This invention relates to exhaust ducts and exhaust stacks and, in particular, such stacks adapted for attachment to the outlet of an exhaust fan which can be either a centrifugal fan or an axial fan.
Conventional discharge stacks of considerable height are well known in industry, these stacks being used to discharge various exhaust gases to atmosphere. Often these conventional stacks must be of substantial height in order that the gases can be discharged effectively without causing undesirable environmental consequences to the surrounding area and persons working or living in the area of the discharge stack. Because of the necessary height of these conventional stacks, they can be quite expensive to build and erect.
It will also be appreciated that many exhaust gases are noxious and therefore it is desirable when constructing an exhaust system for a building or industrial operation to attempt to ensure that these exhaust gases do not persist at low altitudes but instead travel upwardly into the atmosphere. Although the aforementioned tall exhaust stacks can be effective for their intended purpose, not only are they costly but they can also be unsightly and they may exceed height restrictions imposed by zoning by-laws.
In order to approximate the performance of these tall stacks, so called upblast fans with relatively short stacks have been developed. However, it has been found that where an upblast fan uses a short stack of conventional construction, the exhaust fan system can be deficient in its ability to properly exhaust gases upwardly into the atmosphere.
A class of upblast fan that has proven to be relatively effective in the propulsion of exhaust gas upwardly into the atmosphere are recently developed upblast fans employing either radial fans or centrifugal fans having an upwardly directed outlet that is connected to a special exhaust gas nozzle. Representative of this class is U.S. Pat. No. 4,806,076 issued Feb. 21, 1989 to Strobic Air Corporation. This known upblast exhaust fan apparatus includes a split, upwardly extending nozzle with a passive zone section located centrally between first and second inner walls. The inner walls cooperate with first and second outer walls to provide first and second exhaust flow paths that lead to two exhaust outlets at the top end. A wind band is secured to the upper end of the exhaust nozzle housing adjacent the exhaust openings and in spaced relation to the outer walls of this housing. In this way, ambient air can be effectively mixed with the exhaust gases. Another recent U.S. patent which teaches an exhaust fan apparatus of this general type is U.S. Pat. No. 5,439,349 to Kupferberg issued Aug. 8, 1995.
In U.S. Pat. No. 6,676,503 issued Jan. 13, 2004 and entitled EXHAUST GAS NOZZLE FOR FAN, there are described several different embodiments of an exhaust gas nozzle that includes a duct member forming a single exhaust passage that extends between first and second open ends. The duct member is formed by a duct wall having at least two longitudinally extending bent wall portions that are distributed evenly about the periphery of the duct member which extends about its longitudinal axis. Each bent wall portion projects inwardly towards the longitudinal axis as seen in transverse planes in the region of the second end. An annular cap is connected to the duct member of this nozzle and is disposed about the exterior of and in spaced relation to the second end of the duct member.
It is an object of one aspect of the present invention to provide an improved form of exhaust gas discharging apparatus which employs vertically extending wind deflecting members or vanes mounted on the duct device and extending horizontally outwardly from the duct wall. These members or vanes extend vertically below an annular cap provided on the discharging apparatus.