CN219532988U - Heat conduction generating device and heat conductivity coefficient measuring system - Google Patents

Abstract

The utility model discloses a heat conduction generating device, which comprises a heat conduction generating device cavity, a heating component and a temperature measuring component. The surface of the cavity is provided with a liquid injection opening through which normal-temperature liquid can be injected into the space inside the cavity; the heating component comprises a first heating plate and a second heating plate which are both in a flat plate-shaped structure and are used for heating; the first heating plate and the second heating plate are arranged in the cavity body space in parallel with each other; the temperature measuring part comprises first to third temperature measuring parts which are all arranged in the inner space of the cavity and are used for measuring temperature; the first temperature measuring part is arranged on the plane where the first heating plate is arranged, the second temperature measuring part is arranged on the plane where the second heating plate is arranged, and the third temperature measuring part is arranged on the parallel bisecting plane between the first heating plate and the second heating plate. The utility model designs a heat conduction generating device integrating freezing, heating and temperature measurement by utilizing the principle of a classical heat transfer model, and can conveniently measure the heat conductivity coefficient of a normal-temperature liquid substance in a low-temperature solid state.

Description

Heat conduction generating device and heat conductivity coefficient measuring system

Technical Field

The utility model relates to the technical field of thermal property measurement, in particular to a heat conduction generating device and a heat conductivity coefficient measuring system.

Background

Thermal conductivity is the ability of an object to conduct heat, also known as thermal conductivity. Defined as the amount of heat transferred per unit of heat conducting surface per unit of time per unit of temperature gradient (1K temperature decrease over a length of 1 m). The units are watts per meter Kelvin [ W/(mK) ], where K can be replaced by C. The method for measuring the heat conductivity coefficient has been developed in various fields, measuring ranges, precision, accuracy, sample size requirements and the like, and the measuring results of the same sample may be greatly different by different methods, so that the selection of a proper testing method is primary.

The research on the heat conductivity coefficient of normal temperature liquid substances (substances which are generally liquid at the normal temperature of 25 ℃ and are such as water, ethanol, methanol, bromine, mercury, pentane and the like), especially water in the low-temperature solid state, has important application value in refrigeration and the like. At present, the measurement method of the heat conductivity coefficient of the normal temperature liquid substance in the low temperature solid state can be classified into a steady state method, a quasi-steady state method and an unsteady state method. However, steady state methods tend to take longer measurements than the other two methods and require that the temperature field does not change over time. The melting point of the normal-temperature liquid is lower than the ambient temperature under the normal pressure in most cases, so that the overlong measurement time is very easy to expand the heat transfer from the ambient environment to the normal-temperature liquid in the low-temperature solid state, the heat of the normal-temperature liquid is difficult to quantitatively measure, and finally the accuracy of the measured value is influenced. Although the heating time of the unsteady state method is short, the error is larger, the requirement on the sensitivity of the instrument is higher, and the heating method has a plurality of limitations. Therefore, there is a need to develop a technical means for measuring the thermal conductivity of a liquid at normal temperature in a solid state at low temperature, which is more accurate and shorter in time and has no high requirement on the instrument.

Disclosure of Invention

In view of at least one of the drawbacks or the improvements of the prior art mentioned in the background section, the present utility model provides a heat conduction generating device for realizing a more accurate measurement, a shorter time and a less demanding technical means for measuring the thermal conductivity of a liquid at room temperature in a low temperature solid state.

To achieve the above object, in a first aspect, the present utility model provides a heat conduction generating apparatus comprising: a heat conduction generating device cavity, a heating component and a temperature measuring component;

the surface of the cavity of the heat conduction generating device is provided with a liquid injection opening through which normal-temperature liquid can be injected into the inner space of the cavity of the heat conduction generating device;

the heating component comprises a first heating plate and a second heating plate which are both in a flat plate structure and are used for heating; the first heating plate and the second heating plate are arranged in parallel with each other in the inner space of the cavity of the heat conduction generating device;

the temperature measuring parts comprise a first temperature measuring part, a second temperature measuring part and a third temperature measuring part which are all arranged in the inner space of the cavity of the heat conduction generating device and are used for measuring temperature; the first temperature measuring component is arranged at the plane where the first heating plate is located, the second temperature measuring component is arranged at the plane where the second heating plate is located, and the third temperature measuring component is arranged at the parallel bisection plane between the first heating plate and the second heating plate.

