GB2510555A

GB2510555A - Passive ventilation device with heat recovery mode

Info

Publication number: GB2510555A
Application number: GB1221387.2A
Authority: GB
Inventors: Adam Robertson; Anthony Thornhil; Michael Hawley; Richard Hedges
Original assignee: Building Product Design Ltd
Current assignee: Building Product Design Ltd
Priority date: 2012-11-28
Filing date: 2012-11-28
Publication date: 2014-08-13
Anticipated expiration: 2032-11-28
Also published as: GB201221387D0; GB2510555B

Abstract

A passive ventilation device comprises a ventilation terminal 10 for mounting on a roof component 2 of an enclosure 3, the terminal providing first and second pathways between an interior of the enclosure and the exterior, the two pathways each comprising an inlet and outlet and configured to operate substantially independently of one another in at least one mode, the device switchable between the at least one mode and a heat recovery mode where a quantity of the extract airflow is mixed with the supply airflow within the device for re-circulation into the enclosure. A telescopic cylindrical duct arrangement comprising an outer duct 12 with openings 18 and an inner duct 13 with openings 20 allows the first and second pathways to be independent of one another when the openings 18, 20 are out of alignment; in the heat recovery mode the openings 18, 20 are in alignment so that the first pathway merges with the second pathway. Both pathways may behave as extract pathways, and a fan 37 may be used to enhance the heat recovery mode.

Description

IMPROVEMENTS IN PASSIVE-STACK VENTILATION

BACKGROUND

Technical Field

The present invention relates generally to the field of passive-stack ventilation. More particularly, but not exclusively, the present invention concerns a passive-stack ventilation and re-circulation device.

Description of the Related Art

Adequate ventilation in a building is necessitated by the Building Regulations in order to limit the accumulation of moisture and pollutants in an indoor space by removing stale indoor air and replacing it with fresh exterior air.

Both mechanical and natural ventilation systems are available to achieve this objective and meet the requirements of the Regulations.

Natural ventilation is the process of supplying air into, through and removing air from an indoor space without using mechanical systems. It relies upon the natural flow of external air to an indoor space as a result of pressure or temperature differences.

There are two types of natural ventilation that generally occurs in buildings: wind driven ventilation and buoyancy-driven ventilation. Wind provides the driving force for wind driven ventilation, whilst buoyancy-driven ventilation is induced by a directional buoyancy force that results from temperature differences between an indoor space and the exterior.

Therefore, the advantage of natural ventilation is that it does not require an electrical energy supply to drive any components, but takes advantage of natural forces to result in both economic and environmental benefits.

Passive-stack ventilation (PSV) takes advantage of a number of natural forces including a prevailing wind, convection and the Venturi effect. A PSV system usually comprises a roof-mounted extract terminal and takes advantage of inlets! openings between the interior space and the exterior of the building at a lower-level, e.g. windows, doors, vents, controlled by dampers.

In a PSV system, as a prevailing wind moves across the top of an extract outlet (on an extract terminal), the air speed accelerates, which creates a vacuum and draws air up and out of the extract outlet (known as the Venturi effect); the vacuum correspondingly causes air to be drawn into the extract terminal to maintain the pressure in the interior space; through convention, warm rising air is drawn up to replace the extracted air, meanwhile exterior air being supplied into the interior space through the low-level inlets replaces the warm rising air in the interior space. A representation of this effect is demonstrated in Figure la.

Displacement ventilation is a modification of PSV, developed for situations where it is disadvantageous to supply low-level inlets in the building. For example, when a building is unoccupied, it is not recommended to leave windows open. Accordingly, in a displacement system, the extract terminal is divided into a supply chamber and an extract chamber. In this case, as air is extracted through the extract chamber, rising warm air is drawn upwardly, which in turn is replaced by falling cool air, which is replaced by supply air through the supply chamber. A representation of this effect is demonstrated in Figure lb. One problem with the existing systems is that in an effort to freshen" the air in an interior space, heat is lost from the interior space and is replaced by cool or even cold supply air. This can create an unwanted draught and also presents an economic and environmental challenge where heating is used during the colder months of the year.

Mechanical systems using heat exchangers can reduce the problem with heat loss, but the high flow resistance of a heat exchanger requires a fan in the system to create the necessary driving pressure to generate the flow of air through the system in order to operate properly (not truly passive). In a heat exchanger system without a fan, the compromise is usually felt in a stifling and stuffy" internal environment.

