Patent Application
20060231086
1. Field of the Invention
The invention relates to a distribution tee assembly for transferring the products of combustion produced by a multi-position condensing furnace from a heat exchanger to an exhaust vent pipe system.
2. Background Art
Installation of residential or commercial furnaces can be a time consuming and costly process, particularly when space is limited. Because of space limitations, an installation technician may need to orient a furnace one particular way in order to install the furnace in the desired location. When a furnace is configured from the factory to be installed in only one or two different orientations, it may not be able to fit into the desired location. When this occurs, one of a number of events must take place: the furnace must be installed in a different location, a different furnace must be installed, or the existing furnace must be modified in the field to accommodate the desired location. Having an installation technician modify various components of a furnace in the field adds complexity, time and cost to the installation.
Therefore, a need exists for a furnace that can be installed in various vertical and horizontal positions, so as to eliminate the need for extensive modification of furnace components in the field.
One condensing furnace incorporates a transverse flue design which serves to direct the flue products in either transverse direction depending on the location of vent pipe connections.
In many installations, it would be desirable to discharge the products of combustion in either direction. Such a design would allow for greater ease in installation and flexibility in all configurations—upflow, downflow, and horizontal left/right, by allowing an installer to select a connection (left or right) which works best and minimizes furnace modifications that are necessitated at the time of installation.
Earlier designs incorporated a constant diameter transverse portion of the flue tee. But this design effectively creates a “bulkhead” in the transition region. Instead of being directed down and along the appropriate outlet pipe (based on vent pipe location), the products of combustion impinge on a back wall of the flue tee. This tends to create a stagnant region and increases resistance to fluid flow.
Relatedly, it would be desirable to maintain the flue gas flow rate by reducing the pressure drop in a transition region of the flue tee. This in turn would increase the vent length capability of the furnace without increasing combustion air inducer capacity (motor strength and/or flow volume) or increasing the internal diameter of the flue tee.
One U.S. patent that was considered in preparing this application was U.S. Pat. No. 6,588,802 that issued on Jul. 8, 2003. That reference discloses a two-part, clamp-connected chimney flue tee.
Against this background, the invention includes a distribution tee assembly. The assembly transfers the products of combustion from a heat exchanger to an exhaust vent system. The tee assembly includes a distribution tee which has one inlet pipe and two transverse outlet pipes. At their confluence is a transition region. This region is located proximate a back wall of the distribution tee. The region diverts incoming combustion products to the transverse outlet pipes. Located in the transition region is a deflector vane which guides the flow of the products of combustion, thus increasing a vent length capability of the furnace.
Preferably, the deflector vane has a leading edge that is formed at the intersection of a pair of curved walls that is presented to the incoming products of combustion as they enter the transition region and deflects them toward the two transverse outlet pipes.
If desired, one of the two transverse outlet pipes can be blocked, depending on the configuration needs of a particular installation.
FIGS. 1(a)-(c) respectively are perspective, side, and front views of a multi-position furnace, illustrating an environment in which the invention is used;
FIGS. 1(a)-(c) depict a furnace that includes an exhaust tee and related assembly 10. The furnace supplies heated air to a spaced to be heated and is capable of being installed in more than one position. The furnace includes at least one burner and a heat exchanger 12 in communication therewith. The heat exchanger 12 receives the products of combustion from the burner. As is known, the furnace further includes an inducer that is in communication with the heat exchanger. The inducer promotes the flow of products of combustion through the heat exchanger.
Located proximate a back wall of the distribution tee 16 is a transition region 24 in which incoming combustion products are diverted to the transverse outlet pipes 20, 22. The transition region 24 includes a deflector vane 28 that reduces the resistance to flow of the products of combustion, thus increasing a vent length capability of the furnace. As defined herein, the term “vent length capability” means the amount of vent length that can be placed on a furnace without significant detriment to venting capability. As a result of the disclosed invention, it is possible to deploy a longer length of vent pipe for a given furnace than was available following prior art practices.
Preferably, the deflector vane 28 has a leading edge 30 that is formed at the intersection of a pair of curved walls 32, 34. If desired, the leading edge 30 can be curved. The leading edge 30 is presented to incoming products of combustion as they enter the transition region 24 and deflects them toward either or both of the two transverse outlet pipes 20, 22. In an alternative embodiment, the leading edge 30 may be inclined to the longitudinal axis of the inlet pipe 18.
Depending on the needs of the installation, either one of the two transverse outlet pipes 20, 22 may be blocked by means for blocking, such a cap or damper so as selectively to direct the products of combustion.
As best shown in
As illustrated in
If desired, one or more flue collars 42, 44 can be connected at the ends of the outlet pipes 20, 22.
Although in the drawings, the outlet pipes 20, 22 are illustrated as being about 180° apart, it should be realized that the invention is not so limited. If desired, a departure to ±20 degrees from linearality is considered within the scope of the invention.
The flue exhaust tee assembly is designed to accommodate nominal furnace inputs ranging from 30,000 Btu per hour through 132,000 Btu per hour.
The disclosed assembly is designed to discharge the products of combustion in a plane which is perpendicular to the outlet of the combustion air inducer and in either direction. This design allows for greater installation ease and flexibility in all configurations—upflow, downflow, and horizontal left/right by allowing the installer to select which exhaust connection—left or right—works best and minimizes furnace modifications at the time of installation.
The disclosed flue tee design was modeled using computational fluid dynamics (CFD) methods and performance data (volume and temperature of the flue products). Pressures in the flue tee were from a 110,000 input furnace using 15′ of 2″ diameter vent pipe to understand the fluid flow pattern in the flue tee, particularly in the transition region. This analysis identified a stagnant flow condition in the transition region of the flue tee and a “swirling” fluid flow profile downstream of this region, both resulting in higher resistance to flue gas flow (i.e. shorter vent lengths).
Based upon this information, alternate flue tee design concepts were developed and analyzed using CFD methods and the same 110,000 input furnace performance data as the original. This analysis showed that incorporating a curved wall construction in the transition region, and the disclosed deflector vane resulted in a 68% reduction in the required inlet pressure from the inducer to provide the same flow rate exiting the vent pipe.
Based upon this information, SLA samples of the three (3) most promising concepts evaluated on a condensing, multi-position furnace. The prototype flue tee SLA samples differed in the geometry of the transition region, specifically the deflector vane surface and leading edge at the confluence of the flue tee inlet and transverse conduit. To evaluate the proposed flue tee designs, 88,000 and 110,000 Btu per hour input furnaces were selected since they had the highest flue gas flow rate using a 2″ diameter vent pipe. They were the models requiring the greatest increase in vent pipe length when using 2″ diameter pipe. Testing was conducted with each prototype flue tee design, increasing the 2″ diameter vent length by 20′ on the 88,000 input model and 15′ on the 110,000 input model. These actions yielded an 80% and 100% improvement respectively.
Since the vent length improvement of all three flue tee concepts was the same, the flue tee design shown in
Thus there has been disclosed a distribution flue tee 16 and related assembly that includes a deflector vane 28 that is located in the transition region 24 of the distribution flue tee 16. This feature reduces the pressure drop in the transition region of the flue tee and in turn increases the vent length capability of the furnace without increasing combustion air inducer capacity (motor strength and/or flow volume) or increasing the internal diameter of the flue tee.
While embodiments of the invention have been illustrated and described, it is not intended that these embodiments illustrate and describe all possible forms of the invention. Rather, the words used in the specification are words of description rather than limitation, and it is understood that various changes may be made without departing from the spirit and scope of the invention.
