Heat Pump and Burner Combination Water Heating Systems and Methods for Providing Instantaneous and Constant Hot Water

This application claims priority to and the benefit of U.S. Provisional Application No. 63/367,758, filed Jul. 6, 2022, which is hereby incorporated by reference herein in its entirety.

This application is directed to systems and methods to heat water and more particularly is directed to heat pump and burner combination water heating systems and methods for providing instantaneous and constant hot water.

The most common approach for providing hot water in domestic, commercial, and industrial settings involves the use of large tanks for the storage of hot water. Although such heated tank systems can provide hot water at a relatively high flow rate, they are inherently energy inefficient because the water in the tank is continually reheated even when water is not being used on a regular basis.

Another approach to providing hot water involves the use of a tankless water heater system that heats water only when hot water is being used. Such tankless water heater systems, also referred to as on demand water heater systems, can often provide a more energy efficient means of heating water than storage systems using the same type of heating (e.g., gas, electric, etc.). A typical combustion type on demand based water heater uses a combustible fuel gas, such as methane (i.e., natural gas), wherein a gas burner disposed in a combustion chamber below a heat exchanger burns the gas with ambient air, thereby heating the water with a combination of heat radiated from the burner and heat conducted from hot gaseous products of combustion (hereinafter “combustion gasses”) traveling through the walls of the combustion chamber and through the heat exchanger. The combustion gasses travel from the combustion chamber, through the heat exchanger, and vent outside of the building or other enclosure in which the water heating system is disposed. There are also electric tankless water heaters that utilize electricity (rather than combustion gasses) to heat water on demand.

Tankless water heaters eliminate the need for storing volumes of hot water by heating water on demand. These types of gas heater systems are termed “instantaneous” to denote that the water is directly heated on demand and not heated earlier and then stored in a tank for later use.

A water heating system is disclosed herein. The water heating system may be implemented in domestic, commercial, and industrial settings. The water heating system may include a burner, a vapor-compression cycle system (e.g., a heat pump), and a water line in communication with the burner and the vapor-compression cycle system. In some instances, the water heating system may be a tankless (or on demand) water heating system. In other instances, the water heating system may include a tank. Water within the water line may be initially heated by the vapor-compression cycle system before the water enters the burner. In this manner, the water may be preheated using the vapor-compression cycle system before the water is further heated by the burner.

As used herein, the term “preheated” may mean heating the water with a first heating system (such as the vapor-compression cycle system) before heating the water with a second heating system (such as the burner). For example, the water may be heated (i.e., preheated) from its initial temperature at the water inlet by the vapor-compression cycle system before the water enters the burner, where the water may be further heated by one or more heat exchangers of the burner to the desired temperature of the water exiting the outlet. In this manner, “preheating” the water means the water has undergone heating prior to another heating process. Preheating the water may enhance the thermal efficiency of heating processes of the system.

The burner may include a combustion chamber, which may be configured to receive fuel and air (e.g., ambient air). In some instances, the fuel may include natural gas, propane, or the like from a fuel source. Any suitable fuel and fuel source or combinations thereof may be used herein. The combustion chamber may also include an ignitor for igniting the air/fuel mixture into a combustion gas. For example, the combustion chamber may include a main ignitor and a pilot ignitor, which may be supplied with fuel and air. In other instances, the ignitor may be a flame rod or the like. Any suitable ignitor or combination of ignitors may be used herein.

During operation of the water heating system, the combustion chamber may mix and ignite the air/fuel mixture to create hot combustion gases that flow upwardly through the burner to one or more heat exchangers within the burner. The one or more heat exchangers of the burner may also be in communication with the water line. In this manner, the one or more heat exchangers may transfer combustion heat from the combustion gas to the water in the water line to maintain the water at a predetermined heated temperature. In some instances, the burner may include two heat exchangers. The burner may include any suitable number of heat exchangers. For example, the burner may include a primary heat exchanger in communication with the water line and a secondary heat exchanger in communication with the water line. The secondary heat exchanger may initially preheat the water before the water is further heated by the primary heat exchanger. After passing through the one or more heat exchangers, the combustion gasses may exit the burner via a vent (or flue).

The vapor-compression cycle system may include a refrigerant line, which conducts refrigerant through a refrigerant path that encompasses a condenser coil, an expansion valve, an evaporator coil, and a compressor. In some instances, the condenser coil may include a portion of the refrigerant line that wraps around a water inlet line of the water line. The condenser coil may be in any suitable heat exchanger configuration with the water inlet line. Following the condenser coil, the refrigerant may lead to the expansion valve. The expansion valve may receive a fluid input at a high pressure and, depending on the settings within the valve, output the fluid at a lower pressure, allowing the pressurized refrigerant entering the expansion valve to drop in pressure in the evaporator coil and change phase from a liquid to a gas. The compressor may act as a pump to provide pressure to the refrigerant flowing through the refrigerant line to thereby maintain the refrigerant flowing through the closed loop that the refrigerant line defines.

