WO2022170353A1 - Chauffe-eau instantané doté de débitmètre à courbe de réponse de haute précision - Google Patents

Chauffe-eau instantané doté de débitmètre à courbe de réponse de haute précision Download PDF

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Publication number
WO2022170353A1
WO2022170353A1 PCT/US2022/070541 US2022070541W WO2022170353A1 WO 2022170353 A1 WO2022170353 A1 WO 2022170353A1 US 2022070541 W US2022070541 W US 2022070541W WO 2022170353 A1 WO2022170353 A1 WO 2022170353A1
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WO
WIPO (PCT)
Prior art keywords
flowmeter
factors
impeller
water heater
controller
Prior art date
Application number
PCT/US2022/070541
Other languages
English (en)
Inventor
David M. Daniel
David A. Daniel
Original Assignee
Tankless Technologies, Inc.
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Tankless Technologies, Inc. filed Critical Tankless Technologies, Inc.
Priority claimed from US17/592,993 external-priority patent/US11384958B1/en
Publication of WO2022170353A1 publication Critical patent/WO2022170353A1/fr

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Classifications

    • 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
    • F24H9/00—Details
    • F24H9/20—Arrangement or mounting of control or safety devices
    • F24H9/2007—Arrangement or mounting of control or safety devices for water heaters
    • F24H9/2014—Arrangement or mounting of control or safety devices for water heaters using electrical energy supply
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01F—MEASURING VOLUME, VOLUME FLOW, MASS FLOW OR LIQUID LEVEL; METERING BY VOLUME
    • G01F1/00—Measuring the volume flow or mass flow of fluid or fluent solid material wherein the fluid passes through a meter in a continuous flow
    • G01F1/05—Measuring the volume flow or mass flow of fluid or fluent solid material wherein the fluid passes through a meter in a continuous flow by using mechanical effects
    • G01F1/06—Measuring the volume flow or mass flow of fluid or fluent solid material wherein the fluid passes through a meter in a continuous flow by using mechanical effects using rotating vanes with tangential admission
    • G01F1/075—Measuring the volume flow or mass flow of fluid or fluent solid material wherein the fluid passes through a meter in a continuous flow by using mechanical effects using rotating vanes with tangential admission with magnetic or electromagnetic coupling to the indicating device
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01F—MEASURING VOLUME, VOLUME FLOW, MASS FLOW OR LIQUID LEVEL; METERING BY VOLUME
    • G01F1/00—Measuring the volume flow or mass flow of fluid or fluent solid material wherein the fluid passes through a meter in a continuous flow
    • G01F1/05—Measuring the volume flow or mass flow of fluid or fluent solid material wherein the fluid passes through a meter in a continuous flow by using mechanical effects
    • G01F1/10—Measuring the volume flow or mass flow of fluid or fluent solid material wherein the fluid passes through a meter in a continuous flow by using mechanical effects using rotating vanes with axial admission
    • G01F1/12—Adjusting, correcting, or compensating means therefor
    • G01F1/125—Adjusting, correcting, or compensating means therefor with electric, electro-mechanical or electronic means

