Patent Application
20250067469
The present invention relates to a system and method for maintaining the temperature of a fluid.
Water and other fluid heating systems of one form or another are installed in the vast majority of residential and commercial premises in the developed and developing world.
In most countries, water may be heated by electricity for washing, cleaning, drinking and the like. However, water or another heated fluid can also be used for hydronic heating where colder climates prevail.
Of course, as is generally known, the generation of electricity by the burning of fossil fuels contributes to pollution and global warming. For example, in 1996, the largest electricity consuming sector in the United States were residential households, which were responsible for 20% of all carbon emissions produced. Of the total carbon emissions from this electricity-consuming sector, 63% were directly attributable to the burning of fossil fuels used to generate electricity for that sector.
In both developed and developing nations, electricity is now considered a practical necessity for residential and commercial premises and with electricity consumption per household growing at approximately 1.5% per annum since 1990. The projected increase in electricity consumption for the residential sector has become a central issue in the debate regarding carbon emission stabilisation and meeting the goals cited within current climate change management objectives globally.
Where water heating is concerned, electric hot water systems are generally considered to be energy inefficient as they incur heat energy losses. More specifically, in one instance, electric water heaters operate on the principle of storing and heating water to a predetermined temperature where heat energy losses to the atmosphere are incurred. In another, albeit more efficient instance, electric hot water systems can heat water on demand, where heat energy losses are significantly reduced, but are incurred, nevertheless.
Heating of water on demand such that the water temperature reaches a predetermined level within a short period of time enables a system to limit the heat loss inefficiencies that necessarily occur as a result of storing hot water in a tank in anticipation of use. While this is true, heating water instantaneously experiences similar heat loss albeit less than that of a hot water storage tank. Maintaining accurate, absolute temperature stability in a hot water storage tank is not required. Since heated water is heated to a temperature much greater than the water temperature required for use in respect of limiting the growth of Legionella Pn bacteria. Here, when used, the heated water from the storage tank is mixed with cold water to achieve the desired usable water temperature. In this context, fluctuations of heated water temperature within the tank, that could be as much as +/−10° C. would not realistically make a difference to the consumer, where in addition, heated water is invariably delivered using tempering valves of one nature or another.
This is not the case with instantaneous fluid/water heating systems. Here, instantaneous fluid/water heating systems are currently available where both gas, such as natural gas or LPG (Liquefied Petroleum Gas) and electricity are used as the heating energy source. To date, in the case of natural gas, LPG and electrically powered systems, heat exchange technology imparts thermal energy to the fluid to raise the temperature of that fluid to a set level within a relatively short time under controlled conditions. However, the thermal transfer of the heat exchanger cannot be measured, and therefore cannot be controlled, resulting in less than acceptable temperature control. Accurate temperature control where instantaneous, on demand water heaters are concerned, is mandatory to prevent scalding and maintain consumer comfort. Heated water temperature fluctuations of +/−2° C. can be noticed, and where children and the aged or frail are concerned, +10° C. can cause scalding.
In a different application, where hydronic heating systems are concerned, accurately controlled heat loss by maintaining fluid/water temperature stability is equally a mandatory requirement to conserve energy.
It would be desirable to provide a system and method which ameliorates or at least alleviates one or more of the above problems or to provide an alternative.
It would also be desirable to provide a system and method that ameliorates or overcomes one or more disadvantages or inconvenience of known fluid heating systems and methods, particularly relating to accurate temperature control.
A reference herein to a patent document or other matter which is given as prior art is not to be taken as an admission or a suggestion that the document or matter was known or that the information it contains was part of the common general knowledge as at the priority date of any of the claims.
According to an aspect of the present invention, there is provided a system for heating a fluid, the system comprising: two or more cells for retaining a fluid, each cell including one or more electrode pairs positioned therein; the two or more cells arranged along a flow path including an inlet to and an outlet from the two or more cells; a controller configured to: regulate the flow of the fluid from the inlet to the two or more cells; determine at a first cell of the two or more cells, the electrical conductivity of the fluid; determine at the first cell of the two or more cells, the thermal conductivity of the fluid therein; determine from the electrical conductivity of the fluid, a voltage to apply from a power source across the one or more electrode pairs at a current sufficient to heat the fluid in the first cell of the two or more cells; pass the current from the one or more electrode pairs to the fluid to produce a heated fluid in the first cell of the two or more cells; and determine a voltage to apply from the power source across the one or more electrode pairs at a current sufficient to heat the fluid in a second cell of the two or more cells based at least in part on the thermal conductivity of the fluid in the first cell of the two or more cells.
According to one or more embodiments, the controller is further configured to determine the electrical conductivity of the fluid and thereby determine the voltage to apply across the one or more electrode pairs continuously.
According to one or more embodiments, the one or more electrode pairs are segmented into two or more segments, each segment being configured to individually apply voltage by the controller.
