Patent Application
20110211612
Water heaters, such as storage-type water heaters, are now manufactured with an increasing amount of diagnostic and communication capabilities. Home networks are bringing this information to the user through interactive devices that allow the homeowner to interact with the water heater.
Information that is desirable from a water heater includes the amount of hot water available, along with an estimated time to depletion based on the present rate of usage. If the temperature of water in the tank is uniform, then the calculation is straight forward. But in most installations and under high flows, the water temperature stratifies in the tank. In order to make an estimate of the amount of hot water available, in at least one embodiment, an array of temperatures is read at different points of the tank. Through the temperature array, an estimate of the amount of hot water available can be made. Other estimates, such as the amount of time remaining for hot water based on current use, can be made.
One embodiment of the invention includes a system for determining a temperature of a medium, such as water, as measured by each of a plurality of temperature sensors in a temperature sensor array. The system includes a variable frequency voltage supply, a controller, and a temperature sensor array. The temperature sensor array includes at least two temperature sensing units. The first temperature sensing unit includes a temperature sensor coupled to a first capacitor in a parallel-type relationship. The first capacitor has a low impedance (relative to the resistance of the temperature sensor) at frequencies above a first frequency threshold and a high impedance at frequencies lower than the threshold. The second temperature sensing unit is coupled to the first temperature sensing unit in series and includes a second temperature sensor. The controller selectively varies the frequency of the variable frequency voltage supply above and below the first threshold.
In one embodiment, the controller determines a temperature sensed by the second temperature sensor based on the voltage drop across the temperature sensor array when the variable frequency is set above the first frequency threshold. The controller determines the temperature sensed by the first temperature sensor by setting the frequency above the first frequency threshold and comparing the voltage drop when the frequency is above the threshold to the voltage drop when the frequency is below the threshold.
In some embodiments, one or more of the temperature sensing units includes a positive or negative facing diode coupled in a parallel-type relationship with the capacitor and the temperature sensor. In such embodiments, the temperature sensor is bypassed when the alternating current is either positive or negative depending upon the polarity of the diode.
Another embodiment includes a method of determining an amount of hot water in a water heater tank. The method includes determining a plurality of temperatures sensed by each temperature sensor in a temperature sensor array. The array includes a plurality of temperature sensor units and each temperature sensor unit includes a temperature sensor and a resonant circuit. The temperature sensor of each temperature sensor unit can be bypassed by adjusting the frequency of a variable frequency source that provides power to the temperature sensor array. The amount of hot water in the tank is then calculated based on the plurality of sensed temperatures.
In some embodiments, the temperatures are determined by varying the frequency of the variable frequency source. A first voltage drop of the temperature sensor array is measured at a first frequency and a second voltage drop is measured at a second frequency. In some embodiments, the temperature sensed by a first temperature sensor is determined based on the first voltage drop and a temperature sensed by a second temperature sensor is determined based on a difference between the first voltage drop and the second voltage drop.
In some embodiments, the method further determines a flow rate of hot water exiting the water heater tank and calculates a time remaining until the tank is empty based on the amount of hot water in the water heater tank and the flow rate. In some embodiments, the calculated time remaining is then displayed on a user interface.
An apparatus in accordance with one exemplary embodiment of the invention has a structure (e.g., a tank) filled at least partially with a fluid (e.g., water) and a temperature sensor array coupled to the structure. A second apparatus in accordance with another exemplary embodiment of the invention has the temperature sensor array being supported by a structure (e.g., a wall) within or defining a portion of a space (e.g., a room). A third apparatus in accordance with another exemplary embodiment of the invention is a temperature sensor array.
A first process in accordance with an exemplary embodiment of the invention is a method of controlling an apparatus (e.g., a water heater; a heating/cooling/ventilating system) using a temperature sensor array. A second process in accordance with an exemplary embodiment of the invention is a method of determining a plurality of temperatures at a plurality of locations, respectively, using a temperature sensor array.
Other aspects of the invention will become apparent by consideration of the detailed description and accompanying drawings.
Before any embodiments of the invention are explained in detail, it is to be understood that the invention is not limited in its application to the details of construction and the arrangement of components set forth in the following description or illustrated in the following drawings. The invention is capable of other embodiments and of being practiced or of being carried out in various ways. Also, it is to be understood that the phraseology and terminology used herein is for the purpose of description.
For illustrative purposes, embodiments of the invention will be discussed hereafter in the context of a storage-type water heater. However, the invention can be applied to other types of fluid dynamic systems. An HVAC system, for example, can be adapted to incorporate aspects of the invention.