Definitions

  • the present disclosure generally relates to tankless water heaters.
  • Typical tankless water heaters with an impeller flowmeter use a single K factor which is very inaccurate at low flow rates, such as under 1 gallon per minute.
  • the measured flow rate of a single K factor flowmeter is non-linear particularly at low flow rates. Inaccurate flow rate readings at low flow rates lead to the tankless water heater not turning on, or the heater turning on at too low a setting.
  • Tank water heaters keep water heated at all times in a tank, and the heater does not have the capacity to heat the water quickly enough to satisfy potential demand.
  • FIG. 1A is a front view of a tankless water heater utilizing an impeller flowmeter
  • FIG. IB is an electrical block diagram of the tankless water heater of FIG. 1 A;
  • FIG. 2 is a cross section of the impeller positioned proximate a conduit with water flow
  • FIG. 3A is a front view of the tankless flowmeter
  • FIG. 3B is a rear view of the tankless flowmeter
  • FIG. 4 is an exploded view of the flowmeter
  • FIG. 5 is an illustration of the neutrally buoyant impeller
  • FIG. 6 is a graph of the K factor vs. flowrate
  • FIG. 7 is a graph of the K factor curve
  • FIG. 8 is a schematic of the flowmeter onboard memory circuit
  • FIG. 9 is a method of operating the flowmeter.
  • This disclosure includes a tankless water heater with an impeller flowmeter having multiple K factors significantly improving the accuracy of flowmeter readings, particularly at low water flow rates, such as under 1 gallon per minute. Rather than use a single K factor impeller flowmeter in a tankless water heater that is particularly inaccurate at low flow rates, this disclosure provides an impeller flowmeter with multiple K factors to obtain precise flow rate readings to precisely control heating of the water at low flow rates.
  • the flowmeter has an onboard memory with multiple K factors stored for a controller to access and read. These multiple K factors are established for flowrates across the entire dynamic range of the flowmeter at the time it is manufactured. Just enough K factors are determined to provide good curve fitting.
  • the flowmeter onboard memory is programmed with the multiple K factors. As part of the tankless water heating application, the controller reads the multiple K factors from the flowmeter memory on startup and then calculates the K factor curve for the particular flowmeter installed, using a curve-fitting algorithm.
  • Coupled refers to any logical, optical, physical or electrical connection, link or the like by which signals, or light produced or supplied by one system element are imparted to another coupled element. Unless described otherwise, coupled elements or devices are not necessarily directly connected to one another and may be separated by intermediate components, elements or communication media that may modify, manipulate or carry the light or signals.
  • a tank-based water heater Potential disadvantages of a tank-based water heater include large size, because a substantial amount of water must be kept hot to satisfy potential demand, energy inefficiency since water is kept hot even when it may not be used for many hours, and water deposits due to large amounts of slowly moving water which may cause corrosion and leakage of the tank.
  • demand it is not an uncommon occurrence for demand to exceed the supply, such as if many people take showers in a row, and thereby for the water heater to run out of hot water.
  • Tankless water heaters provide solutions to these potential problems of tank-based water heaters, as they are compact and heat water on demand, only when it is needed.
  • Tankless water heaters typically use either natural gas or electricity to heat the water as it flows through, with a flowmeter providing important measurement and feedback data to a controller that regulates the applied power to one or more heating elements to heat the water.
  • Conventional tankless water heater systems have a particularly significant challenge relating to fine levels of control of heated water if flow levels are low (below 1 gallon per minute).
  • This disclosure relates primarily to an electric heater based tankless water heater that incorporates an impeller flowmeter. Note that although this application discusses the subject disclosure primarily in terms of its use with a tankless water heater used to heat water, such as found in many homes, the subject disclosure is clearly usable with any of liquid heating system, in which high heat capacity of the flowing liquid causes need for a high-power heater whose power consumption must thereby be monitored and controlled precisely by measuring and monitoring the flow.
  • Flowmeters are devices for determining the flow rate of a medium (typically liquid or gas) through a delivery channel (typically a pipe). Many flowmeters have been developed over the years based on a range of methods for determining flow rate. These include but are not limited to mass flow meters, positive displacement flow meters electromagnetic flow meters, vortex flow meters, ultrasonic flow meters, turbine flow meters, and impeller flowmeters. Each of these flowmeters have characteristics and tradeoffs that make them suitable for the requirements of a given application.
  • Tankless water heater systems have requirements that make selection of a flowmeter particularly challenging.
