Direct electric resistance liquid heater
The Direct Electric Resistance Liquid Heater comprises a liquid heating chamber containing a plurality of electrodes. The electrodes are spaced apart to create a plurality of channels through which the liquid to be heated passes. The electrodes are each connected to a power supply by one or more switches. A controller controls the switches based upon data received from a temperature sensor, sensing the temperature of the liquid, and/or an electric current sensor, sensing the current utilized by the liquid heater. Selection of the number and spacing of the electrodes, and the number of switches, provides the controller with various current levels options to apply to the liquid to be heated. The current levels available due to the number and spacing of the electrodes and the number of switches, span the range from minimum current to maximum current such that the controller can incrementally increase or decrease the current applied to the liquid to be heated without disrupting other users of the same power source.
1. A liquid heater comprising
a chamber having an inlet and an outlet, and at least three electrodes within said chamber defining a plurality of adjacent channels for liquid flow from said inlet to said outlet whereby the liquid flow is divided between the channels and wherein the liquid is heated by electrical current flow through the liquid between two or more of said at least three electrodes;
an electrical power supply connection; and
at least one switch for each of said electrodes, the at least one switch being arranged to removably connect each of said electrodes to the power supply connection independent of the remaining ones of said electrodes,
the electrodes being non-uniformly spaced apart from one another with different distances between different pairs of mutually-adjacent ones of the electrodes, so that connection of different sets of the electrodes to the electrical power supply connection provides different levels of current passing through the liquid, the levels of current including levels defining a stepwise progression between zero current when none of the electrodes are connected and a maximum current when all of the electrodes are connected, the progression having substantially uniform ratios between the currents of adjacent steps with non-zero current levels.
2. A liquid heater as in claim 1 further comprising
a controller controlling the operation of the at least one switch for each of the electrodes and thereby controlling connection of said electrodes to the electrical power supply connection.
3. A liquid heater as in claim 2 further comprising a temperature sensor sensing the temperature of the liquid, wherein the controller controls the operation of said at least one switch based upon information received from the temperature sensor.
4. A liquid heater as in claim 2 further comprising
a temperature sensor sensing the temperature of the liquid after it passes through the channels, wherein the controller controls the operation of said at least one switch based upon information received from the temperature sensor.
5. A liquid heater as in claim 1 wherein said at least one switch for each of said electrodes are physically attached to said electrodes to facilitate the removal of generated heat from said switch, into said electrode, and into the liquid to be heated.
6. A liquid heater as in claim 2 further comprising
an electric current sensor sensing the amount of electric current being utilized by the liquid heater, wherein said controller controls the operation of said at least one switch for each of said electrodes, based upon information received from said electric current sensor.
7. A liquid heater as in claim 2 further comprising
a temperature sensor sensing the temperature of the liquid, and an electric current sensor sensing the amount of electric current being utilized by the liquid heater, wherein said controller controls the operation of said at least one switch for each of said electrodes, based upon information received from said temperature sensor and from said electric current sensor.
8. A liquid heater as in claim 1 further comprising
a pair of electric current leakage electrodes, one located in said chamber adjacent said inlet, and the other located in said chamber adjacent said outlet, both of said electric current leakage electrodes connected to each other and to an electrically neutral voltage source.
9. A liquid heater as in claim 1 wherein said at least three electrodes are manufactured from a combination of oriented graphite and polymer binder.
10. A liquid heater as in claim 1 wherein there is one switch for each of said electrodes, and the power supply connection has two opposite terminals, and wherein said switches removably connect mutually-adjacent ones of said electrodes to opposite terminals of the power supply connection.
11. A liquid heater as in claim 1 wherein said power supply connection is a three-phase connection having three terminals and said at least one switch for each of said electrodes removably connects each of said electrodes to one of the terminals of the three phase connection.
12. A liquid heater as in claim 1 wherein said power supply connection is a three-phase connection having three terminals and the at least one switch for each of the electrodes includes three switches for each of said electrodes, said switches removably connecting each of said electrodes to each terminal of the three phase connection.
13. A liquid heater as in claim 1 wherein the power supply connection has two opposite terminals and said at least one switch for each of said electrodes connects each of said electrodes to one or the other terminal of the power supply connection.
14. A liquid heater as in claim 1 wherein said controller can connect and disconnect any combination of said electrodes to the power supply connection by operating said switches.
15. A liquid heater as in claim 2 , wherein said controller is operative to control the switches so as to cycle through different combinations of said electrodes that yield similar current levels, whereby the current applied to the liquid is more evenly distributed throughout the liquid and said electrodes are more evenly utilized.
16. A liquid heater as in claim 1 , wherein a greatest difference between the levels of current in any two adjacent steps of the progression is no greater than 10% of the maximum current.
17. A liquid heater as in claim 1 , wherein a greatest ratio between the currents in any two adjacent steps of the progression having non-zero currents is no more than 1.22:1.
18. A liquid heater as in claim 17 , wherein the greatest ratio is no more than 1.1:1.
19. A liquid heater as in claim 1 , wherein a greatest difference between the levels of current in any two adjacent steps of the progression is no greater than 5% of the maximum current.
20. A liquid heater as in claim 1 wherein the number of said electrodes, the number of said switches, and the spacing of said electrodes is sufficient to provide at least 60 different current levels in said stepwise progression.
21. A liquid heater as in claim 4 , wherein said controller controls the application of electrical power to said electrodes based upon the temperature sensed by said temperature sensor and the rate of change of the temperature sensed by said temperature sensor.
22. A liquid heater as claimed in claim 4
wherein said controller periodically determines if the combination of said electrodes connected to the power supply connection needs to be changed to raise or lower the current level applied to the liquid to be heated, based upon information received from said temperature sensor and a desired liquid temperature at said chamber outlet.
23. A liquid heater as in claim 22 wherein said controller limits the rate of change of electrical current applied to said electrodes, thereby limiting surges in power levels that could impact other users of the power source used by the liquid heater.
24. A liquid heater as in claim 23 wherein said controller limits the rate of change of electrical current applied to said electrodes, by adjusting the current applied to said electrodes only to the next highest or lowest available current level provided by a combination of said electrodes, each time said controller periodically determines if there needs to be a change in the current level applied to the liquid to be heated.
25. A liquid heater as in claim 24 wherein said controller limits the rate of change of electrical current applied to said electrodes by only determining if the combination of said electrodes connected to a power supply needs to be changed once every cycle of an alternating current supplied to the power supply connection.
26. A liquid heater as in claim 1 wherein said electrodes are planar, thin, and rectangular.
27. A liquid heater as in claim 1 wherein said chamber and said electrodes are sized and spaced such that the design rate of liquid flow through the channels between said electrodes is in the range of transition between laminar flow and turbulent flow.
28. A liquid heater as in claim 1 wherein a ratio between the maximum current and a minimum non-zero current in said progression is at least 250:1.