According to one or more embodiments, individually applying the voltage across the two or more segments increases or decreases the effective electric current drawn by the fluid by virtue of electrode surface area.
According to one or more embodiments, the two or more segments are of uniform size.
According to one or more embodiments, the two or more segments are of different sizes.
According to one or more embodiments, the one or more electrode pairs are segmented into n segments each having effective surface areas in a ratio of 1:2: . . . :2(n−1).
According to one or more embodiments, the one or more electrode pairs are substantially parallel and positioned in a generally horizontal plane relative to the flow path.
According to one or more embodiments, the one or more electrode pairs are substantially vertical and positioned in a generally vertical plane relative to the flow path.
According to one or more embodiments, the one or more electrode pairs are at least in part coated with an inert electrically conductive material or a non-metallic electrically conductive material including an electrically conductive plastics material, carbon impregnated material, and combinations thereof.
According to one or more embodiments, the one or more electrode pairs are formed at least in part from a material selected from the group consisting of metal or a non-metallic electrically conductive material.
According to one or more embodiments, the one or more electrode pairs are formed from an electrically conductive, inert material including graphite, carbon, and combinations thereof.
According to one or more embodiments, the controller is further configured to measure a flow rate of the fluid flowing through the flow path.
According to one or more embodiments, the controller is further configured to increase or decrease the flow rate of the fluid flowing through flow path to regulate a residency time of the fluid in the two or more cells.
According to one or more embodiments, the controller is further configured to measure a temperature of the fluid flowing through the flow path.
According to one or more embodiments, the controller is further configured to measure the temperature of the fluid at the inlet and outlet; and provide the temperature as feedback to a temperature controller configured to increase or reduce heating of the fluid.
According to one or more embodiments, the two or more one or more cells are serially arranged along the flow path.
According to one or more embodiments, the controller is further configured not to apply the voltage across the one or more electrode pairs if the electrical conductivity of the fluid falls outside a predetermined range.
According to one or more embodiments, the inlet and outlet extend at substantially one hundred and eighty degrees to each other.
According to one or more embodiments, the two or more cells for retaining a fluid are made from an electrically non-conductive light weight plastic material.
According to one or more embodiments, the thermal conductivity of the fluid is determined from at least fluid temperature and cell dimensions.
According to one or more embodiments, the dimensions include a respective height and a respective width of the cell.
According to one or more embodiments, the system includes n cells for retaining a fluid, each cell including one or more electrode pairs positioned therein; and the n cells arranged along a flow path including an inlet to and an outlet from the n cells.
According to an aspect of the present invention, there is provided a method for heating a fluid, the method comprising the steps of: providing two or more cells for retaining a fluid, each cell including one or more electrode pairs positioned therein; arranging the two or more cells along a flow path, the flow path including an inlet to and an outlet from the two or more cells; determining at the first cell of the two or more cells, the electrical conductivity of the fluid; determining at the first cell of the two or more cells, the thermal conductivity of the fluid therein; determining from the electrical conductivity of the fluid a voltage to apply from an external power source, across the one or more electrode pairs at a current sufficient to heat the fluid in the first cell of the two or more cells; passing the current from the one or more electrode pairs to the fluid to produce a heated fluid in the first cell of the two or more cells; and determining a voltage to apply from the power source across the one or more electrode pairs at a current sufficient to heat the fluid in a second cell of the two or more cells based at least in part on the thermal conductivity of the fluid in the first cell of the two or more cells.
According to one or more embodiments, the controller is further configured to determine the electrical conductivity of the fluid and thereby determine the voltage to apply across the one or more electrode pairs continuously.
According to one or more embodiments, the one or more electrode pairs are segmented into two or more segments, each segment being configured to individually apply voltage by the controller.
According to one or more embodiments, individually applying the voltage across the two or more segments increases or decreases the effective electric current drawn by the fluid by virtue of electrode surface area.
According to one or more embodiments, the two or more segments are of uniform size.
According to one or more embodiments, the two or more segments are of different sizes.
According to one or more embodiments, the one or more electrode pairs are segmented into n segments each having effective surface areas in a ratio of 1:2: . . . :2(n−1).
According to one or more embodiments, the one or more electrode pairs are substantially parallel and positioned in a generally horizontal plane relative to the flow path.
According to one or more embodiments, the one or more electrode pairs are substantially vertical and positioned in a generally vertical plane relative to the flow path.
According to one or more embodiments, the one or more electrode pairs are at least in part coated with an inert electrically conductive material or a non-metallic electrically conductive material including an electrically conductive plastics material, carbon impregnated material, and combinations thereof.
According to one or more embodiments, the one or more electrode pairs are formed at least in part from a material selected from the group consisting of metal or a non-metallic electrically conductive material.
According to one or more embodiments, the one or more electrode pairs are formed from an electrically conductive, inert material including graphite, carbon, and combinations thereof.
