EP2198205B1

EP2198205B1 - Sound attenuator for a fan coil

Info

Publication number: EP2198205B1
Application number: EP07838828.7A
Authority: EP
Inventors: Eric C. Pitisci; Frederic C. Albert; Didier G. Joly
Original assignee: Carrier Corp
Current assignee: Carrier Corp
Priority date: 2007-09-25
Filing date: 2007-09-25
Publication date: 2018-11-28
Anticipated expiration: 2027-09-25
Also published as: WO2009041937A1; ES2701871T3; CN101809375A; EP2198205A4; EP2198205A1

Description

Background of the Invention

This invention relates generally to air conditioning systems and, more particularly, to a method and apparatus for reducing sound emanating from the return air opening of a fan coil unit.
Fan coils are commonly provided in air conditioning systems to provide a heat exchange relationship between air that is being returned to the unit from a space to be conditioned, and a medium, in a liquid, vapor or gaseous form, which has been "conditioned" in a closed loop air conditioning system. The fan coil therefore includes a heat exchanger coil through which the medium is circulated and over which the return air is circulated by way of the fan.
As the fan draws the return air into the fan coil unit and over the heat exchanger coil, it necessarily produces a good amount of noise which then tends to emanate in the direction of the space from which the return air is flowing. The fan coil may be connected to the space by way of a duct, in which case the sound may be somewhat attenuated by the air in the duct, but the fan coil may connect directly to the space without an attached duct, in which case, there tends to be no attenuation of the emitted sound. In either case, it is desirable to reduce the amount of sound that is transmitted to the space to be conditioned.
In ducted systems, there is room to install various types of sound attenuating devices, some of which are quite sophisticated and effective, but not without significant expense. In non-ducted systems, however, there has traditionally been no treatment of the sound emanating from the inlet duct of a fan coil.
Another consideration in providing attenuation is that of a pressure drop that may be associated with any sound attenuation system. That is, generally there is a pressure drop that is associated with any type of attenuation system, and it is preferable to obtain as low as a pressure drop as possible while still obtaining the desired degree of sound attenuation.
A fan coil unit including in serial flow relationship, a fan assembly and a heat exchanger coil and a method of reducing the sound emanating from a fan coil that includes a fan assembly with the features of the preamble to claim 1 or claim 4 is disclosed in US 6,419,576 . Other fan coil units and method of reducing sound emanating from a fan coil are disclosed in GB 1 344 268 , WO 2005/073640 , WO 2007/012537 and US 3,330, 379 .

Summary of the Invention

From one aspect, the present invention provides a fan coil unit including in serial flow relationship, a fan assembly and a heat exchanger coil in accordance with claim 1.
From another aspect, the present invention provides a method of reducing the sound emanating from a fan coil that includes a fan assembly in accordance with claim 4.
Preferred embodiments are defined in the dependent claims.
In the drawings as hereinafter described, a preferred embodiment is depicted; however, various other modifications and alternate constructions can be made thereto without departing from the scope of the invention as defined in the claims.

Brief Description of the Drawings

FIG. 1 is an exploded perspective view of a fan coil unit in accordance with the prior art.
FIG. 2 is a perspective view of ducted fan coil unit in accordance with the prior art.
FIG. 3 is a fan coil unit with the present invention incorporated therein.
FIG. 4 is a front perspective view thereof.
FIG. 5 is a side view thereof.
FIG. 6 is a perspective view of the internal components thereof.
FIG. 7 is a longitudinal side view of a fan coil unit with the present invention incorporated therein.

