The subject matter of the present disclosure relates generally to a dual fuel water heater designed to transfer waste heat from an exhaust flue of a gas fuel heating system to an evaporator of an electric heat pump.
Water heaters can provide for the heating and storage of water to be used in, e.g., a residential or commercial structure. While water heaters can be provided in a variety of shapes and sizes, a typical shape includes an elongated cylindrical tank. In some water heaters, the tank may be configured for a vertically upright position and be surrounded by insulation and an exterior wrapper or jacket. A heat source is provided for raising the temperature of water in the tank. The heat energy may be supplied by, e.g., gas burners, electrically-resistant coils, an electric heat pump using a refrigerant cycle, or a combination thereof.
In one construction, a water heater may utilize both gas fuel burners and an electric heat pump using a refrigerant cycle to heat the water in the tank. The gas fuel heating system may place gas burners underneath the tank and provide thermal energy to the tank through combustion of the gas fuel. Additionally, the electric heat pump may wrap a plurality of coils around the cylindrically-shaped exterior wall of the water tank. In this configuration, the coils serve as a heat exchanger, also referred to as a condenser, through which hot refrigerant flows around the tank. This configuration enables heat transfer from the hot refrigerant, through the coils and the tank walls, and then to the water.
Certain challenges exist with this construction, however. Such construction, for example, can have inefficiencies as significant heat loss can occur from the gas fuel heating system in form of exhaust gas exiting through the exhaust flue. Additionally, when a water heater of this construction is operated in conditions that are near or below freezing, the condensation on the evaporator of the heat pump may freeze, impeding air flow over the evaporator. As a result, some water heaters of this construction require a reversing flow valve for the heat pump, a defrost heater, or other similar device to melt the frozen condensate on the evaporator. However, utilizing these or similar devices may lead to an inefficient water heater system and adds complexity to the manufacture and operation of the water heater.
Accordingly, a dual fuel—gas fuel and electric heat pump—water heater having one or more features that can improve the efficiency of the water heater would be useful. More particularly, such a water heater that can capture and utilize the waste heat from the exhaust flue of the gas fuel heating system would be beneficial. Such a water heater that could also remedy frozen condensate on the evaporator would also be useful.
The present disclosure provides a dual fuel—gas fuel and electric heat Pump—water heater that captures waste heat from the exhaust flue of the gas fuel heating system and utilizes it in the evaporator of the electric heat pump. Multiple mechanisms are disclosed for the transfer of heat from the exhaust flue gases to the evaporator. Heat from the exhaust gas that would otherwise be lost is used to help heat refrigerant in the evaporator to improve the efficiency of the system. This heat can also be used to prevent or remove frozen condensate on the evaporator. Multiple features as described herein may be used to further improve heat transfer as well. Additional aspects and advantages of the invention will be set forth in part in the following description, or may be apparent from the description, or may be learned through practice of the invention.
In one exemplary embodiment, the present disclosure provides a water heater that includes a tank for holding water. It may also include a gas fuel heating system configured for heating the water in the tank. The gas fuel heating system may include an exhaust flue, wherein the exhaust flue has an exterior surface. The water heater may also include a heat pump heating system, which may also be configured for heating the water in the tank. The heat pump heating system may include an evaporator. Additionally, the water heater may include a pipe. The pipe may be in thermal communication with the exhaust flue and the evaporator and configured for transferring heat from the exhaust flue to the evaporator. The water heater may also include a fan configured for causing the flow of air past the exhaust flue and over the evaporator.
In another exemplary embodiment, the present disclosure provides a water heater that includes a tank for holding water. It may also include a gas fuel heating system configured for heating the water in the tank. The gas fuel heating system may include an exhaust flue. The water heater may also include a heat pump heating system, which may also be configured for heating the water in the tank. The heat pump heating system may include an evaporator. Additionally, the water tank may include a fan configured for causing an air flow over the evaporator and past the flue so as to provide for heat transfer from the flue to the evaporator.