According to one or more embodiments, the controller is further configured to measure a flow rate of the fluid flowing through the flow path.
According to one or more embodiments, the controller is further configured to increase or decrease the flow rate of the fluid flowing through flow path to regulate a residency time of the fluid in the two or more cells.
According to one or more embodiments, the controller is further configured to measure a temperature of the fluid flowing through the flow path.
According to one or more embodiments, the controller is further configured to measure the temperature of the fluid at the inlet and outlet; and provide the temperature as feedback to a temperature controller configured to increase or reduce heating of the fluid.
According to one or more embodiments, the two or more one or more cells are serially arranged along the flow path.
According to one or more embodiments, the controller is further configured not to apply the voltage across the one or more electrode pairs if the electrical conductivity of the fluid falls outside a predetermined range.
According to one or more embodiments, the inlet and outlet extend at substantially one hundred and eighty degrees to each other.
According to one or more embodiments, the two or more cells for retaining a fluid are made from an electrically non-conductive light weight plastic material.
According to one or more embodiments, the thermal conductivity of the fluid is determined from at least fluid temperature and cell dimensions.
According to one or more embodiments, the dimensions include a respective height and a respective width of the cell.
According to one or more embodiments, the system includes n cells for retaining a fluid, each cell including one or more electrode pairs positioned therein; and the n cells arranged along a flow path including an inlet to and an outlet from the n cells.
According to an aspect of the present invention, there is provided a method for heating a fluid, the method comprising the steps of: passing a fluid along a flow path from an inlet to an outlet, the flow path including at least first and second cells positioned along the flow path such that the fluid passing the first cell subsequently passes the second cell, each cell including at least one electrode pair between which an electric current is passed through the fluid to produce heat therein during its passage along the flow path, and wherein at least one of the cells includes at least one segmented electrode, the segmented electrode comprising a plurality of electrically separable segments allowing an effective surface area of the segmented electrode to be controlled by selectively activating the segments such that upon application of a voltage to the activated electrode segment(s), current drawn will depend in part upon the effective surface area; determining the fluid conductivity at the inlet; determining the thermal conductivity of the fluid in the first cell; determining from measured fluid conductivity a required voltage and current to be delivered to the fluid by the first cell to raise the temperature of the fluid therein by a first amount; determining a heated fluid conductivity resulting from operation of the first cell; determining from the heated fluid conductivity a required voltage and current to be delivered to the fluid by the second cell to raise the temperature of the fluid therein by a second amount based at least in part on the thermal conductivity of the fluid in the first cell; and activating segments of the segmented electrode in a manner to effect delivery of desired current and voltage by the segmented electrode.
The invention will now be described in further detail by reference to the accompanying drawings. It is to be understood that the particularity of the drawings does not superseded the generality of the preceding description of the invention.
In the embodiment shown, the flow path 104, is provided with a single heating cell 102 including a respective set of electrode pairs 102a. However, it will also be appreciated that additional cells may be used.
The system 100 employs a controller 110 that may include a microprocessor that interacts with other components of the system 100 to regulate or measure the flow rate of the fluid, detect earth leakages, measure the temperature at the inlet 106 and/or outlet 108 (or at other positions along the flow path 104), and/or measure the current drawn by the fluid at the heating cell 102 (or at other positions along the flow path 104). The controller 110 also manages the power 112 supplied to the electrodes 102a which when electrically energized allowing the electrically conductive fluid flowing between the electrodes to heat up. In the embodiment shown, the electrodes 102a are segmented into three segments i.e., the bottom half of the electrode pair 102a is split into two parts as shown by 102b. Initially, fluid temperature stability is achieved through the management of an electrical conductivity gradient. Here the power required to achieve the heated fluid at a set temperature is calculated by the controller 110, and the appropriate voltage applied to the fluid via the segmented electrode sections 102a in the flow path 104. Heat energy losses caused by fluid thermal conductivity 114 can be both calculated and predicted and its effect on the heating system 100 temperature stability can be effectively managed. The controller 110 activates selected segments (102b for example) of the segmented electrode sections 102a to effect delivery of constant power calculated that now includes heat transfer energy losses resulting from fluid thermal conductivity to the fluid that effectively ensures very stable fluid temperature.
In one or more embodiments, the heating cells 202, 204 and 206 are housed in, or integral with, a body 214. The body 214 is preferably made from a material that is electrically non-conductive and lightweight, such as synthetic plastic material. Advantageously, this makes the system very lightweight. However, the body 214 may be connected to metallic fixings, such as copper pipes or nipples, that are electrically conductive. Accordingly, earth connections 216 shown in
It will also be appreciated that the system 200 may be required to adhere to various safety standards to undergo insulation resistance tests. For example, the system 200 may need to pass a test that ensures a minimum value of ohmic resistance required to avoid current between galvanically isolated circuits, where isolation is achieved by either inductive or capacitive means, and conductive parts of the system 200. Such a test may give an indication of the relative quality of the insulation system that includes the body 214 material. Being able to manufacture the body 214 from an electrically non-conductive plastic material provides a significant advantage to the prior art heaters described in the background section.