Another problem with existing systems is the lack of adaptability: -the efficiency of a system when ventilating a space is often compromised when the conditions in an interior space are changed, for example, the efficiency of a displacement ventilation device can be decreased when a window is opened. Often a device may not be capable of efficiently taking advantage of new conditions.

It is an object of the present invention to address one or more of the problems of the

prior art as discussed herein or otherwise.

Therefore, it is now desired to provide an improved arrangement for a passive-stack ventilation device! system with a low lesistance heat recovery method.

SUMMARY OF THE INVENTION

In one aspect of the present invention there is provided a passive ventilation device comprising a ventilation terminal for mounting on a roof component of an enclosure, the terminal providing first and second pathways between an interior of the enclosure and an exterior thereof, the two pathways each comprising an inlet and an outlet and being configured to operate substantially independently of one another in at least one mode, wherein the device comprises a mode changing means adapted to switch the operational mode of the device between the at least one mode and a heat recovery mode, where in the heat recovery mode a quantity of the extract airflow is entrained in the supply airflow within the device for re-supply into the enclosure with the supply airflow.

With this arrangement, the device can operate in at least one mode where the pathways operate separately from one another as in a displacement mode, or even in a natural passive mode. However, the device can be easily changed over to a heat recovery mode that reclaims some of the heat being lost through the extracted air, by mixing it with supply air before it enters the enclosure. The supply air is therefore, tempered to avoid draughty conditions, but still supplies a fresh air into the enclosure.

As no heat exchanger is used, the device can remain compact, still achieve a good flow of air through the system and remain passive.

By "passive device", what is meant is a single device using natural forces to drive the ventilation of an enclosure with no additional power! input energy being required to drive the device.

For the avoidance of doubt, by inlet', what is meant is a route into the device and by outlet' what is meant is a route out of the device.

Preferably, the device is also operable in a first mode, where both pathways are substantially independent of one another and configured to operate in the same (interior to exterior) direction to provide a natural extract mode. This tirst mode is suitable where there are other lower level inlets in the enclosure to provide supply airflow into the enclosure. The device may comprise an optional extract fan operable in an auxiliary first mode, whereby extraction is boosted through one of the two pathways in the auxiliary first mode. The other pathway may be closed in this mode by an outlet or inlet closure means on the relevant pathway, or a blocking means in the relevant pathway.

Preferably, the device is further operable in a second mode, where the pathways are substantially independent of one another and configured to operate in opposite directions to provide a displacement mode. Preferably, the first pathway is configured to provide extract airflow from the enclosure to the exterior and the second pathway is configured to provide supply airflow to the enclosure from the exterior. This second mode is suitable where there are no low-level inlets in the enclosure to provide supply airflow.

Preferably, the mode changing means is located between the first and the second pathways. Preferably, the mode changing means comprises merging the first and second pathways at one or more locations between the respective inlets and outlets of the pathways. Preferably, the mode changing means comprises one or more cooperable ventilation openings in both pathways and a control means. Preferably, the control means functions to align and misalign the ventilation openings.

Preferably, the mode changing means is operable to merge the pathways in a mixing zone thereby combining extracted room air with fresh supply air within the device when the ventilation openings are aligned. Preferably, the first pathway merges into the second pathway. Preferably, therefore, the mixing zone is provided in the second pathway.

Preferably, at least a proportion of the extract air from the first pathway is entrained by the supply air through the ventilation openings and into the mixing zone. The proportion of extract air that is entrained into the mixing zone may be controlled by either fully or partially aligning the ventilation openings.

Additionally, or alternatively, the proportion of extract air that is entrained into the mixing zone may be controlled by either fully or partially aligning one or more extract outlets in the device. Accordingly, it may be possible to make the extract outlet larger, such that a greater amount of extract air is extracted and a lesser amount of extract air is entrained into the mixing zone. It may also be possible to make the extract outlet smaller, such that a lesser amount of extract air is extracted and a greater amount of extract air is entrained into the mixing zone.

The manner of controlling the alignment of the ventilation openings and the size of the extract outlets may be independently operable, or linked and/or configured to achieve optimum conditions for entrainment.

Preferably, the mixing zone comprises a mixing chamber in the second pathway.

Preferably, the mixing chamber is located proximal to the second pathway outlet.