Detailed Description of the Invention

Shown in Fig. 1 is a typical ducted fan coil unit 11 in accordance with the prior art. The fan coil unit 11 includes an outer casing 12 in which there is disposed a heat exchanger (not shown) through which refrigerant is circulated and over which air is circulated by way of one or more fan assemblies 13 disposed within the casing 12 as shown. A filter 14 is preferably placed on the upstream side of the fan assemblies 13 to filter out any solid impurities that may be in the air stream. On the upstream side of the casing 12 is a return air plenum 16 having a plurality of openings 17 which are fluidly connected to return air ducts (not shown).
On the downstream side of the casing 12 is a supply air plenum 18 with openings 19 which are fluidly connected to supply air ducts (not shown) from supplying conditioned air to spaces within a building.
By operation of the fan assemblies 13, return air is drawn in through the return air ducts to the return air plenum 16, through the filter 14 and the heat exchanger where the air is conditioned (i.e. either cooled or warmed) after which the conditioned air passes into the supply air plenum 18 and through the openings 19 to supply conditioned air to the supply air ducts. Because of the return air plenum 16 and the return air ducts, any noise emanating from the fan assemblies 13 is substantially muffled by the time it reaches the space from which the return airflow is originating. The same is true for the supply end where the supply air plenum 18 and the supply air ducts provide an attenuation effect to any noise emanating from the supply side of the fan coil unit 11.
Referring now to Fig. 2, the same type of fan coil in 11 is shown but without the return air plenum 16. That is, there is no return air plenum 16 nor any return air ducts. Rather, the filter 14 at the upstream end of the casing interfaces directly with the space from which the return air is flowing. Thus, there is no attenuation of the sound which tends to emanate upstream from the fan assembly 13, and directly into the space from which the return air is flowing.
There is shown in Fig. 3 a similar fan coil unit without a return air plenum 16 or return air ducts. However, at the upstream end of the fan coil unit 11 a sound attenuator assembly 21 is connected thereto for purposes of attenuating the sound that would otherwise would emanate toward the origin of the return air flow. The sound attenuator assembly 21 is connected directly to the upstream end of the fan coil unit such that all air passing into the fan coil unit 11 passes first through the sound attenuator assembly 21.
The sound attenuator assembly 21 is more fully shown in Figs. 4-6. The assembly includes a rectangular casing 22 having an inlet opening 23 leading to an inlet duct 25 and having an outlet 24 at its end. It includes an upper wall 26 and a lower wall 27. As will be seen in Fig. 4, there is disposed within the casing 22 a centrally located, transversely extending, acoustical insulation member 28. Also disposed within the casing 22 are upper and lower wall peripheral acoustical insulation members 29 and 31. These members are shown in greater detail in Figs. 5 and 6.
The acoustical insulation member 28 is cylindrical in form and extends transversely across a central portion of the casing 22 with its ends being secured to the sides of the casing. The peripheral acoustical insulation members 29 and 31 are generally triangular in shape and are mounted in an upstream position with respect to the insulation member 28 as shown. They may me mounted directly to the respective upper wall 26 and lower wall 27 or may be attached to the respective acoustical insulation members 32 and 33, which, in turn, are connected directly to the respective upper wall 26 and lower wall 27. The respective positions of the various acoustical insulation members will be more fully described hereinafter.
A filter 34 may be placed on the upstream end of the sound attenuator assembly 21 to either augment or replace the filter 14 that is provided at the inlet end of the fan coil unit 11 as shown in Fig. 3.
Shown in Fig. 7 is a longitudinal profile of a fan coil unit 11 having a sound attenuator assembly 21 attached to its upstream end thereof. A centrifugal fan or blower 36 is positioned with the casing 12 to draw air in through the sound attenuator assembly 21 and pass the air through a heat exchanger coil 37 after which it flows to a supply air plenum 18, through the supply air ducts, and finally to a spaced to be conditioned.
During operation of the fan 36 noise is produced both by the operation of the drive motor 38 and of the movement of the air as caused by the fan 39. Unless otherwise attenuated, this noise is likely to travel in both the downstream and upstream directions. To prevent or attenuate the sound from traveling in the upstream direction (i.e. out through the inlet duct 25), the sound attenuator assembly 21 with its elements 28, 29 and 31 are provided. The relative positioning of those elements, and to some extent their shape, are designed to absorb, deflect, or attenuate the sound waves which are traveling along an axial direction as indicated by the dashed lines. That is, the sound absorbing elements 28, 29 and 31 are so placed within the duct that there are portions thereof between the entire fan and the entire inlet opening as seen along the axially extending lines. At the same time, however, this arrangement results in a relatively low pressure drop through the assembly 21.
It should be understood that the various shapes and positions of the acoustical insulation members 28, 29 and 31 can be varied within the scope of the claims as desired to meet the requirements of a particular installation. Further, although the invention has been described in terms of use with a non-ducted fan coil unit, it may, as well, be used with a ducted unit.
While the present invention has been particularly shown and described with reference to a preferred mode as illustrated in the drawing, it will be understood by one skilled in the art that various changes in detail may be effected therein without departing from the scope of the invention as defined by the claims.

Claims

A fan coil (11) unit including in serial flow relationship, a fan assembly (13) and a heat exchanger coil, comprising:
a cabinet (12) for housing said fan assembly (13) and heat exchanger, said cabinet (12) having an inlet opening (23) and an inlet duct (25), wherein said inlet duct (25) is rectangular in cross-section and has upper (26), lower (27) and side walls, for serially receiving the flow of return air as it is drawn in by the fan assembly (13); and

at least one sound absorbing element (28, 29, 31) disposed in said inlet duct (25) to absorb sound that emanates from the fan assembly (13) toward said inlet opening (23);

characterised in that said at least one sound absorbing element (28, 29, 31) comprises just three sound absorbing elements (28, 29, 31), with one (28) being cylindrical in form and being generally centrally located, and the other two being a pair of peripheral elements (29. 31) mounted on respective opposite walls (26, 27), wherein the peripheral elements (29, 31) are generally triangular in shape and are mounted in an upstream position with respect to the cylindrical element (28).
A fan coil unit as set forth in claim 1 wherein said at least one sound absorbing element (28, 29, 31) is disposed such that there are portions thereof between the entire fan assembly (13) and said inlet opening (23) as seen along axially extending lines.
A fan coil unit as set forth in any preceding claim and including a filter (14; 34) disposed in said inlet opening (23).
A method of reducing the sound emanating from a fan coil that includes a fan assembly (13), comprising the steps of:
providing a cabinet (12) for housing said fan assembly (13) and having an inlet opening (23) and an inlet duct (25), wherein said inlet duct (25) is rectangular in cross-section and has upper (26), lower (27) and side walls, for serially receiving the flow of return air as it is drawn in by the fan assembly (13); and

providing at least one sound absorbing element (28, 29, 31) disposed in said inlet duct (25) to absorb sound that emanates from the fan assembly (13) toward said inlet opening (23);

characterised in that said at least one sound absorbing element (28, 29, 31) comprises just three sound absorbing elements (28, 29, 31), with one (28) being cylindrical in form and being generally centrally located, and the other two being a pair of peripheral elements (29. 31) mounted on respective opposite walls (26, 27), wherein the peripheral elements (29, 31) are generally triangular in shape and are mounted in an upstream position with respect to the cylindrical element (28).