FORM-2
THE PATENTS ACT, 1970
(39 of 1970)
&
0
THE PATENTS RULES, 2006
COMPLETE SPECIFICATION
(See section 10 and rule 13)
FLUID HEATER AND METHOD FOR EVALUATING AND DISPLAYING HOT FLUID SUPPLY TIME
EMERSON ELECTRIC CO.
an Americal Company
Of 8000 West Florissant Avenue,
St. Louis, MO 63136
United States of America.
The following specification particularly describes the nature of the invention.

FIELD OF INVENTION
The present invention relates to systems and methods for heating the fluids, more particularly, the present invention relates to a fluid heater and a method for heating the fluid above its initial temperature.
DEFINITION OF TERMS USED IN THE SPECIFICATION
1. Thermal Plane: A thermal plane is an intersection area of the cold fluid and the hot fluid, when the cold fluid is mixed with the hot fluid.
BACKGROUND OF THE INVENTION
Fluid heating is a process for heating fluids above its initial temperature. The fluids may be heated by using various energy sources such as fossil fuels, electrical power, solar energy, geothermal heating and the like. The hot fluid, such as hot water, may be utilized domestically and industrially in various applications. Domestically, the hot water is used for bathing, cleaning, cooking, space heating, and the like. In industry, the hot water and the steam produced from the hot water find many applications, such as generating electricity and the like.
Generally, for domestic use, a storage water heater is used for generation of hot water. The storage water heater has inherent limitation that the storage water heater can not supply hot water continuously. After a particular period of time, the storage water heater runs out of hot water. In some storage water heaters, a temperature set point may be adjusted by a user. In such

temperature settable storage type water heaters, the temperature set point may go down eventually whenever there is hot water consumption for longer period of time. Accordingly, in such storage water heaters, the user has no clue about the time duration for which the user is getting hot water.
Some water heaters have been disclosed in the prior art.
U.S. Patent No. 4,527,543 issued on June 9, 1985, discloses a water heater including a tank, a cylindrical jacket, surrounding the tank to provide an insulating space therebetween and a cover member mounted on top of the jacket to close off the top of the insulating space. An insulating wall is provided in the insulating space between the tank and the jacket. The insulating wall is comprised of a plastic envelope member and a wall of insulating material which has been foamed-in-place inside the envelope member.
U.S. Patent No. 4,793,800 issued on December 27, 1988 discloses a gas-fired water heater/boiler apparatus with a unique burner assembly that provides high levels of BTU/hour input making it suitable for commercial installations. The gas burner includes a pair of superimposed tubes, each having evenly distributed perforations of a different uniform size that are rolled flush together and provide a thick walled burner with greatly increased strength and resistance to premature failure while furnishing an optimum flame pattern. The gas burner projects into the interior of a vertical, cylindrical array of finned heat exchanger tubes through which the fluid to be heated is circulated. The water heater/boiler apparatus is compact and

thermally insulated by a pressurized forehearth and may be installed on combustible floors or in closets with zero clearance.
Although, all prior art fluid heaters are used for heating fluids above its initial temperature, these prior art heaters have numerous limitations. For example, these prior art fluid heaters are not able to provide any indication regarding hot fluid supply time. Further, these prior art fluid heaters are not user friendly.
Therefore, there is a need for a fluid heater that is adapted to provide indication regarding hot fluid supply time. Further, there is a need for a fluid heater that is user friendly. Furthermore, there is a need for a fluid heater that is simple in construction and easy to use.
OBJECT OF THE INVENTION
An object of the present invention is to provide a fluid heater and a method that are adapted to evaluate and display hot fluid supply time.
Another object of the present invention is to provide a fluid heater and a method that are user friendly.
Yet another object of the present invention is to provide a fluid heater that is simple in construction and easy to use.

Further object of the present invention is to provide a fluid heater and a method that minimize wastage of power during heating process of the fluid.
SUMMARY OF THE INVENTION
In accordance with one aspect of the present invention there is provided a fluid heater for evaluating and displaying hot fluid supply time. The fluid heater includes a fluid container, a controlling unit, a computational element, and a display means. The fluid container includes a cold fluid inlet means, a hot fluid outlet means, a first heating element, a second heating element, a first temperature sensor and a second temperature sensor. The cold fluid inlet means adapted for supplying cold fluid at the operative bottom of said container. The hot fluid outlet means adapted for discharging the hot fluid from the operative top of said container. The first heating element disposed within said container and spaced apart from the operative bottom. The second heating element is disposed within said container and spaced apart from the operative top. The first temperature sensor is positioned inside said container in proximity to the first heating element. The second temperature sensor is positioned inside said container in proximity to the second heating element. The controlling unit is adapted to receive inputs from said first temperature sensor and said second temperature sensor. Further, the controlling unit is adapted to selectively activate and deactivate one of the first heating element and the second heating element based on the inputs received from the first temperature sensor and the second temperature sensor. The computational element is adapted to compute the hot fluid supply time at a pre-determined set temperature based on at least one input received from said sensors, capacity of said fluid container, and flow rate of