Preferably, the chamber is provided by a duct system communicable with a supply outlet (into the enclosure) and a supply inlet (into the device from the exterior).

Preferably, the mixing chamber is provided by an inner duct and an outer duct.

Preferably, the inner duct is movable telescopically within the outer duct. Alternatively, the inner duct may be rotationally movable within the outer duct. Preferably, the ventilation openings are provided in walls of both the inner and outer ducts, such that movement of the inner duct within the outer duct controls the alignment or misalignment of the ventilation openings.

With a telescopic duct arrangement, preferably, the ducts are movable within a predetermined range into a number of predetermined arrangements. Preferably, in a first predetermined arrangement, the duct arrangement is condensed and the ventilation openings are misaligned (inner duct openings may be below the outer duct openings). Preferably, in a second predetermined arrangement, the duct arrangement is partially extended (between the first and second arrangements) and the ventilation openings are aligned (inner duct openings are in alignment with the outer duct openings). Preferably, in a third predetermined arrangement, the duct arrangement is fully extended and the ventilation openings are misaligned (inner duct openings may be above the outer duct openings).

Accordingly, in the first arrangement, the outlet in the first pathway may be substantially closed, thereby preventing any extract airflow out of the device. This arrangement may be utilised in the auxiliary first mode (boosted extraction).

Further, in the second arrangement, the outlet in the first pathway may be partially open, or smaller, thereby encouraging some extract airflow into and out of the device.

This arrangement is preferably utilised in the heat recovery mode.

Also, in the third arrangement, the outlet in the first pathway may be fully open or extended (larger), thereby encouraging extract airflow into and out of the device. This arrangement may be utilised in the first mode (natural extraction), or the second (displacement) mode.

Preferably, the inner duct is supported in each arrangement by a respective stopper.

Preferably, each stopper is located on an inner wall of the terminal. Accordingly, therefore, the inner duct may comprise an annular flange for cooperation with the stoppers.

In the first arrangement, the inner duct may be suspended within the outer duct by a first predetermined stopper. The first stopper may be provided at a bottom of, or below the outlet to substantially close the outlet.

In the second arrangement, the inner duct may be suspended within the outer duct by a second predetermined stopper. The second stopper may be provided part way up the outlet to provide a partially open or medium-sized outlet.

In the third arrangement, the inner duct may be suspended within the outer duct by a third predetermined stopper. The third stopper may be provided at the top of, or above the outlet to fully open, or provide a large outlet.

The first, second and third stoppers may be provided by a lip. Therefore, an edge portion of the flange may be resiliently flexible in order to allow passage beyond a respective lip stopper and come to rest on top thereof. Alternatively, the stoppers may comprise resiliently flexible components. Alternatively still, the first, second and third stoppers may be provided by other projections within the outer duct on which a lower edge of the inner duct may sit.

The flange of the inner duct preferably provides an air seal with an inner wall of the terminal so as to define upper and lower chambers in the terminal and therefore, the first and second pathways.

Preferably, the first pathway comprises the primary extract pathway. Preferably, the second pathway comprises the supply pathway in the second and heat recovery modes. The second pathway may comprise a primary or additional extract pathway in the first modes and the first auxiliary mode.

Preferably, the first pathway and the second pathways communicate with the enclosure via a base of the terminal. Preferably, therefore, in heat recovery and second modes, the extract inlet (into the device from the enclosure) and the supply outlet (out of the device to the enclosure) are both provided in the base of the terminal.

Preferably, the first pathway and the second pathway share a common base opening out of and into the terminal. Preferably, the pathways are arranged to use different zones of the base opening.

Preferably, the second pathway uses a central portion of the base opening. Preferably, therefore, a part of the second pathway is arranged in a central core of the terminal.

Preferably, the second pathway comprises a substantially vertical channel in the lower chamber of the terminal. Preferably, the vertical channel comprises the duct arrangement.

Preferably, the second pathway further comprises the upper chamber in a top portion of in the terminal. The upper chamber may comprise one or more openings communicable with the exterior (outside). Preferably, the upper chamber is substantially open on all sides to communicate with the exterior. Preterably, the openings are provided by louvres.

Preferably, the first pathway uses a peripheral portion of the base opening. Preferably, therefore, the first pathway is arranged around the core. Preferably, the first pathway comprises an annular channel around the core in the lower chamber of the terminal.