In some constructions of the invention, waste water from a shower can be purified and returned to water tank through dip tube 125. Additionally, shampoo, lotion or other additives can be injected into water from the dip tube 135 before it is used in a shower.
A heating device changes the thermal temperature of the fluid. In the case of the water heater, the heating device 140 (
The heating device 140 is selectively controlled by a controller 145 that activates and deactivates the heating device 140 based on a sensed temperature and, possibly, other information (e.g., use history, external commands, other sensed parameters, etc.). The sensed temperature is sensed by a temperature sensor. The sensed temperature can include or be based on multiple temperatures, as discussed below with a temperature sensor array 150. The sensed temperature, typically, has a correlation (or relation) to the temperature of the fluid in the space.
For example, if the temperature sensed by a temperature sensor falls below a first temperature threshold, referred to as a “lower set point” the controller 145 activates the heating device 140 such that it heats water within the tank 105. The heating device 140 remains activated until the temperature sensed by the temperature sensor exceeds a second temperature, referred to as an “upper set point.”
While one control scheme was just described above, various control schemes are contemplated for when the controller 145 activates the heating device 140 based on the sensed temperature and other information, if present, provided to the controller 145. Thus, the heating device 140 is repetitively activated and deactivated in an attempt to control the temperature sensed by the temperature sensor.
For a specific example with an electric-resistance storage-type water heater, the controller 145 controls a relay 155, which may be electro-magnetic, electronic, or a combination thereof. The relay is electrically connected between electrical mains and an electric-resistance heating element 160. The heating element 160 is a resistive device that generates heat when electrical current flows through the element 160. When the heating element 160 is to be activated, the controller 145 closes the relay 155 such that an electrical current from the electric mains passes through the heating element 160. When the heating element 160 is to be deactivated, the controller 145 opens the relay 155 such that no current flows in the heating element. Similarly, the controller 145 can control a valve for controlling the flow of gas for a burner, the refrigerant of a refrigeration system, or the fluid to be heated in a solar system. Also, the controller 145 may control other devices of the system (e.g., a pump or blower) depending on the type of apparatus and means for moving the fluid. For example, a circulation pump can be used to circulate the fluid within the tank so that an average temperature is achieved for all water within the tank at a given time.
The controller 145 includes control logic, which may be implemented in hardware, software, or a combination thereof. For example, the controller 145 can include a processor 165 and a memory 170. In one exemplary construction, the control logic includes software instructions stored in the memory 170, which may include other data. The software instructions are executed by the processor 165. One exemplary construction of the processor 165 includes at least one conventional processing element, such as a digital signal processor (DSP) or a central processing unit (CPU), that communicates to and drives the other elements within the temperature control system 175.
The controller 145 can include other elements known to skilled in the art, but not discussed herein. Exemplary elements include an analog-to-digital (A/D) converter, an I/O Interface, and a bus.
The temperature control system 175 includes a data interface 180 that enables the controller 145 to exchange information or commands with an external device (e.g., an external controller), and a user interface 185 that enables the controller to exchange information with a user. The user interface 185 may comprise user input devices, such as a keypad, buttons, or switches, which enable a user to input information to the controller 145. The user interface 185 may also comprise user output devices, such as a liquid crystal display (LCD) or other display device, light emitting diodes (LEDs), or other components known for outputting or conveying information to a user. The user input device and the user output device may be combined in a single device, such as a touch display.
It is also envisioned that the user interface 185 may be at another location remote from the control device. In one exemplary construction, a display device, such as a liquid crystal display (LCD), external to the controller 145 communicates with the controller 145 via the data interface 180. As an example, the display device may be mounted on a side of the tank 110. In other examples, the display device may be mounted elsewhere, such as in a bathroom. In still other devices, the controller 145 that evaluates the data from the temperature array 150 is separate from a main water heater controller that controls the operation of the heating element and the controllers are connected through a controller network.
As described above, the controller 145 selectively controls the activation states of the heating device 140 in an attempt to control the temperatures sensed by the temperature array 150. However, due to various factors, such as significant water usage within a relatively short duration, the heating device 145 may be unable to keep the temperature of the water within a desired range or at a desired value.
In one exemplary construction, the controller 145 is configured to automatically estimate the total amount of hot water currently in the tank 110 and to report this amount to a user. As used herein, “hot water” refers to water above a predefined temperature threshold, and “the total amount of hot water currently in the tank 110” refers to the total amount of water currently in the tank 110 above the predefined temperature threshold.
