 .

[0039] For controlling the airflow through an outlet 7 , a cover portion 9 is arranged in a coordinated position with the outlets 7 . In some embodiments there is one cover per outlet . In some embodiments there is a cover for one or more rows of outlets 7 ( for example for one side of the pressure box ) . By moving the cover portion 9 back and forth, the coverage of the outlets can be controlled . The air treatment device 1 includes an actuator unit 12 for moving the cover portion 9 back and forth and thereby regulating the supply air flow Vac . The actuator unit 12 may be provided with a through shaft 23 which is slidably arranged . By the actuator unit 12 displacing the shaft 23 along its longitudinal direction, a linear movement is achieved, which movement is transmitted to the cover parts 9 via an attachment 27 between the shaft 23 and the cover parts 9 . However, other arrangements are also possible .

[0040] The actuator unit 12 is arranged to register the physical position of the shaft 23 , which position in turn corresponds to a k- factor, the k- factor corresponds to the open area of the outlets 7 and the maximum k factor thus corresponds to the maximum open area of the outlets 7 .

[0041] As is known, the K- factor is a flow coef ficient that relates di f ferential pressure AP to airflow rate Q :

[0042] Q = K-SQUARE_ROOT ( AP ) where :

[0043] Q = airflow ( CFM or L / s ) (= Vac in the above ) , • AP = pressure differential (e.g., inin. w.c. or Pa) ,

[0044] • K = device-specific flow coefficient based on geometry

[0045] The pressure box 5 also includes at least one pressure sensor

[0046] 13, for recording the static pressure in the pressure box 5.

[0047] When the supply air flows out from the pressure box 5 it arrives at a mixing chamber 8. The supply air flow, now referred to as Vac, produces, through the induction action, a circulating air flow L2, which is room air drawn through the induction through a heat exchanger 10, arranged in the chilled beam 2.

[0048] As mentioned above, the actuator unit 12 is arranged to register the physical position of the shaft 23. And a controller (such as a processor configured to execute software and / or a PID controller) 15 converts the actual physical position of the shaft 23 to the current k-factor and calculates the actual air flow in the chilled beam 2 using the current static pressure in the pressure box 5.

[0049] The controller 15 may be placed in the room A or in connection with the actuator unit 12. In some embodiments, there is one controller placed in the room A and one controller in connection with the actuator unit 12. All these possibilities will be referred to as the controller 15.

[0050] The pressure in the room A is measured by a pressure sensor 13 connected to the controller 15. The pressure may be measured in the room itself through pressure sensor 17 or in inside the chilled beam through pressure sensor 13 - as in figure 1C, and the controller compares the received pressure measurement from the room and compares it to a set or desired level - the desired level being indicated by a received setting and determines whether and how much the outlets 7 should be opened or closed (by displacing the shaft 23 and thereby moving the covers 9 ) . The determination of how much to open is also or alternatively based on the pressure in the pressure box 5 , as received from the pressure sensor 13 . In the following the (main) pressure measurement will be received from the pressure sensor 13 .

[0051] Figure 2 shows a schematic view of a control algorithm for controlling the actuator unit 12 , where a pressure measurement P ( of the chilled beam pressure Pa ; P=Pa ) is received from the pressure sensor 13 .

[0052] The controller 15 also receives a current setting or position of the actuator shaft 23 , the actuator shaft position Uac, from the actuator unit 12 , the actuator unit 12 also being able to read a current position of the actuator shaft 23 as is known in the prior art . The position of the actuator shaft may be given by the control signal Uac to the actuator unit 12 , as this indicates how far the actuator shaft has been moved .

[0053] In some embodiments , an initial setting or position is received, and as a new setting / position is determined to be set , the new setting / position may be used as the received setting / position . The controller 15 can also set a current setting or position of the actuator shaft 23 , the actuator shaft position Uac, by sending a control signal to the actuator unit 12 . In some embodiments Uac indicates a value between totally open and totally closed ( for example 0- 1 or 0- 100 (%) ) . Based on the actuator shaft position Uac and a given K-factor coefficient (K100) , a current K value is determined. The K-factor coefficient (K100) is specific to the chilled beam and depends on its construction and design and may be determined or measured when constructed. As discussed above, the K-factor coefficient for the chilled beam - being the K100 factor for the whole operating range of the chilled beam - is given by the maximum open area of the cover. As would be known, this may mean no cover or cover at an open position giving the maximum open area. The K factor indicates a relationship between the airflow through the covers and the pressure in the pressure box. The K-factor coefficient for a range (K100-U1, K100-U2) , may thus also be the maximum K100 factor coefficient for that range in some embodiments.