In yet another exemplary embodiment, the present disclosure provides a water heater that includes a tank for holding water. It may also include a gas fuel heating system configured for heating the water in the tank. The gas fuel heating system may include an exhaust flue that facilitates the flow of exhaust, wherein the exhaust includes heated gases from the gas fuel heating system. The water heater may also include a heat pump heating system, which may also be configured for heating the water in the tank. The heat pump heating system may include an evaporator. Additionally, a portion of the exhaust from the exhaust flue may flow over the evaporator.
These and other features, aspects, and advantages of the present disclosure will become better understood with reference to the following description and appended claims. The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the disclosure and, together with the description, serve to explain the principles of the disclosure.
A full and enabling disclosure of the present disclosure, including the best mode thereof, directed to one of ordinary skill in the art, is set forth in the specification, which makes reference to the appended figures, in which:
Reference now will be made in detail to embodiments of the invention, one or more examples of which are illustrated in the drawings. Each example is provided by way of explanation of the invention, not limitation of the invention. In fact, it will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the scope or spirit of the invention. For instance, features illustrated or described as part of one embodiment can be used with another embodiment to yield a still further embodiment. Thus, it is intended that the present invention covers such modifications and variations as come within the scope of the appended claims and their equivalents.
Tank 124 may be positioned within an outer jacket 98 that surrounds tank 124 to create an annular space 146 between tank 124 and jacket 98. Insulation 126 may be provided within annular space 146 to reduce the amount of heat transfer from tank 124 to the environment. Insulation 126 may be provided as foamed-in insulation, but other materials may be used as well.
Tank 124 extends between a pair of end portions or, more particularly, between a bottom portion 170 and a top portion 172. Top portion 172 may include a water outlet 122 with associated coupling 114 and a water inlet 120 with associated coupling 116. Coupling 114 may connect with conduit 110, and coupling 116 may connect with conduit 112, and each may extend through housing 102. In turn, conduits 110 and 112 can each be fitted with couplings 106 and 108, respectively, for connection of water heater 100 to the piping or plumbing associated with a water supply system of, e.g., a commercial or residential structure. Coupling 108 may be connected with, e.g., a pipe delivering a pressurized water supply that flows into tank 124 using dip tube 118. In turn, heated water may be returned to such piping system through the connection provided by coupling 106.
In an alternative embodiment of the present disclosure, however, water outlet 122 may include conduit 110 welded to tank 124 and water inlet 120 may include conduit 112 welded to tank 124, each having no separate couplings for connection to tank 124. Additionally, instead of couplings 106 and 108, conduits 110 and 112 may include a threaded portion and pipe nipples for connection of water heater 100 to the piping or plumbing associated with a water supply system of, e.g., a commercial or residential structure.
Bottom portion 170 of tank 124 may include a circular bottom edge 142 and a bottom wall 128. Beneath bottom wall 128 is a gas fuel heating system 224, which may include a combustion chamber 208. Within combustion chamber 208 may be one or more gas burners 206. Gas burner 206 may be constructed of a circular plate with a series of burner holes 222 positioned along an edge of the circular plate. Gas fuel and air may enter the burner through a burner inlet 220 positioned at a side of the gas plate or, alternatively, burner inlet may be positioned underneath the circular plate. Gas burners 206 heat the water in tank 124 by providing thermal energy to tank 124 through combustion of a gas fuel. A separate pilot light may be provided to ignite the gas fuel and air as it exits burner holes 222, such that flames are provided that come up and around the circular plate. The gas fuel may be supplied by, e.g., a gas line from consumer's house supply 214, which in turn may be connected to a gas control mechanism 216, configured for providing the gas fuel to burners 206 through gas line 218. Other constructions and configurations of gas fuel heating system 224, as are well known in the art, are contemplated by the present disclosure as well.
