DESCRIPTION

The present invention relates to a system comprising an air mixing unit associated with a controlled mechanical ventilation system, equipped with innovative features for an improved management of the air flows towards the destination environments.

The invention falls within the sector of controlled mechanical ventilation systems, recently increasingly used in the construction sector due to the high capacity of ensuring comfort and energy efficiency to the buildings.

The typical operation of a controlled mechanical ventilation unit (hereinafter abbreviated as "VMC") is known to the man skilled in the art and its salient features are briefly outlined here for the sole purpose of facilitating the understanding of the present invention.

In a classic dual flow VMC unit (type of VMC examined herein, as it is the most widespread and energy efficient one) there are at least the following main components:

- ventilation ducts, both in inlet (from the outside the building and up to the rooms intended for receiving the fresh air flows) and in outlet;

- a heat exchanger wherein the two crossed flows of the expulsion air and inlet air flow into, recovering the thermal energy from the first flow to heat (in the cold seasons) or cool (in the hot seasons) the second flow;

- ceiling or wall vents or grills, which allow the transit of the inlet or expulsion air.

In such kind of VMC units, the heat exchanger takes the role of heat recuperator from the expulsion air and the VMC unit that integrates it is also known as "passive VMC"; however other types of VMC are known in which the heat exchange deriving from the crossing of the two air flows is added by the calorific supply coming from a thermodynamic cycle, carried out by a heat pump integrated within the same VMC unit or coming from an external heat pump.

Both the passive and the thermodynamic VMC (with the distinctions between the two systems in terms of costs, bulkiness and efficiency, greater in the second type of VMC) allow obtaining the typical advantages of such a system, ensuring a constant exchange of air inside the building, with consequent elimination of odours, water vapour and other polluting agents from the rooms, and control of the temperature and humidity of the indoor environments.

Other advantages related to the use of a VMC unit reside in the possibility of filtering and treating the inlet air, with benefits for subjects suffering from allergies and pathologies affecting the respiratory system.

In addition to the aforementioned advantages in terms of thermo-hygrometric and hygienic-sanitary behaviour, greater acoustic comfort is obtained with the VMC unit thanks to the reduction in external noise pollution, as there is no need to often opening the windows to ventilate the rooms; at the same time, the system, if properly designed and dimensioned, is acoustically imperceptible. However, the systems with VMCs (in particular those that provide an air posttreatment battery) are not free from drawbacks, mainly associated with the need to provide that the air intake and delivery pipes are equipped with appropriate insulations in order to avoid dispersions of heat, which would affect the overall energy bill: this results in an increase in costs, as well as in the expansion of the dimensional volumes necessary for the installation, not always easy considering the reduced destination spaces (typically false ceilings).

The object of the present invention is to obviate such kind of drawbacks by providing a system comprising an air mixing unit positioned downstream of a passive VMC unit for optimized management of the air flows intended for the environments of the building.

A further object is to indicate means of simple and economic implementation for a reduction of the system installation spaces.

Another object of the invention is to provide such devices as to further increase the acoustic comfort of the building, reducing the sound emissions produced by the system.

These and other objects, which will become clear below, are achieved with a system comprising a passive VMC unit downstream of which an air mixing unit is located, according to claim 1, and with methods of operation of the system according to claim 7 and subsequent.

Other objects may also be achieved by means of the additional features of the dependent claims.

Further features of the present invention shall be better highlighted by the following description of a preferred embodiment, in accordance with the patent claims and illustrated, purely by way of a non-limiting example, in the annexed drawing tables, in which:

- Fig. 1 shows a schematic view of the system comprising a VMC unit and an air mixing unit in accordance with a first operating mode according to the invention;

- Fig. 2 depicts the system of Fig. 1 in accordance with a second operating mode of the system according to the invention;

- Figs. 3. a, 3.b, 3.c are magnified details of three possible shapes of the valves wherefrom the air flows deriving from the system according to the invention and directed to the destination rooms flow out.

The features of a preferred variant of the system comprising the passive VMC unit and the air mixing unit according to the invention are now described using the references contained in the figures. It should be noted that, from here on, the term "flow" means the flow rate of the air flow passing through the various components of the system. Figure 1 shows the system as a whole, which comprises a classic VMC unit of the passive type, i.e. intended for the recovery of heat from the stale air flow H in expulsion from the most odours- and humidity-polluted rooms (generally kitchen and bathrooms).