[0054] In some embodiments, in order to accommodate for a leakage in the chilled beam, a leakage correction factor, qcorr, may be added to the determination of the K-factor. The leakage correction factor can be measured during the design or production phase (possibly for a prototype or for one (or some) sample from the production line. In some embodiments the leakage correction factor is added to the actuator shaft position where Uac is seen as Uac + qcorr. In some embodiments the leakage correction factor is added to the determined current K value where K= K100*Uac + qcorr (or K= K100*Uac + qcorr*K100) .

[0055] Based on the K factor and the received pressure measurement P, an actual or current airflow Vac (=Q) is determined as a function of the K factor (or implicitly the K-factor coefficient if including the determinations above and below) , the pressure and the setting of the motor Uac. In some embodiments the function is Vac = K-A / P = K100-Uac-A / p, where A / P indicates the square root of P.

[0056] Based on a minimum airflow Vmin, a maximum airflow Vmaximum and an airflow when the actuator is inactive VO (the airflows being for the chilled beam) as well as a (currently) set value for the airflow Vset, which is received from a room controller 15a (for example an input console) , the actual control of the actuator unit 12 is achieved through an actuator control signal Uset, which may simply be a voltage level, that is pushed or fed to the actuator unit 12.

[0057] The determinations are made by the controller 15, and the room controller may be part of the controller 15 or communicably connected to the controller 15. In figure 2, it is seen as part of the controller 15.

[0058] In the Swedish patent published as SE 537 916 C2 there is a strict requirement for the shaft 23, covers 9 and outlets 7 to be configured such that a linear change of the flow through the outlet is achieved when regulating Uset linearly.

[0059] However, it would be beneficial if the outlets could also be of any form, regular (rectangular) or irregular (round or oval) . It would also be beneficial if the covers could be of any form, regular (rectangular) or irregular (round or oval) . It would also be beneficial if the shaft 23 for moving the covers would not necessarily have to be linear, but could for example provide a rotating movement of a (round) cover for a (round) outlet. The cover can be of a shape corresponding to the outlet. The cover can also be of a shape different from the outlet. For example, a round (or oval) outlet can have a rectangular ( or square ) cover, or vice versa . Covering for example a round outlet with a rectangular cover would not produce a linear change in flow i f the movement of the cover was linear, as a given movement of the cover would result in a di f ferent si ze of an area being covered depending on the current position .

[0060] Due to manufacturing variances , and / or due to wear and tear, the actuator may not provide a linear movement of the cover ( s ) . Also , possibly due to manufacturing variances , the cover ( s ) and / or the outlet ( s ) may be of an unintended shape .

[0061] As will be discussed in detail below and as is discussed briefly above , the inventors have reali zed a simple and elegant solution for handling any non-linear characteristics in the design or the operation of a chilled beam . Such nonlinear characteristics may be caused by a non-linear shape of an outlet , a non-linear shape of a cover for an outlet , a nonlinear shape of a movement of a cover relative an outlet , manufacturing or operating irregularities in an actuator ( for example trans forming an expected linear behavior to a nonlinear behavior ) .

[0062] A simple and elegant solution that the inventors have reali zed through inventive reasoning and are proposing is based on operating the chilled beam based on a series of approximations of the actual operating characteristics of the chilled beam, where the possibly non-linear characteristics ( as indicated by for example the K- factor ) is approximated by linear sections . The chilled beam will therefore be controlled linearly within each section providing a predictable control even when the characteristics ( shapes and / or movements ) of the chilled beam are non-linear. This also enables individual control of the cover ( s ) .

[0063] A series of measurements (or determinations) is required of the characteristics of the chilled beam, which shows the airflow for different actuator settings.

[0064] The measurements may be made in the design phase and may then be partially based on determinations (calculations) . The measurements may also or alternatively be made in the development phase and may then be partially based on determinations (calculations) . The measurements may also or alternatively be made in the production +phase or in the manufacturing phase and may then also be partially based on determinations (calculations) .

[0065] Such a measurement may be made piecewise (for partial ranges) or for the full range of operation. The measurements provide data representing a (non-linear) operating range of the chilled beam, plotting the control input (of the actuator) to the flow output through the outlets. The flow output provides the K-factor coefficient as in figure 3.

[0066] The K-factor coefficient can be determined by the output flow being measured at different openings. The different K-factors can be stored associated with an outlet / cover opening and a given K-factor can thus be determined based on a setting for the actuator which in turn implies an opening.

[0067] In some embodiments the flow output is represented by the position of the shaft, wherein the K-factor is based on the position of the shaft. Figure 3 shows a graph plotting the measurements of the operating characteristics of the chilled beam and the series of approximations . The slopes of the approximations correspond to the K- factor coef ficients K100 for the various ranges of actuator settings , as indicated by the corresponding outlet openings in figure 3 , where a first range of actuator settings U1 corresponds to a first K- factor coef ficient K100-U1 and a second range of actuator settings U2 corresponds to a second K- factor coef ficient K100-U2 .

