Abstract: A water heater includes an outer casing defining a longitudinal axis, an axial direction being defined as extending along the longitudinal axis. The water heater further includes a combustor for production of hot flue gases, a primary heat exchanger including a tube positioned within the outer casing, and a secondary heat exchanger including a plurality of plates coupled together by brazing to form a brazed plate heat exchanger. The secondary heat exchanger includes a first set of passages defined between the plates, and a second set of passages defined between the plates and alternating with the first set of passages in the axial direction. The primary and secondary heat exchangers are in fluid communication such that the flue gases flow through the second set of passages before being exhausted, and water to be heated flows through the first set of passages to a delivery point for use upon demand.

Abstract: A water heater includes an inner water tube coil and an outer water tube coil separated by a drum baffle. The inner and outer coils extend above a top edge of the drum baffle by at least a full turn of each coil. A flue gas bypass path is defined between a top edge of the drum baffle and a top insulation layer above the inner and outer coils. Flue gases flow radially though the inner coil, up along the drum baffle, through the flue gas bypass path, and downwardly over the outer coil to heat water flowing through the inner and outer coils. The water flows into the outer coil at the bottom of the coil, winds upwardly through the outer coil in countercurrent flow with respect to the flue gases, then down through the inner coil.

Abstract: A water heater system includes a gas burner configured to selectively produce flue gases, and a heat exchanger for heating water in the water heater system. The water heater system is operable in a heating mode, and a standby mode. An exhaust assembly is in communication with the heat exchanger, and includes a condensate collector configured to receive the flue gases and condensate. A first temperature sensor is positioned to sense a temperature of the condensate within the condensate collector. The first temperature sensor is configured to detect a rate of temperature change of the condensate. A controller is configured to determine a leakage when the rate of temperature change adjusts from a first state to a second state when the water heater system is in the standby mode after the water heater system was in the heating mode.

Abstract: A water heater includes an inner water tube coil and an outer water tube coil separated by a drum baffle. The inner and outer coils extend above a top edge of the drum baffle by at least a full turn of each coil. A flue gas bypass path is defined between a top edge of the drum baffle and a top insulation layer above the inner and outer coils. Flue gases flow radially though the inner coil, up along the drum baffle, through the flue gas bypass path, and downwardly over the outer coil to heat water flowing through the inner and outer coils. The water flows into the outer coil at the bottom of the coil, winds upwardly through the outer coil in countercurrent flow with respect to the flue gases, then down through the inner coil.

Abstract: A water heater includes an outer casing defining a longitudinal axis, an axial direction being defined as extending along the longitudinal axis. The water heater further includes a combustor for production of hot flue gases, a primary heat exchanger including a tube positioned within the outer casing, and a secondary heat exchanger including a plurality of plates coupled together by brazing to form a brazed plate heat exchanger. The secondary heat exchanger includes a first set of passages defined between the plates, and a second set of passages defined between the plates and alternating with the first set of passages in the axial direction. The primary and secondary heat exchangers are in fluid communication such that the flue gases flow through the second set of passages before being exhausted, and water to be heated flows through the first set of passages to a delivery point for use upon demand.

Abstract: A water heater system includes a tank for storing water; a flue assembly positioned within the tank, the flue assembly adapted to transfer heat from flue gases within the flue assembly to water in the tank; a burner in fluid communication with an inlet end of the flue assembly and operable in at least a high input mode and a low input mode to deliver the flue gases to the flue assembly, the exhaust assembly having a threshold temperature above which the exhaust assembly is not suitable; and an exhaust assembly including a fan, wherein at least in the low input mode, the flue gases condense in the flue assembly, and wherein operation of the fan reduces a temperature of the flue gases in the exhaust assembly to below the threshold temperature at least in the high input mode.

Abstract: A water heater system includes a gas burner configured to selectively produce flue gases, and a heat exchanger for heating water in the water heater system. The water heater system is operable in a heating mode, and a standby mode. An exhaust assembly is in communication with the heat exchanger, and includes a condensate collector configured to receive the flue gases and condensate. A first temperature sensor is positioned to sense a temperature of the condensate within the condensate collector. The first temperature sensor is configured to detect a rate of temperature change of the condensate. A controller is configured to determine a leakage when the rate of temperature change adjusts from a first state to a second state when the water heater system is in the standby mode after the water heater system was in the heating mode.

Abstract: A water heater system includes a tank having internal capacity no greater than 1 gallon, a water inlet, and a water outlet. A flow of water into the tank through the water inlet and out of the tank through the water outlet is a downstream water flow. An absence of downstream water flow is a standby condition of the water heater. The water heater includes a heating element for heating water in the tank, a first temperature sensor positioned to sense a temperature of the water flowing into the tank, and a second temperature sensor positioned to sense a temperature of the water flowing out of the tank. The water heater further includes a damper upstream of the second temperature sensor to reduce fluctuations in the temperature readings of the second temperature sensor to reduce false detection of downstream water flow.

Abstract: A water heater system includes a tank having internal capacity no greater than 1 gallon, a water inlet, and a water outlet. A flow of water into the tank through the water inlet and out of the tank through the water outlet is a downstream water flow. An absence of downstream water flow is a standby condition of the water heater. The water heater includes a heating element for heating water in the tank, a first temperature sensor positioned to sense a temperature of the water flowing into the tank, and a second temperature sensor positioned to sense a temperature of the water flowing out of the tank. The water heater further includes a damper upstream of the second temperature sensor to reduce fluctuations in the temperature readings of the second temperature sensor to reduce false detection of downstream water flow.