In the embodiment shown, the flow path 208, is provided with three heating cells 202, 204 and 206 including respective sets of electrode pairs 202a, 204a and 206a. However, it will also be appreciated that additional or fewer heating cells can be used. The electrodes may be metal or a non-metallic conductive material such as conductive plastics material, carbon, carbon impregnated material or the like.
It is important that the electrode substrate and coatings are selected from a group of electrically conductive materials (or combinations of materials) to minimise chemical reaction and/or electrolysis while heating water.
The electrode pairs may also be manufactured from an electrically conductive, inert material such as graphite, carbon and combinations thereof. They may also be manufactured such that they are sectioned into different electrodes but share a common substrate or the like.
In one or more embodiments, one electrode of each electrode pair 202a, 204a and 206a is segmented into two or more segments (e.g., 202ai and 202aii for pair 202a and 204ai and 204aii for pair 204, and so forth), each segment being configured to individually apply voltage. The segmented electrode of each electrode pair 202a, 204a and 206a, is connected to a common switched electrical supply path 218 via separate voltage supply power control devices Q1, Q2, . . . , Qn, while the other of each electrode pair 202b, 204b and 206b are connected to the incoming voltage supply 220 respectively. The separate voltage supply power control devices Q1, Q2, . . . , Qn switch the common electrical supply in accordance with the power management control provided by the controller 222. The controller 222 may include a microprocessor that interacts with other components of the system 200 to regulate or measure the flow rate of the fluid, detect earth leakages, measure the temperature at the inlet 210 and/or outlet 212 (or at other positions along the flow path 208), and/or measure the current drawn 224 by the fluid at the heating cells 202, 204 and 206 (or at other positions along the flow path 208).
Electrical current supplied to heating cell 202, which may also be supplied to heating cells 204 and 206, is measured by current measuring device(s) 224. Only one current measuring device 224 is shown. However, it will be appreciated that the current at each heating cell 202, 204 and 206 may be measured by individual current measurement devices 224. For example, current measurements made by a hall current sensor electrically connected the output of power control devices Q1, Q2, . . . , Qn are communicated to the power management controller 222.
In one or more embodiments, the current measuring devices 224 are coupled to the power control devices Q1, Q2, . . . , Qn so as to be operable to determine the current being drawn from the power supply 220 by the fluid. A current amplifier may be used to amplify the output signal of the current measuring devices 224. The amplified signal is then received by the controller 222 and is compared with a threshold level. The calculated current threshold level will typically be set as a range of ampere, so that the current drawn by the fluid remains equal to or as close as equal to the threshold level only when the fluid is flowing through the flow path 208. While the system 200 is in use, the controller 222 will continue to compare the current measuring device(s) 224 output with the threshold level and make appropriate adjustments to the selection of combinations of electrode pairs, as well as making appropriate adjustments to the voltage supplied to the electrode pairs 202a, 204a and 206a so as to maintain a substantially constant current to heat the fluid, while consistently ensuring that the current handling capability of the electrical supply is not exceeded. However, when the system 200 enters a state of non-use, such as entering a standby mode, the controller 222 will remove the voltage applied to the heating cells 202, 204 and 206 accordingly.
By way of non-limiting example, the current measuring device(s) 224 may be able to sense, slight increases in the detected flow of electrical current through the fluid so as to determine the ideal voltage to apply across the electrode pairs 202a, 204a and 206a to heat the fluid. That is, the current measurement(s) are supplied as an input signal via input interface 232 to controller 222 which acts as a power supply controller. As will be appreciated by those skilled in the art, the input interface may include, but are not limited to, a rotary encoder, a keyboard, a keypad, a touch screen, soft keys, and the like.
In one or more embodiments, the controller 222 may also receive signals via input interface 232 from a flow rate measurement device or flow switch incorporating flow rate limiting 226 located near the inlet 210 to the body 214. The volume of the fluid passing between any pair of electrodes 202a, 204a and 206a may be accurately determined by measuring the flow rate. Similarly, the residency time for which a given volume of the fluid will receive electrical power from the electrodes may be determined by measuring the flow rate of the fluid through the passage. It will be appreciated that the flow rate may be limited by one or more threshold values associated with the flow rate and/or the pumping or regulation of the fluid.
Accordingly, the current flowing through the fluid can be used as a measure of the electrical conductivity, or the specific conductance of that fluid and hence allows determination of the required change in applied voltage and electrode combinations selected required to keep the electric current drawn adequate for heating and maintaining that heat extremely efficiently.