Further, the inner space of the cavity of the heat conduction generating device is a column with an equal cross section; the first heating plate and the second heating plate are parallel and completely cover the cross section of the inner space of the cavity of the heat conduction generating device.

Further, the inner space of the cavity of the heat conduction generating device is a cylinder.

Further, the cross-sectional diameter of the inner space of the heat conduction generating apparatus cavity is not less than 6 times the spacing between the first heating plate and the second heating plate.

Further, the first heating sheet and the second heating sheet are polyimide heating films.

Further, the temperature measuring part is a PT100 temperature sensor.

In a second aspect, the present utility model provides a thermal conductivity measurement system comprising a heating power supply, a temperature transmitter, a data processor and a thermal conductivity generation device according to any one of the preceding claims;

the heating power supply is used for providing electric energy for the heating component;

the temperature transmitter is used for converting the temperature signal acquired by the temperature measuring component into a transportable standardized output signal;

the data processor is used for analyzing the standardized output signal and obtaining the heat conductivity coefficient of the normal-temperature liquid substance in the low-temperature solid state through data operation processing.

Further, the device also comprises a heat preservation device;

the heat preservation device wraps the heat conduction generating device in the heat preservation device so as to preserve heat of a heat conduction process occurring in the heat conduction generating device.

In general, the above technical solutions conceived by the present utility model, compared with the prior art, enable the following beneficial effects to be obtained:

the device or the system designs a heat conduction generating device integrating freezing, heating and temperature measurement by utilizing the principle of a classical one-dimensional quasi-steady-state heat conduction model, and can conveniently measure the heat conductivity coefficient of a normal-temperature liquid substance in a low-temperature solid state by utilizing the heat conduction generating device, so that the measurement is more accurate, the time is shorter and the device has no high requirement on instruments.

Drawings

In order to more clearly illustrate the technical solutions of the embodiments of the present utility model, the drawings that are required to be used in the embodiments will be briefly described below, and it is apparent that the drawings in the following description are only some embodiments of the present utility model, and other drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.

FIG. 1 is a schematic diagram of a one-dimensional quasi-steady-state thermal conduction model provided by an embodiment of the utility model;

fig. 2 is a schematic plan view of a heat conduction generating apparatus according to an embodiment of the present utility model;

fig. 3 is a schematic perspective view of a heat conduction generating device according to an embodiment of the present utility model;

fig. 4 is a schematic structural diagram of a thermal conductivity measurement system according to an embodiment of the present utility model.

Detailed Description

The present utility model will be described in further detail with reference to the drawings and examples, in order to make the objects, technical solutions and advantages of the present utility model more apparent. It should be understood that the specific embodiments described herein are for purposes of illustration only and are not intended to limit the scope of the utility model. In addition, the technical features of the embodiments of the present utility model described below may be combined with each other as long as they do not collide with each other.

The terms first, second, third and the like in the description and in the claims or in the above drawings, are used for distinguishing between different objects and not necessarily for describing a sequential or chronological order. Furthermore, the terms "comprising," "including," and "having," and any variations thereof, are intended to cover a non-exclusive inclusion. For example, a process, method, system, article, or apparatus that comprises a list of steps or elements is not limited to only those listed or inherent to such process, method, article, or apparatus but may alternatively include other steps or elements not listed or inherent to such process, method, article, or apparatus.