  • Flowmeters for tankless water heater systems must provide highly accurate water flow measurements across a wide dynamic range (from less than .2 GPM to greater than 5 GPM), quick response time to rapid changes in flow, and low pressure drop across the flowmeter even at the high end of its dynamic flow range.
  • the flowmeters must be resistant to degradation over time and jamming by hardwater deposits and particulates inherent to the water piping environment. These characteristics must be achieved in a small physical space, at a relatively low financial cost.
  • flow meters that have optimal characteristics are industrial in nature and not available at a price point that is practical for use in tankless water heater systems. Flow meters that are practical (low-cost turbine and impeller, are typically inaccurate, wear out too quickly, and/or produce high resistance to flow such that there is a significant pressure drop across the flow meter, thereby unacceptably restricting the flow of water.
  • FIG.1A there is illustrated a tankless water heater 10 having a fluid input at 12, a fluid output at 14, a conduit 16 extending between the input 12 and the output 14, and an impeller flowmeter 18 in line with the conduit 16 and measuring a flow rate of a fluid, such as water or gas, passing through the conduit 16.
  • the flowmeter 18 measures the fluid flow rate and generates flow rate signals that are sent to a controller 20.
  • a heater 22 having a heating element is configured to controllably heat the water flow in the conduit 16 as a function of the measured flow rate, and a heat temperature setting.
  • FIG. IB An electrical block diagram of the tankless water heater 10 is shown in FIG. IB.
  • the impeller flowmeter 18 as shown in Figure 2, generates a pulsing flow rate signal on data line 24 as the medium (water) flows through the conduit 16, causing an impeller 26 to spin on an axle.
  • Magnets 28 embedded in impeller blades 30 rotate past a magnetic field sensor 32 (typically a hall-effect switch).
  • the frequency of the electrical pulse signal produced is proportional to the rate of flow. The faster the flow, the higher the pulse frequency.
  • the number of pulses the flowmeter 10 produces for a given volume of water is referred to as the K factor for the flowmeter.
  • K factor The number of pulses the flowmeter 10 produces for a given volume of water.
  • a flowmeter that produces 1800 pulses per gallon would have a K factor of 1800.
  • the controller 20 receives the pulsing flow rate signal on data line 24 from the magnetic field sensor 32 and uses the information along with the K factor to calculate the flow rate of the fluid. The calculated flow rate is then used by the controller 20 to determine the response of the system. In the case of the tankless water heater 10, the calculated flow rate is used by the controller 20, along with the sensed inlet water temperature, to control the amount of power applied to heating elements of heater 22 to achieve the targeted outlet water temperature.
  • FIG. 3 A illustrates a front view of the tankless water meter 18, and FIG. 3B illustrates a rear view of the tankless water meter 18.
  • FIG. 4 there is illustrated an exploded view of the flowmeter 18.
  • Two important features are a neutral buoyancy impeller 26, and an onboard memory 40 containing multiple calibration K factors specific to each flowmeter 18 produced, for use in a curve-fitted response by the controller 20.
  • the flowmeter 18 has a body 42 and a bore 44 therein that receives the impeller 26.
  • the neutral buoyancy impeller 26, as shown in FIG. 5, is neutrally buoyant in the fluid it measures, such as water, and provides superior sensitivity and responsiveness at the very low flow end of the flowmeter dynamic range. A significant factor that limits low flow performance in impeller flowmeters is friction.
  • the impeller 26 Since the impeller 26 is submerged in the medium, if the impeller 26 is too light it will be buoyant in the medium and the impeller shaft will press upwards against the bore 44 it rotates within.
  • the ideal impeller design is one where the cumulative weight of all the components of the impeller (wheel, shaft, embedded magnets) is equal to the weight of the equivalent volume of the medium, such as water.
  • the net density of the impeller 26 is equal to the density of the water in which it is immersed, resulting in the buoyant force balancing the force of gravity.
  • the impeller achieves the equivalent of weightlessness, thus minimizing the force of friction.
  • an example impeller design is listed in Table 1.
  • the water weight equivalent for the volume occupied by the example impeller shown in Figure 5 is calculated at 3.3 grams.
  • Two example impeller designs were designed from different materials as listed in Table 1.
  • Impeller Design B achieves the optimal neutral buoyancy matching the 3.3 grams of water weight equivalent for the impeller volume, while Design A is negatively buoyant.
  • Minimum activation is the flowrate where the impeller first begins to rotate, although rotation may be hesitant and irregular.
  • Minimum Q is the flowrate where the impeller rotates in a regular steady periodic manner, such that it is useful for reliable flow measurements and calculations. Performance results comparison is as shown in Table 2.
