Water heater with mix tank fluid time delay for causal feedforward control of hot water temperature

Patent metadata

Field	Value
Publication number	US-RE49883-E
Application number	US-202117452265-A
Country	US
Kind code	E1
Filing date	Oct 26, 2021
Priority date	Dec 20, 2018
Publication date	Mar 26, 2024
Grant date	Mar 26, 2024

Abstract

A water heater includes a heat exchanger. A controllable three-way proportional valve provides a proportionally controllable flow to the hot water inlet of the heat exchanger and a boiler return water outlet. A mixing tank mixes a cold water and a hot water. The mixing tank provides a time delayed mixed water. A temperature sensor is disposed in or on the mixing tank to measure a temperature of the time delayed mixed water to provide a time delayed mixed water temperature. A feedforward control process running on a processor adjusts a proportional operating position of the controllable three-way proportional valve to regulate a temperature of hot water at the hx domestic hot water outlet based on the temperature of the time delayed mixed water temperature. A method for controlling a hot water temperature of a water heater a water heater using a flowmeter based feedforward control are also described.

First claim

What is claimed is:

1. A water heater comprising:
a heat exchanger (hx) having a hx hot water inlet, a hx water return outlet, a hx domestic cold water inlet, and a hx domestic hot water outlet;
a controllable three-way proportional valve having a boiler water hot water inlet adapted to accept a boiler water, and to provide a proportionally controllable flow to said hx hot water inlet and a boiler return water outlet, and said boiler return water outlet adapted to return a boiler return water to a boiler;
a mixing tank (mt) having a mt cold water inlet adapted to receive a cold water from a source of domestic cold water, a mt hot water inlet, and a mt mixed water outlet, said mixing tank to mix said cold water and a hot water from said mt hot water inlet, and said mixing tank to provide a time delayed mixed water;
a constant flow pump fluidly coupled to and disposed between said hx domestic hot water outlet and said mt hot water inlet;
a temperature sensor disposed in or on said mixing tank to measure a temperature of said time delayed mixed water to provide a time delayed mixed water temperature;
a processor operatively coupled to said temperature sensor and operatively coupled to said controllable three-way proportional valve, said processor to run a feedforward control process based on said temperature of said time delayed mixed water to control a flow of boiler water into said heat exchanger; and
wherein said feedforward control process adjusts a proportional operating position of said controllable three-way proportional valve to regulate a temperature of hot water at said hx domestic hot water outlet based on said temperature of said time delayed mixed water temperature.

2. The water heater of claim 1 , wherein said constant flow pump comprises a variable speed pump having a plurality of preset or selectable constant flow rates.

3. The water heater of claim 1 , wherein said mixing tank comprises at least two chambers separated by at least one baffle with at least one opening in said at least one baffle.

4. The water heater of claim 3 , wherein said at least two chambers comprise a mixing chamber and a fluid time delay chamber.

5. The water heater of claim 4 , wherein said at least one baffle comprises an open V-shaped bend to enhance a mixing action in said mixing chamber.

6. The water heater of claim 3 , wherein said at least one opening in said at least one baffle is disposed about adjacent to a first end of said mixing tank.

7. The water heater of claim 6 , wherein said temperature sensor is disposed in said first end of said mixing tank.

8. The water heater of claim 1 , wherein said mixing tank comprises a plurality of baffles, each baffle having at least one opening to provide a serpentine flow path through said mixed tank.

9. The water heater of claim 1 , further comprising one or more additional delay tanks disposed between said mixing tank and said hx domestic cold water inlet.

10. The water heater of claim 1 , further comprising one or more additional lengths of fluid time delay pipes disposed between said mixing tank and said hx domestic cold water inlet.

11. The water heater of claim 1 , wherein said time delayed mixed water temperature provides a causal feed forward control of said controllable three-way proportional valve for a stable regulation of said hot water at said hx domestic hot water outlet.

12. The water heater of claim 1 3, wherein said temperature sensor is disposed in an end of said mixing tank about adjacent to said at least one opening in said at least one baffle.

13. The water heater of claim 1 , wherein said heat exchanger and said mixing tank are mechanically coupled to a common mounting skid.

14. The water heater of claim 1 , wherein said feedforward control process comprises a polynomial process equation of 2 nd order or greater.

15. The water heater of claim 1 , further comprising a domestic hot water temperature sensor thermally coupled to hot water flowing from said hx domestic hot water outlet and operationally coupled to said controller processor, a domestic hot water temperature value measured by said domestic hot water temperature sensor as input to an additional feedback process running on said processor to remove offset error between said domestic hot water temperature value and a desired domestic hot water temperature setpoint value.

16. The water heater of claim 1 15, further comprising a domestic cold water inlet temperature sensor thermally coupled to cold water flowing into said water heater and operationally coupled to said controller processor, a domestic cold water temperature value measured by said domestic hot water temperature sensor as additional input to said feedforward process running on said processor to improve an accuracy of said temperature of hot water at said hx domestic hot water outlet.

17. A method for controlling a hot water temperature of a water heater comprising:
providing a heat exchanger having a hx cold water inlet fluidly coupled to a source of cold water and a mix tank, said mix tank having a cold water inlet and a constant flow hot water inlet;
mixing said source of cold water with a constant flow of hot water from said heat exchanger in said mix tank to provide a mixed water;
delaying said mixed water by a fluid delay time to provide a fluid time delayed mixed water;
measuring a temperature of said fluid time delayed mixed water in said mixing tank to provide a temperature measurement of said fluid time delayed mixed water; and
setting by a processor running a feedforward control process, a position of a proportional valve based on said temperature measurement of said fluid time delayed mixed water to control a flow of boiler water into said heat exchanger.

18. A water heater comprising:
a heat exchanger (hx) having a hx hot water inlet, a hx water return outlet, a hx domestic cold water inlet, and a hx domestic hot water outlet;
a controllable three-way linearized proportional valve having a boiler water hot water inlet adapted to accept a boiler water, and to provide a proportionally controllable flow to said hx hot water inlet and boiler return water outlet, and said boiler return water outlet adapted to return a boiler return water to a boiler;
a flow rate sensor disposed in fluid communication with said hx domestic cold water inlet to provide a domestic cold water flow rate;
a processor operatively coupled to said flowrate sensor and operatively coupled to said controllable three-way linearized proportional valve, said processor to run a feedforward control process based on said domestic cold water flow rate to control a flow of boiler water into said heat exchanger; and
wherein said feedforward control process adjusts a proportional an operating position of said controllable three-way linearized proportional valve to regulate a temperature of hot water at said hx domestic hot water outlet based on said domestic cold water flow rate.

19. The water heater of claim 18 20, further comprising a constant flow pump fluidly coupled to and disposed between said hx domestic hot water outlet and said mt hot water inlet.

20. The water heater of claim 18 , further comprising a mixing tank (mt) having a mt cold water inlet adapted to receive a cold water from a source of domestic cold water, a mt hot water inlet, and a mt mixed water outlet, said mixing tank to mix said cold water and a hot water from said mt hot water inlet, and said mixing tank to provide a time delayed mixed water.

Assignees

• Watts Regulator Co

Inventors

• Daniels Mark
• Voicu Adrian

Classifications

• F24D19/1051 Primary

  for domestic hot water · CPC title

• F24D3/1091

  Mixing cylinders · CPC title

• F24D17/001

  with accumulation of heated water · CPC title

• F24D17/0031

  with accumulation of the heated water · CPC title

• F24D17/0078

  Recirculation systems · CPC title