Abstract: A water heater includes a water tank for storing water to be heated and a thermosiphon tube in the water tank. The thermosiphon tube has a first end in a bottom portion of the water tank and a second end in a top portion of the water tank. At least a portion of a condenser tube of a heat pump is surrounded by the thermosiphon tube to define a water flow channel between the thermosiphon tube and the condenser tube. The condenser tube is at an elevated temperature compared to water temperature in the water flow channel due to a refrigerant cycle of the heat pump. A water pump is configured to flow water through the water flow channel to heat the water in the water flow channel and deliver the heated water into the top portion of the water tank through the second end of the thermosiphon tube.

Abstract: A water heater system includes a tank having internal capacity no greater than 1 gallon, a water inlet, and a water outlet. A flow of water into the tank through the water inlet and out of the tank through the water outlet is a downstream water flow. An absence of downstream water flow is a standby condition of the water heater. The water heater includes a heating element for heating water in the tank, a first temperature sensor positioned to sense a temperature of the water flowing into the tank, and a second temperature sensor positioned to sense a temperature of the water flowing out of the tank. The water heater further includes a damper upstream of the second temperature sensor to reduce fluctuations in the temperature readings of the second temperature sensor to reduce false detection of downstream water flow.

Abstract: A water heater system includes a tank for storing water; a flue assembly positioned within the tank, the flue assembly adapted to transfer heat from flue gases within the flue assembly to water in the tank; a burner in fluid communication with an inlet end of the flue assembly and operable in at least a high input mode and a low input mode to deliver the flue gases to the flue assembly, the exhaust assembly having a threshold temperature above which the exhaust assembly is not suitable; and an exhaust assembly including a fan, wherein at least in the low input mode, the flue gases condense in the flue assembly, and wherein operation of the fan reduces a temperature of the flue gases in the exhaust assembly to below the threshold temperature at least in the high input mode.

Abstract: A water heater includes a tank containing water to be heated and a thermal displacement conduit communicating between a portion of the tank and a receptacle. Water is displaced out of the portion of the tank, through the conduit, and to the receptacle during thermal expansion of the water during heating.

Abstract: An energy storage system including a thermal energy storage apparatus configured to store thermal energy, an electrical energy storage apparatus configured to electrical energy, and a controller including a memory and an electronic processor. The controller is configured to monitor one or more characteristics of at least one selected from the group consisting of the thermal energy storage apparatus and the electrical energy storage apparatus.

Abstract: A water heater includes a water tank for storing water to be heated and a thermosiphon tube in the water tank. The thermosiphon tube has a first end in a bottom portion of the water tank and a second end in a top portion of the water tank. At least a portion of a condenser tube of a heat pump is surrounded by the thermosiphon tube to define a water flow channel between the thermosiphon tube and the condenser tube. The condenser tube is at an elevated temperature compared to water temperature in the water flow channel due to a refrigerant cycle of the heat pump. A water pump is configured to flow water through the water flow channel to heat the water in the water flow channel and deliver the heated water into the top portion of the water tank through the second end of the thermosiphon tube.

Abstract: A method of recovering waste heat includes pressurizing a flow of working fluid and transferring heat from a hot gas stream to the flow of working fluid in at least two successively arranged heat transfer sections. At least some of the working fluid is converted to a superheated vapor by the transfer of heat, and passes through an expander to recover useful work. A portion of the flow of working fluid is directed along a branch after having passed through at least one of the heat transfer sections, and bypasses the expander and at least one of the heat transfer sections before being recombined with the working fluid that has passed through the expander. The total flow rate of working fluid can be adjusted to regulate the temperature of the hot gas stream downstream of the heat transfer sections, and the amount of fluid that bypasses along the branch can be adjusted to regulate the temperature of the superheated vapor.

Abstract: A water heater includes a tank containing water to be heated and a thermal displacement conduit communicating between a portion of the tank and a receptacle. Water is displaced out of the portion of the tank, through the conduit, and to the receptacle during thermal expansion of the water during heating.

Abstract: A method of recovering waste heat includes pressurizing a flow of working fluid and transferring heat from a hot gas stream to the flow of working fluid in at least two successively arranged heat transfer sections. At least some of the working fluid is converted to a superheated vapor by the transfer of heat, and passes through an expander to recover useful work. A portion of the flow of working fluid is directed along a branch after having passed through at least one of the heat transfer sections, and bypasses the expander and at least one of the heat transfer sections before being recombined with the working fluid that has passed through the expander. The total flow rate of working fluid can be adjusted to regulate the temperature of the hot gas stream downstream of the heat transfer sections, and the amount of fluid that bypasses along the branch can be adjusted to regulate the temperature of the superheated vapor.

Abstract: An internal double wall condenser for a tank-type heat pump water heater. The condenser includes inlet and outlet sections designed for low heat transfer and a coil section designed for high heat transfer. The condenser includes first and second inner tubes that conduct refrigerant, and an outer tube surrounding the inner tubes. The outer tube has a circular cross-section in the inlet and outlet sections and a barbell cross-section in the coil section. The barbell cross-section includes first and second conduits that contain and are in heat transfer contact with the respective first and second inner tubes, and a connecting portion that interconnects the first and second conduits and increases the heat transfer surface. The barbell cross-section is made by deforming the outer condenser tube such that opposite walls are brought together between the two inner tubes.

Abstract: A waste heat recovery system includes a hot gas stream flow path, a pump, an expander, a first working fluid flow path fluidly connecting a pump outlet and an expander inlet, a second working fluid flow path fluidly connecting an expander outlet and a pump inlet, a first heat exchange section that transfers heat from the hot gas stream to working fluid traveling along the first working fluid flow path, a second heat exchange that transfers heat from the hot gas stream to working fluid traveling along the first working fluid flow path between the pump and the first heat exchange section, and a third working fluid flow path fluidly connecting a first point of the first working fluid path to a second point of the second working fluid path to permit at least a portion of the working fluid to bypass the first heat exchange section and the expander.