fluid to and from said fluid container. The display means is communicably coupled to the controlling unit. The display means is adapted to display the computed supply time.
Typically, a third sensor is positioned inside said container in-between the first temperature sensor and the second temperature sensor.
In accordance with one embodiment of the present invention, the cold fluid inlet means includes a fourth sensor to calculate the cold fluid flow rate into the container.
Typically, the fourth sensor is a turbine flow sensor.
Additionally, the fluid heater may include a fifth sensor disposed within the hot fluid outlet means and adapted to facilitate calculation of the hot fluid flow rate from the container.
Preferably, the fluid heater is a storage type water heater.
Typically, the display means includes a warning indicating means for providing a warning signal when said fluid container contains minimum amount of the hot fluid.
In one embodiment of the present invention, the display means is a Liquid crystal Display (LCD).

In another embodiment of the present invention, the display means is a light-emitting diode (LED).
Alternatively, the display means is a cathode ray tube (CRT).
In accordance with another aspect of the present invention there is provided a method for evaluating and displaying hot fluid supply time from a fluid heater. The method includes following steps of supplying cold fluid at the operative bottom of a fluid container. Heating the fluid contained inside said container to a pre-determined set temperature by a first heating element and a second heating element. Further, the method includes a step of, selectively activating and deactivating one of the first heating element and the second heating element based on the inputs received from a first temperature sensor and a second temperature sensor by a controlling unit. Further, the method includes a step of, discharging the hot fluid from the operative top of said container. Furthermore, computing the hot fluid supply time at the predetermined set temperature based on at lest one input received from a first temperature sensor and a second temperature sensor disposed within said container, capacity of said fluid container, and flow rate of fluid to and from said fluid container by a computational element. Moreover, the method includes a step of displaying the computed supply time at a display means.
Additionally, the method includes a step of providing a warning signal when said fluid container contains minimum amount of the hot fluid.

Furthermore, the method includes a step of measuring temperature of the operative middle of said container by a third sensor positioned in-between the first temperature sensor and the second temperature sensor,
Further, the method includes a step of calculating the cold fluid flow rate into said fluid container by a fourth sensor.
BRIEF DESCRIPTION OF THE FIGURES
The invention will now be briefly described in relation to the accompanying drawings, in which:
Figure 1 illustrates a block diagram of a fluid heater for evaluating and displaying hot fluid supply time, in accordance with one embodiment of the present invention;
Figure 2 illustrates a perspective view depicting a fluid container of the fluid heater shown in Figure 1 is communicably coupled to a display means of the fluid heater shown in Figure 1;
Figure 3 illustrates a schematic representation of the fluid container of Figure 2;
Figures 4a illustrates a schematic representation of a display screen of a display device of the display means of Figure 2, depicting minimum amount of time is available for which a user is supplied with hot fluid;

Figure 4b illustrates a schematic representation of the display screen of the display means shown in Figure 2, depicting no availability of hot fluid inside the fluid heater;
Figure 4c illustrates a schematic representation of the display screen of the display means of Figure 2, depicting a half-way mark of the hot fluid supply time;
Figure 4d illustrates a schematic representation of the display screen of the display means of Figure 2, in accordance with another embodiment of the present invention;
Figure 4e illustrates a schematic representation of the display screen of the display means of Figure 2, in accordance with yet another embodiment of the present invention;
Figure 4f illustrates a schematic representation of the display screen of Figure 4e, depicting the hot fluid supply time;
Figure 4g illustrates a schematic representation of the display screen of Figure 4e, depicting minimum amount of time that is available for which a user is supplied with the hot fluid;
Figure 4h illustrates a schematic representation of the display screen of Figure 4e, depicting no availability of the hot fluid inside the fluid heater;

