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This invention generally relates to the field of ventilation air ducts and more particularly, to modular ducts with easy and fast installation properties.
Ventilation air ducts are usually made of sheet metal that carry cooled or heated air to all rooms of a building. It is well known in the art that ventilation ducts often have to be installed on the roofs because it is inconvenient to have them inside the building for space limitations, cost or other reasons. Exposed outside ducts are expensive to mount. Sections of ventilation air ducts must be fabricated and hoisted on the roof or they may have to be built on site. It is also well known that once on the roof, the sections are mounted on brackets tighten on a system of mounting brackets and/or lay on wooden beams on a flat roof. The anchoring of the sections is time consuming since the mounting brackets and/or beams need to be installed first and then the sections need to be anchored to the mounting brackets and/or beams.
It would be highly desirable to be provided with a ventilation air duct system which is installed in a faster and more efficient way as known duct systems.
One aim of the present invention is to provide a ventilation air duct comprising light-modular sections that can be easily hoisted and installed on a flat roof of a building.
Another aim of the present invention is to provide cost-effective solar air preheating.
In accordance with the present invention, there is provided a roof-mounted ventilation air duct adapted to be connected to a ventilation unit on a flat roof of a building comprising a plurality of duct sections adapted to be connected end to end in fluid flow communication to form a fluid passage for allowing air to flow therethrough, wherein at least some of said plurality of duct sections are provided with a ballast receiving portion, and a ballast material adapted to be disposed on said ballast receiving portion for anchoring the duct sections to the flat roof under the weight of the ballast material, the duct sections and the ballast material having a combined weight which is selected to render said duct sections immovable to side winds on the flat roof of the building.
In accordance with a further general aspect of the present invention, there is provided a building comprising: a flat roof; a ventilation unit mounted on said flat roof; and a roof ventilation air duct seated directly on said flat roof and operatively connected to the ventilation unit, the ventilation air duct comprising a plurality of duct sections adapted to be connected end-to-end in fluid flow communication to form a fluid passage for allowing air to flow theretrough, wherein at least some of said plurality of said duct sections have a seat within the fluid passage for receiving a ballast material, the ballast material anchoring the duct sections to the flat roof, the duct sections and the ballast material having a combined weight which is selected to render said duct sections immovable to side winds on the flat roof of the building.
In accordance with a still further general aspect of the present invention, there is provided an air duct section adapted to be connected to a ventilation unit of a building comprising: a body extending from a first open end to a second open end and forming a fluid passage for allowing air to flow theretrough, said first and second open ends being adapted to be connected in fluid flow communication with first and second similar air duct sections, respectively; a seat within the passage; and a ballast material adapted to be disposed on said seat within the fluid passage such as to be in contact with the air flowing therethrough, the duct section and the ballast material having a combined weight which is selected to anchor by gravity the duct section to an underlying support surface.
Reference will now be made to the accompanying drawings, showing by way of illustration, a preferred embodiment thereof, and in which:
FIG. 1 is a schematic perspective view of a ventilation system mounted on a flat roof section of a building;
FIG. 2 is a schematic perspective view of a section of a roof-mounted ventilation air duct adapted to be connected to similar duct sections and comprising a top lid that can be opened to place a ballast material in the duct section for anchoring the duct section to the roof; and
FIG. 3 is a cross-section of a roof-mounted ventilation duct having a perforated solar panel for preheating the air before being dispensed into the building.
It will be noted that throughout the appended drawings, like features are identified by like reference numerals.
FIG. 1 illustrates a ventilation system 10 mounted on a flat roof R of a building B. The ventilation system 10 generally comprises a conventional ventilation unit 12 adapted to draw fresh air into the building B via ventilation air duct 14. The ventilation unit 12 is also coupled with supply ducts 15. The ventilation air duct 14 comprises a plurality of duct sections 14a, 14b, 14c . . . and 15a, 15b, 15c, adapted to be serially connected in fluid flow communication. The duct sections 14a, 14b, 14c . . . and 15a, 15b, 15c can be made out of galvanized steel, stainless steel and fiberglass-polyester or other suitable materials for exterior ductwork. Best results are obtained with UV-resistant polymer casings with insulation inside.
As shown in FIG. 2, each duct section 14 defines an air passage 16. The duct sections 14a, 14b 14c . . . 15a, 15b, 15c can be of any suitable cross-sectional shape, but preferably of low profile. According to the illustrated embodiment, the duct sections have a rectangular cross-section formed by top, bottom and side walls 18, 20 and 22. The bottom wall 20 can be provided with built-in legs 20a for supporting the duct sections directly on the flat roof R. The duct sections 14a, 14b, 14c . . . 15a, 15b, 15c are connected end-to-end by means of any suitable attaching device 23, such as clips or the like. The top wall 18 can be provided in the form of a lid hinged to one of the side wall 22, thereby allowing the lid to be pivoted between open and closed positions. A lock (not shown) is provided to selectively maintain the lid in its closed position. The lid can be opened to provide access to air passage 16, A ballast material 24, for instance in the form of bulk matter, is placed inside the air passage 16 on the inner surface of the bottom wall 20. The bottom wall 18 thus acts as a seat for receiving the ballast material 24. The weight of the ballast material 24 is selected to firmly anchor the duct section on the building roof R. The ballast material can be provided in the form of gravel, which is readily available and can be handled easily.