As per prior art, such VMC comprises a heat exchanger VMC.HE therein acting as a heat recuperator (consisting, for example, of a static cross-flow plate recuperator), wherein the air flows adduced through the following pipes flow into:

- an intake duct P.H of the stale air flow H, sucked by a fan F.OUT towards such heat exchanger VMC.HE in order to be sent, subsequent to the heat exchange, towards the outside of the building as an exhausted air flow E through an outlet duct P.E;

- an inlet duct P.F of the fresh air flow F taken from the outside and directed to such exchanger VMC.HE in order to be sent to the indoor environments, after the heat exchange, as fresh air flow R through a delivery duct P.R, pushed by a fan F.IN.

In the schematic example of Fig. 1, said VMC unit is therefore provided with two fans F.OUT and F.IN, located respectively in the ducts P.H, P.R adapted to suck the stale air flow H in expulsion and to push the fresh air flow R towards the noble rooms of the building, typically the bedrooms and the living room: however, the presence of additional fans may be provided to assist in and increase the flow rate of such air flows, arranged respectively in the aforementioned outlet P.E and intake P.F ducts.

According to the present invention, the fresh air flow R obtained in outlet of the VMC unit just described flows into an air mixing unit 1 (hereinafter abbreviated as "mixing unit 1 "), located downstream of said VMC unit and connected in series thereto, in fact interposing between such VMC unit and the distribution ducts 6 for sending the air flow towards the destination rooms.

As visible in Figs. 1 and 2, the mixing unit 1 has a box-like tructure wherein the following zones and constituent elements are identifiable (listed according to the order of spatial arrangement starting from the most contiguous one to the delivery duct P.R of the fresh air flow R exiting from the YMC):

- an inlet plenum 2, comprising:

- a first opening 2.1 in direct fluid connection with said delivery duct P.R of the fresh air flow R coming from the VMC, and

- a second opening 2.2, equipped with closing means 2.3, provided for the inlet of the recirculating air flow X coming from the room in which said mixing unit 1 is installed (or from other rooms connected to said mixing unit 1);

- a fan 3, operated or not according to the energy needs of the system, as explained later;

- one or more heat exchangers 4, among which, for example, a direct expansion battery or an air-water exchanger (hereinafter referred to as "heat exchange battery 4" or "battery 4"), fed by heat transfer fluids coming from one or more sources external to the system, not shown in the figure, such as for example hot or refrigerated water supplied by a boiler or by a chiller or by a heat pump, condensing or evaporating fluid coming from a heat pump, domestic hot water recirculating from a water heater;

- an outlet plenum 5 representing the outlet area of the mixing unit 1, in direct communication with the ducts 6 for sending the processed air flow A towards the destination environments.

"Processed air A" should be understood as the air flow obtained exiting from said mixing unit 1, variously resulting in terms of flow rate and calorific supply according to the desired thermo-hygrometric changes in the destination environments and according to the different operating modes of the system, later described.

In order to guarantee such thermo-hygrometric conditions, it is sometimes sufficient that the processed air flow A is equal to the fresh air flow R, while for heavier energy loads a greater flow is necessary, i.e. equal to the fresh air flow R plus a certain recirculating air flow X. Returning to the details of said mixing unit 1, the second opening 2.2 of such inlet plenum 2 is provided with closing means 2.3, such as for example a nonreturn valve that closes by gravity and/or pressure of the delivery fan F. IN of the VMC or through a motorized gate, adapted to prevent the return of the fresh air flow R coming from the VMC and creating a pressure in said inlet plenum 2.

The processed air flow A exiting from said mixing unit 1 is conveyed into the distribution ducts 6 towards the destination rooms, preferably with the aid of special air valves 7 (located in the outlet plenum 5 of the mixing unit 1, or integrated in or in the proximity of any diffusion vents 8 towards said rooms, or, again, in any portion of said distribution ducts 6).

