DESC:FIELD OF THE INVENTION:
[001] The present disclosure relates to the field of measurement of the extent of freezing in a phase change material.More particularly, the present disclosure relates to using piezoelectric sensors to measure the extent of freezing in a phase change material.

BACKGROUND:
[002] The background description includes information that may be useful in understanding the present invention. It is not an admission that any of the information provided herein is prior art or relevant to the presently claimed invention, or that any publication specifically or implicitly referenced is prior art.
[003] During the process of freezing / melting, temperature of a substance / material remains constant, and hence temperature measurement cannot indicate the proportion of solid vs. liquid. No simple method is available to determine the proportion of solid and liquid during phase change / transition (freezing / melting) of a substance. Laboratory based and other methodologies are complicated and are difficult to implement in practical situations. The measurement is however important in scenarios where thermal storage tanks /heat exchangers are used or where a controlled freezing or melting is required.
[004] A simple system is required to quantify the amount of freezing (ratio of solid to liquid) in systems where the level of freezing is critical to operation of a unit. For example, a container containing ice that cools the commodities around it should send such information to the freezing engine so as to start freezing again at the right time as this allows the system to be operated only when it is required to be.
[005] European Patent Application No. EP2622340A1 discloses determination of phase change of a biopharmaceutical material based on propagation of pulse by a transmitter, and sensing of the reflection by a sensor. However, this system may not be appropriate and workable in all situations due to requirement of sending and receiving/ detecting an ultrasonic signal.
[006] All publications herein are incorporated by reference to the same extent as if each individual publication or patent application were specifically and individually indicated to be incorporated by reference. Where a definition or use of a term in an incorporated reference is inconsistent or contrary to the definition of that term provided herein, the definition of that term provided herein applies and the definition of that term in the reference does not apply.
[007] In some embodiments, the numbers expressing quantities of ingredients, properties such as concentration, reaction conditions, and so forth, used to describe and claim certain embodiments of the invention are to be understood as being modified in some instances by the term “about.” Accordingly, in some embodiments, the numerical parameters set forth in the written description and attached claims are approximations that can vary depending upon the desired properties sought to be obtained by a particular embodiment. In some embodiments, the numerical parameters should be construed in light of the number of reported significant digits and by applying ordinary rounding techniques. Notwithstanding that the numerical ranges and parameters setting forth the broad scope of some embodiments of the invention are approximations, the numerical values set forth in the specific examples are reported as precisely as practicable. The numerical values presented in some embodiments of the invention may contain certain errors necessarily resulting from the standard deviation found in their respective testing measurements.
[008] As used in the description herein and throughout the claims that follow, the meaning of “a,” “an,” and “the” includes plural reference unless the context clearly dictates otherwise. Also, as used in the description herein, the meaning of “in” includes “in” and “on” unless the context clearly dictates otherwise.
[009] The recitation of ranges of values herein is merely intended to serve as a shorthand method of referring individually to each separate value falling within the range. Unless otherwise indicated herein, each individual value is incorporated into the specification as if it were individually recited herein. All methods described herein can be performed in any suitable order unless otherwise indicated herein or otherwise clearly contradicted by context. The use of any and all examples, or exemplary language (e.g. “such as”) provided with respect to certain embodiments herein is intended merely to better illuminate the invention and does not pose a limitation on the scope of the invention otherwise claimed. No language in the specification should be construed as indicating any non-claimed element essential to the practice of the invention.

OBJECTSOF THE INVENTION:
[0010] An object of the present disclosure is to provide a method and system for measuring the extent of freezing in a phase change material using piezoelectric sensors.
[0011] An object of the present disclosure is to provide a method and system for measuring the extent of freezing in a phase change material using piezoelectric sensors that allows different phase change materials & piezoelectric sensors to be used as per requirements.
[0012] An object of the present disclosure is to provide a method and system for measuring the extent of freezing in a phase change material using piezoelectric sensors that allows the level of freezing during latent cooling to be determined, where temperature measurement does not apply.
[0013] An object of the present disclosure is to provide a method and system for measuring the extent of freezing in a phase change material using piezoelectric sensors to enable simple and reliable measurement.

SUMMARY OF THE INVENTION:
[0014] The present disclosure, in a broad aspect, provides a method and system for measuring the extent of freezing in a phase change material using piezoelectric sensors.
[0015] In accordance with one aspect of this disclosure, there is provided a method for measuring the extent of freezing in a phase change material, the method comprising the steps of placing at least one piezoelectric sensor in a phase change material; measuring the voltage generated by said at least one piezoelectric sensor due to change in pressure caused by freezing or melting of at least a portion of the phase change material; and determining the extent of freezing in the phase change material using at least one measurement of the voltage generated.
[0016] In accordance with another aspect of this disclosure, there is provided a system for measuring the extent of freezing in a phase change material, the system comprising at least one piezoelectric sensor placed in a phase change material; a device for measuring the voltage generated by said at least one piezoelectric sensor due to change in pressure caused by freezing or melting of at least a portion of the phase change material; and a converter module for determining the extent of freezing in the phase change material using at least one measurement of the voltage generated.