Figure 4i illustrates a schematic representation of the display screen of Figure 4e, depicting the hot fluid supply time for steady state condition i.e. when no fluid is drawn;
Figure 5 illustrates a schematic representation of the fluid container of the fluid heater of Figure 1 depicting a fourth sensor, in accordance with yet another embodiment of the present invention;
Figure 6 illustrates a flow chart depicting a method for evaluating and displaying hot fluid supply time from a fluid heater, in accordance with one embodiment of the present invention;
Figure 7 illustrates a flow chart depicting operation of the fluid heater of Figure 1; and
Figure 8 illustrates a table depicting the hot fluid supply time calculation at various scenarios.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
Preferred embodiments will now be described in detail with reference to the accompanying drawings. The preferred embodiments do not limit the scope and ambit of the invention. The description provided is purely by way of example and illustration.
A fluid heater of the present invention is adapted for evaluating and displaying hot fluid supply time, in addition to heating fluids, such as water,

above its initial temperature. More specifically, the fluid heater of the present invention is adapted for providing a user a time indicating means that enables the user to plan its further course of action based on the time for which the hot fluid, such as the hot water, is available to the user. The fluid heater of the present invention is adapted to provide a user at least one of a visual indication, a sound indication and the like, for depicting the time duration for which the hot fluid supply is available to a user. The fluid heater of the present invention facilitates the user to decide whether to start and continue using hot fluid or to wait or to reduce the output flow rate of the hot fluid. More specifically, the fluid heater of the present invention may be more useful during various occasions such as frosty winter season, before taking bath, and the like.
Referring to Figure 1, a block diagram depicting a fluid heater 1000 for evaluating and displaying hot fluid supply time is depicted. In one embodiment of the present invention, the fluid heater is a storage type water heater. However, the present invention is not limited to any particular type of water heater; the present invention may also be used for various other fluid heaters known in the art. The fluid heater 1000 includes a fluid container 100, a controlling unit 200, a computational element 300, and a display means 400.
Referring to Figure 2 and Figure 3, a schematic representation of the fluid container 100 is depicted. Further, the fluid container 100 is adapted to be fully filled with the fluid. The fluid, such as water, contained inside the fluid container 100 may be heated by various energy sources such fossil fuels, electricity, solar energy or the like. The fluid container 100 may be used for

providing hot fluids to a user for performing various operations, such as, bathing, cleaning, cooking and the like.
More specifically referring to Figure 3, the fluid container 100 includes a cold fluid inlet-means 102, a hot fluid outlet means 104, a first heating element 106, a second heating element 108, a first temperature sensor 110, and a second temperature sensor 112. The cold fluid inlet means 102 is adapted for supplying the cold fluid at the operative bottom 114 of the container 100. More specifically, the cold fluid inlet means 102 is adapted to supply the cold fluid inside 116 the fluid container 100. The cold fluid inlet means 102 is adapted to be pressurized in a way such that when the user draws hot fluid form the operative top 118, the same amount of cold fluid gets replaced at the operative bottom 114. The hot fluid outlet means 104 is adapted for discharging the hot fluid contained inside the fluid container 100. More specifically, the hot fluid outlet means 104 is adapted for discharging the hot fluid from the operative top 118 of the fluid container 100.
The first heating element 106 is disposed within the container 100 and spaced apart from the operative bottom 114. The first heating element 106 is adapted to heat the fluid contained inside the fluid container 100. The first heating element 106 is adapted to heat the fluid contained in the operative bottom portion 114 of the fluid container 100. The first heating element 106 is adapted to be activated for heating when the fluid temperature drops below a pre-deterrnined set temperature. The pre-determined set temperature may be set by the user based on the user's requirement.

The second heating element 108 is disposed within the container 100 and spaced apart from the operative top 118. The second heating element 108 is adapted to heat the fluid contained inside the fluid container 100. Specifically, the second heating element 108 is adapted to heat the fluid contained in the operative top 118 of the fluid container 100. The second heating element 108 is adapted to be activated for heating when the fluid temperature drops below the pre-determined set temperature. Further, the second heating element 108 and the first heating element 106 are adapted to be deactivated or turned off, when the fluid attains the pre-determined set temperature.
The first temperature sensor 110 is positioned inside 116 the container 100 in proximity to the first heating element 106. The first temperature sensor 110 is adapted to detect the temperature of the fluid proximate the first heating element 106. In one embodiment of the present invention, the first temperature sensor 110 is adapted to facilitate activation and de-activation of the first heating element 106, based on the detected temperature of the fluid in the container 100. The first temperature sensor 110 is also adapted to take part in detection of movement of a thermal plane. 120, based on the detected temperature of the fluid in the container 100. The thermal plane 120 is formed due to mixing of the hot fluid and the cold fluid. The thermal plane 120 is adapted to move upward when the hot fluid is discharged out of the container 100. In other words, when the hot fluid is discharged out of the fluid container 100, the thermal plane 120 is formed between the hot fluid and the cold fluid.