The study of the heat conductivity of the normal temperature liquid (the substances which are generally liquid at the normal temperature of 25 ℃ and such as water, ethanol, methanol, bromine, mercury, pentane and the like), particularly the study of the heat conductivity of water in the low temperature solid state has important application value in refrigeration and the like, so the utility model takes water as one embodiment of the normal temperature liquid to describe the measurement means of the heat conductivity of the water in the low temperature solid state (namely, ice) in detail, and the measurement means of the heat conductivity of other normal temperature liquid in the low temperature solid state are similar and are not repeated.

At present, the measurement method of the heat conductivity coefficient of ice can be classified into a steady state method, a quasi-steady state method and an unsteady state method. However, steady state methods tend to take longer measurements than the other two methods and require that the temperature field does not change over time. The melting point of ice under normal pressure is lower than the ambient temperature in most cases, so that the heat transfer from the ambient environment to the ice is extremely easy to expand due to the overlong measurement time, the quantitative measurement of the heat is difficult, and the accuracy of the measured value is finally affected. Although the unsteady state method has short heating time, the error is larger, the requirement on the sensitivity of the instrument is higher, and the heating method has a plurality of limitations. Based on the state of the art, the utility model provides a method for measuring the thermal conductivity coefficient of ice based on a quasi-steady state method, which has the advantages of more accurate measurement, shorter time and no high requirement on instruments, thereby achieving the effect of compromise.

Referring to the one-dimensional quasi-steady state thermal conduction model schematic diagram of fig. 1, according to the conduction equation, for a flat plate with thickness of 2b and radius of infinity r in a quasi-steady state stage of planar thermal solution in an infinite object, when heating with constant power as planar heat source on the whole plane, the temperature change only occurs in the X direction.

According to the one-dimensional heat conduction differential equation:

given the boundary values, any instantaneous temperature distribution along the direction perpendicular to the ice layer can be solved.

The boundary conditions under the heat source conditions are as follows:

when t=0, T (x, 0) =t ₀ =constant;

at x=b and,x=0, ++>

Wherein t is time; b is the thickness of the flat sample; t (x, 0) is the temperature at which the ice layer is in the x position, time t=0; t (x, T) is the instantaneous temperature of the ice layer at the x position for a time T; q _C The heat flow was heated for constant power, equal to a constant under experimental conditions.

Solving the one-dimensional heat conduction differential equation to obtain the general solution of the temperature distribution along the vertical direction of the ice layer at any moment, wherein the general solution is as follows:

wherein a is the heat conduction diffusion coefficient of ice, which satisfies the following conditions:

F ₀ the fourier standard is satisfied:

the method comprises the following steps:

from the general solution, at x=0, the change over time of T (0, T) is:

in the above formula for different F ₀ Value of F ₀ More than or equal to 0.5, i.eThe number of stages in the equation is very small and negligible. The parabolic vertex of the temperature distribution within the plate is at x=0, and the temperature at any point within the plate is a linear function of time. The temperature difference between any two points is a constant number independent of time, namely:

according to the above equation, the excess temperature at the center point for the quasi-steady state phase is:

the excess temperature on the boundary heating surface is:

the temperature difference between the center point and the boundary heating surface is:

the relationship that the thermal conductivity is calculated to be satisfied is:

based on the technical principle related to the one-dimensional quasi-steady-state heat conduction model of the device or the system, the central idea of the design of the ice heat conduction coefficient measurement system is as follows: designing an integrated heat conduction generating device for measuring temperature by using a heating film as a plane heat source and a temperature sensor; the temperature sensor PT100 is used as a temperature sensor (the temperature sensor PT100 is a resistance type temperature sensor made of platinum (Pt)), the sensor is connected with a temperature transmitter, the transmitter is connected with a PC end processor, a regulated power supply supplies power to a heating film and a foam box is used for preserving heat of a heat conduction generating device, so that temperature changes of different positions at each moment can be observed, and the heat conductivity coefficient of ice is measured. A schematic structural diagram of the ice thermal conductivity measurement system is shown in fig. 4.