[0068] One example of the measurements includes , but is not limited to , measure a plurality of pressures and also the flow rates at such pressures and thereby get flow rates corresponding to pressures , from which the K- factor can be determined . The K- factor can be determined ( in linear cases ) as the derivate or slope of the relationship between the pressure and the flow rate .

[0069] As stated above , the measurement may be made during designing (prototyping) which enables for taking into account non-linear constructions ( shapes of outlets for example ) .

[0070] As is also stated above , the measurement may also or alternatively be made during the development phase which enables for taking into account variances .

[0071] As is also stated above , the measurement may also or alternatively be made during manufacturing which enables for taking into account variances of the actual products . The measurement need not be made individually for each unit , but can be made for a series of units , assuming they have somewhat the same variances . And, the measurement may be made during operation (for example at regular intervals) which enables for taking into account wear-and-tear .

[0072] The measurements may be repeated, whereby the chilled beam is able to adapt to changing circumstances. One such changing circumstance may be a change in the room A. For example, if parts of the outlets are blocked, this will affect the flow through that outlet, and also through other outlets.

[0073] The series of approximation therefore enable the chilled beam to operate based on a linear algorithm (as disclosed in the Swedish patent published as SE 537 916 02) , but operating according to different K-factor coefficients depending on the opening of the outlets (nozzles) .

[0074] Each sector is thus associated with a range of control input, and therefore a K-factor coefficient (or manner of determining the K-factor coefficient) within that range.

[0075] Figure 4 shows how the control algorithm of figure 2 may be adapted to allow for such approximations. As can be seen the only difference is that the K-factor coefficient (K100) is no longer a constant but is determined as a function of the current setting for the actuator. The function is in one embodiment, simply a selection of a constant K-factor coefficient corresponding to a range that the current actuator setting is in, so that a first range U1 corresponds to a first K-factor coefficient (K100-U1) , and second range U2 corresponds to a second K-factor coefficient (K100-U2) , and so on and as is shown in figure 3. In each range, the determination of the k-factor is thus linear based on a K100 for that range. As a skilled person would realize, the function giving the K-factor coefficient (K100) based on the actuator setting Uac, may be done as part of determining the K-factor, where the k-factor to be used is given directly by the K-function.

[0076] As the K-factor to be used is utilized, it becomes the current K-factor .

[0077] In some embodiments the series of approximation is squared. In some embodiments the series of approximations is cubic.

[0078] In some embodiments the series of approximations is given as a spline function. However, the series of approximations need not have continuous derivates (i.e. same derivate on either side of a measuring point) .

[0079] In some embodiments the series of approximation is given as a linear interpolation (as in figure 3) .

[0080] Using a linear series of approximation provides a simpler regulative control of the chilled beam.

[0081] The chilled beam (specifically the control logic (SW) of the controller 15) is therefore configured to receive as input the cover positions or rather the control parameter (signal indicating a desired opening) , and the respective approximated K-factors (as given by the K-function) . Based on the received current control signal, the chilled beam will then select the corresponding K-factor based on the series of approximations and operate according to the corresponding K- factor while the control signal is in the range of the K- factor .

[0082] The controller 15 also comprises a computer-readable memory enabling the controller to store the series of approximations .

[0083] Figure 5 shows a flowchart for a method for performing the control as discussed with reference to figures 2 , 3 and 4 . The method is for use in an air treatment device 1 comprising a chilled beam 2 having outlets 7 and covers 9 , wherein each outlet 7 is associated with a cover 9 and wherein the cover 9 is controlled by an actuator unit 12 . The method comprises receiving 510 an indication of a current position Uac of the actuator unit 12 , receiving a pressure measurement of a pressure Pa in the chilled beam 2 from a pressure sensor 13 , and receiving a desired setting for the airflow Vset . The method further comprises , in response thereto , determining 520 a K- factor corresponding to the control signal , wherein the K- factor is indicative of the flow through the outlet 7 at a given position of the cover 9 and for a pressure of the chilled beam 2 , and wherein the k- factor is determined linearly based on a K- factor coef ficient K100 and the indication of the current position of the actuator Uac, determining 530 a current airflow Vac based on the k- factor and determining a control signal Uset for the actuator unit 12 based on the current airflow Vac and the desired airflow setting Vset , wherein the method is characteri zed in that the method further comprises determining 520 the K- factor coef ficient K100 based on a series of approximations of operating characteristics of the chilled beam 2 , wherein the series of approximations gives a K- factor coef ficient K100_Ul , K100-U2 for a range of the current position of the actuator Uac, and wherein a first K-factor coefficient K100-U1 for a first range U1 is different from a second K-factor coefficient K100-U2 for a second range U2.

