Ventilation terminal

Abstract

 The ventilation terminal (10) delivers air from a supply duct to a space served by the duct. A lobed array (22), along which are arranged a plurality of lobes (23) separates a primary flow passage (31) and an ejector flow passage (32). The height of the lobes (23) increases from upstream to downstream along the array (22). The lobed array (22) is configured so that a lobe in one passage is a trough in the other passage. The primary flow passage (31) conducts air from an air supply duct upstream through the terminal (10) to a terminal air outlet (12). Ejector mixing interaction between the air flow in the primary flow passage (31) as air passes through the lobed array (22) causes air flow in the ejector passage (32) from a recirculating air inlet (33) to the terminal air outlet (12). The mixing interaction also causes the recirculating air flow to mix with the primary air flow as the two streams exit the terminal air outlet (12), reducing effective total flow velocity and therefore noise as well as reducing drafts and hot or cold spots in the space served by the terminal (10).

Description

Background of the Invention

[0001] This invention relates generally to ventilation systems. More particularly, the invention relates to terminals for diffusing and distributing air from a ventilation supply duct into a space such as a room.

[0002] Ventilation systems are widely used to distribute air within enclosed spaces such as rooms in buildings or ships, or cabins of motor vehicles or aircraft. The distributed air may be heated, cooled, dehumidified, filtered or otherwise conditioned or purified by specialized equipment adapted to the purpose. Common to nearly all ventilation systems are terminals at the outlet ends of the ducts supplying air to the space or spaces to be ventilated.

[0003] A terminal serves several functions. One is to distribute the air exiting the terminal as widely as possible in order to minimize the number of duct terminals required to serve a given space. Another is to mix the air exiting the terminal with air already in the space so as to promote uniform distribution of air having a desired condition (e.g. temperature, humidity) within the space and thus to prevent drafts and "dead," hot or cold areas. The terminal should contribute as little as possible to system pressure losses and also as little as possible to system radiated noise.

[0004] Many prior art ventilation terminals attempt to achieve their design objectives by diffusing the air stream from the supply duct through the terminal to an outlet having a much greater area than that of the duct and by turning the airstream at the outlet into one or more directions by an arrangement of deflectors, baffles or vanes. The losses through such a terminal can be large because the relatively large spreading or diffusion angle causes separated air flow at the inner surface of the diffuser section of the terminal (a condition known as diffuser stall), with a resultant energy dissipation in turbulence. Stall at the inner surface of the diffuser also reduces air flow through that region and results in a high velocity jet at the center of the terminal air flow passage. The high velocity jet has embedded turbulence from the diffuser stall. This high velocity jet generates high noise levels when it passes through and impinges on the exit deflectors. Because of the relatively high pressure loss through such a terminal, the ventilation system fan or fans must operate at a higher loading to achieve desired air flow rates and thus the fans produce greater noise levels than if the terminal were not in the system.

[0005] At least one prior art ventilation air terminal, see Kurth et al., U.S. Patent 2,825,274 issued 4 March 1958, has an ejector that induces air from the spaces served by the terminal to mix with the flow of conditioned air from the air supply duct. But, while the '274 terminal is an improvement over terminals without an ejector, standard ejectors (without lobes) do not operate effectively within the constraints of the short mixing length of a ventilation terminal and therefore increase the pressure loss through the terminal. The stream of air entering the terminal and the stream of mixed air exiting the terminal are in close proximity, leading to re-ingestion or "short circuiting" of the mixed air and therefore reducing the mixing and coverage effectiveness of the terminal.

Summary of the Invention

[0006] The present invention is a ventilation air terminal incorporating a mixer ejector. The terminal offers improved mixing, reduced pressure loss and reduced radiated noise.

[0007] The terminal delivers air from an upstream supply duct through a primary flow passage in the terminal to an outlet. One boundary of the primary flow passage is a lobed array. The lobed array has a plurality of lobes aligned longitudinally along the array. The height of the lobes increases gradually in an upstream to downstream direction along the array. On the other side of the lobed array is an ejector flow passage. The configuration of the lobes is such that a lobe in one flow passage is a trough in the other flow passage. Viewed from downstream, the lobes have a wave-like appearance. The ejector flow passage conducts air from a recirculating air inlet to the outlet of the terminal. The lobes produce streamline vortices and other stirring mechanisms thus producing rapid mixing with low losses. This mixing interaction between the air flow in the primary flow passage as the air passes through the lobed array and the air in the ejector flow passage causes air to flow in the ejector flow passage from the recirculating air inlet to the air outlet. The mixing interaction also causes the recirculating air to mix with the primary air that is discharged from the terminal. The terminal draws air from the space it serves and mixes this recirculated air with the supply air before discharging the mixed airstreams to the space. The terminal thus reduces any large variation in condition, e.g. temperature, between the supply air and the ambient air within the space so that unpleasant drafts as well as hot or cold spots are reduced. The mixing action also serves to reduce the total velocity of the air exiting the terminal into the space with a resultant reduction in air flow noise produced by the terminal.