The electrical conductivity and hence the specific conductance of the fluid will change with rising temperature, thus causing a specific conductance gradient along the path of fluid flow 208. In one or more embodiments, the controller 222 also receives signals via signal input interface 232 from an input temperature measurement device 228 to measure the temperature of the fluid at the inlet 210. An output temperature measurement device 230 may also be provided for measuring the temperature of the fluid at the outlet 212. Signals from the input temperature measuring device 228, and the output temperature measurement device 230 are provided as feedback to the controller 222 to allow the fluid temperature correctly calculated, and to also be continuously monitored.
The system 200 of the present embodiment is further capable of adapting to variations the fluid conductivity, or specific conductance, whether arising from the particular location at which the system is installed or occurring from time-to-time at a single location or by virtue of changes in the fluid temperature. In this regard the fluid conductivity, or specific conductance is determined as being directly proportional to the electric current drawn by the fluid flowing through the heating cells 202, 204 and 206. Advantageously, these changes can also be interpreted by the controller 222 and used for diagnostic purposes. For example, a higher or lower than expected conductivity of the water may indicate a poor water quality, mineral content, or similar. An indication of this could be sent by the controller 222 to a display means configured to provide advanced diagnostic features through ports or over-the-air (e.g., using various types of wireless communication techniques) 234. Other diagnostic information may be sent in this manner including but not limited to inlet temperature, outlet temperature, power usage rate, fluid quality and conductivity increases or deterioration, power consumption, voltage, flow fare, error codes and other diagnostic information, and the like. Similarly, the controller 222 may also receive information from a user interface including but not limited to set maximum applied power levels, co-ordinate power consumption with other device, set maximum and minimum fluid temperature limits, change temperature settings while in operation or in standby, error and failure management information, on or off messages.
Variations in the fluid conductivity, or specific conductance will cause changes in the amount of electrical current drawn by each electrode for a given applied voltage. This embodiment monitors such variations and ensures that the system 200 draws a desired level of current by using the determined conductivity, or specific conductance value to initially select a commensurate combination of electrode segments before allowing the system to operate. The electrodes represented by 202a, 204a, 206a are segmented into a number of electrode segments, 202ai and 202aii, 204ai, 204aii, 206ai, and 206aii.
For each respective electrode, the ai segment is fabricated to typically form about one third or two thirds of the active area of the electrode, the “202ai/202aii, 204ai/204aii and 206ai/206aii segments are fabricated to typically form about two thirds or one third of the active area of the electrode and so on. Selection of appropriate segments or appropriate combinations of segments thus allows the effective area of the electrode to be any one of three available values for electrode area. Consequently, for highly conductive fluids a smaller electrode area may be selected so that for a given voltage the current drawn by the electrode is prevented from rising above desired or safe levels, while yet maintaining the required current to be drawn to heat the fluid. Conversely, for poorly conductive fluids, a larger electrode area may be selected so that the required current will be drawn to affect the desired heating. Selection of segments can be simply made by activating or deactivating the power switching devices Q1, . . . Qn as appropriate.
In particular, the combined surface area of the selected electrode segments is specifically calculated to ensure that the rated maximum electrical current values of the electrical supply system are not exceeded.
Advantageously, by providing a plurality of segmented heating cells 202, 204 and 206, the present invention allows each segmented heating cell 202, 204 and 206 to be powered in a manner that allows for predicted changes in energy supplied resulting from changes in fluid electrical conductivity with increasing fluid temperature and commensurate fluid thermal conductivity heat energy losses to be calculated. The thermal conductivity, or k value, specifies the rate of heat transfer in any homogeneous material. If a material has a k value of 1, it means a 1 m cube of material will transfer heat at a rate of 1 watt for every degree of temperature difference between opposite faces. The k value is expressed as 1 W/mK.
For example, water electrical conductivity increases or decreases with an increase or decrease in temperature, on average by around 2% per degree Celsius. While this percentage variation is commonly known, and predictably, energy supplied can be varied accordingly, what is not known is the extent to which this calculated variation in the energy supplied is affected by heat loss due to fluid thermal conductivity. Simplistically accepting changes to energy supplied due to this variation in fluid temperature without taking fluid thermal conductivity heat energy loss into account, will deliver inaccurate and unstable temperature control.
Where fluid is to be heated by degrees Celsius, for example from ambient temperature to 60 degrees Celsius or 90 degrees Celsius, inlet fluid electrical conductivity can be substantially different to outlet fluid electrical conductivity. The fluid electrical conductivity differences are additionally affected by segmented electrode section heat energy losses caused by fluid thermal conductivity. Nevertheless, sequentially subjecting the fluid to resistive heating at successive segmented heating cells along the flow path allows each segmented heating cell to be powered in proportion to the predicted fluid electrical conductivity changes, that can accommodate the calculated and/or predicted heat energy losses, thereby delivering stable fluid temperature through each segmented electrode section. Thus, each individual segmented heating cell may have voltage and ensuing current draw correctly applied that is applicable to the predicted fluid electrical conductivity combined with calculated heat energy losses within that limited segmented heating cell temperature range rather than attempting to apply voltage and current in respect of a single or averaged conductivity value across the entire system applicable temperature range.
