Classifications

• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
  • F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
  • F25B47/00—Arrangements for preventing or removing deposits or corrosion, not provided for in another subclass
  • F25B47/02—Defrosting cycles
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
  • F25D—REFRIGERATORS; COLD ROOMS; ICE-BOXES; COOLING OR FREEZING APPARATUS NOT OTHERWISE PROVIDED FOR
  • F25D21/00—Defrosting; Preventing frosting; Removing condensed or defrost water
  • F25D21/002—Defroster control
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F24—HEATING; RANGES; VENTILATING
  • F24H—FLUID HEATERS, e.g. WATER OR AIR HEATERS, HAVING HEAT-GENERATING MEANS, e.g. HEAT PUMPS, IN GENERAL
  • F24H4/00—Fluid heaters characterised by the use of heat pumps
  • F24H4/02—Water heaters
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
  • F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
  • F25B47/00—Arrangements for preventing or removing deposits or corrosion, not provided for in another subclass
  • F25B47/02—Defrosting cycles
  • F25B47/022—Defrosting cycles hot gas defrosting
  • F25B47/025—Defrosting cycles hot gas defrosting by reversing the cycle
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
  • F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
  • F25B49/00—Arrangement or mounting of control or safety devices
  • F25B49/02—Arrangement or mounting of control or safety devices for compression type machines, plants or systems
  • F25B49/022—Compressor control arrangements
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
  • F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
  • F25B2339/00—Details of evaporators; Details of condensers
  • F25B2339/04—Details of condensers
  • F25B2339/047—Water-cooled condensers
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
  • F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
  • F25B2700/00—Sensing or detecting of parameters; Sensors therefor
  • F25B2700/21—Temperatures
  • F25B2700/2117—Temperatures of an evaporator
  • F25B2700/21174—Temperatures of an evaporator of the refrigerant at the inlet of the evaporator
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
  • F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
  • F25B2700/00—Sensing or detecting of parameters; Sensors therefor
  • F25B2700/21—Temperatures
  • F25B2700/2117—Temperatures of an evaporator
  • F25B2700/21175—Temperatures of an evaporator of the refrigerant at the outlet of the evaporator