[0008] One may configure the terminal of the present invention in more than one embodiment, such as one discharging along the same line as the direction of flow through the supply duct, or in which the discharge airstream is at some other angle.

Brief Description of the Drawings

[0009] The accompanying drawings form a part of the specification. Throughout the drawings, like reference numbers identify like elements.

[0010] FIG. 1 is an isometric view, partially broken away, of one embodiment of the terminal of the present invention.

[0011] FIG. 2 is a top plan view, partially broken away, of the terminal depicted in FIG. 1.

[0012] FIG. 3 is a sectioned, through line III-III in FIG. 2, elevation view of the terminal depicted in FIG. 1.

[0013] FIG. 4 is a second isometric view of the terminal depicted in FIG. 1.

[0014] FIG. 5 is a sectioned, through line V-V in FIG. 2, elevation view of the terminal depicted in FIG. 1.

[0015] FIG. 6 is a schematic diagram showing air flow through the terminal depicted in FIG. 1.

[0016] FIG. 7 is an isometric view of another embodiment of the terminal of the present invention.

[0017] FIG. 8 is a bottom plan view of the terminal depicted in FIG. 7.

[0018] FIG. 9 is a sectioned, through line IX-IX in FIG. 7, of the terminal depicted in FIG. 7.

[0019] FIG. 9 is a sectioned, through line VII-VII in FIG. 7, eleva tion view of the terminal depicted in FIG. 7.

[0020] FIG. 10 is a schematic diagram showing air flow through the terminal depicted in FIG. 7.

Description of the Preferred Embodiments

[0021] FIGS. 1 through 5 depict one embodiment of the terminal of the present invention. FIG. 1 is an isometric view, partially broken away, FIG. 2 is a top plan view, partially broken away, FIG. 3 is a sectioned side elevation view, FIG. 4 is an isometric view from another angle and FIG. 5 is a sectioned elevation view of a portion of the terminal. In this embodiment, a ventilation terminal discharges air from a ventilation duct into a space at right angles to the direction of the inlet air. A terminal of this configuration would be appropriate where flush mounting with a surface such as a ceiling is not required or desired. FIGS. 1 through 5 show ventilation terminal 10, the major components of which are inlet duct 13, terminal casing 14, baffle plate 15 and lobed array 22.

[0022] Air from an upstream air supply duct (not shown) enters inlet duct 13 of terminal 10 through air inlet 11. All of the air entering terminal 10 through air inlet 11 (primary air) must flow through primary flow passage 31, which is formed and defined by terminal casing 14 and lobed array 22, before exiting terminal 10 through air outlet 12. Air from the space served by terminal 10 (recirculating air) can enter the terminal through recirculating air inlet 33 in baffle plate 15. To exit through air outlet 12, recirculating air entering terminal 10 through recirculating air inlet 33 must pass through ejector flow passage 32. Ejector flow passage 32 is formed by and between baffle 15 and lobed array 22.

[0023] Lobed array 22 has a plurality of radially arranged lobes 23 aligned so that they conform longitudinally to the stream of primary air flowing from inlet duct 13 to air outlet 12 through primary air passage 31. Lobes 23 penetrate alternately into both primary flow passage 31 and ejector flow passage 32 so that a lobe in one of the passages is a trough in the other. The height of lobes 23 increases gradually in an upstream to a downstream direction along the array. When viewed from downstream (FIG. 5), lobes 23 have a wave-like appearance. Taken together, lobed array 22, primary flow passage 31 and ejector air passage 32 form a mixer ejector.

[0024] FIG. 6 shows schematically the operation of terminal 10. Primary air enters terminal 10 through air inlet 11. As the primary air passes through terminal 10 it turns and passes through the lobes and troughs of lobed array 22 in primary flow passage 31. Ejector mixing interaction between the air flow in primary air passage 31 and the air in ejector air passage 32 causes a flow of air in passage 32 from recirculating air inlet 33 to air outlet 12, causing air from the space served by terminal 10 to be drawn into the terminal and mixed with the primary air stream from the ventilation supply duct.