The respective core components of the ice thermal conductivity measuring system are described below.

(1) Heat conduction generating device

The experimental device for measuring the heat conductivity coefficient of the ice is different from the experimental device for measuring the heat conductivity coefficient of solid materials such as rubber, resin and the like, namely, the heat conductivity coefficient of the ice is measured more complicated. The second reason is that the ice is made by freezing distilled water to ice at about-40 ℃ and converting the distilled water from liquid state to solid state, and the ice needs to be supported by a container all the time in the process and the experiment; secondly, the experimental range of ice temperature is low. In experiments, the ice should be prevented from being exposed to the air as much as possible, so that the heat preservation work is important, and the ice needs to be tightly wrapped by the heat preservation material to minimize errors.

Therefore, in order to reduce the difficulty of measuring the thermal conductivity of ice, one embodiment of the present utility model designs an integrated heat conduction generating apparatus, as shown in fig. 2. According to the principle model, the whole ice block is regarded as four parts, a film heating plate is preset at the positions of 1/4 and 3/4 of the thickness, and a sticking type temperature sensor is preset at the positions of 1/4,1/2 and 3/4 of the thickness. A suitable device model with an outer layer of ice pieces wrapped is made using solidworks. In order to enable the heating plate to form a more uniform temperature field, preferably, the heat conduction generating device adopts a cylindrical structure, as shown in fig. 3, a narrow slit is formed in the side face of the cylinder, water can be poured into the cylindrical structure from the narrow slit, a clamping groove is formed in the narrow slit, a heating plate and a temperature sensor can be fixed, the distance between the two heating plates is 2b, and the distance between the heating plate and the nearest cylindrical bottom face of the heating plate is b.

In practice, as long as referring to the one-dimensional quasi-steady-state heat conduction model of fig. 1, two thin film heating plates are designed to be parallel, and then a temperature sensor is respectively arranged at the plane where the two thin film heating plates are located and at the parallel bisection plane between the two thin film heating plates, the technical principle of the one-dimensional quasi-steady-state heat conduction model can be utilized for measurement to obtain the heat conductivity coefficient of ice. The two thin film heating plates are not necessarily parallel to the cylindrical bottom surface, and are not necessarily spaced apart from the nearest cylindrical bottom surface by a distance b. Furthermore, the heat conduction generating apparatus does not have to adopt a cylindrical structure, and may adopt a cross-sectional column such as a triangular column, a rectangular column, or the like. The two thin film heating plates are parallel and completely cover the cross section of the internal space of the heat conduction generating device, so that a more uniform temperature field can be realized. The heat conduction generating apparatus is finally designed as the structure of fig. 2 and 3 because it is more regular, easier to calculate and deduce, and easier to design and manufacture.

In addition, the diameter of the ice blocks needs to be larger than the total thickness of the ice layers as much as possible, namely, the diameter of the ice blocks is more than 6 times of 2b (the distance between two heating plates) so as to be approximate to an infinite flat plate model, and the difficulty of freezing the ice blocks needs to be reduced as much as possible, so that water leakage and other conditions are prevented. If the cross section of the heat conduction generating device is in other non-circular shapes, the ice block diameter is still as large as possible as the total thickness of the ice block, and the ice block can be approximated to an infinite flat plate model only when the spacing between the two farthest points of the other shapes is more than 6 times of the spacing of 2 b.

And finally, a physical object can be manufactured by utilizing a 3D printing technology. The heating plate and the temperature sensor are preset and fixed, distilled water is added, the heating plate and the temperature sensor are placed into a refrigerator to be frozen and molded, and then the heating plate and the temperature sensor are transferred to dry ice to be frozen to a lower temperature, so that the integrated heat conduction generating device with measurement can be obtained.