The second temperature sensor 112 is positioned inside the fluid container 100 in proximity to the second heating element 108. The second temperature sensor 112 is adapted to detect the temperature of the fluid proximate the second heating element 108. Additionally, the second temperature sensor 112 is adapted to take part in detection of movement of the thermal plane 120, based on the detected temperature of the fluid in the container 100. Moreover, the second temperature sensor 112 is also adapted to facilitate activation and deactivation of the second heating element 108, based on the detected temperature of the fluid in the container 100.
In one embodiment of the present invention, the container 100 may include a third sensor 122 positioned inside the container 100 in-between the first temperature sensor 110 and the second temperature sensor 112. The third sensor 122 is a temperature sensor. The third sensor 122 is adapted to detect the temperature of the fluid contained in the middle portion of the fluid container 100. The third sensor 122 is adapted to take part in detection of movement of the thermal plane 120, based on the detected temperature of the fluid in the middle portion of the container 100. The first temperature sensor 110, the second temperature sensor 112, and the third sensor 122 may be one of a thermister, a thermocouple, PT 100 sensor, a solid state temperature sensor such as AD 500, and the like.
Although, in the present embodiment of the present invention, three temperature sensors are used, the present invention may include more than three temperature sensors for better tracking of the movement of the thermal plane 120. More specifically, the movement of the thermal plane 120 may be more precisely tracked due to increasing number of temperature sensors. The

first temperature sensor 110, the second temperature sensor 112, and the third sensor 122 are communicably coupled to the controlling unit 200.
Now referring back to Figure 1, the controlling unit 200 is adapted to receive inputs from the first temperature sensor 110, the second temperature sensor 112, and the third sensor 122. Further, the controlling unit 200 is adapted to receive inputs from the first temperature sensor 110, the second temperature sensor 112, and the third sensor 122 by means of various wired or wireless communication means known in the art. In one embodiment of the present invention, the controlling unit 200 includes the computational element 300. The controlling unit 200 may be one of the various controlling units known in the art, such as a microcontroller and the like. The controlling unit 200 may be configured in the form of an IC (Integrated Cireaft) chip. The controlling unit 200 may be disposed on an outside portion of the container 100. However, in other embodiment of the present invention, the controlling unit 200 may be positioned at any other location for receiving inputs from the first temperature sensor 110, the second temperature sensor 112, and the third sensor 122. The controlling unit 200 may be adapted to selectively activate and deactivate one of the first heating element 106 and the second heating element 108, based on the inputs received from the first temperature sensor and the second temperature sensor.
More specifically, the controlling unit 200 is adapted to activate or turn ON the second heating element 108 when the temperature of the fluid detected by the second temperature sensor 112 is less than the pre-determined set temperature. Further, the second temperature sensor 112 is de-activated or turned off, when the temperature of the fluid detected by the second

temperature sensor 112 is greater than the pre-determined set temperature. Similarly, the controlling unit 200 is adapted to activate or turn ON the first heating element 106 when the temperature of the fluid detected by the first temperature sensor 110 is less than the pre-determined set temperature. In such case before activating the first heating element, the controlling unit 200 detects with the help of the second temperature sensor 112, whether the fluid near the second heating element 108 is not too hot than the pre-determined set temperature. Further, the first heating element 106 is de-activated or turned off, when the temperature of the fluid detected by the first temperature sensor 110 is greater than the pre-determined set temperature. The controlling unit 200 may be adapted activate or turn ON the first heating element 106 and the second heating element 108, one at a time. In one embodiment of the present invention, the controlling unit 200 is adapted to give priority to the second heating element 108 over the first heating element 106.
The computational element 300 is adapted to compute the hot fluid supply time at the pre-determined set temperature based on at least one input received from the sensors 110, 112, and 122, capacity of the container 100, and flow rate of fluid to and from the container 100. In one embodiment of the present invention, the movement of the thermal plane 120 may indicate the flow rate of the fluid to and from the fluid container 100. The computational element 300 is adapted to detect movement of the thermal plane 120, by receiving inputs from the temperature sensors 110, 112, and 122. More specifically, if the hot fluid output flow rate changes, such as output flow rate accelerates or retards, the computational element 300 may update the hot fluid supply time prediction by considering the time required

for the thermal plane 120 to move from the first temperature sensor 110 to the third sensor 122 or from the third sensor 122 to the second temperature sensor 112.
Additionally, in other embodiments of the present invention, the computational element 300 is adapted to compute the hot fluid supply time at the pre-determined set temperature based on one of the additional inputs, such as wattage of heating elements in case of electricity powered fluid heater, British Thermal Unit per hour (BTU/Hr) for gas fired appliances, and temperature of cold fluid at inlet. However, the wattage of the heating elements and the BTU/Hr of gas powered appliances are constant for a particular system but they may change for different fluid heaters.
Referring to Figure 2 and Figures 4a to 4i, the display means 400 communicably coupled to the controlling unit 200 by means a communication means 450 (shown in Figure 2) is depicted. In one embodiment of the present invention, the communication means 450 is a UART (universal asynchronous receiver/transmitter) link. However, in other embodiments of the present invention, the display means 400 is communicably coupled to the controlling unit 200 by means of various wired or wireless communication means known in the art. The display means 400 is adapted to display the computed supply time. The display means 400 is adapted to provide indication regarding the hot fluid supply time. The display means 400 includes a display screen 402 and a user interface 420. The display screen 402 is adapted to use an angular scale 404 and a pointer 406 to provide an indicating means regarding the hot fluid supply time. The pointer 406 is adapted to move angularly along the angular