[0025] The configuration of air outlet 12 is that of a diffuser, lowering the static pressure at the outlet and thus increasing the secondary air flow through terminal 10. Terminal 10 does not require a diffuser but, in addition to lowering the static pressure, the diffuser improves the secondary air pumping power of terminal 10. This is because vortices generated in the primary and secondary air streams by lobes 23 energize the diffuser boundary layer and allow relatively large diffuser angles without stalling. The absence of stall means that the full energy of the primary air stream is available to pump the secondary air stream (with about 90 to 95 percent efficiency).

[0026] FIGS. 7 through 9 depict another embodiment of the terminal of the present invention. FIG. 7 is an isometric view, partially broken away, FIG. 8 is a bottom plan view, and FIG. 9 is a sectioned side elevation view of the terminal. In this embodiment, a ventilation terminal discharges air from a ventilation duct into a space with no change of direction through the terminal. The configuration of this embodiment of the invention allows the terminal to be mounted flush with a surface, such as a ceiling. FIGS. 7 through 9 show ventilation terminal 10', the major components of which are inlet duct 13', terminal casing 14', inner wall member 16' and lobed array 22'.

[0027] Air from an upstream air supply duct (not shown) enters inlet duct 13' of terminal 10' through air inlet 11'. Lobed array 22' joins with the downstream end of inlet duct 13', therefore all of the air entering terminal 10' through air inlet 11' (primary air) must flow through primary flow passage 31', which is surrounded and defined by lobed array 22', before exiting terminal 10' through air outlet 12'. Air from the space served by terminal 10' (recirculating air) can enter the terminal through recirculating air inlet 33', which is an annular opening surrounding air outlet 12'. To exit through air outlet 12', air entering terminal 10' through recirculating air inlet 33' must pass through recirculating flow passage 34' and ejector flow passage 32'. Recirculating flow passage 34' is an annular space formed between the inner wall of terminal casing 14' and the outer wall of inner wall member 16'. Ejector flow passage 32' is an annular space formed by and between the inner wall of inner wall member 16' and lobed array 22'.

[0028] Lobed array 22' has a plurality of lobes 23' aligned longitudinally along the array. Lobes 23' penetrate alternately into both primary flow passage 31' and ejector flow passage 32' so that a lobe in one of the passages is a trough in the other. The height of lobes 23' increases gradually in an upstream to a downstream direction along the array. When viewed from downstream (FIG. 7), lobes 23' have a wave-like appearance. Taken together, lobed array 22', primary flow passage 31' and ejector flow passage 32' form a mixer ejector.

[0029] FIG. 10 shows schematically the operation of terminal 10'. Primary air enters terminal 10' through air inlet 11'. The primary air passes through terminal 10', passing through the lobes and troughs of lobed array 22' in primary flow passage 31'. Ejector mixing interaction between the air flow in primary flow passage 31' and the air in ejector flow passage 32' causes a flow of air to and through passage 32' from secondary air inlet 33', through recirculating air passage 34 and then to air outlet 12', causing air from the space served by terminal 10' to be drawn into the terminal and mixed with the primary air stream from the ventilation supply duct. If desired, turning vanes or deflectors may be fitted at air outlet 12' to provide wider diffusion of the discharge of the terminal. The lower velocities at the outlet would result in lower noise from such turning vanes, compared to conventional vaned terminals.

Claims

1. A ventilation terminal (10, 10') comprising:
a terminal casing (14, 14');
   an inlet duct (13, 13') in upstream air flow relationship with said terminal casing and through which a stream of primary air can be delivered to said terminal casing;
   a primary flow passage (31, 31') that provides a flow path for said primary air through said terminal casing from said inlet duct to an air outlet (12, 12');
   a lobed array (22, 22') centrally located within said terminal casing and in downstream flow relationship with said inlet duct, said lobed array having
      a plurality of lobes (23, 23') longitudinally aligned with said stream of primary air and increasing gradually in height in an upstream to downstream direction along said array; and
   an ejector flow passage (32, 32'), adjacent said primary flow passage but separated from said primary flow passage by said lobed array and defined by said lobed array and a wall (15,16'), that provides a flow path for recirculating air from a recirculating air inlet (33, 33') to said air outlet.

2. The ventilation terminal of claim 1 further comprising
   a recirculating flow passage (34') that provides a flow path for recirculating air from said recirculating air inlet (33') to said ejector flow passage.

Drawing