Upblast Exhaust Apparatus With A Variable Outlet Nozzle

Abstract

A radial upblast exhaust apparatus includes a fan housing having a fan inlet to receive air to be exhausted and a fan outlet to expel air to be exhausted. An upper housing is positioned immediately above the fan housing. It includes a first wall section and a second wall section each shaped as a partial conical section being concaved toward each other. The upper housing forms an air outlet nozzle. A mechanism changes the outlet area of the outlet nozzle in order to provide a variable area outlet for the fan.

Description

CROSS-REFERENCED TO RELATED APPLICATION

This application claims the benefit of U.S. Provisional Application No. 60/875,902, which was filed on De. 20, 2006, which is incorporated herein by reference in its entirety.

FIELD OF THE INVENTION

This invention relates to exhaust fans, and more particularly to an upblast exhaust fan which has an outlet nozzle having a variable outlet area.

BACKGROUND OF THE INVENTION

Conventional exhaust systems typically have a fan with a stack or nozzle 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 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.

U.S. Pat. No. 4,806,076, Andrews, shows a nozzle in which two converging flow paths are defined by two respective passageways. A fan 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 relationship with respect to an upper end of the fan and nozzle 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, Andrews, 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, Kupferberg, 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 exhausted from the bifurcated tubular member.

Typically, the wind band is located in spaced relation with respect to an outer wall of the fan housing and nozzle. 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.

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.

One conventional exhaust system that attempts to reduce fan noise at the nozzle or outlet portion to an acceptable level is shown in U.S. Pat. No. 6,112,850, Secrest et al. entitled “Acoustic Silencer Nozzle”, 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.

The exhaust fans discussed in the foregoing patents have a need for changing the air flow through the nozzle. The need also exists in other variations of fans including axial and centrifugal fans.

SUMMARY OF THE INVENTION

In accordance with the invention exhaust fans have a variable outlet nozzle in an upper housing in the discharge path of the fan.

One of the purposes of the nozzle of the present invention is to increase the velocity of the air being discharged into the atmosphere. The prior art nozzle had a fixed outlet area. The outlet area and the flow through the fan determine the outlet velocity of the air at the discharge to the nozzle. (Velocity=Flow/Area). As the demand for air (Flow) to be exhausted through the building is increased, the velocity at the discharge increases. The velocity is a component of the energy required by the fan to move the air. The higher the velocity, the more energy required to move the same quantity of air. The ability to increase the nozzle outlet area will decrease the air velocity and save energy.

In addition, there is typically a minimum velocity that needs to be maintained. If the required flow through the fan falls to a point that the minimum velocity cannot be maintained, additional bypass air from outside of the building must be pulled in through the fan. The fan motor requires additional energy to move this bypass air. The ability to reduce the nozzle area allows the fan to maintain the minimum outlet velocity without the need for bypass air. This elimination of the bypass air also has substantial energy savings.

It is an object of the present invention to provide a variable area outlet for the fan.

The foregoing and other objects, features and advantages of the invention will be better understood from the following more detailed description and appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a prior art radial updraft exhaust fan;

FIG. 2 shows the upper housing with the outlet nozzle having a relatively large outlet area; and

FIG. 3 shows the upper housing with the outlet nozzle in a position with a smaller area.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

Referring to FIG. 1, a radial upblast exhaust apparatus includes a mixing plenum 10 that sits below the fan housing 14. The mixing plenum 10 has a fan inlet 12 to receive air from the building ductwork 13 to be exhausted. A nozzle/windband assembly 16, from which the air is exhausted, is positioned immediately above the fan housing. A wind band 19 increases the dilution of the exhaust air.

Referring to FIGS. 2 and 3, nozzle/windband assembly 16 includes two nozzle halves, 18 and 20, each shaped as a partial conical section. Nozzle sections 18 and 20 are concave toward each other and are spaced from one another.

The nozzle sections 18 and 20 each include an inner wall 21 and an outer wall 22. The inner wall 21 has flexible panels 21a, 21b, 21c, 21d which are movable about an axis to change the outlet area of the outlet nozzle. The flexible panels form the inner walls of each of the nozzle sections. Flexible panels 21a, 21b, 21c, 21d move in unison as a drive mechanism 24 propels a rod or linkage 23 to change the outlet area of the outlet nozzle. For example, the outlet area is changed from that of FIG. 2 to the smaller area of FIG. 3 which increases the exhaust velocity.

Alternatively, the drive mechanism can be manually or automatically operated to change the outlet area of the nozzle.

In accordance with the present invention the outlet area of the outlet nozzle can be changed. Various modifications are within the true spirit and scope of the invention. The appended claims cover all such modifications.

Claims

1. An exhaust apparatus comprising:

a fan housing having a fan inlet to receive air to be exhausted and a fan outlet to expel air to be exhausted; and

an upper housing positioned above said fan housing, said upper housing defining a central opening, and an annular air outlet nozzle that is disposed adjacent the central opening and is in fluid flow communication with said fan housing through said fan outlet to receive exhaust gas therefrom, the upper housing including a first wall section and a second wall section, each wall section being shaped as a partial conical section being concave toward the other wall section, said wall sections forming a radial upblast exhaust apparatus;

wherein the outlet nozzle defines an outlet area that is adjustable so as to provide a variable discharge of gas, and the first and second wall sections of the upper housing each includes an inner wall and an outer wall that is outwardly displaced from the inner wall, wherein the inner and outer walls define the air outlet nozzle therebetween, and the inner wall is movable so as to change the outlet area of said outlet nozzle.

2. (canceled)

3. (canceled)

4. The exhaust apparatus of claim 1 wherein said inner walls each have a flexible panel which is moveable so as to move the inner walls with respect to the outer walls and change the outlet area of said outlet nozzle.

5. The exhaust apparatus recited in claim 4, wherein the inner walls have panels which are movable about an axis so as to change the outlet area of said outlet nozzle.

6. The exhaust apparatus recited in claim 5 wherein said flexible panels are interconnected to move in unison about an axis of each flexible panel.

7. The exhaust apparatus recited in claim 6 further comprising a mechanism for changing the outlet area of said outlet nozzle to provide a variable discharge of gas, wherein the mechanism comprises:

a drive mechanism connected to one of said flexible panels;

and a means for driving said drive mechanism to adjust said flexible panels to change the outlet area of said outlet nozzle.

8. The exhaust apparatus recited in claim 7 wherein said drive mechanism comprises:

a drive screw connected to one of said flexible panels;

and a motor for driving said drive screw to adjust said flexible panels to change the outlet area of said outlet nozzle.

9. The exhaust apparatus recited in claim 8, wherein said drive screw is manually operated to change the outlet area of said nozzle.

10.-28. (canceled)

29. An exhaust apparatus comprising:

a fan housing having a fan inlet to receive air to be exhausted and a fan outlet to expel air to be exhausted; and

an upper housing positioned above said fan housing, said upper housing defining a central opening, and an annular air outlet nozzle that is disposed adjacent the central opening and is in fluid flow communication with said fan housing through said fan outlet to receive exhaust gas therefrom;

wherein the outlet nozzle defines an outlet area that is adjustable so as to provide a variable discharge of gas, the upper housing includes a first wall section and a second wall section, the first and second wall sections each include an inner wall and an outer wall that is outwardly displaced from the inner wall, the inner and outer walls define the air outlet nozzle therebetween, and the inner wall is movable with respect to the other wall so as to change the outlet area of said outlet nozzle.