Stoves and furnaces – Liquid heater
Reexamination Certificate
2000-07-07
2001-10-02
Lu, Jiping (Department: 3749)
Stoves and furnaces
Liquid heater
C122S018400, C122S367100, C165S173000
Reexamination Certificate
active
06295980
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates generally to liquid heaters and particularly to swimming pool and spa heaters, which transfer heat from products of combustion to water as it is being circulated through a heat exchanger.
2. Description of the Prior Art
Water heaters for swimming pools or spas generally comprise a burner unit, an insulated combustion chamber above the burner, and a heat exchanger above the insulated combustion chamber for facilitating heat transfer between heated air in the insulated combustion chamber and water contained in the heat exchanger. A heat exchanger header manifold is provided at one end of the heat exchanger to connect water inlet and outlet ports to a plurality of water tubes in the heat exchanger. A return header is provided at the tube ends located at another end of the heat exchanger.
Typically, the manifold header and the return manifold are made from cast iron or brass to withstand the high temperature and pressure conditions. The design of these prior art headers results in a relatively large area of surface-to-surface contact between the header and manifold and the tube supporting plate at each end of the heat exchanger. Such an arrangement is shown in U.S. Pat. No. 5,138,007. As is set forth in that patent, prior art headers reached temperatures necessitating the use of copper or other high temperature piping material for the last several feet of piping leading to the header, in place of less expensive plastic piping.
While the invention defined in the aforementioned patent permits the use of direct plastic piping connections to the manifold, the use of metallic materials for the manifold headers and return manifolds have distinct disadvantages. Those materials add considerable weight to the unit, thereby increasing handling and shipping costs. Further, as noted above, the relatively large area of surface-to-surface contact between the tube supporting plates and the headers causes the transfer of heat to the headers. Relatively cool water flowing through the manifold header results in condensation which, when mixed with low pH combustion gases, can be corrosive to the metal structure of the heating unit and other internal components.
Attempts have been made to overcome these problems by fabricating the manifold header from plastic to reduce manufacturing and shipping costs. The use of such headers has resulted in leaks and condensation within the heat exchanger. Even high temperature plastics may not be able to withstand the temperatures generated on internal components if large surface areas of the headers are in surface-to-surface contact with the tube supporting plate.
SUMMARY OF THE INVENTION
The present invention relates to improved manifold and return headers for a swimming pool or spa heater. The heater comprises a burner, an insulated combustion chamber above the burner, a heat exchanger assembly above the combustion chamber for facilitating heat transfer between heated air in the combustion chamber and a liquid contained in the heat exchanger assembly.
The heat exchanger assembly has a plurality of parallel, hollow tubes mounted between a pair of flat mounting plates and defining a plurality of fluid passages through the plates. The manifold header comprises a cylindrical or tubular, elongated body portion having an outer surface and an interior cavity. Interior partitions separate the cavity into a feed chamber, a return chamber, and an exit chamber. The body portion of the manifold header has a plurality of parallel, hollow ports projecting from its outer surface, which are sealed against one of the plates to provide fluid communication between the fluid passages of the hollow tubes and the header. The hollow ports contact the plates in zones that immediately surround the tubes so that the zone of contact is cooled by the fluid passing through the tube since the temperature of that fluid is less than the temperature of the plate in more remote areas. Also, the projecting ports tend to space the tubular body portion from the plate to avoid conductive heating of the body portion by the plate.
The manifold header is provided with a plurality of parallel hollow bosses, which project substantially tangentially from the tubular body portion and which have plate-engaging faces substantially coplanar with plate-engaging faces of the projecting ports. Bolts extend through the hollow bosses to affix the header to the plate.
The bosses are located in closely spaced adjacency to the ports so that minimal heat is transferred to the header. Since direct contact between the header and the plate is largely avoided, the header is constructed from engineered resin such as PBT reinforced with randomly dispersed glass fibers.
In like manner, the return header is constructed of fiber-reinforced plastic and comprises a tubular, elongated body portion having an outer surface and an interior cavity. An interior partition separates the cavity into a first chamber and a second chamber. The first chamber is connected by the heat exchanger tubes to the feed chamber and the return chamber of the header manifold and the second chamber is connected by the heat exchanger tubes to the return chamber and the exit chamber of the manifold header.
The body portion of the return header has a plurality of parallel, hollow ports projecting from its outer surface which are sealed to the other one of the tube mounting plates to provide fluid communication between the fluid passages of the hollow tubes and the cavity. The hollow ports contact the plate in zones which immediately surround the tubes so that the zone of contact is cooled by the fluid passing through the tube, since the temperature of the fluid is less than the temperature of the plate in more remote areas. Also, the projecting ports tend to space the tubular body portion from the plate to avoid conductive heating of the body portion by the plate.
The return header is also provided with a plurality of parallel, hollow bosses which project tangentially from the tubular body portion and which have plate-engaging faces substantially coplanar with the plate-engaging faces of the projecting ports. Bolts extend through the hollow bosses to affix the header to the plate. The bosses are located in closely spaced adjacency to the ports so that minimal heat is transferred to the header.
The heat exchanger assembly further includes a main manifold associated with the manifold header. The main manifold is plastic and serves to connect the manifold header to the pool or spa pump and to the pool or spa.
REFERENCES:
patent: 4856824 (1989-08-01), Clausen
patent: 5138007 (1992-08-01), Meister
patent: 5178211 (1993-01-01), Bauer et al.
patent: 5318007 (1994-06-01), Afshar
patent: 6026804 (2000-02-01), Schardt et al.
Afshar M. Reza
Lopez Fulton J.
Lu Jiping
Pac-Fab, Inc.
Pearne & Gordon LLP
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