As per prior art, said air valves 7 may consist of manual or motorized calibration gates, controllable in modulating mode, to regulate the flow rate of the processed air A inside the ducts 6 through the rotation of respective fins 7.2 or an equivalent blade 7.2 or other technically equivalent mobile shutter 7.2, although reference is hereinafter always made, also for simplicity of graphic representation, to a blade 7.2.

According to the present invention, such air valves 7 may be designed so that the passage of a minimum flow rate of the processed air A is always ensured, even in the event that the air valve is closed, i.e. when the blade 7.2 is perpendicular to the flow of said processed air A.

According to the main variant, not shown in the figure, such object is achieved through the provision of a hole made in the centre of the blade 7.2 of the air valve 7, a device that allows obtaining a double order of advantages: it makes the changes in the flow rate of the processed air flow A less evident in the transition among the various rotation stages of the blade 7.2 and, above all, it acts as an accelerator for such flow, directing it mostly towards the centre of the destination room.

In the detailed Figures 3. a, 3.b and 3.c, three further variants of air valve 7 alternative to the main variant just mentioned of the central hole for the passage of a minimum flow rate of processed air flow A, also with the air valve 7 closed, are shown by way of example.

In the example of Fig. 3. a, such always-open passage is represented by an opening 7.1 obtained on a portion of the blade 7.2; in the example of Fig. 3.b, instead, the minimum flow rate of the processed air flow A is ensured by the passage 7.1 defined by a portion of blade 7.1 having such a length as not reaching the side wall of the duct 6; finally, in the example of Fig. 3.c, the rotation of the blade 7.2 is blocked in a position just sufficient to allow the transit of the processed air flow A through the two lateral passages defined by the blade 7.2 and the walls of the duct 6.

According to the invention, the system comprising the VMC unit and the mixing unit 1 described above is adapted to operate according to various operating modes, each of which produces a different processed air flow A in terms of flow rate and caloric content, depending on the operation or not of the constituent elements of said mixing unit 1 and according to the energy needs of the system.

It is understood that what in short described applies to a use of the system in both cold and hot seasons, the processed air flow A being the result of energy components aimed at respectively heating or cooling said processed air A.

Such operating modes of the system object of the present invention are hereinafter summarized, all of which, as their common denominator, have a first step consisting in the inflow of fresh air R coming from the VMC (at least in the minimum quantities required by the hygienic-sanitary standards), flowing into the mixing unit 1 through the first opening 2.1 of the inlet plenum 2.

Zero Mode: such mode is the one provided when the thermo-hygrometric conditions of the environment do not substantially need to be actively modified by the battery 4, and there is the only need to guarantee the fresh air flow R after its treatment in the VMC.

In this case, said battery 4 is not operational and the fan 3 is not operated: the fresh air flow R from the inlet plenum 2 to the outlet plenum 5 through said batteiy 4 and up to the destination rooms is ensured only by the delivery fan F.IN of the VMC. Said fresh air flow R may however be considered consisting of processed air flow A, since, by passing through the VMC unit, it undergoes thermo- hygrometric changes: however, in such Zero Mode, the processed air flow A has flow rate and thermal power substantially similar to those of the fresh air flow R coming from the VMC, since no mixing with the recirculating air flow X or heat exchange through the battery 4 takes place.

A variant of the system, not shown in the figure but useful in such Zero Mode of operation, may provide for the opening of a bypass duct of the battery 4, in order not to subject said fresh air flow R to unnecessary pressure drops through the same battery 4, when this is not operational.

First Mode: the First Operating Mode is applicable when the passage of the fresh air flow R through the battery 4 is sufficient to produce the processed air flow A to the thermo-hygrometric conditions necessary for the destination environments. According to this First Mode, the fan 3 of the mixing unit remains switched off and only the fresh air flow R passes through the battery 4 in order to be subjected to the heat exchange with the heat transfer fluids coming from one or more external thermal sources.

The second opening 2.2 of the inlet plenum 2 is closed by the closing means 2.3, so that the fresh air flow R cannot exit therefrom.

The processed air A thus obtained passes through the outlet plenum 5 to be conveyed towards the destination rooms by the distribution ducts 6.

