Test device and calculation method for determining thermal conductivity of ice based on steady-state method

Abstract

The application discloses a testing device and a calculation method for determining the thermal conductivity of ice based on a steady-state method, and belongs to the technical field of ice thermal conductivity measurement. The application discloses a testing device and a calculation method for determining the thermal conductivity of ice based on a steady-state method, and belongs to the technical field of ice thermal conductivity measurement.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of thermal conductivity coefficient measurement of ice, and particularly relates to a testing device and a calculation method for measuring the thermal conductivity coefficient of ice based on a steady-state method. BACKGROUND

[0002] Heat conduction phenomenon is widespread in nature, and the ability of a material to transfer heat is measured by the thermal conductivity coefficient, which is an important thermal property of a material. The thermal conductivity coefficient refers to the heat passing through a unit area per unit time under the condition of stable heat transfer, with a unit temperature difference on both sides of a unit thickness of the material.

[0003] For the measurement method of the thermal conductivity coefficient, the main research methods are the steady-state method and the transient method. The steady-state method establishes a temperature field that does not change with time, while the temperature field in the transient method is non-constant. The steady-state method has a simple test principle, high accuracy and repeatability, and it takes a long time to build a stable temperature gradient, thus having a long test period.

[0004] In the existing steady-state method for measuring the thermal conductivity coefficient of ice, the ice is gradually heated. Since the test period is relatively long, the ice will gradually melt during the heating process, resulting in that the measured thermal conductivity coefficient is not only the ice but also the ice-water mixture, and thus the measured thermal conductivity coefficient is inaccurate. SUMMARY

[0005] In order to overcome the deficiencies in the prior art, the application provides a testing device and a calculation method for measuring the thermal conductivity coefficient of ice based on a steady-state method, which aims to solve the technical problem of how to change the existing calculation method of the thermal conductivity coefficient of ice and make the calculation of the thermal conductivity coefficient applicable to actual experiments.

[0006] In order to achieve the above-mentioned purpose, the testing device for measuring the thermal conductivity coefficient of ice based on a steady-state method comprises an adiabatic cylinder, a semiconductor refrigeration sheet fixed on the inner wall of the adiabatic cylinder, and an adiabatic body fixed on the upper surface wall of the semiconductor refrigeration sheet. An experimental hole is formed in the adiabatic body and penetrates the adiabatic body in the vertical direction. The end surface of the experimental hole is circular. The testing device further comprises a first metal film sensor and a second metal film sensor for measuring the temperature of the ice in the experimental hole and the temperature of the semiconductor refrigeration sheet, respectively. The testing device further comprises a metal sheet, the projection of which on the horizontal plane exactly covers the projection of the experimental hole on the horizontal plane. The testing device further comprises a temperature sensor for monitoring the temperature of the metal sheet and a stopwatch for monitoring the cooling time of the metal sheet.

[0007] Further, a layer of asbestos is fixed on the inner wall of the adiabatic cylinder, and the semiconductor refrigeration sheet is fixed on the inner wall of the asbestos layer.

[0008] The asbestos layer can effectively prevent heat dissipation of the outer edge of the semiconductor refrigeration sheet, so that the refrigeration efficiency of the semiconductor refrigeration sheet is higher.

[0009] Further, the upper end surface wall of the heat insulation cylinder is above the semiconductor refrigeration sheet, and the upper end surface wall of the heat insulation cylinder is above the upper end surface wall of the heat insulator.

[0010] The heat insulation cylinder has better wrapping effect on semiconductor refrigeration, slows down the temperature loss of the semiconductor refrigeration sheet in the air, and makes the refrigeration utilization rate of the semiconductor refrigeration sheet higher.

[0011] Further, the metal sheet is an aluminum sheet with a thickness of 1mm.

[0012] The aluminum sheet is easy to obtain; secondly, the specific heat capacity of the aluminum sheet is known, and the thickness of 1mm is to ignore the heat dissipation of the side surface of the aluminum sheet, which is convenient for subsequent calculation.