[0084] In some embodiments the K-factor, K100, is the K-factor for a measurement point ending the range - as measured, wherein the K-factor chosen for the K100 factor is the highest K-factor of the two endpoints of a range. Looking at figure 3 showing one example of three measurement points PO, Pl and P2 where each measurement point can provide a K-factor for the measured pressure and flow rate at that measurement point. In some embodiments the K-factor coefficient for a range can thus be determined as the highest K-factor for an endpoint, which in figure 3 would be for range U2, the higher of the K-factors for points Pl and P2 - which would be the K-factor for P2.

[0085] In other words, the K-factor coefficient for a range becomes the higher of the K-factors (slopes) at the endpoints. If a first endpoint gives KI (the slope at point Pl) and a second endpoint gives K2 (the slope at point P2) , the K-factor coefficient (K100) for that range is set as K100 = max (KI, K2 ) . In most cases, and in some embodiments the K-factor coefficient is the K-factor for the second point (the second point indicating a larger open area - the cover is opened more - than the first point) ; K100 = K2.

[0086] For the example of figure 3, the K-factor coefficient K100-U2 for the second range U2 is given by K100-U2=max (KI, K2 ) which in this case is equal to K100-U2 = K2.

[0087] In some embodiments the K-factor, K100, is the average of two K-factors for two (adjacent) measurement points ending the range - as measured. The K-factor coefficient K100 is thus given as (Kl+K2) / 2.

[0088] In some embodiments the K-factor coefficient, K100, is determined as the slope between two (adjacent) measurement points ending the range - as measured. The K-factor coefficient K100 is thus given as KI + S* (K2-Kl) / d, d being a difference between the measurement points and S being a value related to the control signal. The difference may be related to the distance between actual positions of the shaft at the measurement points. The difference may alternatively be related to a difference in opening area of the outlet (s) at the measurement points. The difference may alternatively be related to a difference in control signals of the shaft at the measurement points. S is defined based on how d is defined (which in turn is defined based on how 0mis defined) and is basically the difference between the signal value in the first measurement point and the current operating point.

[0089] An alternative manner of expressing this is using arrays of measurements of K Kmat the various measurement points and for the openings ( / nozzles) Omat the measurement points. In some embodiments the series of approximations is thus given as

[0090] KlOOi = Kmi + (Kmi+i - Kmi) / (Omi+i - Om±) • (M - Om±) where index i is a numbering of a range,

[0091] KlOOi is the K-factor coefficient in the range i

[0092] Km= an array with the (different) K-factors for the different outlets as measured,

[0093] Om= an array of the corresponding outlets' openings as measured (Om±+i - Om± = d in the above) , and M = current signal related value (M - O' S in the above) .

[0094] When Omindicates a position of the actuator, M is given as the current control signal* the maximum position of the actuator.

[0095] When 0mindicates a size of an opening of the outlet, M is given as the current control signal*the maximum area of the outlet (s) , N; M = UacN.

[0096] As would be understood, the method may comprise any or some operations as discussed herein with reference to figures 2, 3 or 4 even though not shown explicitly in the flowchart of figure 5, wherein such additional operations are included in the operations shown.

[0097] The procedure may be summarized as measuring airflow at different actuator openings and pressures. This can be done in design, development, manufacturing, or even during operation. The actuator position (Uac) is then plotted against airflow for a given pressure and the K-factor at each measurement point may be calculated as the slope of the airflow-pressure relationship. The actuator range is split into segments (Ul, U2, ...) between measurement points and a K-factor coefficient (K100) is assigned to each segment. This is usually the highest K-factor of the two measurement points at either of the ends of that segment or the slope between the two measurement points. The control logic then uses the K100 for the segment that the current actuator position is in, as given by the desired setting, and then calculates the actual K- factor linearly within that segment. The (maximum) K-factors can be stored in a K-factor table. If outlet geometry, blockage, or wear changes performance, the measurements can be repeated and update the K-factor table.

[0098] This segmented approach can also be adapted to non-linear fitting (squared, cubic, spline) , but linear interpolation is simplest .

[0099] As has also been discussed briefly above, the inventors have realized that at small flows, the resulting operation will be incorrect when using a linear control, as for example leakage in the chilled beam will become prominent skewing the operating characteristics. The inventors are therefore proposing a simple and elegant solution where a special low- flow K-factor will be used.

[0100] The low-flow K-factor indicates a non-linear behaviour in the low-flow region, for example caused by leakage, and is to be used to determine the K-factor to be used when a control signal for the actuator is below a lower limit.

[0101] The K-factor to be used is determined based on the K-factor for the linear control at the lower limit (KL_Limit or referenced KL in figures 6 and 7) , the actual opening of the covers (UAC) , and the low-flow K-factor Ko. In some embodiments the K-factor to be used, K is determined by where

[0102] K= K-factor to be used KL_Limit= determined K- factor corresponding to a lower limit of a linear model

[0103] Ko= low- flow K- factor, i . e the K- factor imposed by the leakage when the chilled beam is closed .

