Ventilation – Chimney or stack – Chimneytop or stacktop structure
Reexamination Certificate
2000-03-29
2002-08-13
Joyce, Harold (Department: 3749)
Ventilation
Chimney or stack
Chimneytop or stacktop structure
C454S016000
Reexamination Certificate
active
06431974
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates in general to a gas exhaust system, and particularly, the present invention relates to an acoustical wind band for use with an exhaust device for exhausting gas from, for example, the interior of a building. The invention is especially useful in improving the entrainment of environmental air into the exhaust fume thereby improving the discharge velocity of the exhaust gas and therefore the effective stack height of the exhaust device and also in improving the sound attenuation of noise from the exhaust device or exhaust device outlet.
BACKGROUND OF THE INVENTION
Conventional exhaust systems are typically manufactured having a fan and a nozzle device for pulling a gas out of the interior of a building and then increasing the velocity of the exiting air in order to properly dispel the air and also to avoid re-entrainment of the discharged air. In this regard, reference is made to U.S. Pat. No. 4,806,076, issued to Andrews, and U.S. Pat. No. 5,439,349, issued to Kupferberg, which are designed to provide a high velocity jet for exhausting atmosphere and other gases. These exhaust fans are typically mounted on the roof areas of buildings and are used to carry exhaust gases as high as possible above the roof line of the building so as to ensure an effective final dilution of the gases within the greatest possible volume of ambient air and to ensure their dispersal over a large area with maximum dilution.
For example, the radial upblast exhaust fan apparatus described and shown in U.S. Pat. No. 4,806,076 has a nozzle in which two converging flow paths are defined by two respective passageways. A fan means is positioned within the fan housing to urge exhaust gases to flow upwardly through the exhaust paths. A passive zone located between the two flow paths supplies environmental air for mixing by induction into the contaminated gases being exhausted through the converging flow paths.
In addition, prior art devices for exhausting gases to atmosphere can have a wind band, or annular ring, that may be positioned vertically extending in general parallel relationship with respect to an upper end of the fan or nozzle housing in order to facilitate mixing of the exhausted gas with ambient environmental air. For example, a wind band can be provided at one end of the two passages at the outlets of the radial upblast exhaust fan apparatus described and shown in U.S. Pat. No. 4,806,076, to provide an entrainment of fresh air to mix with and dilute the gases exhausting from the two passageways. Another conventional wind band is shown and described in U.S. Pat. No. 5,439,349, which describes a ring defining an annulus provided at the outlet end of a bifurcated stack to induce ambient air to mix with the spent air exhausting from the bifurcated tubular member.
Typically, the wind band is located in spaced relation with respect to an outer wall of the fan or nozzle housing by, for example, a wind band bracket means. In this manner, when gases are exhausted through the discharge of the exhausting device, ambient environmental air will be introduced between the space, formed between the outer wall of the exhausting device and the side wall of the wind band, and mix with and dilute the exhausting gases. However, conventional wind bands are limited in the amount of entrainment that they can achieve due to their design and construction.
In addition, conventional exhaust fans for moving large volumes of air often generate high levels of noise which is undesirable. As a result, a wide variety of fan silencing equipment has been proposed to absorb fan noise, thereby reducing fan noise to an acceptable level. However, conventional silencers are typically used at the fan portion of the device, and thus do not control noise at the nozzle or outlet portion. These conventional silencers are undesirable for several reasons, including because they lead to an increase in the overall height of the fan device and they are limited to a relatively low air distribution velocity (on the order of less than about 3000 feet per minute) in which they are effective (e.g., provide maximum attenuation without themselves generating any significant additional noise).
One conventional exhaust system that attempts to reduce fan noise at the nozzle or outlet portion to an acceptable level is pending U.S. patent application entitled “Acoustic Silencer Nozzle”, Ser. No. 09/390,796, filed Sep. 7, 1999, which describes a high velocity silencer nozzle for reducing the amount of noise generated by the exhausting gases as they exit through the exhausting device. The acoustic silencer nozzle provides acoustically absorbing media or resonating chambers adjacent the converging exhaust paths of the nozzle. In this manner, the noise at the nozzle or outlet portion is reduced and a tighter plume of high discharge flow is achieved. However, these conventional silencers are limited in their ability to block noise, such as line of sight noise, from the exhausting gas at the outlet portion or portions of the exhaust device.
Therefore, a need exists for a device that improves the entrainment of ambient environmental air with the exhausting gases and also that improves sound attenuation of the discharging gases at the outlet portion of the fan, nozzle, stack, silencer, ducting, or the like, while still maintaining a relatively low height of the exhausting device and providing a relatively high air distribution velocity, without adding significantly to system pressure.
SUMMARY OF THE INVENTION
The present invention is directed to an apparatus, system, and method for improving the entrainment of ambient environmental air with the exhaust gas passing through the acoustical wind band and for improving the attenuation of sound from the exhaust gas exiting the exhaust device. The acoustic wind band apparatus can be used with a gas exhaust device having a discharge outlet portion for exhausting gas in a gas exhaust system. The acoustical wind band includes a plurality of spaced apart wind band sections, each wind band section having a top end defining a top opening, a bottom end defining a bottom opening, and one or more side walls disposed between and connecting the top end to the bottom end. The plurality of wind band sections are disposed circumferentially and in vertical spaced relation over the discharge outlet portion of the gas exhaust device and extending generally upward therefrom.
The acoustic wind band apparatus includes a plurality of passages formed around a peripheral of the acoustical wind band and disposed circumferentially about the discharge outlet portion. Each passage draws a flow of gas from environmental atmosphere outside the acoustical wind band to induce a flow of environmental gas from therebelow to mix with and dilute gas from the discharge outlet portion inside the acoustical wind band. The number of the plurality of passages corresponds to a number of the plurality of wind band sections. The acoustic wind band includes at least a first passage formed between one of a top wall and a side wall of the exhaust device and the side wall of the lower most wind band section and at least a second passage formed between a second wind band section side wall and the first wind band side wall.
Each sections can include one of a cylindrical shape, a straight conical shape, a curved conical shape, a square shape, and a rectangular shape. The bottom opening and the top opening can comprise one of a circular shape, a square shape, and a rectangular shape. Preferably, the side walls of adjacent sections of the plurality of wind band sections are parallel with respect to one another. Each wind band section has a smallest diameter or width greater than a diameter or width of the discharge outlet portion.
Preferably, the first, lowest most, wind band section is positioned over and about the discharge portion and each vertically successive section is larger than the preceding section and each vertically successive section is positioned over and about the preceding section. Alternatively, the first,
Gans Charles A.
Tetley Paul Antony
Boles Derek S.
Joyce Harold
Met Pro Corporation
Woodcock & Washburn LLP
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