Preferably therefore, the first pathway is disposed around the second pathway between the duct arrangement and an inner wall of the terminal. The lower chamber may comprise one or more openings communicable with the exterior (outside). Preferably, the openings are provided by louvres.

Accordingly, the lower chamber and the upper chamber of the terminal may vary in proportion as a result of the extension and contraction of the telescopic duct system.

The terminal may remain of fixed height and the upper chamber may therefore, decrease in height as the lower chamber increases in height (due to expansion of the telescopic duct system).

Preferably, the openings of the upper and lower chambers corresponding to inlets or outlets for the respective pathways may comprise a continuous series of openings divided into two variable sets. Therefore, the openings located between the first to the third predetermined arrangements of the ducts of the lower chamber may be re-assigned to either the first or second pathway, according to the arrangement of the ducts.

Preferably, at least the lower chamber of the terminal comprises a substantially cylindrical form, comprising multiple substantially cylindrical modules and components, although other arrangements are anticipated.

BRIEF DESCRIPTION OF THE DRAWINGS

For a better understanding of the invention, and to show how exemplary embodiments may be carried into effect, reference will now be made to the accompanying drawings in which: Figure la (PRIOR ART) is a schematic view ol the air Ilow generated by a conventional passive-stack ventilation (PSV) system; Figure lb (PRIOR ART) is a schematic view of the air flow generated by a conventional passive displacement ventilation system; Figure 2 is a schematic view of a passive ventilation system according to an exemplary embodiment of the invention in a first heat recovery mode; Figure 3 is a schematic view of a passive ventilation system according to an exemplary embodiment of the invention in a first heat recovery mode; Figure 5 is a schematic view of the passive ventilation system of Figure 2 in a second displacement mode; Figure 5 is a schematic view of the passive ventilation system of Figure 2 in a third natural extract mode; and Figure 6 is a schematic view of the passive ventilation system of Figure 2 in a fourth boosted extract mode.

DETAILED DESCRIPTION OF THE EXEMPLARY EMBODIMENTS

Figures 2 -5 are schematic views of a passive ventilation system according to an exemplary embodiment of the invention.

As shown in Figures 2 to 4, a passive ventilation device (1) according to the invention comprises a ventilation terminal (10) for mounting on a roof component (2) of an enclosure (3), the terminal (10) providing a first pathway and a second pathway between an interior of the enclosure (3) and an exterior thereof, the two pathways comprising an inlet and an outlet (31/14, 15/35), respectively and being configured to operate substantially independently of one another in at least a one mode, wherein the device comprises a mode switching means adapted to change the operational mode of the device between the at least one mode and a heat recovery mode, where in the heat recovery mode a quantity of the extract airflow (A) is entrained in the supply airflow (B) in the device (1) for supply into the enclosure (3).

Figure 1 shows an exemplary body of the device (1).

The terminal (10) comprises a substantially cylindrical outer housing (11) with a pitched roof (ba) and a substantially open bottom (lob). The bottom (lOb) is fitted with damper-operated louvres (1 Oc) that are located between a fully open and a partially open position.

The housing (11) is roughly divided into upper (11 a) and lower (11 b) chambers. The lower chamber (llb) comprises a telescopic cylindrical duct arrangement mounted therein comprising an outer duct (12) and an inner duct (13). The upper chamber (11 a) occupies the space between the lower chamber (11 b) and the roof (1 Oa). Accordingly, the lower chamber (11 b) expands and contracts according to the telescopic arrangement of the ducts (15, 16), and the upper chamber (ha) contracts and expands in response thereto.

An outer wall of the housing (11) corresponding to the upper chamber (11 a) comprises an upper set of louvres (14), so as to allow airflow into and out of the upper chamber (11 a). A lower set of louvres (15) is arranged below the upper set of louvres (14). The upper and lower sets of louvres (14, 15) vary in proportion as a result in the variation in height of the upper and lower chambers (11 a, 11 b).

The outer duct (12) comprises a substantially cylindrical hollow wall with opposing top and bottom open ends (12a, 12b). The outer duct (12) is fixedly mounted centrally within the lower portion of the housing (11), so as to be suspended from approximately half way up the housing (11) and extend downwardly therein to terminate just above the bottom (lOb) of the terminal (10). The outer duct (12) is mounted via one or more struts (17) extending between the outer duct (12) and an inner wall of the housing (11).