Further, the water within the tank 110 often is not at a uniform temperature such that water in different areas of the tank 110 often has significantly different temperatures. This process is referred to as stratification. Further, the temperature profile of the water in the tank 110 can vary over time as water usage changes. Indeed, as water is drawn from the tank 110 and replenished, convection currents in the tank 110 can disrupt the current temperature profile. The temperature readings of the temperature sensors T1-T6 (
The estimated amount of hot water in the tank 110 can be expressed in a variety of ways. In one example, the controller 145 may report that a number of gallons (or liters) of hot water is currently in the tank 110, where the number is from zero to the total volume capacity of the tank 110 depending on the temperature characteristics of the water in the tank 110. In another implementation, the estimated amount of hot water may be expressed as a percentage of the overall volume capacity of the tank 100. As a specific example, if the total capacity of the tank 110 is forty gallons and if the controller 145 determines that the total amount of hot water currently in the tank 110 is twenty gallons, then the controller 145 may report that the tank 110 is fifty percent full of hot water. Various other techniques for expressing the estimated amount of hot water in the tank 110 are possible, including by graphical and animated means. Further, based on the temperature profile over time or through the use of a flowmeter, the controller 145 can predict when the water heater 100 runs out of hot water.
It is also envisioned that the temperature sensor array 150 can be used to track hot water usage. For a simple example, if the controller 145 determines the amount of hot water available in the tank 110 or the temperature profile of the tank 110 over time, the controller 145 can estimate the amount of hot water used. The controller 145 can use this information to develop a history of usage for the water heater 110, predict future usage of the water heater 110, and develop predictive algorithms to heat the water.
Various methodologies may be employed to estimate the total amount of hot water currently in the tank 110. In one exemplary implementation, the controller 145 estimates the total amount of hot water currently in the tank 110 based on the readings of the temperature sensors T1-T6. Further information can be used to estimate the total amount of hot water currently in the tank, such as the size or dimensions of the tank 110.
One temperature sensor array 150 that can be used with the invention is the temperature sensor array 150 shown in
For a specific example, when the source, Vs, is 10 khz and 10 volts, the impedance of capacitors C1-C4 are considered small as compared to resistors R1-R4. The voltage measured at node V when Vs is positive will be the voltage across R6 due to the diode D5 shorting R5. From the measured voltage, the resistance of R6 can be determined. The resistance of resistor R6 has a relation to the temperature sensed by the thermistor T6, and the sensed temperature has a relation to the fluid near the thermistor T6. When Vs is negative, diode D6 shorts resistor R6, the voltage measured at node V is the voltage across resistor R5. From the measured voltage, the resistance of R5 can be determined. The resistance of resistor R5 has a relation to the temperature sensed by the thermistor T5, and the sensed temperature has a relation to the fluid near the thermistor T5.
Continuing the specific example, when the source, Vs, is 10 hz and 10 volts, the impedance of capacitors C1, C2 are considered small as compared to resistors R1, R2. The voltage measured at node V when Vs is positive will be the voltage across resistors R6, R4 due to diodes D5, D3 shorting resistors R5, R3. From the measured voltage, the resistance of resistor R4 can be determined from the previous knowledge of resistor R6. The resistance of resistor R4 has a relation to the temperature sensed by the thermistor T4, and the sensed temperature has a relation to the fluid near the thermistor T4. When Vs is negative, diodes D6, D4 short resistors R6, R4, and the measured voltage at node V is the voltage across resistors R5, R3. From the measured voltage, the resistance of resistor R3 can be determined from the previous knowledge of resistor R5. The resistance of resistor R3 has a relation to the temperature sensed by the thermistor T3, and the sensed temperature has a relation to the fluid near the thermistor T3.
Continuing further with the specific example, when the source, Vs, is 0.1 hz (or a direct current (DC) source), 10 volts, and positive, diodes D5, D3, D1 short resistors R5, R3, and R1. The voltage measured at node V is the voltage across resistors R6, R4, R2. From the measured voltage, the resistance of resistor R2 can be determined from the previous knowledge of resistors R6, R4. The resistance of resistor R2 has a relation to the temperature sensed by the thermistor T2, and the sensed temperature has a relation to the fluid near the thermistor T2. When Vs is negative, diodes D6, D4, D2 short resistors R6, R4, R2, and the measured voltage at node V is the voltage across resistors R5, R3, R1. From the measured voltage, the resistance of resistor R1 can be determined from the previous knowledge of resistors R5, R3. The resistance of resistor R1 has a relation to the temperature sensed by the thermistor T1, and the sensed temperature has a relation to the fluid near the thermistor T1.
In other constructions, additional circuit elements can be included in each temperature sensing unit. In
Furthermore, although the example above describes a variable frequency voltage supply, other constructions of the invention may utilize other variable frequency power supplies designed to operate various types of resonant circuits.