The compressor may pump the gaseous refrigerant received from the evaporator coil forward, increasing the pressure and temperature of the refrigerant and causing the now hotter refrigerant gas to flow through the condenser coil. The hot refrigerant may be separated from water within the water inlet line by the refrigerant line wall and the wall of the water inlet line, both of which may be metallic and therefore relatively heat conductive. Thus, as the refrigerant travels through the length of the condenser coil, the refrigerant may transfer heat through the walls to the cooler water within the water inlet line. Any suitable heat exchanger configuration between the condenser coil and the water inlet line may be used herein.

As refrigerant flows through the condenser coil, it may change phase from gas to liquid. Still under the pressure provided by the compressor, however, the now liquid refrigerant may flow from the condenser to the expansion valve, which may drop the pressure of the liquid refrigerant as it enters the evaporator coil.

In some instances, the evaporator coil may be located within the burner (e.g., within the vent hood and/or vent (or flue) of the burner). The rising combustion gas within the vent may pass across the evaporator coil and transfer heat therewith. That is, within the evaporator coil, the now lower pressure refrigerant draws heat energy from the combustion gas flowing over evaporator coil and transitions to a gaseous phase. Any suitable heat exchanger configuration between the evaporator coil and the combustion gases within the vent of the burner may be used herein. The now warmer gaseous refrigerant may be discharged from the evaporator coil and then returned to the compressor and the cycle may be repeated.

In certain embodiments, in operation, water (e.g., cold water) may enter the water heating system through the inlet water line. At least a segment of the inlet water line may be surrounded by hot refrigerant coils (e.g., the condenser coil) or other heat exchanger devices. For example, the exchange of heat between the condenser coil and inlet water line may be archived by wrapping hot refrigerant tubes around the inlet water line or a double tube heat exchanger arrangement may be used. The size and form of the heat exchanger arrangement can be adjusted according to the application and thermal demand. That is, any suitable heat exchanger arrangement between the inlet water line and the vapor-compression cycle system may be used here.

In this manner, water in the inlet water line is preheated by the vapor-compression cycle system before the water line enters the condensing heat exchanger of the burner, which may be referred to as a secondary heat exchanger. The water may gain heat from flue gases passing through the secondary heat exchanger and may be further preheated by the secondary heat exchanger of the burner. The preheated water may then enter the primary heat exchanger in the burner to increase its temperature to its desired set point.

The refrigerant of the secondary heat exchanger may transfer its heat to the water in the inlet water line, after which the refrigerant may then enter the expansion valve. The refrigerant may undergo the expansion process in the expansion valve to become a low pressure, low temperature fluid. The refrigerant may then enter the evaporator coil, which may be either an integral part of secondary heat exchanger or may be disposed in vent hood and/or vent or elsewhere in the burner. The evaporator coil may be any suitable heat exchanger. The refrigerant may gain heat from flue gas in the evaporator coil, thus further cooling the flue gas. After the evaporator coil, the refrigerant may convert to vapor and may then enter the compressor to become a high pressure, high temperature refrigerant. The vapor-compression cycle may then be repeated.

These and other embodiments of the disclosure will be described in more detail through reference to the accompanying drawings in the detailed description that follows. This brief introduction, including section titles and corresponding summaries, is provided for the reader's convenience and is not intended to limit the scope of the claims, nor the proceeding sections. Furthermore, the techniques described above and below may be implemented in a number of ways and in a number of contexts. Several example implementations and contexts are provided with reference to the following figures, as described below in more detail. However, the following implementations and contexts are but a few of many.

Turning now to the drawings,schematically depict an example water heating systemin accordance with one or more embodiments of the disclosure. In some instances, the water heating systemmay be a tankless water heating system. That is, the water heating systemmay be configured to provide on demand continuous hot water. In other instances, the water heating systemmay include a tank.

The water heating systemmay include a burner, a vapor-compression cycle system, and a water linein communication with the burnerand the vapor-compression cycle system. In some instances, the vapor-compression cycle systemmay be referred to as a heat pump or the like. Water within the water linemay be initially heated by the vapor-compression cycle systembefore the water enters the burner. In this manner, the water may be preheated using the vapor-compression cycle systembefore the water is further heated by the burner.

In some instances, the water linemay include a water inlet lineand a water outlet line. The water line, water inlet line, and the water outlet linemay form a single water line from a water source to a water outlet. The water inlet linemay be in communication with the vapor-compression cycle systembefore the burnerso as to preheat the water within the water inlet linebefore the water line enters the burner.