The lower set of louvres (15) discontinues at a point that corresponds with the top end (15a) of the outer duct (12), so as to allow airflow into and out of the lower chamber (lib). The wall of the outer duct (12) comprises a series of openings (18) arranged around an upper portion thereof.

The inner duct (13) comprises a substantially cylindrical hollow wall with top and bottom open ends (13a, 13b). Dimensionally, the inner duct (13) is only slightly smaller in diameter than that of the outer duct (12) and is shorter than the outer duct (12). The inner duct (13) is slidably mounted within the outer duct (12). An annular flange (19) projects outwardly from the top open end (16a) of the inner duct (13) and extends to the inner wall of the housing (11). The outermost edge of the flange (19) is turned downwardly so as to provide a small annular rim (19a) there around. The wall of the inner duct (13) comprises a series of openings (20) arranged approximately below the halfway point and are proportioned and aligned to correspond with the openings (18) of the outer duct (12).

The slidable movement of the inner duct (13) within the outer duct (12) is restricted by upper and lower stoppers (21, 22). The upper stopper (21) is provided by the inner wall of the housing (11) at a height of approximately two thirds of the height of the housing (11) from the bottom (lob). The lower stopper (22) is provided below the lower set of louvres (15). Both stoppers (21, 22) comprise one or a series of abutments, or an annular projecting rim. The stoppers (21, 22) define a range of movement for the inner duct (13). Therefore, the upward range of movement of the inner duct (13) is limited by an outer edge of the flange (18) abutting the underside of the upper stopper (21), where the duct arrangement is in a fully extended position. The downward range of movement is limited by the bottom end (16b) of the inner duct (13) abutting the lower stopper (22), where the duct arrangement is in a fully contracted position. In the contracted position, the rim (19a) of the flange (19) tucks behind an annular lip (23) provided by the inner wall a! the housing (11), which also provides an air seal between the inner duct (13) and the inner wall of the housing (11).

In both the fully extended and fully contracted positions, the openings (18, 20) of the outer duct (12) and the inner duct (13), respectively are out of alignment. Therefore, the first and second pathways are substantially independent of one another.

As shown more clearly in Figure 4, with the inner duct (13) in the fully extended position, the first pathway providing the extract airflow (A -black arrows) from the enclosure (3) to the exterior comprises: an extract inlet (31) provided in an annular peripheral region of the open bottom (lob); an extract channel (32) bounded by the outer and inner ducts (12, 13) and the inside wall of the terminal (10); an extended extract chamber (33) bounded by the wall of the inner duct (13) and the flange (19); and a extended extract outlet provided by the lower set of louvres (13). The second pathway providing the supply airflow (B -white arrows) from the exterior to the enclosure (3) comprises: a contracted supply inlet (35) provided by the upper set of louvres (12); the upper chamber (ha) contracted in size; a supply channel (36) bounded by the outer and inner ducts (12, 13); and a supply outlet provided by a central portion of the open bottom (lob). As shown in Figure 4, the two pathways remain substantially independent of one another to pertorm a supply and extract function.

As shown in Figure 5, it is possible for both pathways to behave as extract pathways when arranged as in Figure 4. The device (1) will passively switch to such a natural extract mode from the first mode when another supply inlet into the enclosure (3) is provided, such as an open window or door.

Between the fully extended and the fully contracted positions, the inner duct (13) may occupy an intermediate position, in which it is partially extended. To effect this position, the inner wall of the housing (11) provides an intermediate stopper (37) between the lower stopper (22) and the upper stopper (21). With the rim (19a) of the flange (19) resting on the intermediate stopper (36) the extract chamber (33) is partially contracted to approximately half size along with the contracted set of extract louvres (15). In this position, the openings (18, 20) of the outer and inner ducts (12, 13) respectively, are in alignment.

As shown more clearly in Figures 2 and 3, the first pathway merges with the second pathway via the aligned openings (18, 20) in order to function in the heat recovery mode. The downward passage of supply air through the channel (34) of the duct arrangement (12, 13) draws a proportion of the (warmer) extract air from the extract IS channel (32) into the outer! inner duct (12, 13) arrangement, where it mixes with the supply air (mixing zone). The air in the mixing zone of the channel (34) becomes an intermediate temperature and the air is supplied into the enclosure (3) through the outlet (35).

The outer duct (12) comprises a large diameter sweep fan (37) fitted within a lower part of the outer duct (12) and extending there across. When this fan (37) is switched on in a supply' direction, the heat recovery mode may be enhanced, by speeding up the flow of supply air into the channel (34) and entraining a greater amount of extract air through the openings (18, 20) into the mixing zone.