The duct sections 14a, 14b 14c . . . 15a, 15b, 15c and the ballast material 24 have a combined weight which is selected to render the duct sections immovable to side winds on the flat roof of the building. This advantageously provides a fastener-less anchoring system. The duct sections 14a, 14b, 14c . . . 15a, 15b, 15c are laid on the roof R without further anchoring which does not cause damages on the roof surface. This advantageously obviates the need for the installation of a duct support on the building roof (i.e. no roof modification). It is noted that only some of the duct sections can be provided with an openable lid. The ballast material 24 does not necessarily need to be placed in each and every section.
The ballast material 24 is preferably provided as a thermal mass placed in heat exchange relationship with the duct sections 14a, 14b, 14c . . . 15a, 15b, 15c and the air flowing therethrough in order to store heat during daytime and release it in to the air flowing through the air passage 16 over night or, during the summer season, store coolness overnight and release it during the day. The thermal mass (i.e. the ballast material) acts as a temperature damper during days when solar radiations fluctuate, particularly on partly cloudy days. The thermal mass may store sensible heat, as would be case with gravel, or latent heat, as would be the case if a phase-change material were used. The ballast material 24, when placed inside the air passage 16, also acts as a turbulator agent to increase heat transfer to the air flowing through the duct sections 14a, 14b, 14c . . . 15a, 15b, 15c However, it is understood that the ballast material 24 could be placed outside of the duct sections 14a, 14b and 14c and 15a, 15b, 15c. For instance, each duct section 14a, 14b and 14c, 15a, 15b, 15c could be provided on opposed longitudinal sides thereof with integral gutter-like channels (not shown) to provide a seat for receiving the ballast material and anchor the duct sections to the building roof R. According to this example, the duct sections could be provided without any lid. The ballast material could also be otherwise attached to the duct sections as long as the duct sections are secured to the roof by the weight of the ballast material.
FIG. 3 shows one duct section 14d having a triangular cross-section and an equator-facing solar collector panel 28 integrated as one of the sidewall of the duct section for absorbing the incident solar radiation. The triangular shape is advantageous in that it prevents water or snow accumulation on top of the duct sections. The triangular shape also renders the duct sections less prone to movement due to side winds by deflecting the lateral incoming outside air.
The collector panel 28 can be hinged to the other side wall 22 or the bottom wall 20 of the duct section 14d to provide access to the interior of the duct section and allow pouring of the ballast material 24 inside the duct section. The collector panel 28 can be coated on the outside with a solar radiation absorbing material, such as dark paint. Far more desirable than dark paint would be a “selective coating” with high absorption for solar radiation and little infra-red heat emission at temperatures occurring at the collector panel on a sunny day, to keep total energy losses low.
Alternatively, the collector panel 28 can have a plurality of inlet air openings over its surface, or can be made of glazing or transparent material to facilitate heating of the ballast material 24 and, thus, the preheating of the air drawn through the duct sections. This effect is particularly beneficial during autumn and spring, and even summer, when preheating of the air may not be wanted during daytime but needed in the evening or later in the night.
Such a perforated air heating panel can be used with an inclination of preferably 70 degrees above horizontal in Canadian climates or adjusted for optimal energy output in other parts of the world. The outside air is being heated as it travels through the perforated plate. This advantageously allows to preheat the air before being dispensed into the building B.
Solar energy utilization of the duct sections 14a, 14b, 14c, 14d . . . can be useful in an industry where large amounts of outside air are to be heated to a set point as high as possible, as frequently as possible. An example of such an industry is a building admitting over 10 000 cubic feet per minute (cfm) of fresh air which must be heated to 70° F. or more, seven days a week, twenty-four hours per day.
In another non-illustrated embodiment, the sections of the air duct may comprise two sections, one through which incoming fresh air is drawn into the building and one through which the outgoing air from the building is being expelled. Both sections are separated by a thin conductive plate, such as a sheet metal of steel or aluminum. This allows using the roof-mounted conduits as a heat exchanger.
The ventilation ducts 14 and 15 can be easily installed by hoisting the lightweight duct sections on the building roof R using a crane or the like. The sections are preferably designed so that they are stackable, in order to hoist more than one piece at a time with the crane. The sections are then laid down directly onto the roof deck and connected together end-to-end. Then, the ballast material 24 is poured into the duct sections 14a, 14b, and 14c . . . in order to anchor the duct sections to the roof and resist wind dislodgement.
The present ventilation duct anchoring method have several advantages that can be generally summarized as follows: quick installations, no damage to roof surface, high immovability, thermal stability, better air tightness than ducts made on site, easy access to duct interior, heat storage (thermal mass or by means of phase-change material), solar gain application (integrated collector panel), watershed design (triangular shape).
While the invention has been described with particular reference to the illustrated embodiments, it will be understood that numerous modifications thereto will appear to those skilled in the art. For instance, the present duct anchoring method is not limited to roof applications. Accordingly, the above description and accompanying drawings should be taken as illustrative of the invention and not in a limiting sense.
While the invention has been described in connection with specific embodiments thereof, it will be understood that it is capable of further modifications and this application is intended to cover any variations, uses, or adaptations of the invention following, in general, the principles of the invention and including such departures from the present disclosure as come within known or customary practice within the art to which the invention pertains and as may be applied to the essential features hereinbefore set forth.