[0104] Liimit= the control signal at the upper end of the range where the leakage becomes prominent .

[0105] UAC = control signal for the actuator, indirectly giving the relative opening of the outlet ( as a value 0- 1 , or as a percentage ) .

[0106] When producing the chilled beam, tolerances in edge pressing, material and assembly have resulted in the chilled beam having a certain basic flow .

[0107] The individual chilled beam is then tested in the final assembly to determine this basic flow Q being representative of KO . The testing works in such a way that you connect the chilled beam to an external test equipment and then order the chilled beam actuator to close the noz zles of the chilled beam, followed by pressuri zing the pressure box . The pressure is maintained in the chilled beam plenum chamber, whereby the test equipment measures the basic flow that the individual chilled beam has .

[0108] Through this test , the basic flow chilled beam has been obtained . The base flow and the static pressure (which was used to derive the base flow) can then be used to calculate KO through the formula

[0109] T1 Ko is then saved in the controller 15 of the chilled beam as an input parameter.

[0110] After installing the chilled beam, the current K-factor for the chilled beam is then calculated based on the opening degree of the nozzle, similar to SE 537 916 as discussed in relation to figure 2 above or based on the series of approximations as discussed in relation to figures 3 and 4 above .

[0111] Figure 6 shows a schematic and illustrative plot of K-factors to the setting of the actuator, where the slope represents the K-factor coefficient K100.

[0112] Figure 7 shows a schematic and illustrative plot of K-factors to the setting of the actuator, where a series of approximations (as in figure 3) is indicated and within each range of actuator settings, the slope represents the K-factor coefficient K100 of that range.

[0113] As can be seen in both figure 6 and figure 7, when the actuator setting reaches a lower limit, the K-factor is determined differently (the slope changes) and is determined as in equation (2) above.

[0114] When the nozzle opening degree (as given by the shaft position) is less than LLimit, the formula above is used to calculate the K-factor on the chilled beam together with the pressure in the pressure box and the relative nozzle opening (actuator setting) . Which then provides a more accurate regulation of the supply air flow than only using the teachings of SE 537 916. Figure 8 shows how the control algorithm of figure 2 may be adapted to allow for use with such K-factors taking leakages into account. As can be seen the only difference is that the K-factor is no longer determined simply on the constant K- factor coefficient, but when the actuator setting (i.e. control signal to the actuator) goes below the lower limit L- Limit, the K-factor but is determined through the equation (2) above, indicated as K(K0) in figure 8.

[0115] Figure 9 shows a flowchart for a method for performing the control as discussed with reference to figures 5, 6, 7 and 8. The method is for use in an air treatment device 1 comprising a chilled beam 2 having outlets 7 and covers 9, wherein each outlet 7 is associated with a cover 9 and wherein the cover 9 is controlled by an actuator unit 12. The method comprises receiving 910 an indication of a current position Uac of the actuator unit 12, receiving a pressure measurement of a pressure Pa in the chilled beam 2 from a pressure sensor 13, and receiving a desired setting for the airflow Vset. The method further comprises, in response thereto, determining 920 a K-factor corresponding to the control signal, wherein the K- factor is indicative of the flow through the outlet 7 at a given position of the cover 9 and for a pressure of the chilled beam 2, and wherein the k-factor is determined linearly based on a K-factor coefficient K100 and the indication of the current position of the actuator Uac, and determining 930 a current airflow Vac based on the k-factor and determining a control signal Uset for the actuator unit 12 based on the current airflow Vac and the desired airflow setting Vset, wherein the method is characterized in that the method further comprises determining 920 the K-factor based on the K- factor coef ficient when the indication of a current position Uac of the actuator unit 12 falls above a lower limit L-Limit and determining the K- factor based on a leakage k- factor KO when the indication of a current position Uac of the actuator unit 12 falls below the lower limit L-Limit .

[0116] As would be understood, the method may comprise any or some operations as discussed herein with reference to figures 5 , 6 , 7 and 8 even though not shown explicitly in the flowchart of figure 9 , wherein such additional operations are included in the operations shown .

[0117] The teachings of taking leakages into account as discussed in relation to figures 6 , 7 , 8 and 9 may also or alternatively be combined with the teachings as discussed in relation to figures 3 , 4 and 5 ( as is also indicated already in figure 7 ) . Such a combination provides a more accurate regulation of the supply air flow than only using the teachings discussed in relation to figures 3 , 4 and 5 .