BRIEF DESCRIPTION OF THE DRAWINGS:
[0017] Fig. 1 is a drawing of embodiments of a piezoelectric sensor;
[0018] Fig. 2 is a schematic drawing illustrating a piezoelectric sensor (transducer) in a container containing phase change material.

DETAILED DESCRIPTION OF THE DRAWINGS:
[0019] The method and system for measuring the extent of freezing in a phase change material using piezoelectric sensors in accordance with the present disclosure will now be described with reference to the exemplary embodiments shown in the accompanying drawings. The exemplary embodiments are explained particularly with reference to measurement of the extent of freezing in a phase change material using piezoelectric sensors.
[0020] The expression ‘machine readable media’ used hereinafter in the specification refers to RAM, ROM, EPROM, EEPROM, CD-ROM or other optical disk storage, magnetic disk storage or other magnetic storage devices, or any other medium which can be used to carry or store desired program code in the form of machine-executable instructions or data structures and which can be accessed by a general purpose or special purpose computer or other machine with a processor.
[0021] The expression ‘computer program product’ is defined as a manufactured product embodied in a machine readable medium as defined herein above.

Definitions
[0022] In the present disclosure:
[0023] “phase change material” means any material that is capable of freezing and melting by releasing and absorbing heat respectively. For example, water can be used as a phase change material.
[0024] “piezoelectric sensor” means any piezoelectric material / device which generates a voltage in response to change in pressure applied to it. The piezoelectric sensor may also be referred to as a transducer herein.
[0025] In accordance with one aspect of this disclosure, there is provided a method for measuring the extent of freezing in a phase change material, the method comprising the steps of placing at least one piezoelectric sensor in a phase change material; measuring the voltage generated by said at least one piezoelectric sensor due to change in pressure caused by freezing or melting of at least a portion of the phase change material; and determining the extent of freezing in the phase change material using at least one measurement of the voltage generated.
[0026] In one more embodiment of the method of the present disclosure, the phase change material is either water or any other material that is capable of freezing and melting by releasing and absorbing heat respectively.
[0027] In another embodiment of the method of the present disclosure, the extent of freezing is reckoned as a ratio of solid to liquid in the phase change material.
[0028] In yet another embodiment of the method of the present disclosure, the piezoelectric sensor is made of piezoelectric ceramics or single crystal materials or any other material with piezoelectric properties.
[0029] In yet one more embodiment of the method of the present disclosure, determining the extent of freezing in the phase change material using at least one measurement of the voltage generated, comprises of mapping said at least one measurement of voltage generated to at least one value indicating the extent of freezing.
[0030] In a further embodiment, mapping said at least one measurement of voltage generated to at least one value indicating the extent of freezing, is enabled by calibration of measurements of the voltage generated for at least one type of piezoelectric sensor and at least one type of phase change material during freezing or melting of the phase change material.
[0031] In another further embodiment, mapping said at least one measurement of voltage generated to at least one value indicating the extent of freezing, includes amplification or conditioning of the voltage generated by said at least one piezoelectric sensor.
[0032] In one more embodiment of the method of the present disclosure, multiple piezoelectric sensors are placed at different locations in a container containing the phase change material for more accurate measurement of the extent of freezing.
[0033] In accordance with another aspect of this disclosure, there is provided a system for measuring the extent of freezing in a phase change material, the system comprising at least one piezoelectric sensor placed in a phase change material; a device for measuring the voltage generated by said at least one piezoelectric sensor due to change in pressure caused by freezing or melting of at least a portion of the phase change material; and a converter module for determining the extent of freezing in the phase change material using at least one measurement of the voltage generated.
[0034] The converter module of this system can be implemented using any computing devices such as but not limited to PCs, servers, laptops, notebook computers, tablets, mobile phones, or smart phones whether in standalone mode or connected to other devices.
[0035] In one embodiment, the converter module as described herein above may be implemented as a computer program product.
[0036] In another embodiment, the computer program product is tangibly implemented on a machine readable media.
[0037] The exemplary embodiments of the present disclosure are described in greater detail hereafter with reference to the accompanying exemplary Drawings.
[0038] Piezo-electric materials exhibit the property of generating voltage on application of pressure. The present disclosure is a method and system to measure the ratio of liquid and solid in a phase change material near its freezing/melting point. As a material melts, distance between its molecules increases. During the process of melting, temperature of the entire media remains constant and hence its measurement cannot indicate the required ratio. The measurement is however important in scenarios where a machinery/cooling equipment etc. like in a thermal storage tanks/heat exchanger where a controlled freezing or melting is required.
[0039] The present disclosure uses the fact that the change in intermolecular interaction with phase change produces a change in pressure on a surface submerged in a phase change material. The present disclosure includes a sensor made of suitable piezoelectric material with an exposed surface area that can sustain the pressure of a frozen substance. This piezoelectric sensor produces a voltage output when pressure is applied.
[0040] A piezoelectric sensor may be made of piezoelectric ceramics or single crystal materials or any other material with piezoelectric properties.
[0041] As illustrated in Fig. 1, when mechanical pressure (stress) is applied to a single sheet of piezo-ceramic (piezoelectric sensor) in the longitudinal direction (parallel to polarization), a voltage is generated which tries to return the piece to its original thickness. Similarly, when pressure is applied to a sheet in a transverse direction (perpendicular to polarization), a voltage is generated which tries to return the piece to its original length and width. The surrounding molecules apply pressure to the surface of the transducer which is compressed or flexed which is turn induces electrical generation.
[0042] The voltage generated by a piezoelectric sensor can be measured by a device such as a voltmeter, amplification / conditioning circuit or any other device capable of measuring / detecting voltage.