  • Impeller Design B performance is clearly superior to that of Design A.
  • the neutral buoyancy design achieves the lowest pressure drop, the lowest activation flowrate and the lowest minimum Q.
  • the end result, from a flowmeter design perspective, is a flowmeter that uses the Impeller Design B will have an extended low flow range at a reduced resistance to flow (lower PSI drop).
  • the second innovation is the onboard multiple K factor memory 40.
  • Present commonly available flowmeters are provided with a single K factor, where the K factor is the number of pulses a flowmeter produces for a given volume of water by the manufacturer.
  • This single K factor is intended to be used in the end application to calculate the flow rate across the entire dynamic range of the flowmeter.
  • the K factor versus flowrate for flowmeters remains fairly constant across the middle of the flowmeter dynamic range. However, at the low end of the dynamic range, the K factor begins to drop such that the calculated flowrate becomes more and more inaccurate.
  • FIG. 6 shows how the K factor varies vs flowrate for a flowmeter with a single K factor.
  • the K factor remains fairly constant. However, as the flowrate drops below 2 GPM, the K factor begins to drop off in a non-linear way. This inaccuracy in the K factor at the low end of the dynamic range, especially under 1 GPM, is particularly problematic for tankless water heater applications, as the controller relies on the accuracy of the calculated flow rate, along with the sensed inlet water temperature, to control the amount of power applied to the heating elements of heater 22 to achieve the targeted outlet water temperature. At low flow rates, it becomes particularly challenging for the controller to respond properly to changes in flowrates.
  • the flowmeter may not measure any flow rate when the flowrate is under 0.5 GPM due to friction, losses, and other variables.
  • the heater would not be activated at all and thus the water would not be heated.
  • An improvement in this disclosure is a means for the flowmeter 18 having the onboard memory 40 with multiple K factors stored for the controller 20 to access and read. These multiple K factors are established for flowrates across the entire dynamic range of the flowmeter 18 at the time it is manufactured. Just enough K factors are determined to provide good curve fitting.
  • the flowmeter onboard memory 40 is programmed with the multiple K factors. As part of the tankless water heating application, the controller 20 reads the multiple K factors from the flowmeter memory 40 on startup, and then calculates the K factor curve for the particular flowmeter installed, using a curve-fitting algorithm.
  • FIG. 7 shows how a flowmeter that would normally be assigned a single K factor of 1200 has multiple K factors determined across the dynamic range of the flowmeter according to this disclosure.
  • 11 flowrates were tested, and the associated K factors determined. These 11 K factors, are then used to establish an accurate K factor curve, as shown in FIG. 7.
  • the K factor used is 960 and is used to determine an accurate flowrate.
  • the K factor is 1260.
  • the flowmeter accuracy is maintained across the entire dynamic range of flowrates.
  • the K factor 960 at .2 GPM is at least 20% less than the 1260 K factor at 6.4 GPM.
  • critical accuracy is achieved for calculating the correct amount of power to apply to the heating elements of heater 22 to optimally achieve the targeted outlet water temperature.
  • This tankless water heater 10 has a significantly improved system response and performance.
  • FIG 8 is an illustration of an example flowmeter onboard memory circuit 40 design arranged as a simple serial EEPROM, U3 (24FC01) accessible by the controller 20 via a standard serial interface such as I2C bus.
  • an I2C bus extender circuit, U2, (P82B715DR) is used to allow the flowmeter 18 to be placed some distance away from the controller 20, while maintaining signal integrity.
  • FIG. 9 there is illustrated a method 900 for programming and operating the flowmeter 18.
  • the flowmeter 18 is electronically characterized at the factory to determine multiple K factors across an operating range of flowrates. In an example, 11 K factors are determined as previously described. This characterization determines K factors that are unique to each flowmeter 18 and takes into account the specific features of each flowmeter. Even with uniform manufacturing techniques, each flowmeter has unique features.
  • the determined multiple K factors are programmed into the flowmeter memory 40 of the flowmeter 18.
  • An example curve of the determined multiple K factors are shown in FIG. 7.
  • the controller 20 uses flowmeter 18 to measure the flow rate of fluid communicating through the conduits 16 from input 12 to output 14. This measured flow rate is communicated as data signals via data line 24, and the data signals may be a series of pulses as previously described. Other types of data signals may be provided to controller 20, and limitation to pulses is not to be inferred.
  • the controller 20 of the flowmeter 18 controls the power delivered to the heating elements of heater 22 to precisely control the heating of the fluid.
  • the heating of the fluid is precise at the low end of the flow rate such that the water temperature of the fluid delivered from output 14 is accurate and as desired.