As shown in Figure 6, it is possible to bypass the first pathway to provide a boosted extract mode via the second pathway, for example, when fumes need to be removed.

In order to effect the boost extract mode, the fan (37) is switched on in an extract' direction and the first pathway is closed by placing the inner duct (13) in a contracted position. The fan (37) draws air rapidly from the enclosure into the channel (34), into the upper chamber (1 la) and out through the extended upper set of louvres (14).

Accordingly, an adaptable device is provided that can be used to supply a variety of different operational modes, by altering a single feature of the device: a natural passive ventilation mode taking advantage of a further opening in the enclosure; a displacement ventilation mode when the enclosure needs to remain secure; and a heat recovery mode, which avoids loss of intentional heat from the enclosure and the

introduction of unwanted draughts.

Use of a bi-directional the fan (37) in device (1) provides the additional operability of a boosted extract mode, a boosted displacement mode and a boosted heat recovery mode, intended for use on a temporary basis.

The arrangement is economical and environmentally friendly, without compromising on efficiency of the ventilation delivered.

The mode changing means is robust and straightforward to operate.

Although a few preferred embodiments have been shown and described, it will be appreciated by those skilled in the art that various changes and modifications might be made without departing from the scope of the invention.

Claims

CLAIMS1. A passive ventilation device comprising a ventilation terminal for mounting on a roof component of an enclosure, the terminal providing first and second pathways between an interior of the enclosure and an exterior thereof, the two pathways each comprising an inlet and an outlet and being configured to operate substantially independently of one another in at least one mode, wherein the device comprises a mode changing means adapted to switch the operational mode ot the device between the at least one mode and a heat recovery mode, where in the heat recovery mode a quantity of the extract airtlow is entrained in the supply airflow within the device for re-supply into the enclosure with the supply airflow.
2. A device according to claim 1, wherein the device is also operable in a first mode, CV) where both pathways are substantially independent of one another and configured to operate in the same (interior to exterior) direction to provide a natural extract r mode. r
3. A device according to claim 2, wherein the device comprises an optional extract fan operable in an auxiliary first mode, whereby extraction is boosted through one of the two pathways in the auxiliary first mode.
4. A device according to claim 3, wherein the other pathway is closed by an outlet or inlet closure means on the relevant pathway, or a blocking means in the relevant pathway.
5. A device according to claim 3, wherein the other pathway is closed by a blocking means in the relevant pathway.
6. A device according to any one of claims 1 to 5, wherein the device is further operable in a second mode, where the pathways are substantially independent of one another and configured to operate in opposite directions to provide a displacement mode.
7. A device according to claim 6, wherein the first pathway is configured to provide extract airflow from the enclosure to the exterior and the second pathway is configured to provide supply airflow to the enclosure from the exterior.
8. A device according to any one of claims 1 to 7, wherein the mode changing means is located between the first and the second pathways.
9. A device according to claim 8, wherein the mode changing means comprises merging the first and second pathways at one or more locations between the respective inlets and outlets of the pathways.

CV)
10. A device according to claim 9, wherein the mode changing means comprises one or more cooperable ventilation openings in both pathways and a control means. r
11. A device according to claim 10, wherein the control means functions to align and misalign the ventilation openings.