According to this First Operating Mode, the fan 3 is not operated and said processed air A is the result of only the fresh air flow R coming from the VMC, energetically added by the calorific supply deriving from the heat exchange carried out by the battery 4.

Second Mode: the Second Operating Mode is applied when the fresh air flow R is not sufficient to produce the processed air flow A to the thermo-hygrometric conditions required in the destination environments.

In this Second Operating Mode, the fan 3 is operating and increases the flow rate of the fresh air flow R coming from the VMC, also making the recirculating air flow X flow into the mixing unit 1 through the second opening 2.2 of its inlet plenum 2 (which in the First Mode was closed by the locking means 2.3).

The mixture of the two fresh R and recirculating air X flows then passes through the battery 4, where the heat exchange takes place: in this Second Operating Mode, the processed air A directed to the outlet plenum 5 of the mixing unit 1 and from here to the destination rooms through the ducts 6 is therefore the result of the mixture of the fresh air R and recirculating air X flows, said mixture being added by the calorific supply deriving from the heat exchange provided by the battery 4.

Third mode: finally, according to a Third Operating Mode, the fan 3 of the mixing unit 1 is activated and there is the mixing of the two fresh R and recirculating air X flows as in the Second Operating Mode described above. However in this Third Mode the battery 4 is not operational and such mixture passes through it without undergoing any heat exchange, in order be conveyed as a processed air flow A to the destination rooms through the distribution ducts 6. Basically, in this Third Mode, the processed air flow A is the result of the mixing between the fresh air flow R with the addition of the calorific supply provided by the recirculating air flow X only.

A variant of the system, not shown in the figure but useful in such a Third Operating Mode, may provide for the opening of a bypass duct of the battery 4, in order not to subject said mixture of fresh air R and recirculating air X flows to useless pressure drops through the same non-operational battery 4.

The operating modes of the system, object of the present invention, may be summarized in the table below, which identifies the content of the processed air flow A according to the activation or not of the constituent elements of the mixing unit 1 :

From the above description, the advantages achievable with the system comprising the VMC unit and the mixing unit 1 according to the invention are clear, the main one of which concerns the possibility of reducing the spaces necessary for the installation and the related costs: in fact, in a standard system with separate VMC units and air post-treatment units, in each destination room it is necessary to provide two ducts, one for the fresh air flow R and one for the recirculating air flow X, unlike the system described here in which only one distribution duct 6 is sufficient for every destination environment.

Furthermore, with respect, for example, to a system comprising a thermodynamic cycle VMC unit or a VMC unit with annexed air post-treatment unit, in the system described here only one step of heat exchange occurs with the battery 4 of the mixing unit 1 (thus reducing the necessary heat exchangers from two to one), in place of the dual stage of heat exchange carried out both by the thermodynamic cycle VMC unit of the prior art or by the known VMC unit with annexed air post-treatment unit.

It follows that, in the system described here, it is no longer necessary to provide the insulation of the delivery duct P.R towards the mixing unit 1, since it does not carry fresh air flows R already heated or cooled and therefore there is no need to avoid the dispersion of the calorific power, to be provided only later through the constituent elements of the mixing unit 1 : this results in a considerable reduction in costs and less installation space.

Finally, the system of the present invention, still with respect to the systems comprising thermodynamic cycle VMC units, ensures reduction in general noise during operating modes that do not require the fan 3 to be switched on.

It is clear that several variants of the system described above are possible for the man skilled in the art, without departing from the novelty scopes of the inventive idea, as well as it is clear that in the practical embodiment of the invention the various components described above may be replaced with technically equivalent ones.

For example, it is clear that in the operating modes of the system where fan 3 is active (i.e. in the Second Mode and Third Mode described above), it can work in modulating mode as per known art, i.e. adjusting the flow rate by varying its speed according to the quantity of air valves 7 open in the distribution ducts 6, and/or the degree of opening of their mobile shutter 7.2 and/or, in general, the heat demand required by the individual rooms of destination.

Moreover the attached figures show the presence of a single mixing unit 1 downstream of the VMC unit: however, more mixing units 1 may be provided, located one per zone of the building or one per room, connected in series to as many delivery ducts P.R exiting from the VMC unit, still operating in accordance with the same operating modes described above for the variant with a single mixing unit 1.