[0118] The series of approximations for the K- factor and the leakage K factor may thus beneficially be combined and figure 10 shows how the control algorithm of figure 2 may be adapted to allow for use with K- factors taking leakages into account in combination with approximations , as is also shown already in figure 7 . As can be seen the only di f ference is that the K- factor is no longer determined simply on the constant K- factor coef ficient , but when the actuator setting goes below the lower limit L-Limit , the K- factor is determined through the equation 2 above , indicated as K (K0 ) in figure 10 ( and in figure 8 ) . And when the actuator setting goes above the lower limit L-Limit , the K- factor is determined through the K- function as discussed in relation to figure 4 giving the K- factor to be used for which range the actuator setting is currently within .

[0119] Figure 11 shows a flowchart for a method for performing the control as discussed with reference to figures 2 , 3 , 4 , 5 , 6 , 7 , 8 , 9 and 10 . The method is for use in an air treatment device 1 comprising a chilled beam 2 having outlets 7 and covers 9 , wherein each outlet 7 is associated with a cover 9 and wherein the cover 9 is controlled by an actuator unit 12 . The method comprises receiving 1110 an indication of a current position Uac of the actuator unit 12 , receiving a pressure measurement of a pressure Pa in the chilled beam 2 from a pressure sensor 13 , and receiving a desired setting for the airflow Vset . The method further comprises , in response thereto , determining 1120 a K- factor corresponding to the control signal , wherein the K- factor is indicative of the flow through the outlet 7 at a given position of the cover 9 and for a pressure of the chilled beam 2 , and wherein the k- factor is determined linearly based on a K- factor coef ficient K100 and the indication of the current position of the actuator Uac, determining 1130 a current airflow Vac based on the k- factor and determining a control signal Uset for the actuator unit 12 based on the current airflow Vac and the desired airflow setting Vset , wherein the method is characteri zed in that the method further comprises determining 1120 the K- factor coef ficient K100 based on a series of approximations of operating characteristics of the chilled beam 2 when the indication of a current position Uac of the actuator unit 12 falls above a lower limit L-Limit , wherein the series of approximations gives a K- factor coef ficient K100-U1 , K100-U2 for a range of the current position of the actuator Uac, and wherein a first K-factor coefficient K100-U1 for a first range

[0120] U1 is different from a first K-factor coefficient K100-U1 for a first range Ul, and determining the K-factor based on a leakage k-factor KO when the indication of a current position Uac of the actuator unit 12 falls below the lower limit L- Limit .

[0121] As would be understood, the method may comprise any or some operations as discussed herein with reference to figures 2, 3, 4, 5, 6, 7, 8, 9 and 10 even though not shown explicitly in the flowchart of figure 11, wherein such additional operations are included in the operations shown.

Claims

1. CLAIMS1. An air treatment device (1) comprising a controller (15) , a chilled beam (2) having outlets (7) and covers (9) , wherein each outlet (7) is associated with a cover (9) and wherein each cover (9) is movable by an actuator unit (12) , wherein the controller (15) is arranged to receive an indication of a current position (Uac) of the actuator unit (12) , receive a pressure measurement of a pressure (Pa) in the chilled beam (2) from a pressure sensor (13) , receive a desired setting for the airflow (Vset) , and in response thereto determine a K-factor corresponding to the desired setting for the airflow (Vset) , wherein the K-factor is indicative of the flow through the outlet (7) at a given position of the cover (9) and for a pressure of the chilled beam (2) , and wherein the k-factor is determined linearly based on a K- factor coefficient (K100) and the indication of the current position of the actuator (Uac) , determine a current airflow (Vac) based on the k-factor and determine a control signal (Uset) for the actuator unit (12) based on the current airflow (Vac) and the desired airflow setting (Vset) , wherein the air treatment device (1) is characterized in that the controller (15) is further configured to determine the K-factor based on the K-factor coefficient when the indication of a current position (Uac) of the actuator unit (12) falls above a lower limit (L-Limit) and determine the K-factor based on a leakage k-factor (KO) when the indication of a current position (Uac) of the actuator unit (12) falls below the lower limit (L-Limit) .

2. The air treatment device (1) according to claim 1, wherein the controller is further configured to determine the K-factor to be used aswhereK= K-factor to be usedKL_Limit= determined K-factor corresponding to a lower limit of a linear modelKo= low-flow K-factor, i.e the K-factor imposed by the leakage when the chilled beam is closed.Liimit= the opening of the outlet at the end of the range where the leakage becomes prominent.UAC= the current relative opening of the outlet as given by the actuator control signal.