In one or more embodiments, the controller 222 receives the various monitored inputs and performs necessary calculations with regard to electrode active area selection, desired electrode pair voltages and currents to heat the fluid flowing through the flow path 208. The controller 222 controls the supply of voltage from either of an internal power supply or the external power supply (as described with reference to
The voltage supply is separately controlled by the separate control signals from the controller 222 to the power switching devices Q1, . . . , Qn. It will therefore be appreciated that, based upon the various parameters for which the controller 222 receives representative input signals, a computing means under the control of a software program or firmware within the controller 222 calculates the control pulses required by the power switching devices in order to supply the required voltage to impart the desired temperature of the fluid flowing through the flow path 208, as will be discussed with reference to
In a number of embodiments, the controller 222 may receive a desired temperature of the fluid via a temperature, for example, information, a message, and a signal transmitted from an electronic device to a temperature adjustment device in order to operate the temperature adjustment device at a specific temperature. Further, the temperature control instruction may include information, a message, and a signal transmitted from an electronic device to a temperature adjustment device in order to turn on/off the temperature adjustment device.
In a number of embodiments, the controller 222 also converts readings from the current measuring device(s) 224, temperature measurement devices 228 and 230, flow rate measurement device or flow switch incorporating flow rate limiting 226, power switching devices Q1, . . . , Qn etc. into digital values and communicates messages based on those digital values to a digital communication device 232. It should also be appreciated that filtering methods can also be used, such as those, but not limited to including, moving average filters, evenly weighted moving average filters, the like, or a combination of these filters, which may be particularly suitable for implementation in firmware. The messages can then be sent to other devices (e.g., computers, smartphones, tablets, laptop computers, desktop computers, server computers, among other forms of computer systems) via a hardwired digital communication service, such as, but not limited to, BUS technology, Ethernet, RS485 or the like, or a wireless connection such as 802.11 Wi-Fi network or Bluetooth™ for processing by an application or interface 234 or cloud computing platform. Advantageously, this can provide remote monitoring and/or configuration of the system 200, making it convenient for operators to modify parameters, such as flow rates or electrical power, based on the properties of the fluid being heated. For example, decreasing the flow rate and/or increasing the temperature when solution conductivities are low. In addition, system maintenance and management can also be facilitated via the digital communication method adopted.
The time for which a given volume of fluid will receive electrical power from the electrodes may be determined by reference to the flow rate of fluid through the fluid flow path by the flow rate measurement device or flow switch incorporating flow rate limiting 226. The temperature increase of the fluid is proportional to the amount of electrical power applied to the fluid. The amount of electrical power required to raise the temperature of the fluid a known amount, is proportional to the specific heat of the fluid, the mass (volume) of the fluid being heated, and the increase in fluid temperature required through the flow path including each segmented heating cells 202, 204 and 206. The measurement of electrical current flowing through the fluid can be used as a measure of the electrical conductivity, or the specific conductance of that fluid, and hence allows selection of segments to be activated together with control and management of the required change in applied voltage required to keep the applied electrical power constant or at a desired level. The electrical conductivity, and hence the specific conductance of the fluid being heated will change with temperature, thus causing changes in the specific conductance gradient along the path of fluid flow. Calculations related to variation of applied power is combined with calculated heat energy loss incurred by fluid thermal conductivity based on a combination of the following relationships.
−Power(Psys) Relationship (1)
Energy(Joules)=Specific Heat Capacity×Mass×Temp-Change Thermal Heat Equation
The Power, that is energy per unit of time (joules/sec=power) required to increase the temperature of a body of fluid may be determined by the relationship:
For analysis purposes, the specific heat capacity of water, for example, may be considered as a constant between the temperatures of 0° C. and 100° C. The density of water being equal to 1, may also be considered constant. The Specific Heat of water can be labelled “k”. Volume/Time is the equivalent of flow rate (Fr). Thus the energy per unit of time (power) required to increase the temperature of a body of fluid may be determined by the relationship:
Thus, if the required temperature change is known, the flow rate can be determined then the power for required for the heating system as a whole can be calculated.
However, it is preferable for the power to be independently calculated and delivered to each segmented heating cell individually. In this instance, Dt for the heating system must then be divided by the number of segmented heating cells—Dt(sec)
In one instance, the power can be calculated by measuring or predicting the inlet and output temperature of each segmented heating cells (P(sec)—where:
−Power(Psec) Relationship (2)
The power required per cell can be calculated by measuring or predicting the output temperature by each segmented heating cell—where:
The calculated power delivered to each segmented heating cell can be varied by measuring the current drawn by each cell that results from changes in fluid conductivity.