The exhaust air from the combustion of gas fuel in combustion chamber 208 exits through an exhaust flue 174. Exhaust flue 174 may extend through the center of tank 124 and out through housing 102, where it may then connect with a vent to, e.g., the consumer's chimney 204 using a draft hood 202. Exhaust flue 174 may have a diameter that is approximately twice the size shown in
Mounted to top 172 is housing 102, which houses an electric heat pump heating system 104 using a refrigerant cycle. Heat pump heating system 104 may be used to heat the water in tank 124 in conjunction with or in alternative to gas fuel heating system 224. Heat pump heating system 104 employs coils 130 to circulate hot refrigerant around tank 124 and heat water in tank 124. Coils 130 operate as a heat exchanger or, more particularly, as a condenser for heat pump heating system 104. As will be understood by one of skill in the art, compressed refrigerant vapor flowing through coils 130 condenses to a liquid in coils 130 to provide heat to water in tank 124. The refrigerant in coils 130 then flows through an expansion valve, wherein the refrigerant is depressurized and the temperature of the refrigerant drops. The refrigerant then flows through an evaporator 178, wherein air may be moved past evaporator 178 to begin warming the refrigerant prior to the refrigerant being compressed and sent back around tank 124. A fan 226, configured for creating a flow of air over evaporator 178 in an air flow direction F, may be provided. Water heater 100 is provided by way of example only. Using the teachings disclosed herein it will be understood that other configurations, constructions, or shapes for water heater 100 with heat pump heating system 104 and gas fuel heating system 224 may be used as well.
The configuration of water heater 100 is provided by way of example only. As will be understood by one of skill in the art using the teachings disclosed herein, the present invention includes water heaters of other constructions and configurations as well.
For reasons previously stated, it is desirable to capture the waste heat from exhaust flue 174 of gas fuel heating system 224 and utilize it in evaporator 178 of heat pump heating system 104. Such a configuration will provide a heat pump heating system having increased efficiency, as well as providing increased efficiency in water heater 100 as a whole. Additionally, the waste heat from exhaust flue 174 may be utilized to defrost evaporator 178, or prevent evaporator 178 from accumulating frost.
In one exemplary embodiment, pipe 176 may be comprised of a solid material for transferring heat by conduction, whereas in another exemplary embodiment pipe 176 may carry a heat transfer fluid for transferring heat using the sensible and/or latent heat of the fluid. As used herein with regard to pipe 176, the term “pipe” is not limited to a circular shape in cross-section or to a tube and refers, instead, to a medium for conducting heat as described herein.
In one exemplary embodiment the transfer fluid may be a single phase fluid. As used herein, a “single phase fluid” is a material that does not change phases as it passes through pipe 176 and is heated and cooled by exhaust flue 174 and evaporator 178.
When a single phase fluid is used, pipe 176 may be positioned along exhaust flue 174 and evaporator 178 so as to allow the fluid to act as a thermosyphon, where natural convection will move fluids in pipe 176 from exhaust flue 174 to evaporator 178. More particularly, as shown in the exemplary embodiment of
In yet another exemplary embodiment, pipe 176 may carry a phase change fluid. As used herein, a phase change fluid refers to a material that is capable of storing a relatively large amount of energy when it changes phase between, e.g., a gas and liquid or between a liquid and a solid. By way of example, for pipe 176 of the present disclosure, phase change fluids that may be used include dichlorodifluromethane, trichlorofluromethane, benzene, methanol, ammonia, water, mercury, and mixtures thereof. Other materials may be used as well. By way of example, where a phase change material is used, the configuration of pipe 176 can be similar to that shown in
Referring now to
In another exemplary embodiment, as shown in
Pipe 176 may be affixed to evaporator 178 in a number of ways. In one exemplary embodiment, pipe 176 may be welded to evaporator 178. As previously discussed, in an alternative exemplary embodiment, pipe 176 may be fitted integrally to evaporator 178 by positioning pipe 176 within grooves 190 defined by evaporator 178. This embodiment is illustrated in
Referring now to
Referring now to
In yet another exemplary embodiment of the present disclosure, shown in
In still another exemplary embodiment of the present disclosure, waste heat from exhaust flue 174 may be transferred to evaporator 178 by diverting a portion of the exhaust air, including heated gases from gas fuel heating system 224, from exhaust flue 174 over evaporator 178, as is shown in
This written description uses examples to disclose the invention, including the best mode, and also to enable any person skilled in the art to practice the invention, including making and using any devices or systems and performing any incorporated methods. The patentable scope of the invention is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they include structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal languages of the claims.