[0043] In one exemplary embodiment, components of the present disclosure can include a Piezoelectric material, an Amplification/conditioning circuit, and a Controller/Receiver. In an aspect, the system can include a piezoelectric sensor (transducer) that gives a voltage output as the pressure on its surface changes, wherein the piezoelectric sensor can be interfaced with a controller circuit using an intermediate circuit that may include an operational amplifier that converts the voltage output of the transducer to the range in which a controller can take the signal as an input.
[0044] For example, the transducer produces 0 Volts at 0 pressure and 10 Volts at a particular pressure that indicates that the phase change material is completely frozen. The controller is such that it takes 0 to 3 Volts as input. The two ranges can be mapped so that 3 Volts means 10 Volts of transducer output which is equivalent to the maximum pressure.
[0045] The values received by the controller are then post-processed to determine the extent of freezing. The controller can either just send signals to display the percentage of freezing by suitable post processing or can send signal to operate a particular component of a refrigeration or other system in a particular manner.
[0046] The piezoelectric sensor can be placed into the container containing the phase change material. As cooling takes place, the temperature of the liquid phase change material starts dropping. As soon as the temperature reaches the freezing point of the phase change material, latent cooling starts. This means that the liquid phase change material starts converting to solid. From the onset of latent cooling till all liquid converts to solid, the liquid phase and the solid phase co-exist in thermal equilibrium, i.e. the temperature of the media remains constant. Fig. 2 illustrates a piezoelectric sensor (transducer) in a container containing phase change material.
[0047] The inter-molecular distance starts decreasing and the liquid converts to solid. The piezoelectric transducer senses the change in pressure applied (stress) on its surface to determine the amount of freezing. Depending upon the size of the container containing the phase change material and the construction of heat exchanger cooling the material, multiple such transducers can be placed at strategic location in the container for best results. The output from each transducer is post-processed where odd ones may be singled-out and the rest are averaged out to give a fair idea about the extent of freezing (the post processing may be customized according to the application). The selection of the piezoelectric sensor (transducer) is dependent on the maximum amount of intermolecular force produced at maximum freezing. It depends of material properties including density, freezing point etc. The calibration of the sensing and post-processing system would vary with the phase change material in question.
[0048] Piezoelectric materials’ properties vary slightly over a range of temperature. Since, the temperature in case of phase change measurement remains constant, the variation does not have to be taken into account.
[0049] It is required that the relationship (mapping) of variation of voltage with ratio of solid to liquid is known. In order to design a system for a particular phase change material, the system would have to be calibrated accordingly. The pressure is mapped with voltage; the voltage would have to be mapped with the ratio of solid and liquid phases. This is required because different phase change materials would have different intra-molecular structure. The calibration can be done by using known ratios of solid and liquid in a phase change substance and by using the present invention to generate voltage. The voltage can then be mapped to the ratio of solid to liquid.
[0050] In an apsect, it would be appreciated that the method of placement of piezoelectric modules/sensor(s) can affect the nature/variation of the voltage being generated. For instance, in one embodiment/implementation, the piezoelectric sensor can rest flat, wherein, in another aspect/embodiment, it may so happen that one of the edges are attached to a vertical section, wherein the nature of the voltage variation will change but the principle will remain the same. Any other configuration/pattern of incorporating the piezoelectric sensor(s) within the phase change material is well within the scope of the present disclosure. For instance, the piezoelectric sensor(s) can be configured as any or a combination single sheets, multi-layer sheets, 2-layer elements, single/multi layer plates, bend elements, stack motors, multi-layer motors, extenders, stack, series or parallel configuration/operation, X and Y poling configurations, transverse directions, or any other pattern as may be desired.
[0051] In an aspect, the present disclosure has widespread applications, for example, in ice banks in HVAC systems, vaccine storage equipment, cold rooms using eutectic plates, refrigerated transport containers etc.
[0052] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise.
[0053] It will be further understood that the terms "comprises" or "comprising," when used in this specification, specify the presence of stated features, integers, steps, operations, elements, or components, but do not preclude or rule out the presence or addition of one or more other features, integers, steps, operations, elements, components, or groups thereof.
[0054] The use of the expression “at least” or “at least one” suggests the use of one or more elements, as the use may be in one of the embodiments to achieve one or more of the desired objects or results.
[0055] The numerical values mentioned for the various physical parameters, dimensions or quantities are only approximations and it is envisaged that values higher/lower than the numerical values assigned to the parameters, dimensions or quantities fall within the scope of the disclosure, unless there is a statement in the specification specific to the contrary.
[0056] Wherever a range of values is specified, a value up to 10% below and above the lowest and highest numerical value respectively, of the specified range, is included in the scope of the disclosure.
[0057] The process steps, method steps, algorithms or the like may be described in a sequential order, such processes, methods and algorithms may be configured to work in alternate orders. In other words, any sequence or order of steps that may be described does not necessarily indicate a requirement that the steps be performed in that order. The steps of processes described herein may be performed in any order practical. Further, some steps may be performed simultaneously, in parallel, or concurrently.
[0058] The aim of this specification is to describe the invention without limiting the invention to any one embodiment or specific collection of features. Person skilled in the relevant art may realize the variations from the specific embodiments that will nonetheless fall within the scope of the invention.
[0059] It may be appreciated that various other modifications and changes may be made to the embodiment described without departing from the spirit and scope of the invention.

