Patent Application
20080223313
This invention relates to the field of gas and/or oil fired water heaters and more particularly to an efficient system for utilizing gas and/or oil combustion to heat water.
Water heaters for commercial and home use are well known in the industry. The most common water heaters have a water tank and a series of heat exchange tubes immersed in the water. Hot gasses from the combustion of gas and/or oil are circulated through the tubes, thereby heating the tubes and transferring heat to the surrounding water. These water heaters utilize what is known thermal stacking—hot water moves toward the top of the tank. In such, the heat exchanger is located toward the bottom of the tank in the coolest water to maximize condensing. This type of design requires a tall water heater tank requiring space and not allow for multiple heaters to be stacked. Any mixing of the hot water with the cold or conduction through the tank walls will increase the temperature of the water at the bottom of the tank and reduce condensation and hence, reduce efficiency.
In general, the efficiency of the amount of heat energy delivered to the water from the combustion (hot gasses) is proportional to the difference in temperature between the water and the hot gasses. It is further proportional to the area of the heat exchange tubes—the greater the area, the higher the efficiency. For example, water that is at 55° accepts more heat from gasses that are at a particular temperature than water that is at 95°. As the water heats, more heat from the hot gasses passes out the exhaust system into the atmosphere.
To reduce the amount of wasted heat, multi-stage water heaters have been devised to increase the length, an therefore area, of the exchange tubes. For example, U.S. Pat. No. 4,938,204 to Adams which is hereby incorporated by reference. The disclosed water heater extends the length/area of heat exchange through the use of a second set of heat exchangers. In one embodiment, the second set of heat exchangers are immersed within the same hot water as the first set while in a second embodiment, each is submersed in a separate water tank, the water outflow from the tank with the second set of heat exchangers feeding the water inflow of the other water tank. In this design, the cold water in a first tank is heated by the first set of heat exchangers, and then the exhaust heat from the first set of heat exchangers passes through a second set of heat exchangers immersed within the second tank. The described embodiments have improvements in efficiency over prior water heaters, but requires two large-sized water tanks, both having an outer surface exposed to ambient air, a major factor in energy loss. Additionally, the efficiency of this heater is less than optimal because a percentage of its efficiency is in the form of trapped water vapor that, in this design, is exhausted out the flue as waste along with the other products of combustion. Furthermore, in its two-stage embodiment, two individual tanks are required, stacked one above the other, disallowing stacking in multiple water heater applications. Additionally, the lower tank cannot be used for hot water storage.
What is needed is a high efficiency water heater that effectively transfers as maximum amount of heat from the heat source to the water while reducing losses to the ambient air.
In one embodiment, a water heater is disclosed including a burner and a sealed outer tank with tubing for transferring heat from the burner into water residing in the sealed outer tank. A sealed inner tank is housed within the sealed outer tank and has tubing for transferring additional heat from the first tubing into water residing in the sealed inner tank. Cold water is supplied into the sealed inner tank and there are apetures for transferring some of the water residing in the sealed inner tank into the sealed outer tank. Hot water exits from the sealed outer tank to a hot water output pipe.
In another embodiment, a method of heating water is disclosed including burning fuel to produce hot gases and heating a first mass of water with a first heat exchanger that is coupled to receive the hot gases. Heat remaining after the hot gases pass through the first heat exchanger is used to heat a second mass of water. The first mass of water is partially isolated from the second mass of water and the first mass of water is contained substantially within the second mass of water.
In another embodiment, a water heater is disclosed including a sealed outer tank that has a cold water inlet aperture, a hot water outlet aperture, a heat input aperture, intermediate hot gas output apertures, an intermediate hot gas input aperture and exhaust apertures. A source of heat is connected to the heat input aperture and consequently to a firing chamber within the sealed outer tank. Heat exchange tubes are coupled at a first end to a second end area of the firing chamber and coupled at a second end to the plurality of intermediate hot gas output apertures. A heat transfer chamber is coupled at a first end to the intermediate hot gas input aperture and coupled at the second end to the first end of a second plurality of heat exchange tubes. The second end of the second plurality of heat exchange tubes is coupled to the exhaust apertures. A manifold with two chambers has a first chamber that passes hot gases from the intermediate hot gas output apertures to the intermediate hot gas input aperture and a second chamber that passes exhaust gases from the exhaust apertures to an exhaust coupling. A sealed inner tank encloses the heat transfer chamber and the second heat exchange tubes and is fluidly interfaced near a first end to the cold water input aperture and near a second end to at least one warm water aperture. The warm water apertures pass water from the sealed inner tank to the sealed outer tank.
The invention can be best understood by those having ordinary skill in the art by reference to the following detailed description when considered in conjunction with the accompanying drawings in which:
Reference will now be made in detail to the presently preferred embodiments of the invention, examples of which are illustrated in the accompanying drawings. Throughout the following detailed description, the same reference numerals refer to the same elements in all figures.
Referring to
A conventional gas, oil or gas/oil burner 52 is the source of hot gasses. Cold water enters into the cold water inlet pipe 20 and hot water exits out of the hot water outlet pipe 40. Exhaust gases exit through an exhaust 68 with is normally connected to a chimney or other vent. Because of humidity in the hot gases condensing when contacting the colder heat exchange jackets, a condensation drain 70 is provided in some embodiments. Hot gases are routed through the heat exchanger then out the exhaust.
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It is anticipated that, rather than passing intermediate hot gases out of the outer tank and then back into the outer tank through the manifold, in another embodiment an equivalent apparatus passes intermediate hot gases directly within the outer tank.
After exiting the heat exchange tubes 62, the hot gases (at a further reduced temperature) exit through a second chamber 64 of the manifold 50 and exit through the exhaust coupling 68. Any condensation exits through a condensation outlet 70.
Water enters the water heater 10 through the cold water inlet 20 and into the bottom of the inner condensing chamber jacket 22, passing over the heat transfer chamber 60 and the second set of heat exchange tubes 62 before exiting through warm water apertures 26 and into the outer tank 12. The water 28 in the outer tank 12 is heated by the firing chamber 54 and the first set of heat exchange tubes 56 and the hot water 28 then exits the water heater 10 through the hot water outlet 40.
Equivalent elements can be substituted for the ones set forth above such that they perform in substantially the same manner in substantially the same way for achieving substantially the same result.
It is believed that the system and method of the present invention and many of its attendant advantages will be understood by the foregoing description. It is also believed that it will be apparent that various changes may be made in the form, construction and arrangement of the components thereof without departing from the scope and spirit of the invention or without sacrificing all of its material advantages. The form herein before described being merely exemplary and explanatory embodiment thereof. It is the intention of the following claims to encompass and include such changes.