IS
12. A device according to any one of claims 9 to 11, wherein the mode changing means is operable to merge the pathways in a mixing zone thereby combining extracted room air with fresh supply air within the device when the ventilation openings are aligned.
13. A device according to any one of claims 9 to 12, wherein first pathway merges into the second pathway.
14. A device according to claim 13, wherein the mixing zone is provided in the second pathway.
15. A device according to any one of claims 12 to 14, wherein at least a proportion of the extract air from the first pathway is entrained by the supply air through the ventilation openings and into the mixing zone.
16. A device according to claim 15, wherein the proportion of extract air that is entrained into the mixing zone is controlled by either fully or partially aligning the ventilation openings.
17. A device according to claim 15, wherein the proportion of extract air that is entrained into the mixing zone is controlled by either fully or partially aligning one or more extract outlets in the device.
18. A device according to claim 17, wherein it is possible to make the extract outlet larger, such that a greater amount of extract air is extracted and a lesser amount of extract air is entrained into the mixing zone.
19. A device according to claim 17, wherein it is possible to make the extract outlet i-smaller, such that a lesser amount of extract air is extracted and a greater amount C'tJ 15 of extract air is entrained into the mixing zone.
20. A device according to any one of claims 17 to 19, wherein the manner of controlling the alignment of the ventilation openings and the size of the extract outlets is independently operable.
21. A device according to any one of claims 17 to 19, wherein the manner of controlling the alignment of the ventilation openings and the size of the extract outlets is linked and/or configured to achieve optimum conditions for entrainment.
22. A device according to any one of claims 12 to 21, wherein the manner of controlling the alignment of the ventilation openings and the size of the extract outlets is the mixing zone comprises a mixing chamber in the second pathway.
23. A device according to claim 22, wherein the manner of controlling the alignment of the ventilation openings and the size of the extract outlets in the mixing chamber is located proximal to the second pathway outlet.
24. A device according to any one of claims 23, wherein the chamber is provided by a duct system communicable with a supply outlet (into the enclosure) and a supply inlet (into the device from the exterior).
25. A device according to claim 24, wherein the mixing chamber is provided by an inner duct and an outer duct.
26. A device according to claim 25, wherein the inner duct is movable telescopically within the outer duct.

CD
27. A device according to claim 26, wherein the ventilation openings are provided in walls of both the inner and outer ducts! such that movement of the inner duct within the outer duct controls the alignment or misalignment of the ventilation openings.
28. A device according to claim 27, wherein in a first predetermined arrangement, the duct arrangement is condensed and the ventilation openings are misaligned (inner duct openings is below the outer duct openings).
29. A device according to any one of claims 27 to 28, wherein in a second predetermined arrangement, the duct arrangement is partially extended (between the first and second arrangements) and the ventilation openings are aligned (inner duct openings are in alignment with the outer duct openings).
30. A device according to any one of claims 27 to 29, wherein in a third predetermined arrangement, the duct arrangement is fully extended and the ventilation openings are misaligned (inner duct openings is above the outer duct openings).
31. A device according to any one of claims 27 to 30, wherein the inner duct is supported in each arrangement by a respective stopper.
32. A device according to claim 31 wherein each stopper is located on an inner wall of the terminal.
33. A device according to claim 32, wherein the inner duct comprises an annular flange for cooperation with the stoppers.
34. A device according to claim 33, wherein the flange of the inner duct provides an air seal with an inner wall of the terminal so as to define upper and lower chambers in the terminal and therefore, the first and second pathways.
35. A device according to any one of claims 1 to 34, wherein the first pathway CV) comprises the primary extract pathway.
36. A device according to any one of claims 1 to 34, wherein the second pathway comprises the supply pathway in the second and heat recovery modes.N

CJ
37. A device according to any one of claims 3 to 34, wherein the second pathway lb comprises a primary or additional extract pathway in the first modes and the first auxiliary mode.
38. A device according to any one of claims 1 to 37, wherein the first pathway and the second pathways communicate with the enclosure via a base of the terminal.
39. A device according to claim 38, wherein in heat recovery and second modes, the extract inlet (into the device from the enclosure) and the supply outlet (out of the device to the enclosure) are both provided in the base of the terminal.
40. A device according to any one of claims 1 to 39, wherein the first pathway and the second pathway share a common base opening out of and into the terminal.
41. A device according to claim 40, wherein the pathways are arranged to use different zones of the base opening.
42. A device according to claim 41 wherein the second pathway uses a central portion of the base opening.
43. A device according to claim 42, wherein the second pathway comprises a substantially vertical channel in the lower chamber of the terminal.
44. A device according to claim 43, wherein the second pathway further comprises the upper chamber in a top portion of in the terminal having one or more openings communicable with the exterior (outside).
45. A device according to any one of claims 41 to 44, wherein the first pathway uses a CD peripheral portion of the base opening.
46. A device according to claim 45, wherein the first pathway comprises an annular channel around the core in the lower chamber of the terminal.N

CJ
47. A device according to claim 46, wherein the first pathway is disposed around the second pathway between the duct arrangement and an inner wall of the terminal.
48. A device according to claim 47, wherein the lower chamber comprises one or more openings communicable with the exterior (outside).
49. A device according to claim 48, wherein the openings of the upper and lower chambers corresponding to inlets or outlets for the respective pathways comprises a continuous series of openings divided into two variable sets.