scale 404 for indicating hot fluid supply time at a particular instance. The user interface 420 includes a down arrow key 422, an up arrow key 424, an ON/ Standby/vacation button 426, and a High-Demand key 428. The high-Demand key 428 is adapted to facilitate temporary increase in the predetermined set temperature.
In one embodiment of the present invention, the display means 400 includes a warning indicating means 408 (shown in Figure 4a) for providing a warning signal when the fluid container 100 contains minimum amount of the hot fluid. In other words, the warning indicating means 408 is adapted to provide a warning signal when the thermal plane 120 passes the second temperature sensor 112. The warning indicating means 408 may be in various forms such as an alarm sound, a continuous visual blinking, and the like. The alarm sound denotes the user a warning sign regarding availability of minimum amount of hot fluid in the fluid container, without looking at the display means 400.
Figure 4a illustrates the position of the pointer 406 when the fluid container 100 contains minimum amount of the hot fluid. Position of the pointer 406 indicates the hot fluid is available for short duration of time and the warning signal is activated at this position of the pointer 406. Also the alarm icon will be flashed on the display screen 402. Figure 4b illustrates a position of the pointer 406 depicting no availability of the hot fluid inside the fluid container 100 at the pre-determined set temperature. At such instance, "Please wait" message may be flashed on the display screen 402. Figure 4c illustrates a position of the pointer 406 indicating a half-way mark of the hot fluid supply time. More specifically, the position of the pointer 406 indicates

considerable amount of time is available for which the user may use the hot fluid.
Figure 4d indicates the display screen 402 of the display means 400, in another embodiment of the present invention. The display screen 402 of the present embodiment includes the angular scale 404, the pointer 406, the warning indicating means 408, a hotness indicating block 410, a hot fluid indicating means 412, a caution message 414 and the like. As depicted, the warning indicating means 408 is crossed by a diagonally placed line for indicating de-activated state of the warning indicating means 408. The hotness indicating block 410 is adapted to indicate the temperature of the fluid contained inside the fluid container 100. The display screen 402 of the present invention is adapted to display the caution message 414 such as, "Caution: Risk of Scalding increases with hotter water". Further, the display screen 402 of the present embodiment indicates the current status of the fluid heater 1000 by flashing one of the messages such as, "Standby", "On" or "Vacation", on the display screen. Further, the display screen 402 is also adapted to indicate "ERROR" message thereon.
Figure 4e indicates the display screen 402 of the display means 400, in yet another embodiment of the present invention. The display screen 402 as shown in the present embodiment includes a circular scale 416 and the pointer 406. The pointer 406 is adapted to move angularly along the circular scale 416 for indicating the hot fluid supply time at a particular instance. Figure 4f illustrates a position of the pointer 406 depicting a particular time period, such as 15 minutes, for which the hot fluid may be available to the user. Further, Figure 4g illustrates a position of the pointer 406 depicting

minimum amount of the hot fluid contained inside the fluid container 100. Also the alarm icon 408 may be flashed on the display screen 402, at this position of the pointer 406. Figure 4h illustrates a position of the pointer 406 depicting no availability of the hot fluid inside the fluid container 100 at the pre-determined set temperature. At such instance, "Wait" message may be flashed on the display screen 402. Additionally, Figure 4i illustrates the position of the pointer 406 depicting the hot fluid supply time for steady state condition i.e. when no fluid is drawn from the fluid container 100. More specifically, the pointer 406 denotes the hot fluid supply time at the maximum out flow rate at the steady state condition i.e. when no fluid is drawn from the fluid container 100.
In one embodiment of the present invention, the display means 400 is a Liquid crystal Display (LCD). The Liquid crystal Display (LCD) may be adapted to display the computed supply time in the form of a Dot matrix display, a seven-segment display, an Alpha numeric display, a graphic display, customized LCD modules, and the like. In another embodiment of the present invention, the display means 400 is a light-emitting diode (LED). The LED may be adapted to display the computed supply time in the form of a seven-segment display, a bar graph display, a customized display and the like. In yet another embodiment of the present invention, the display means 400 is a cathode ray tube (CRT).
Further, the display means 400 may be installed inside a bathroom so that the user may get information regarding the hot fluid stock while consuming it. Alternatively, the display means 400 may be mounted outside bathroom if fluid consumption for other applications than bath is needed.