The calculated power delivered to each segmented heating cell can be varied by predicting the current that will be drawn by each cell that results from predictable changes in fluid conductivity.
Flow rate (Fr) is determined by the flow rate sensor. Segmented cell temperature change is either measured or predicted, that will be less than equal to the difference between incoming fluid temperature and the desired set temperature that is divided by the number of segmented heating cells—Dt(sec). Power required for the fluid heating system is calculated using:
In one or more embodiments of the present invention, the electrical current flowing between the electrodes within the first segmented heating cell, and hence through the fluid, is measured or predicted thereby providing a means to calculate fluid specific conductance for that individual segmented heating cell.
In one embodiment, the controller 222 may include a microprocessor that interacts with other components of the system 200 to regulate or measure the flow rate of the fluid, detect earth leakages, measure the temperature at the inlet 210 and/or outlet 212 (or at other positions along the flow path 208), and/or measure the current drawn 224 by the fluid at the heating cells 202, 204 and 206 (or at other positions along the flow path 208). Having calculated the electrical power for the fluid heating system (Psys) allows the power that should be applied to the fluid passing between the segmented electrodes of each segmented heating cells to be calculated (TPsec). The average voltage that needs to be applied to effect the desired temperature change for each individual segmented heating cell can then be calculated, and appropriate segments in each segmented electrode heating cell can then be selected, and activated.
Relationship (5) below, facilitates the calculation of the electrical power to be applied as accurately as possible, almost instantaneously. When applied to water heating systems, this eliminates the need for unnecessary water wastage otherwise required to initially pass through the system before facilitating the delivery of water at the required temperature. This provides the potential for saving water or other fluid and conserves energy.
Having determined the electrical power that should be supplied to the fluid passing between the segmented heating cells the computing means may then calculate and predict the voltage that should be applied to each segmented electrode heating cell (ES) as follows.
Once the power required for the segmented electrode heating cell has been predicted or calculated, and the current drawn by the first heating cell segmented electrode (n) has been measured then:
As part of the initial heating sequence, the applied voltage may be set to a relatively low value in order to determine the initial specific conductance of the fluid passing between the electrodes in the first heating cell. The application of voltage to the electrodes will cause current to be drawn through the fluid passing therebetween thus enabling determination of the specific conductance of the fluid, being directly proportional to the current drawn therethrough. Accordingly, having determined, or predicted the electrical power that should be supplied to the fluid flowing between the electrodes in each segmented heating cell, it is possible to determine the required voltage that should be applied to those electrodes in order to increase the temperature of the fluid flowing between the electrodes in each segmented heating cell by the required amount. The instantaneous current being drawn by the fluid is preferably continually monitored for change along the length of the fluid flow path. Any change in instantaneous current drawn at any position along the passage is indicative of a change in electrical conductivity or specific conductance of the fluid. The varying values of specific conductance apparent in the fluid passing between the electrodes in the electrode cells, effectively defines the specific conductivity gradient along the heating path.
Preferably, various parameters are continuously monitored and calculations continuously performed to determine the electrical power that should be supplied to the fluid and the voltage that should be applied to the electrodes in order to raise the temperature of the fluid to a preset desired temperature in a given period. It will be appreciated that various control implementations are possible. For instance, the system 200 may include, in a number of embodiments, an artificial intelligence-based control mechanism, which may in use, in part, cloud-based services. As noted, the decision whether to increase or decrease the flow rate (i.e., increasing or decreasing the residency time the fluid stays in the heating cells) or voltages (and subsequent current draw) may be based on multiple sensor inputs through interface 224 provided to the controller 222 (or to another platform via wireless transceiver or interface 232). This coordination of communication and calculations may occur automatically, within the controller 222, an application or an application hosted in the cloud. Further, the controller 222 may implement machine-learning based on the input data. Based on this information, the system 200 may pre-emptively make changes to the flow rate, voltages, temperature and the like.
It will be appreciated that the communication can be carried out using any suitable digital communication protocols, including, Wi-Fi 802.11, 6LowPan/ZIGBEE™ 802.15, Ethernet 802.3, 802.11 and 802.15.4, and RS485. That may include a bus, a cable, a wireless communication channel, a radio-based communication channel, the Internet, a local area network (LAN), a wireless local area network (WLAN), a wide area network (WAN), a cellular communication network, or any Internet Protocol (IP) based communication network and the like.
The wireless transceiver or digital communication device 232 may also be adapted to facilitate communication between a remote firmware update mechanism and the controller 222. As will be appreciated by those skilled in the art, the remote firmware update mechanism together with the controller 222 may be adapted to periodically check for updates from a remote repository, download firmware updates and to compare downloaded firmware to existing firmware to determine the necessity of installing the downloaded firmware and the like.