ADVANTAGES OF THE INVENTION:
[0060] The present disclosure provides a method and system for measuring the extent of freezing in a phase change material using piezoelectric sensors.
[0061] The present disclosure provides a method and system for measuring the extent of freezing in a phase change material using piezoelectric sensors that allows different phase change materials & piezoelectric sensors to be used as per requirements.
[0062] The present disclosure provides a method and system for measuring the extent of freezing in a phase change material using piezoelectric sensors that allows the level of freezing during latent cooling to be determined, where temperature measurement does not apply.
[0063] The present disclosure provides a method and system for measuring the extent of freezing in a phase change material using piezoelectric sensors to enable simple and reliable measurement.
,CLAIMS:We Claim:

1. A system for measuring the extent of freezing in a phase change material, the system comprising:
at least one piezoelectric sensor placed in the phase change material;
a device for measuring voltage generated by said at least one piezoelectric sensor due to change in pressure caused by freezing or melting of at least a portion of the phase change material; and
a converter module for determining the extent of freezing in the phase change material using at least one measurement of the voltage generated.
2. The system of claim 1, wherein converter module is implemented using a computing devices selected from any or a combination of a PC, a server, a laptop, a notebook computer, a tablet, a mobile phone, or a smart phone.
3. The system of claim 1, wherein the at least one piezoelectric sensor has an exposed surface area that sustains the pressure of a frozen substance and produces the voltage output when pressure is applied.
4. The system of claim 1, wherein at least one piezoelectric sensor is made of any or a combination of a piezoelectric ceramic or single crystal material.
5. The system of claim 1, wherein the system further comprises an amplification circuit and a controller, wherein the at least one piezoelectric sensor gives the voltage output as the pressure on its surface changes to the controller using an intermediate circuit that comprises the amplification circuit, wherein the amplification circuit converts the voltage output of the at least one piezoelectric sensor to the range in which a controller can take the signal as an input.
6. A method for measuring the extent of freezing in a phase change material, the method comprising the steps of:
placing at least one piezoelectric sensor in a phase change material;
measuring voltage generated by said at least one piezoelectric sensor due to change in pressure caused by freezing or melting of at least a portion of the phase change material; and
determining the extent of freezing in the phase change material using at least one measurement of the voltage generated.
7. The method of claim 6, wherein the phase change material is water or a material capable of freezing and melting by releasing and absorbing heat respectively.
8. The method of claim 6, wherein the step of determining the extent of freezing comprises the step of mapping said at least one measurement of voltage generated to at least one value indicating the extent of freezing, wherein the mapping is enabled by calibration of measurements of the voltage generated for at least one type of piezoelectric sensor and at least one type of phase change material during freezing or melting of the phase change material.
9. The method of claim 8, wherein mapping said at least one measurement of voltage generated to the at least one value indicating the extent of freezing comprises amplification or conditioning of the voltage generated by said at least one piezoelectric sensor.
10. The method of claim 6, wherein multiple piezoelectric sensors are placed at different locations in a container containing the phase change material for measurement of the extent of freezing.