[0013] The calculation method for determining the thermal conductivity of ice based on the steady-state method comprises the following steps:

[0014] S1: pour water into the experimental hole, use the semiconductor refrigeration sheet to cool the water, and make the water into ice; place the metal sheet above the ice, and the lower surface wall of the metal sheet is attached to the upper surface wall of the ice;

[0015] S2: use the first metal film sensor and the second metal film sensor to monitor the temperature of the ice and the temperature of the semiconductor refrigeration sheet respectively; when the temperature of the ice and the temperature of the semiconductor refrigeration sheet no longer change, use the first metal film sensor and the second metal film sensor to record the temperature T1 of the ice and the temperature T2 of the semiconductor refrigeration sheet respectively; use the temperature sensor to record the temperature T of the metal sheet at this time;

[0016] S3: take the metal sheet off the ice and place it on the upper surface wall of the semiconductor refrigeration sheet, use the temperature sensor to monitor the temperature t of the metal sheet again, and use the stopwatch to record the cooling time s, and establish a curve of time s and temperature t;

[0017] S4: in the curve, calculate the slope n of the curve when the temperature is T; and bring it into the calculation formula of the thermal conductivity of ice:

[0018]

[0019] Wherein, c is the specific heat capacity of the metal sheet; m is the mass of the metal sheet; l is the thickness of the ice; n is the slope of the curve when the temperature is T; ΔT is T2-T1; d is the diameter of the metal sheet.

[0020] Beneficial effects:

[0021] The device and method for calculating the thermal conductivity of ice adopts a cooling process. Compared with the existing steady-state method, the ice in the device and method will not appear in the state of ice-water mixture due to long-term heating in the steady-state method, so the measured thermal conductivity of ice will not be inaccurate due to ice-water mixture. BRIEF DESCRIPTION OF DRAWINGS

[0022] Figure 1 is a structural schematic diagram of the whole device;

[0023] Figure 2 is a structural schematic diagram of the metal film sensor;

[0024] Figure 3 is a structural schematic diagram of the device measuring the temperature of the aluminum sheet covering the ice;

[0025] Figure 4 is a graph of the temperature change of the aluminum sheet placed on the semiconductor refrigeration sheet over time.

[0026] 1, adiabatic cylinder; 2, asbestos layer; 3, semiconductor refrigeration sheet; 4, thermal insulation; 5, experimental hole; 6, aluminum sheet; 7, second metal film sensor; 8, power supply device; 9, support; 10, wire; 11, metal platinum sensing sheet; 12, stopwatch; 13, temperature sensor. DETAILED DESCRIPTION

[0027] In order to make the purpose, technical scheme and advantages of the embodiments of the present application clearer, the technical scheme of the present application will be described clearly and completely below with reference to the drawings. Obviously, the described embodiments are part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0028] The test device for determining the thermal conductivity of ice based on the steady-state method comprises an adiabatic cylinder 1. In this embodiment, the adiabatic cylinder 1 is a square cylinder with a square frame-shaped end face, and only the upper surface wall is missing. In other embodiments, it can also be other shapes. The lower surface wall of the adiabatic cylinder 1 is fixed with a support 9 for supporting the adiabatic cylinder 1. The inner wall of the adiabatic cylinder 1 is attached with an asbestos layer 2, which wraps the inner wall of the adiabatic cylinder 1. In this embodiment, the thickness of the asbestos layer 2 is 25 mm, and in other embodiments, it can also be other thicknesses, for making the adiabatic cylinder 1 have the function of thermal insulation.

[0029] The inner wall of the asbestos layer 2 is fixed with a semiconductor refrigeration sheet 3. The cold end of the semiconductor refrigeration sheet 3 is in the adiabatic cylinder 1, and the hot end is outside the adiabatic cylinder 1. The cold end of the semiconductor refrigeration sheet 3 is shown in the attached drawings. The size of the cold end in this embodiment is 20cm*20cm*14cm. The adiabatic cylinder 1 is fixed with a power supply device 8 for supplying power to the semiconductor refrigeration sheet 3. The outer wall of the semiconductor refrigeration sheet 3 is in close contact with the inner wall of the asbestos layer 2. The upper end surface of the semiconductor refrigeration sheet 3 is lower than the upper end surface of the adiabatic cylinder 1.

[0030] The upper end surface of the semiconductor refrigeration sheet 3 is fixed with an adiabatic body 4 made of asbestos. The adiabatic body 4 is in the shape of a cylinder, and the axis of the adiabatic body 4 is in the vertical direction. The lower end surface of the adiabatic body 4 is in close contact with the upper end surface of the semiconductor refrigeration sheet 3. The upper end surface of the adiabatic body 4 is lower than the upper end surface of the adiabatic cylinder 1. In this embodiment, the adiabatic body 4 is arranged at the center of the semiconductor refrigeration sheet 3. In this embodiment, an experimental hole 5 is formed in the adiabatic body 4. The experimental hole 5 is in the shape of a cylindrical hole, and the axis of the experimental hole 5 coincides with the axis of the adiabatic body 4. The upper and lower ends of the experimental hole 5 penetrate the upper and lower surfaces of the adiabatic body 4. The diameter of the experimental hole 5 is 200mm, and the height is 5mm.