The method 300 starts at start block 302, at step 304 the electrical conductivity, or specific conductance of a fluid is determined at the inlet to a first heating cell including a first electrode pair. In one or more embodiments, the electrical conductivity, or specific conductance is determined by the amount of current drawn by the fluid while an initial voltage is applied across the first electrode pair from a voltage supply power control device (i.e., Q1 as discussed with reference to
At step 306, from the electrical conductivity, or specific conductance of the fluid, the power to pass across the first electrode pair at a current sufficient to heat the fluid to a set temperature is determined. At step 308, the fluid and system thermal conductivity is determined. The fluid heating process incurs heating losses within the system that impact fluid temperature stability, which needs to be determined if the fluid temperature stability is to be accurately maintained. The heat loss caused by fluid thermal conductivity occurs post application of the calculated power (step 306) to increase the fluid temperature to the set level and is combined with the calculated system power being applied. At step 310, the power required to achieve the heated water set temperature is calculated by the controller, and the appropriate voltage applied to the fluid by the segmented electrode sections. Heat energy losses caused by the fluid thermal conductivity can be both calculated and predicted at its effects on the heating system temperature stability is managed at step 310.
At step 306, from the electrical conductivity, or specific conductance of the fluid a voltage to apply across the first electrode pair at a current sufficient to heat the fluid to the set temperature is determined. At step 314, the electrode segment combination is determined. For example, where the segmented electrode is divided into three segments, the segments may have relative effective areas in a ratio of 1:2:4, that is, the segments preferably constitute four sevenths, two sevenths and one seventh of the total effective electrode area, respectively. In one or more embodiments, all of the segments may be activated for fluids that are of relatively low conductivity, or specific conductance, and one or more of the segments may be activated for fluids that are of relatively high conductivity, or specific conductance.
Once the applied voltage and electrode segment combination has been determined, the current drawn by the fluid is then measured at step 316.
At step 322 it is determined whether the current limit of the system has been exceeded. If the system current limit has exceeded the limit, the process ends at step 324. If the system current limit has not exceeded the limit, at step 320 it is determined whether there is sufficient current to heat the fluid to a set temperature.
In one or more embodiments, the method returns over step 322 such that the electrical conductivity, or specific conductance is continuously determined and appropriate adjustments to the voltages supplied and electrode segment combinations in all heating cells 202, 204 and 206 are made so as to maintain a substantially constant current to maintain the fluid at a set temperature. Advantageously, by returning over step 322 the method is capable of adapting to variations in the fluid's conductivity, or specific conductance, whether arising from the water properties or that may vary from time-to-time or based on a particular location.
In one or more embodiments, steps 316 to 322 may be repeated for n heating cells until the method ends at step 324.
It will be appreciated that some embodiments may be comprised of one or more generic or specialized controllers or processors (or “processing devices”) such as microcontrollers, microprocessors, digital signal processors, customized processors and field programmable gate arrays (FPGAs) and unique stored program instructions (including both software and firmware) that control the one or more processors to implement, in conjunction with certain non-processor circuits, some, most, or all of the functions of the method and/or apparatus described herein. Alternatively, some or all functions could be implemented by a state machine that has no stored program instructions, or in one or more application specific integrated circuits (ASICs), in which each function or some combinations of certain of the functions are implemented as custom logic. Of course, a combination of the two approaches could be used.
The term “coated”, as used herein with reference to “coated electrodes”, may refer to the attachment of a material on the outer surface of another material. The attachment may be partial or whole coverage of the surface of the other material and may be by any mechanical, chemical, or other force or bond.
The term “manufactured” may refer to production of one or more electrode pairs that can be manufactured from an electrically conductive, inert material such as graphite, carbon and combinations thereof.
The term “heat exchanger”, as used herein may refer to a device for transferring heat from one medium to another. Examples of heat exchangers include radiators, which can include coils, plates, fins, pipes, and combinations thereof.
The term “fluid”, as used herein may refer to gases, liquids, gels and combinations thereof. A cooling fluid, or coolant, assists in transferring heat within a thermal circuit. In some examples, a solid conductor may be substituted for a heat transfer fluid.
Where the terms “comprise”, “comprises”, “comprised” or “comprising” are used in this specification (including the claims) they are to be interpreted as specifying the presence of the stated features, integers, steps or components, but not precluding the presence of one or more other features, integers, steps or components, or group thereof.
While the invention has been described in conjunction with a limited number of embodiments, it will be appreciated by those skilled in the art that many alternative modifications and variations in light of the foregoing description are possible. Accordingly, the present invention is intended to embrace all such alternative, modifications and variations as may fall within the spirit and scope of the invention as closed.
This application claims the benefit of U.S. Provisional Patent Application Ser. No. 63/534,460, filed Aug. 24, 2023, the disclosure of which is incorporated herein by reference.
| Number | Date | Country | |
|---|---|---|---|
| 63534460 | Aug 2023 | US |