3. The air treatment device (1) according to claim 1 or 2, wherein the leakage K-factor (KO) corresponds to an airflow(Q) through the chilled beam at a given static pressure of the chilled beam (Pstatic) when the chilled beam is closed and is determined as4. The air treatment device (1) according to any preceding claim, wherein the controller (15) is further configured to determine the K-factor based on a leakage k-factor (KO) when the indication of a current position (Uac) of the actuator unit (12) falls below the lower limit (L-Limit) and34to determine the K-factor coefficient (K100) based on a series of approximations of operating characteristics of the chilled beam (2) when the indication of a current position (Uac) of the actuator unit (12) falls above a lower limit (L- Limit) , wherein the series of approximations gives a K-factor coefficient (K100-U1, K100-U2) for a range of the current position of the actuator (Uac) , wherein a first K-factor coefficient (K100-U1) for a first range (Ul) is different from a second K-factor coefficient (K100-U2) for a second range (U2) .

5. The air treatment device (1) according to any preceding claim, wherein a linear regulation of the current position of the actuator unit (12) provides a non-linear regulation of the airflow .

6. An air treatment system (4) comprising an air treatment device (1) as in any preceding claim7. The air treatment system (4) according to claim 6 comprising the controller (15) .

8. A method for use in an air treatment device (1) comprising a chilled beam (2) having outlets (7) and covers (9) , wherein each outlet (7) is associated with a cover (9) and wherein each cover (9) is movable by an actuator unit (12) , wherein the method comprises receiving an indication of a current position (Uac) of the actuator unit (12) , receiving a pressure measurement of a pressure (Pa) in the chilled beam (2) from a pressure sensor (13) ,receiving a desired setting for the airflow (Vset) , and in response thereto determining a K-factor corresponding to the control signal, wherein the K-factor is indicative of the flow through the outlet (7) at a given position of the cover (9) and for a pressure of the chilled beam (2) , and wherein the k-factor is determined linearly based on a K-factor coefficient (K100) and the indication of the current position of the actuator (Uac) , determining a current airflow (Vac) based on the k-factor and determining a control signal (Uset) for the actuator unit (12) based on the current airflow (Vac) and the desired airflow setting (Vset) , wherein the method is characterized in that the method further comprises determining the K-factor based on the K-factor coefficient when the indication of a current position (Uac) of the actuator unit (12) falls above a lower limit (L-Limit) and determining the K-factor based on a leakage k-factor (KO) when the indication of a current position (Uac) of the actuator unit (12) falls below the lower limit (L-Limit) .

9. A method for use in an air treatment device (1) comprising a chilled beam (2) having outlets (7) and covers (9) , wherein each outlet (7) is associated with a cover (9) and wherein the cover (9) is controlled by an actuator unit (12) , wherein the method comprises receiving an indication of a current position (Uac) of the actuator unit (12) , receiving a pressure measurement of a pressure (Pa) in the chilled beam (2) from a pressure sensor (13) , receiving a desired setting for the airflow (Vset) , and in response theretodetermining a K-factor corresponding to the control signal, wherein the K-factor is indicative of the flow through the outlet (7) at a given position of the cover (9) and for a pressure of the chilled beam (2) , and wherein the k-factor is determined linearly based on a K-factor coefficient (K100) and the indication of the current position of the actuator (Uac) , determining a current airflow (Vac) based on the k-factor and determining a control signal (Uset) for the actuator unit (12) based on the current airflow (Vac) and the desired airflow setting (Vset) , wherein the method is characterized in that the method further comprises determining the K-factor coefficient (K100) based on a series of approximations of operating characteristics of the chilled beam (2) when the indication of a current position (Uac) of the actuator unit (12) falls above a lower limit (L- Limit) and determining the K-factor based on a leakage k-factor (KO) when the indication of a current position (Uac) of the actuator unit (12) falls below the lower limit (L-Limit) , wherein the series of approximations gives a K-factor coefficient (K100-U1, K100-U2) for a range of the current position of the actuator (Uac) , and wherein a first K-factor coefficient (K100-U1) for a first range (Ul) is different from a second K-factor coefficient (K100-U2) for a second range (U2) .

10. An air treatment system (4) comprising a controller (15) configured to perform the method of claim 8 or 9.

11. An air treatment device (1) comprising a controller (15) , a chilled beam (2) having outlets (7) and covers (9) , wherein each outlet (7) is associated with a cover (9) and wherein the37cover (9) is controlled by an actuator unit (12) , wherein the controller (15) is configured to receive an indication of a current position (Uac) of the actuator unit (12) , receive a pressure measurement of a pressure (Pa) in the chilled beam (2) from a pressure sensor (13) , receive a desired setting for the airflow (Vset) , and in response thereto determine a current K-factor corresponding to the indication of a current position (Uac) , wherein a K-factor is indicative of the flow through the outlet (7) at a given position of the cover (9) and for a pressure of the chilled beam (2) , and wherein the current k-factor is determined linearly based on a K-factor coefficient (K100) and the indication of the current position of the actuator unit (Uac) , the K-factor coefficient being the K-factor at a maximal opening of the outlet (7) , determine a current airflow (Vac) based on the current k- factor and determine an actuator control signal (Uset) for the actuator unit (12) to be used based on the current airflow (Vac) and the desired airflow setting (Vset) , wherein the air treatment device (1) is characterized in that the controller (15) is further configured to determine the K-factor coefficient (K100) to be used based on a series of approximations of the cooling baffle (2) , wherein the series of approximations gives series of a K- factor coefficients (K100-U1, K100-U2, K100) each for a range of positions of the actuator unit (Uac) , wherein a first K- factor coefficient (K100-U1, K100) for a first range (Ul) is different from a second K-factor coefficient (K100-U2, K100) for a second range (U2) , wherein the K-factor coefficient tobe used is the K-factor coefficient for the range of positions of the actuator unit (Uac) that the current position of the actuator unit (Uac) falls within.