Definitions

• ambient air of the external environment may be relatively cold (for example, near the freezing point of water) and relatively humid.
• the working fluid and the surface of the evaporator
• frost may form on the surface of the evaporator. This frost may form as ice crystals with air trapped between them. Because both frost and air are poor conductors of heat, the frost may function as an insulator between the evaporator and the external environment. In addition, the frost may block the flow of air through the evaporator. Thus, if the frost is not removed, the overall efficiency of the heat pump heater unit may be reduced.
• Some techniques for defrosting include positioning electric-resistance heating elements near or adjacent to the evaporator. When electric current passes through these resistive elements, the heating elements generate heat from their resistance to the electrical current. This heat may be transferred to the frost on the evaporator and/or the surface of the evaporator itself, melting the frost. However, because electric-resistance heating elements generate heat directly, they may consume a significant amount of electricity (and are often inefficient).
• Additional techniques involve reversing the flow of working fluid in the refrigerant cycle.
• heated working fluid as opposed to cooled working fluid
• the evaporator which then effectively functions as a condenser. Heat from the working fluid then transfers to the evaporator, melting the frost.
• reversing the flow of the working fluid may also result in the heat pump heater unit removing heat from the water flowing through the heat pump heater unit and transferring the heat to the external environment, which cools the water to be heated. This cooled water may be returned to the top of a hot water storage tank and drawn for immediate use during a demand draw of hot water.
• a water heating system includes a compressor unit fluidly coupled to a first heat exchanger and a controller operatively coupled to the compressor unit.
• the controller is configured to operate the compressor unit in a heating mode to circulate refrigerant between the compressor unit and the first heat exchanger in a first direction, determine a loss of superheat in the first heat exchanger while the compressor unit is operating in the heating mode, and initiate a defrosting sequence in response to determining the loss of superheat in the first heat exchanger.
• the controller is configured to monitor a temperature of refrigerant exiting the first heat exchanger during the defrosting sequence and initiate a termination sequence in response to the temperature of the refrigerant exiting the first heat exchanger exceeding a threshold.
• the controller is configured to operate the compressor unit in a defrosting mode during the defrosting sequence.
• the compressor unit is configured to circulate refrigerant between the compressor unit and the first heat exchanger in a second direction in the defrosting mode. The second direction is opposite the first direction.
• the first heat exchanger functions as an evaporator when the compressor unit is operating in the heating mode and the first heat exchanger functions as a condenser when the compressor unit is operating in the defrosting mode.
• the controller is configured to determine the loss of superheat in the first heat exchanger based on a comparison of (i) an inlet refrigerant temperature of the first heat exchanger and (ii) an outlet refrigerant temperature of the first heat exchanger.
• the controller is configured to determine the loss of superheat in the first heat exchanger in response to the outlet refrigerant temperature of the first heat exchanger not exceeding the inlet temperature of the first heat exchanger over a predetermined time duration.
• the controller is configured to initiate the preheating sequence in response to determining the loss of superheat in the first heat exchanger.
• the water heating system includes a fan operatively coupled to the controller. The fan is configured to provide airflow to the first heat exchanger. The controller is configured to initiate the termination sequence by operating the fan to provide airflow to the first heat exchanger and configuring the compressor unit to operate in the heating mode. In other features, the controller is further configured to operate the water pump to provide a third water flow rate through the second heat exchanger during the defrosting sequence. The third water flow rate is greater than the first flow rate and lower than the second water flow rate.
• the controller 502 determines whether the refrigerant section temperature T ev_A is below a threshold (at decision block 604). Since the refrigerant section temperature T ev_A indicates the temperature of refrigerant entering the evaporator(s) 122, the refrigerant section temperature T ev_A may be used to determine whether the evaporator(s) 122 are likely at a temperature where they are at risk of forming frost. In scenarios where the refrigerant section temperature T ev_A is below the threshold, the evaporator(s) 122 may be at risk of forming frost.
• the controller 502 In response to the controller 502 determining that the evaporator section temperature T ev_B is not greater than the evaporator section temperature T ev_A ("N" at decision block 708), the controller 502 runs the timer (at block 710). In the process 700, the controller 502 determines whether the timer has expired (at decision block 712). In various implementations, the timer expiration may be set to a value in a range of between about five minutes and about 15 minutes. For example, the timer may be set to expire at about eight minutes.
• FIGS. 8-10 are a flowchart of an example defrost process 800.
• FIG. 8 is a flowchart of a preheating sequence of the example process 800. The preheating sequence may minimize the amount of cold water directed to a hot water circuit or to the tank 102 as a result of the defrost process 800.
• the controller 502 initializes and starts a preheat timer (at block 802).
• the controller 502 shuts off water flow in the water circuit 114 (at block 804) while continuing to run the compressor unit 116 in the heating mode, continuing to transfer heat from the refrigerant circuit 112 to stagnant water in the condenser 118.
• the controller 502 stops the pump 130.
• the controller 502 measures one or more characteristics of the refrigerant (at block 806).
• the characteristics include one or more of the refrigerant liquid line temperature T liq_line (e.g., computed based on sensor signals from the temperature sensor 134), the discharge refrigerant pressure P dis (e.g., computed based on sensor signals from the pressure sensor 316), and the discharge refrigerant temperature T dis (e.g., computed based on sensor signals from the temperature sensor 318).
• the controller 502 determines whether any of the one or more characteristics of the refrigerant exceeds a limit (at decision block 808).
• the limit for the refrigerant liquid line temperature T liq_line may be about 150° F.
• the limit for the discharge refrigerant pressure P dis may be about 310 psi.
• the limit for the discharge refrigerant temperature T dis may be about 220° F. Checking whether any of the characteristics of the refrigerant exceeds the relevant limit may ensure that the operational limitations of the refrigerant circuit 112 are not exceeded by the transfer of heat to the stagnant body of water from the water circuit 114 present in the condenser 118.
• FIG. 9 is a flowchart of a first defrost stage of the example process 800.