The vapor-compression cycle systemmay include a refrigerant line, a compressor, a condensercomprising a condenser coil, an expansion valve, and an evaporatorcomprising an evaporator coil. The refrigerant linemay be a closed loop having a refrigerant therein. As the refrigerant circulates through the closed loop of the vapor-compression cycle system, the refrigerant is alternately compressed and expanded, changing the state of the refrigerant from a liquid to a vapor. As the refrigerant changes state, heat is absorbed and expelled by the vapor-compression cycle system.

The condenser coilmay be disposed about the water inlet lineso as to preheat the water within the water inlet linebefore the water enters the burner. For example, the compressormay pump the refrigerant to increase the pressure and temperature of the refrigerant. In some instances, the compressormay be a rotary compressor or the like. Any suitable compressor may be used herein. The refrigerant gas may flow through the condenser coil. The refrigerant may be separated from water within the water inlet lineby the refrigerant line wall and the wall of the water inlet line. For example, the condenser coilmay be wrapped around the water inlet line. The condenser coiland the water line may be made of a metallic material and therefore relatively heat conductive. Thus, as the refrigerant travels through the length of the condenser coil, the refrigerant may transfer heat through the walls to the cooler water within the water inlet line. Any suitable heat exchanger configuration between the condenserand the water inlet linemay be used herein. For example, the water inlet linemay include a heat exchanger tank or the like disposed thereabout and in communication with and part of the vapor-compression cycle system.

After the refrigerant exchanges heat with the water in the inlet water line, the refrigerant may be expanded by the expansion valve. The refrigerant may undergo the expansion process in the expansion valveto become a low pressure, low temperature fluid.

After the expansion valve, the refrigerant may then enter the evaporator coil. In some instances, the evaporator coilmay be disposed within the vent (or flue) of the burnerso as to exchange heat with the combustion gases of the burner. For example, the burnermay include a combustion chamber, a fuel sourcein communication with the combustion chamber, a primary heat exchanger, a secondary heat exchanger, a vent, and a vent hood.

The combustion chambermay be configured to receive fuel from the fuel source. The combustion chambermay also be configured to receive air from any suitable air source. The fuel and air may be mixed and ignited in the combustion chamber. Ignition of the air/fuel mixture may create hot combustion gases that flow upwardly through the burnerto the primary heat exchanger, the secondary heat exchanger, and the vent hood, which may direct the combustion cases to the vent.

In certain embodiments, the primary heat exchangermay be in communication with the water line. The rising combustion gas within the burner may pass across the primary heat exchangerand transfer heat between the water in the water line and the combustion gases. Similarly, in certain embodiments, the secondary heat exchangermay be in communication with the water line. The rising combustion gas within the burner may pass across the secondary heat exchangerand transfer heat between the water in the water line and the combustion gases. In some instances, the secondary heat exchangermay be located downstream (relative to the combustion gases) of the primary heat exchanger. In this manner, the combustion gasses may first pass through the primary heat exchangerand then pass through the secondary heat exchanger.

After the water in the water inlet linehas been preheated by the vapor-compression cycle system, the secondary heat exchangermay further preheat the water within the water line. For example, in certain embodiments, the water linemay initially enter the burnerand pass through the secondary heat exchangerin order to preheat the water within the water linebefore the water is further heated by the primary heat exchanger. After the primary heat exchangerexchanges heat with the water, the water linemay exit the primary heat exchanger to the water outlet line.

After passing through the secondary heat exchangerand the primary heat exchanger, the combustion gasses may enter the vent hood, which may direct the combustion gases to the vent. The evaporator coilmay be disposed within the vent hoodor ventso as to exchange heat with the combustion gases of the burner. The evaporator coilmay be located downstream (relative to the combustion gases) of the primary heat exchangerand the secondary heat exchanger. The rising combustion gas within the burner may pass across the evaporator coil and transfer heat between the combustion gases and the refrigerant within the evaporator coil. For example, within the evaporator coil, the refrigerant draws heat energy from the combustion gas flowing over evaporator coiland transitions to a gaseous phase. The evaporatormay be located at any suitable location within the burner.

The water heating systemmay include a bypass linefor bypassing the burnerand the vapor-compression cycle system. For example, the bypass linemay be disposed between the water inlet lineand the water outlet line. In some instances, a bypass valvemay be disposed on the bypass line. When the bypass valveis open, water may travel from the water inlet linedirectly to the water outlet line, thereby bypassing the burnerand the vapor-compression cycle system. In other instances, when the bypass valveis closed, the water within the water inlet linemay travel through the water lineand exchange heat with the vapor-compression cycle systemand the burner.