An alternative temperature sensor array 150 that can be used with the invention is the temperature sensor array 150 shown in
For a specific example, when the source, Vs, is 10 khz and 10 volts, the impedance of capacitors C1-C4 are considered small as compared to resistors R1-R4. The voltage measured at node V1 will be the voltage across R5. From the measured voltage, the resistance of R5 can be determined. The resistance of resistor R5 has a relation to the temperature sensed by the thermistor T5, and the sensed temperature has a relation to the fluid near the thermistor T5. The voltage measured at node V2 will be the voltage across R6. From the measured voltage, the resistance of R6 can be determined. The resistance of resistor R6 has a relation to the temperature sensed by the thermistor T6, and the sensed temperature has a relation to the fluid near the thermistor T6.
Continuing the specific example, when the source, Vs, is 10 hz and 10 volts, the impedance of capacitors C1, C2 are considered small as compared to resistors R1, R2. The voltage measured at node V1 will be the voltage across resistors R3 and R5. From the measured voltage, the resistance of resistor R3 can be determined from the previous knowledge of resistor R5. The resistance of resistor R3 has a relation to the temperature sensed by the thermistor T3, and the sensed temperature has a relation to the fluid near the thermistor T3. The voltage measured at node V2 will be the voltage across resistors R4 and R6. From the measured voltage, the resistance of resistor R4 can be determined from the previous knowledge of resistor R6. The resistance of resistor R4 has a relation to the temperature sensed by the thermistor T4, and the sensed temperature has a relation to the fluid near the thermistor T4.
Continuing further with the specific example, when the source, Vs, is 0.1 hz (or a direct current (DC) source), 10 volts, and positive, the voltage measured at node V1 is the voltage across resistors R1, R3, and R5. From the measured voltage, the resistance of resistor R1 can be determined from the previous knowledge of resistors R3 and R5. The resistance of resistor R1 has a relation to the temperature sensed by the thermistor T1, and the sensed temperature has a relation to the fluid near the thermistor T1. The voltage measured at node V2 is the voltage across resistors R2, R4, and R6. From the measured voltage, the resistance of resistor R2 can be determined from the previous knowledge of resistors R4 and R6. The resistance of resistor R2 has a relation to the temperature sensed by the thermistor T2, and the sensed temperature has a relation to the fluid near the thermistor T2.
In one arrangement, each temperature sensor T1-T6 would be equally spaced from the top to the bottom of the tank on the inside of the tank 110. For example, the temperatures sensors T1-T6 can be mounted on the inside wall of the tank 110 or on the dip tube 125. With this arrangement, the determined resistances of resistors R1-R6 have a direct relationship to the fluid temperature surrounding the respective temperature sensors T1-T6. In another arrangement, each temperature sensor T1-T6 would be equally spaced from the top to the bottom of the tank 110 on the outside of the tank 110. The temperature sensors T1-T6 are mounted to the tank and are thermally connected to the tank 110. With this arrangement, the determined resistances of resistors R1-R6 have an indirect relationship to the fluid near the respective temperature sensors T1-T6.
In another construction, the temperature sensors T1-T6 can be added to an existing water heater tank by replacing the existing dip tube 125 with a dip tube that includes sensors T1-T6 installed along the length of the replacement dip tube.
It is also envisioned that the temperature sensors T1-T6 could be unequally spaced. The temperature of the fluid near the bottom of the tank is typically uniform. Therefore, the density of the sensors T1-T6 may increase as the temperature sensor array progresses from the bottom of the tank toward the top of the tank.
Furthermore, although the system described above uses only the temperature sensor array 150 to determine the amount of hot water in the tank, other construction of the invention may use other methods in lieu of or in addition to the temperature sensor array 150 to determine the amount of hot water in the tank. These methods may include, for example, sonar configured to bounce at the interface between cold and hot water, a refrigerant filled copper tube that detects pressure changes caused by varying temperatures, a laser diopler or floating balls to determine the depth of the hot water, painting the tank with resistive ink to monitor changes in temperature, and load sensing positioned under the tank to detect changes in mass due to varying temperatures of a consistent volume of water.
Thus, the invention provides, among other things, a new and useful temperature sensor array, an apparatus including the temperature sensor array, and a method of obtaining a plurality of temperatures using the temperature sensor array.
Various features and advantages of the invention are set forth in the following claims.
This application claims the benefit of co-pending U.S. Provisional Patent Application No. 61/305,825, filed on Feb. 18, 2010, and co-pending U.S. Provisional Patent Application No. 61/372,596, filed on Aug. 11, 2010, the content of each are hereby incorporated by reference.
| Number | Date | Country | |
|---|---|---|---|
| 61305825 | Feb 2010 | US | |
| 61372596 | Aug 2010 | US |