Referring to Figure 5, in one embodiment of the present invention, the cold fluid inlet means 102 includes a fourth sensor 124 to calculate the cold fluid flow rate into the fluid container 100. In one embodiment of the present invention, the fourth sensor 124 is a turbine flow sensor. The fourth sensor 124 is adapted to facilitate calculation of the cold fluid flow rate into the fluid container 100, from an electrical signal output generated by the fourth sensor 124. The fourth sensor 124 is adapted to increase the accuracy of the fluid heater 1000. In another embodiment of the present invention, the fluid heater 1000 may include a fifth sensor (not shown) disposed within the hot fluid outlet means. The fifth sensor may be similar to the fourth sensor 124. The fifth sensor is adapted to facilitate calculation of the hot fluid flow rate from the fluid container 100.
Now referring to Figure 6, a flow chart depicting a method 2000 for evaluating and displaying hot fluid supply time from a fluid heater is depicted. At 500, cold fluid is supplied at the operative bottom 114 of a fluid container, such as the fluid container 100. At 600, the cold fluid supplied inside the fluid container 100 is heated to a pre-determined set temperature by a first heating element, such as the first heating element 106, and a second heating element, such as the second heating element 108. The first heating element 106 and the second heating element 108 are adapted to be turned off, when the fluid temperature inside the fluid container 100 reaches the pre-determined set temperature. Similarly, the first heating element 106 and the second heating element 108 are adapted to be turned on, when the fluid temperature inside the fluid container 100 drops below the predetermined set temperature.

At 650, the first heating element 106 and the second heating element 108 are selectively activated and deactivated by the controlling unit 200 based on the inputs received from the first temperature sensor 110 and the second temperature sensor 112. More specifically, the controlling unit 200 is adapted to activate or turn ON the second heating element 108 when the temperature of the fluid detected by the second temperature sensor 112 is less than the pre-determined set temperature. Further, the second temperature sensor 112 is de-activated or turned off, when the temperature of the fluid detected by the second temperature sensor 112 is greater than the pre-determined set temperature. Similarly, the controlling unit 200 is adapted to activate or turn ON the first heating element 106 when the temperature of the fluid detected by the first temperature sensor 110 is less than the pre-determined set temperature. In such case before activating the first heating element, the controlling unit 200 detects with the help of the second temperature sensor 112, whether the fluid near the second heating element 108 is not too hot than the pre-determined set temperature. Further, the first heating element 106 is de-activated or turned off, when the temperature of the fluid detected by the first temperature sensor 110 is greater than the pre-determined set temperature. The controlling unit 200 may be adapted activate or turn ON the first heating element 106 and the second heating element 108, one at a time. In one embodiment of the present invention, the controlling unit 200 is adapted to give priority to the second heating element 108.
At 700, the hot fluid is discharged from the operative top 118 of the fluid container 100. Accordingly, to compensate the discharged quantity of the hot fluid, the cold fluid inlet means 102 is pressurized enough so that when

the user draws the hot fluid from the operative top 118, the amount of the hot fluid drawn from the operative top 118 is replaced by the cold fluid at the operative bottom 114.
At 800, the hot fluid supply time is calculated at the pre-determined set temperature based on at least one input received from the first temperature sensor 110 and the second temperature sensor 112 disposed within the fluid container 100, capacity of the fluid container 100, and flow rate of fluid to and from the fluid container 100 by the computational element 300. In one embodiment of the present invention, the movement of the thermal plane 120 may indicate the flow rate of the fluid to and from the fluid container 100. The computational element 300 is adapted to detect movement of the thermal plane 120, by receiving inputs from the temperature sensors 110, and 112.
At 900, the computed supply time is displayed at the display means 400. In one embodiment of the present invention, the method 2000 includes a step of providing a warning signal, such as the warning indicating means 408, when the fluid container 100 contains minimum amount of the hot fluid.
Additionally, in one embodiment of the present invention, the method 2000 includes a step of measuring temperature of the operative middle of the fluid container 100 by a third sensor, such as the third sensor 122, positioned in-between the first temperature sensor 110 and the second temperature sensor 112. More specifically, if the hot fluid output flow rate changes, such as output flow rate accelerates or retards, the computational element 300 may update the hot fluid supply time prediction by considering the time required