12. The air treatment device (1) according to claim 11, wherein the series of approximations is a linear interpolation of measurements of the characteristics.

13. The air treatment device (1) according to claim 11, wherein the series of approximations is given asKlOOi = Kmi + (Kmi+i - Kmi) / (Omi+i - 0m±) • (M - 0m±) where index i is a numbering of a range,KlOOi is the K-factor coefficient in the range iKm= an array with the (different) K-factors for the different outlets as measured,0m= an array of the corresponding outlets' openings as measured (0m±+i - 0m± = d in the above) , andM = current signal related value (M - 0m±= S in the above) .

14. The air treatment device (1) according to any of claims 11 to 13, wherein the measurements of the characteristics originate from a design phase and / or a development phase.

15. The air treatment device (1) according to any of claims 11 to 14, wherein at least one cover (9) is associated with more than one outlet (7) .

16. The air treatment device (1) according to any of claims 11 to 15, wherein at least one cover is of a non-rectangular shape .

17. The air treatment device (1) according to any of claims 11 to 16, wherein at least one cover is arranged to move in a non-linear fashion.

18. The air treatment device (1) according to any of claims 11 to 17, wherein at least one outlet (9) is of a non-rectangular shape .

19. The air treatment device (1) according to any of claims 11 to 18, wherein the controller (15) is further configured to determine the k-factor based on the K-factor coefficient (K100) , the indication of the current position of the actuator unit (Uac) and a leakage correcting factor (qcorr) .

20. The air treatment device (1) according to any of claims 11 to 19, wherein the controller (15) is further configured to determine the K-factor coefficient (K100) based on the series of approximations when the indication of a current position (Uac) of the actuator unit (12) falls above a lower limit (L- Limit) and to determine the K-factor based on a leakage k- factor (KO) when the indication of a current position (Uac) of the actuator unit (12) falls below the lower limit (L-Limit) .

21. The air treatment device (1) according to claim 11 to 20, wherein a linear regulation of the current position of the actuator unit (12) provides a non-linear regulation of the airflow .

22. An air treatment system (4) comprising an air treatment device (1) as in any of claims 11 to 21.

23. A method for use in an air treatment device (1) comprising a chilled beam (2) having outlets (7) and covers (9) , wherein each outlet (7) is associated with a cover (9) and wherein the cover (9) is controlled by an actuator unit (12) , wherein the method comprises receiving an indication of a current position (Uac) of the actuator unit (12) , receiving a pressure measurement of a pressure (Pa) in the chilled beam (2) from a pressure sensor (13) , receiving a desired setting for the airflow (Vset) , and in response thereto determining a K-factor corresponding to the control signal, wherein the K-factor is indicative of the flow through the outlet (7) at a given position of the cover (9) and for a pressure of the chilled beam (2) , and wherein the k-factor is determined linearly based on a K-factor coefficient (K100) and the indication of the current position of the actuator unit (Uac) , the K-factor coefficient being the K-factor at a maximal opening of the outlet (7) , determining a current airflow (Vac) based on the current k-factor and determining an actuator control signal (Uset) for the actuator unit (12) based on the current airflow (Vac) and the desired airflow setting (Vset) , wherein the method is characterized in that the method further comprises determining the K-factor coefficient (K100, K100-U1, K100-U2) based on a series of approximations for the cooling baffle (2) , wherein the series of approximations gives a K- factor coefficient (K100-U1, K100-U2, K100) for a range of the current position of the actuator unit (Uac) , and wherein a first K-factor coefficient (K100-U1, K100) for a first range (Ul) is different from a second K-factor coefficient (K100-U2,K100) for a second range (U2) , wherein the K-factor coefficient to be used is the K-factor coefficient for the range of positions of the actuator unit (Uac) that the current position of the actuator unit (Uac) falls within.

24. The method according to claim 23, wherein the method further comprises determining the K-factor further based on a leakage k- factor (KO) when the indication of a current position (Uac) of the actuator unit (12) is below a lower limit (L-Limit) indicating a low air flow.

25. An air treatment system (4) comprising a controller (15) configured to perform the method of claim 23 or 24.42

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