• the controller 502 shuts off the fan 124 (at block 814). Shutting off the fan 124 stops airflow from the fan 124 flowing over the evaporator(s) 122.
• the controller 502 stops the compressor unit 116 from pumping refrigerant (at block 816). For example, the controller 502 stops the compressor 302.
• the controller 502 switches the compressor unit 116 from the heating mode to the defrosting mode (at block 818).
• the controller 502 moves the slide 314 from the first position (e.g., corresponding to the heating mode) to the second position (e.g., corresponding to the defrosting mode).
• the controller 502 may initiate a time delay (at block 820). Adding a time delay may allow refrigerant to migrate throughout the refrigerant circuit 112, equalizing the pressure of refrigerant throughout the circuit.
• Equalizing the refrigerant pressure before reversing the direction of refrigerant flow in the refrigerant circuit 112 may reduce the stress experienced by various components of the circuit (since portions of the circuit previously filled with high-pressure refrigerant will be filled with low-pressure refrigerant and portions of the circuit previously filled with low-pressure refrigerant will be filled with high-pressure refrigerant when the direction of flow is reversed).
• the time delay may be in a range of between about one minutes and about 15 minutes. In some examples, the time delay may be omitted.
• the controller 502 starts the pump 130 (at block 822).
• the controller 502 may control the pump 130 to deliver a low water flow rate V w (e.g., as measured by the flow meter 140) in the water circuit 114.
• the controller 502 may set the water flow rate V w to a value in a range of between about 0.5 gallons per minute (GPM) and about 1 GPM.
• the controller 502 starts the compressor unit 116 (at block 824).
• the controller 502 commands the compressor 302 to run, and the compressor unit 116 begins delivering compressed refrigerant to the refrigerant circuit 112 in the defrosting mode.
• the controller 502 determines whether the refrigerant liquid line temperature T liq_line falls below a first threshold (at decision block 828).
• the first threshold may be set to a temperature near (but above) the freezing point of water.
• the first threshold may be set in a range of between about 33° F and about 50° F.
• the first threshold may be set to about 45° F.
• the first threshold may be set to prevent ice formation in the water circuit 114 side of the condenser 118.
• the refrigerant may remove enough heat from the condenser 118 such that the temperature of the condenser 118 approaches or falls below freezing, which may cause ice crystals to form in the water circuit 114.
• the controller 502 determines that the liquid line temperature T liq_line is not below the first threshold ("N" at decision block 828)
• the controller 502 continues monitoring sensor signals from the temperature sensor 134 (at block 824).
• the controller initiates a second defrost stage (at block 830 of FIG. 10 ).
• FIGS. 10 and 11 are a flowchart of the second defrost stage of the example process 800.
• the controller 502 initializes and starts a first timer (at block 830).
• the controller 502 increases the speed of the pump 130 to increase the water flow rate V w in the water circuit 114 by an increment ⁇ V (at block 832).
• the controller 502 monitors sensor signals from the flow meter 140 and increases the speed of the pump 130 to achieve incremental increases in the water flow rate ⁇ V over the old water flow rate V old to achieve a new water flow rate V new .
• the controller 502 monitors the liquid line temperature T liq_line (at block 834).
• the controller 502 computes the liquid line temperature T liq_line based on sensor signals from the temperature sensor 134. In the example process 800, the controller 502 determines whether the liquid line temperature T liq_line falls below a second threshold (at decision block 836). The liquid line temperature T liq_line falling below the second threshold may indicate a fault condition (for example, an abnormally low refrigerant line temperature). In various implementations, the second threshold may be set to about 2° F.
• controller 502 may determine a fault condition and the process 800 ends. In response to the controller 502 determining that the liquid line temperature T liq_line does not fall below the second threshold ("N" at decision block 836), the controller 502 determines whether the first timer has expired (at decision block 838). In response to the controller 502 determining that the first timer has not expired (“N” at decision block 838), the controller 502 increments the first timer (at block 840) and continues monitoring the liquid line temperature T liq_line (at block 834). In response to the controller 502 determining that the first timer has expired (“Y” at decision block 838), the controller 502 determines whether the new water flow rate V new is above a maximum water flow rate V max (at decision block 842).
• maximum water flow rate V max may be set to a value that allows sufficient heat transfer between water entering the water circuit 114 via the inlet port 126 and the condenser 118 to prevent ice buildup in the condenser 118 while minimizing the amount of cooled water provided to the tank 102 via the outlet port 128.
• the maximum water flow rate V max is below the water flow rate V w during normal heating operations.
• the maximum water flow rate V max may be in a range of between about 1 GPM and about 5 GPM. For example, the maximum water flow rate V max may be about 2.5 GPM.
• the controller 502 In response to the controller 502 determining that the new water flow rate V new is less than the maximum water flow rate V max ("Y" at decision block 842), the controller reinitializes and restarts the first timer (at block 830) and increases the speed of the pump 130 to achieve another incremental increase in the water flow rate ⁇ V (at block 832).
• the process 800 continues operating the compressor unit 116 in the defrost mode and the water pump 130 to achieve the maximum water flow rate V max until a predetermined time period expires or a terminating condition is met (e.g., as shown in FIG. 11 , beginning at block 844).
• the controller 502 initializes and starts a second timer (at block 844).
• the controller 502 monitors the evaporator section refrigerant temperature T ev_A (at block 846). For example, the controller 502 determines evaporator section refrigerant temperature T ev_A based on sensor signals from the temperature sensor(s) 136. In the example process 800, the controller 502 determines whether the evaporator section refrigerant temperature T ev_A is greater than a limit (at decision block 848).
• the limit may be set to a temperature substantially above the freezing point of water. For example, the limit may be set to a temperature in a range of between about 43° F and about 59° F.

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• Engineering & Computer Science (AREA)
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• Thermal Sciences (AREA)
• Mechanical Engineering (AREA)
• General Engineering & Computer Science (AREA)
• Chemical & Material Sciences (AREA)
• Combustion & Propulsion (AREA)
• Heat-Pump Type And Storage Water Heaters (AREA)

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Citations (3)

• 2025
  • 2025-01-17 EP EP25152667.9A patent/EP4589221A1/de active Pending
  • 2025-01-17 CA CA3262411A patent/CA3262411A1/en active Pending
  • 2025-01-17 US US19/030,642 patent/US20250237426A1/en active Pending

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