(2) Temperature transmitter

The thermocouple and the thermal resistor are adopted as temperature measuring elements (temperature sensors), temperature signals are output from the temperature measuring elements and sent to a transmitter module, and after being processed by circuits such as voltage stabilizing filtering, operational amplification, nonlinear correction, V/I conversion, constant current and reverse protection, the signals are converted into transportable standardized output signals (4-20A current signals and 0-5V/0-10V voltage signals which are in linear relation with temperature), and RS485 digital signals are output.

(3) Thermal insulation container

The heat-insulating container in the embodiment consists of foam, a square cavity with the right size is dug in the heat-insulating container, the heat conduction generating device can be wrapped by the square cavity, and the additional size just meets the requirement of a foam plug capable of leading out a lead. In experiments, the ice should be prevented from being exposed to air as much as possible, so that the heat preservation work is important, and therefore, it is preferable that the heat conduction generating device is tightly wrapped by the heat preservation material to minimize measurement errors.

The working principle of the ice heat conductivity coefficient measuring system is as follows: the polyimide heating film heats the contacted ice layers, the heating power of each side of the ice layers is 0.5 times of the rated power of the ice layers, the PT100 temperature sensor collects the temperature of the contact point, temperature data are recorded, a temperature curve is drawn, text data can be derived after the measurement is completed, and matlab is imported for data analysis. The process of measuring the thermal conductivity of ice may mainly include the following steps.

(1) Firstly, a heat conduction generating device is manufactured, namely a polyimide heating plate is preset in a cylindrical water container with a narrow slit, distilled water is poured into the cylindrical water container through a clamping groove to fix the position, and a temperature sensor is arranged in the cylindrical water container to fix the cylindrical water container.

(2) The heat transfer generating device is placed in a refrigerator, after it solidifies into ice, and transferred to a dry ice environment for freezing to a desired lower temperature.

(3) And (3) connecting a circuit, connecting the polyimide heating plate to a regulated power supply, connecting a temperature sensor to a temperature transmitter, and connecting the other end of the transmitter to a computer processor.

(4) After the line inspection is confirmed to be correct, the heat conduction generating device is taken out of the dry ice, placed into a foam box with proper size, the position of the lead is adjusted, and the other foam block is covered (the lead outlet is reserved).

(5) And (5) switching on the stabilized voltage power supply to regulate the voltage to 24V, and observing the temperature change at the display end of the computer processor. Note that since the temperature rise is slow, a waiting for tolerance is required.

(6) And (3) ending the experiment before the temperature rises to 0 ℃, stopping temperature measurement, and turning off the power supply of each device.

(7) And drawing a lambda-delta T curve, wherein delta T is the result obtained by taking the average value of temperatures at 1/4 and 3/4 of the ice thickness of the sample and the temperature of the intermediate layer, and lambda is the heat conductivity coefficient.

To find critical time conditions meeting the experimental model, i.e. F ₀ When the temperature difference is more than or equal to 0.5, the temperature difference can be regarded as a constant value, and the heat conductivity coefficient is obtained to obtain t ₀ And not less than 42.96s, and only analyzing the result after 43 seconds.

In order to be similar to the condition of an infinite flat plate established by a one-dimensional quasi-steady-state heat conduction model as far as possible, the ice layer should be as thin as possible, but the influence of the probe thickness of the temperature sensor is reduced as far as possible in actual operation, and b=10mm is achieved by integrating all factors; s is the cross section area of the heat conduction generating device, and the diameter of the cross section is set to be 100mm; the voltage and current values of the polyimide heating film during heating are seen according to the regulated power supply, and the heating power is calculated, so that the constant q can be obtained _c The method comprises the steps of carrying out a first treatment on the surface of the Since the polyimide heating film has a heat conversion of about 50% and a power of 15W, the polyimide heating film has a heat conversion of about

Due to the formula derived previouslyIt is known that the difference between the average value of the temperatures at 1/4 and 3/4 of the thickness of the ice layer and the temperature of the intermediate layer is obtained, and the thermal conductivity of ice in the temperature environment can be obtained.