for the thermal plane 120 to move from the first temperature sensor 110 to the third sensor 122 or from the third sensor 122 to the second temperature sensor 112.
Further, in one embodiment of the present invention, the method 2000 includes a step of calculating the cold fluid flow rate into the fluid container 100 by means of a fourth sensor, such as the fourth sensor 124. The fourth sensor 124 may be a turbine flow sensor.
Although, the present invention has been described with respect to storage type water heaters, the present invention is not limited to any particular type of fluid heaters. The principles of the present invention may also be used in various types of heaters such as multipoint heaters and the like.
Now referring to Figure 7, a flow chart 3000 depicting operation of the fluid heater 1000 is depicted. More specifically, the flow chart 3000 depicts method of calculation of the hot fluid supply time at various stages of the hot fluid supply cycle. At 3110, the fluid container 100 is filled with the cold fluid, such as water. The temperature of the cold fluid supplied is less than the pre-determined set point. Accordingly, as per the requirement of the user for the hot fluid, the user may actuate the fluid heater 1000. At 3120, one of the first heating element 106 and the second heating element 108 may be selectively activated and de-activated for heating the cold fluid to the predetermined set point. At 3130, the hot fluid temperature contained inside the fluid container 100 is equal to the pre-determined set point. At this instance the hot fluid supply time is calculated as:

,. . n ,. . . Maximum Hot fluid Volume contained inside the fluid container
Hot fluid supply time (Minimum) = :
Maximum output flow rate
At 3140, the movement of the thermal plane 120 is investigated across the first temperature sensor 110. If the movement of the thermal plane is sensed by the first temperature sensor 110, the flow chart 3000 proceeds to a step of 3150, otherwise, the flow chart 3000 proceeds backs to the step of 3130. At 3150, the movement of the thermal plane 120 indicates dispensing of the hot fluid from the fluid container 100. At 3160, the flow rate of the hot fluid from the fluid container 100 may be calculated by activating the first heating element 106 and tracking temperature profile near the first temperature sensor 110.
At 3170, the flow rate of the hot fluid is detected. If the flow rate of the hot fluid is equivalent to zero, the flow chart 3000 proceeds to a step of 3180, otherwise, the flow chart proceeds to a step of 3200. At 3180, the hot fluid supply time is calculated as follows:
Volume of Hot fluid left in the fluid container
Hot fluid supply time (Minimum) =
Maximum output flow rate
From the step of 3180, the flow chart moves to a step of 3190. At 3190, the controlling unit 200 investigates whether the heat supplied is sufficient or not. If the heat supplied is sufficient, then the flow chart 3000 moves to the step of 3130 and if the heat supplied is not sufficient, then the flow chart 3000 moves to the step of 3160.
At 3200, the hot fluid supply time is calculated as follows:

Volume of Hot fluid left in the fluid container
Hot fluid supply time = —
Current output flow rate
In case of the display means 400 mounting outside bathroom if fluid consumption for other applications than bath is needed. In such case, time read by the user may decrease once the user starts the fluid consumption for bath as well. In such case, the user is unable to track this decrease in time or the user may not see instantaneous time displayed over the display screen 402. In such case, the user reads time displayed before entering bathroom. Such time corresponds to the hot water outflow at that particular instance. Thus, for taking into consideration further consumption by the user for a bath i.e. by subtracting Offset time from Current Time.
Volume of Hot fluid left in the fluid container
Hot fluid supply time =
Current output flow rate + Max. Flow rate for bath
At 3210, the hot fluid supply time is compared with full scale value. If the hot fluid supply time is greater than full scale value, the flow chart 3000 moves to a step of 3220, otherwise, the flow chart 3000 moves to a step of 3230. At 3220, the hot fluid supply time is equal to the full scale value. At 3230, the hot fluid is consumed by the user. At 3240, the hot fluid flow rate is verified by tracking passage of the thermal plane 120 across the second temperature sensor 112. The flow rate may also be detected by activating the second heating element 108 and tracking temperature profile near the second temperature sensor 112 after the thermal plane 120 passes the second temperature sensor 112. At 3250, the hot fluid supply time is checked. If the hot fluid supply time is zero, the flow chart moves to the step of 3260,

otherwise, the flow chart moves to a step of 3270. At 3260, the controlling unit 200 facilitates the display means 400 to display the message "Please Wait" or "Wait" and then the flow chart moves to the step of 3190.
At 3270, the hot fluid supply time is compared with the alarming time. If the hot fluid supply time is less than the alarming time, the flow chart 3000 moves to the step of the 3280, otherwise, the flow chart moves to the step of 3190. At 3280, the warning indicating means 408 may be displayed on the display screen 402 of the display means 400. The warning indicating means 408 may be in various forms such as an alarm sound, a continuous visual blinking, and the like. After the step of 3280, the flow chart 3000 moves to the step of 3190.
Referring to Figure 8, a table depicting calculation of the hot fluid supply time at various operating scenarios of the fluid heater 1000 is illustrated. The parameter "Maximum output flow rate for bath" is constant depending upon structural configuration of shower outlet.
TECHNICAL ADVANCEMENTS AND ECONOMIC
SIGNIFICANCE
A fluid heater and a method for evaluating and displaying hot fluid supply time of the present invention are simple in construction and easy to use. Furthermore, the fluid heater and the method are adapted to evaluate and display the hot fluid supply time continuously during the utilization of the fluid heater. Accordingly, the fluid heater and the method of the present invention is user friendly. Moreover, the fluid heater and the method