The water heating systemmay include one or more controllersfor controlling the various operations and functions of the water heating systemand the components thereof. The controllermay be an independent controller or integrated with the water heating systemof components thereof. A single controller may be used or multiple controllers may be used to control the operation of the water heating system. For example, each component of the water heating systemmay include a controller or one or more controllers may be used to control operation of the various components of the water heating system. The controllermay be in wireless communication and/or hard wired to the water heating systemand the components thereof. The controllermay include at least a memory and one or more processing units (or processor(s)). The processor(s) may be implemented as appropriate in hardware, software, firmware, or combinations thereof. Software or firmware implementations of the processor(s) may include computer-executable or machine-executable instructions written in any suitable programming language to perform the various functions described herein. Moreover, the processor may be associated with a network, a server, a computer, or a mobile device.

is a flow diagram depicting an illustrative methodfor heating water in accordance with one or more embodiments of the disclosure. At blockof method, heat may be exchanged with water in the water linewith the vapor-compression cycle system. For example, the condenser coilmay be disposed about the water inlet lineso as to preheat the water within the water inlet linebefore the water enters the burner. The refrigerant gas may flow through the condenser coil. In some instances, as the refrigerant travels through the length of the condenser coil, the refrigerant may transfer heat through the walls to the cooler water within the water inlet line. Any suitable heat exchanger configuration between the condenserand the water inlet linemay be used herein. For example, the water inlet linemay include a heat exchanger tank or the like disposed thereabout and in communication with and part of the vapor-compression cycle system.

After preheating the water with the vapor-compression cycle system, heat may be exchanged with water in the water linewith the burnerat blockof the method. For example, the rising combustion gas within the burnermay pass across the primary heat exchangerand transfer heat between the water in the water line and the combustion gases. Similarly, the rising combustion gas within the burnermay pass across the secondary heat exchangerand transfer heat between the water in the water line and the combustion gases. In certain embodiments, the water linemay initially enter the burnerand pass through the secondary heat exchangerin order to preheat the water within the water linebefore the water is further heated by the primary heat exchanger.

At blockof the method, heat may be exchanged between the evaporatorof the vapor-compression cycle systemand gas within the burner. For example, the evaporator coilmay be disposed within the vent hoodor ventso as to exchange heat with the combustion gases of the burner. The evaporatormay be located at any suitable location within the burner. The rising combustion gas within the burnermay pass across the evaporator coiland transfer heat between the combustion gases and the refrigerant within the evaporator coil. For example, within the evaporator coil, the refrigerant draws heat energy from the combustion gas flowing over evaporator coiland transitions to a gaseous phase.

is a flow diagram depicting an illustrative methodfor bypassing a water heating system in accordance with one or more embodiments of the disclosure. At blockof the method, water may be directed to the water linefrom the water inlet line, where the water may be preheated by exchanging heat with the vapor-compression cycle system. At blockof the method, the water may be further heated within the burner.

At blockof the method, the vapor-compression cycle systemand the burnermay be bypassed. This step may be optional. For example, the water heating systemmay include a bypass linefor bypassing the burnerand the vapor-compression cycle system. In some instances, the bypass linemay be disposed between the water inlet lineand the water outlet line. A bypass valvemay be disposed on the bypass line. When the bypass valveis open, water may travel from the water inlet linedirectly to the water outlet line, thereby bypassing the burnerand the vapor-compression cycle system. In other instances, when the bypass valveis closed, the water within the water inlet linemay travel through the water lineand exchange heat with the vapor-compression cycle systemand the burner.

It should be apparent that the foregoing relates only to certain embodiments of the present application and that numerous changes and modifications may be made herein by one of ordinary skill in the art without departing from the general spirit and scope of the disclosure.

Although specific embodiments of the disclosure have been described, numerous other modifications and alternative embodiments are within the scope of the disclosure. For example, any of the functionality described with respect to a particular device or component may be performed by another device or component. Further, while specific device characteristics have been described, embodiments of the disclosure may relate to numerous other device characteristics. Further, although embodiments have been described in language specific to structural features and/or methodological acts, it is to be understood that the disclosure is not necessarily limited to the specific features or acts described. Rather, the specific features and acts are disclosed as illustrative forms of implementing the embodiments. Conditional language, such as, among others, “can,” “could,” “might,” or “may,” unless specifically stated otherwise, or otherwise understood within the context as used, is generally intended to convey that certain embodiments could include, while other embodiments may not include, certain features, elements, and/or steps. Thus, such conditional language is not generally intended to imply that features, elements, and/or steps are in any way required for one or more embodiments.