The device or the system designs a heat conduction generating device integrating freezing, heating and temperature measurement by utilizing the principle of a classical one-dimensional quasi-steady-state heat conduction model, and can conveniently measure the heat conductivity coefficient of a normal-temperature liquid substance in a low-temperature solid state by utilizing the heat conduction generating device, so that the measurement is more accurate, the time is shorter and the device has no high requirement on instruments.

The foregoing is merely exemplary embodiments of the present disclosure and is not intended to limit the scope of the present disclosure. That is, equivalent changes and modifications are contemplated by the teachings of this disclosure, which fall within the scope of the present disclosure. Other embodiments of the disclosure will be apparent to those skilled in the art from consideration of the specification and practice of the disclosure herein. This application is intended to cover any variations, uses, or adaptations of the disclosure following, in general, the principles of the disclosure and including such departures from the present disclosure as come within known or customary practice within the art to which the disclosure pertains. It is intended that the specification and examples be considered as exemplary only, with a scope and spirit of the disclosure being indicated by the claims.

The technical features of the above embodiments may be arbitrarily combined, and all possible combinations of the technical features in the above embodiments are not described for brevity of description, however, as long as there is no contradiction between the combinations of the technical features, they should be considered as the scope of the description.

It will be readily appreciated by those skilled in the art that the foregoing description is merely a preferred embodiment of the utility model and is not intended to limit the utility model, but any modifications, equivalents, improvements or alternatives falling within the spirit and principles of the utility model are intended to be included within the scope of the utility model.

Claims (8)

1. A heat conduction generating apparatus, comprising: a heat conduction generating device cavity, a heating component and a temperature measuring component;

the surface of the cavity of the heat conduction generating device is provided with a liquid injection opening through which normal-temperature liquid can be injected into the inner space of the cavity of the heat conduction generating device;

the heating component comprises a first heating plate and a second heating plate which are both in a flat plate structure and are used for heating; the first heating plate and the second heating plate are arranged in parallel with each other in the inner space of the cavity of the heat conduction generating device;

the temperature measuring parts comprise a first temperature measuring part, a second temperature measuring part and a third temperature measuring part which are all arranged in the inner space of the cavity of the heat conduction generating device and are used for measuring temperature; the first temperature measuring component is arranged at the plane where the first heating plate is located, the second temperature measuring component is arranged at the plane where the second heating plate is located, and the third temperature measuring component is arranged at the parallel bisection plane between the first heating plate and the second heating plate.

2. The heat transfer and generation apparatus of claim 1, wherein the interior space of the heat transfer and generation apparatus cavity is a constant cross-section cylinder; the first heating plate and the second heating plate are parallel and completely cover the cross section of the inner space of the cavity of the heat conduction generating device.

3. The heat transfer and generator of claim 2, wherein the interior space of said heat transfer and generator chamber is cylindrical.

4. A heat transfer and generator as claimed in claim 3, wherein the cross-sectional diameter of the interior space of the heat transfer and generator chamber is not less than 6 times the spacing between the first and second heating plates.

5. The heat transfer generator of claim 1, wherein said first heating plate and said second heating plate are polyimide heating films.

6. The heat conduction generating apparatus of claim 1, wherein the temperature measuring part is a PT100 temperature sensor.

7. A thermal conductivity measurement system comprising a heating power supply, a temperature transmitter, a data processor, and the thermal conductivity generation device of any one of claims 1 to 6;

the heating power supply is used for providing electric energy for the heating component;

the temperature transmitter is used for converting the temperature signal acquired by the temperature measuring component into a transportable standardized output signal;

the data processor is used for analyzing the standardized output signal and obtaining the heat conductivity coefficient of the normal-temperature liquid substance in the low-temperature solid state through data operation processing.

8. The thermal conductivity measurement system according to claim 7, further comprising a thermal insulation device;

the heat preservation device wraps the heat conduction generating device in the heat preservation device so as to preserve heat of a heat conduction process occurring in the heat conduction generating device.