minimize wastage of power during heating process of the fluid, because the first heating element and the second heating element are turned off as the fluid in the container attains the pre-determined set temperature. Yet another object of the present invention is to provide a fluid heater and a method that are adapted to evaluate a simpler and easily understandable specification for a buyer before purchasing a fluid heater in terms of the amount of time the fluid heater is adapted to supply the hot fluid at the pre-determined set temperature.
While considerable emphasis has been placed herein on the components and component parts of the preferred embodiments, it will be appreciated that many embodiments can be made and that many changes can be made in the preferred embodiments without departing from the principles of the invention. These and other changes in the preferred embodiment as well as other embodiments of the invention will be apparent to those skilled in the art from the disclosure herein, whereby it is to be distinctly understood that the foregoing descriptive matter is to be interpreted merely as illustrative of the invention and not as a limitation.

We claim:
1. A fluid heater for evaluating and displaying hot fluid supply time,
the fluid heater comprising:
a) a fluid container comprising,
i. a cold fluid inlet means adapted for supplying cold fluid
at the operative bottom of said container; ii. a hot fluid outlet means adapted for discharging the hot
fluid from the operative top of said container; iii. a first heating element disposed within said container and
spaced apart from the operative bottom; iv. a second heating element disposed within said container
and spaced apart from the operative top;
in proximity to the first heating element; vi. a second temperature sensor positioned inside said container in proximity to the second heating element;
b) a controlling unit adapted to receive inputs from said first temperature sensor and said second temperature sensor and adapted to selectively activate and deactivate one of the first heating element and the second heating element based on the inputs received from the first temperature sensor and the second temperature sensor;
c) a computational element adapted to compute the hat fluid supply time at a pre-determined set temperature based on at least one input received from said sensors, capacity of said fluid container, and flow rate of fluid to and from said fluid container; and

c) a display means communicably coupled to the controlling unit, the display means adapted to display the computed supply time.
2. The fluid heater as claimed in claim 1, further comprising a third sensor positioned inside said container in-between the first temperature sensor and the second temperature sensor.
3. The fluid heater as claimed in claim 1, wherein the cold fluid inlet means comprises a fourth sensor to calculate the cold fluid flow rate into the container.
4. The fluid heater as claimed in claim 3, wherein the fourth sensor is a turbine flow sensor.
5. The fluid heater as claimed in claim 1 or claim 3, comprising a fifth sensor disposed within the hot fluid outlet means and adapted to facilitate calculation of the hot fluid flow rate from the fluid container.
6. The fluid heater as claimed in claim 1, wherein the display means is a Liquid crystal Display (LCD).
7. The fluid heater as claimed in claim 1, wherein the display
means is a light-emitting diode (LED).

8. The fluid heater as claimed in claim 1, wherein the display means is a cathode ray tube (CRT).
9. The fluid heater as claimed in claim 1, wherein the fluid heater is a storage type water heater.
lO.The fluid heater as claimed in claim 1, wherein the display means includes a warning indicating means for providing a warning signal when said fluid container contains minimum amount of the hot fluid.
11. A method for evaluating and displaying hot fluid supply time from a fluid heater, the method comprising following steps:
a) supplying cold fluid at the operative bottom of a fluid container;
b) heating the fluid contained inside said container to a predetermined set temperature by a first heating element and a second heating element;
c) selectively activating and deactivating one of the first heating element and the second heating element based on the inputs received from a first temperature sensor and a second temperature sensor by a controlling unit;
d) discharging the hot fluid from the operative top of said
container;
e) computing the hot fluid supply time at the pre-determined set
temperature based on at least one input received from the first
temperature sensor and the second temperature sensor disposed

within said container, capacity of said container, and flow rate
of fluid to and from said container by a computational element;
and
f) displaying the computed supply time at a display means.
12.The method as claimed in claim 11, further comprising a step of providing a warning signal when said container contains minimum amount of the hot fluid.
13. The method as claimed in claim 11, further comprising a step of measuring temperature of the operative middle of said container by a third sensor positioned in-between the first temperature sensor and the second temperature sensor.
14.The method as claimed in claim 11, further comprising a step of calculating the cold fluid flow rate into said container by a fourth sensor.