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  • Physics & Mathematics (AREA)
  • Fluid Mechanics (AREA)
  • General Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • Electromagnetism (AREA)
  • Thermal Sciences (AREA)
  • Chemical & Material Sciences (AREA)
  • Combustion & Propulsion (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Measuring Volume Flow (AREA)

Abstract

Chauffe-eau instantané doté d'un débitmètre à roue à aubes comportant de multiples facteurs K, permettant d'améliorer considérablement la précision des lectures du débitmètre, en particulier à des débits d'eau faibles, par exemple inférieurs à 1 gallon par minute. Au lieu d'utiliser un débitmètre à roue à aubes doté d'un seul facteur K dans un chauffe-eau instantané, ledit débitmètre étant particulièrement imprécis à des débits faibles, la présente divulgation offre un débitmètre à roue à aubes doté de multiples facteurs K, afin d'obtenir des lectures précises de débit en vue de commander avec précision le chauffage de l'eau à des débits faibles. Le débitmètre comporte une mémoire embarquée dotée de multiples facteurs K stockés, pouvant être accédés et lus par un dispositif de commande. Lesdits multiples facteurs K sont établis pour des débits sur toute la plage dynamique du débitmètre au moment de la fabrication de ce dernier. Des facteurs K sont déterminés en quantité juste suffisante pour assurer un bon ajustement de courbe. La mémoire embarquée du débitmètre est programmée avec les multiples facteurs K.
PCT/US2022/070541 2021-02-04 2022-02-04 Chauffe-eau instantané doté de débitmètre à courbe de réponse de haute précision WO2022170353A1 (fr)

Applications Claiming Priority (4)

Application Number Priority Date Filing Date Title
US202163145636P 2021-02-04 2021-02-04
US63/145,636 2021-02-04
US17/592,993 US11384958B1 (en) 2021-02-04 2022-02-04 Tankless water heater with a high-accuracy response-curve flowmeter
US17/592,993 2022-02-04

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Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4581946A (en) * 1982-06-21 1986-04-15 Masahiro Kanayama Instrumental error compensation circuit for flow meter
DE4230208A1 (de) * 1991-09-09 1993-03-11 Vaillant Joh Gmbh & Co Verfahren zum steuern der auslauftemperatur und vorrichtung zum steuern der auslauftemperatur
WO2010122348A2 (fr) * 2009-04-23 2010-10-28 Elster Metering Limited Débitmètre pour fluide

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4581946A (en) * 1982-06-21 1986-04-15 Masahiro Kanayama Instrumental error compensation circuit for flow meter
DE4230208A1 (de) * 1991-09-09 1993-03-11 Vaillant Joh Gmbh & Co Verfahren zum steuern der auslauftemperatur und vorrichtung zum steuern der auslauftemperatur
WO2010122348A2 (fr) * 2009-04-23 2010-10-28 Elster Metering Limited Débitmètre pour fluide

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