[0031] The experimental device also includes an aluminum sheet 6 in the shape of a disc. The diameter of the aluminum sheet 6 is 200mm, which is consistent with the diameter of the experimental hole 5. In this embodiment, the thickness of the aluminum sheet 6 is 1mm, and in other embodiments, it can also be of other thicknesses.

[0032] The experimental device also includes two metal film sensors, which are referred to as a first metal film sensor and a second metal film sensor 7. As shown in Figure 2 , the metal film sensor includes a metal platinum sensing sheet 11 and a wire 10. The metal film sensor is connected to a display device through the wire 10, and the temperature can be displayed. The first metal film sensor is arranged in the experimental hole 5, i.e., the adiabatic body 4 is arranged on the first metal film sensor (not shown), and the first metal film sensor does not contact the semiconductor refrigeration sheet 3. The first metal film sensor is used to monitor the temperature of the ice. The second metal film sensor 7 is fixed on the cold end of the semiconductor refrigeration sheet 3, and is used to monitor the temperature of the cold end of the semiconductor refrigeration sheet 3.

[0033] As shown in Figure 3 , the experimental device also includes a temperature sensor 13 and a stopwatch 12. The model of the temperature sensor 13 is TM-902C, and the temperature measurement range is from -50 degrees Celsius to 1300 degrees Celsius. The temperature sensor 13 is used to monitor the temperature of the aluminum sheet.

[0034] This embodiment also includes a calculation method for determining the thermal conductivity of ice based on the steady-state method, which is used in cooperation with the above-mentioned experimental device. The calculation method includes the following steps:

[0035] S1: pour water into the experimental hole, cool the water with a semiconductor refrigeration sheet, make the water into ice, the ice is uniform in texture and cylindrical, the thickness of the ice layer is 5mm; place an aluminum sheet above the ice, the axis of the aluminum sheet coincides with the axis of the experimental hole, the lower surface wall of the aluminum sheet is attached to the upper surface wall of the ice, the aluminum sheet is used to prevent the ice surface from contacting air; the semiconductor refrigeration sheet continuously maintains cooling;

[0036] S2: use the first metal film sensor and the second metal film sensor to monitor the temperature of the ice and the temperature of the semiconductor refrigeration sheet respectively; when the temperature of the ice and the temperature of the semiconductor refrigeration sheet no longer change, use the first metal film sensor and the second metal film sensor to record the temperature T1 of the ice and the temperature T2 of the semiconductor refrigeration sheet respectively; use the temperature sensor to record the temperature T of the aluminum sheet at this time;

[0037] S3: take the aluminum sheet off the ice and place it on the upper surface wall of the semiconductor refrigeration sheet, the axis of the aluminum sheet is arranged vertically; the semiconductor refrigeration sheet continuously maintains cooling, use the temperature sensor to monitor the temperature t of the aluminum sheet again, and use the stopwatch to record the time s of cooling, and establish a curve of time s and temperature t;

[0038] S4: in the curve, calculate the slope n of the curve when the temperature is T. Substitute into the formula for calculating the thermal conductivity of ice:

[0039]

[0040] wherein c is the specific heat capacity of the aluminum sheet; m is the mass of the aluminum sheet; l is the thickness of the ice, which is 5mm in this embodiment; n is the slope of the curve when the temperature is T; ΔT is the temperature of the refrigeration sheet monitored by the second metal film sensor, minus the temperature of the aluminum sheet monitored by the temperature sensor; d is the diameter of the aluminum sheet.

[0041] The principle of this embodiment is that:

[0042] According to Fourier's law, when the first metal film sensor monitors that the temperature of the ice no longer changes, and at the same time, the temperature of the refrigeration sheet monitored by the second metal film sensor also does not change, this is the steady temperature field, the temperature of the aluminum sheet monitored by the temperature sensor at this time is T1, and the temperature of the semiconductor refrigeration sheet is T2. The heat flowing through the ice is equal to the heat dissipation amount of the aluminum sheet placed alone on the semiconductor refrigeration sheet, that is, φ O = cmn, c is the specific heat capacity of the aluminum sheet, m is the mass of the aluminum sheet, and n is the slope at the steady temperature T1;

[0043] The ratio of the heat flowing through the ice to the heat of the aluminum sheet is 1; by substituting 1 and cmn into the Fourier's law formula, the thermal conductivity can be solved as ΔT is T2-T1; l is the thickness of the ice; S is the heat dissipation area of the aluminum sheet; and d is the diameter of the aluminum sheet.

[0044] According to the test conditions of the embodiment, the temperature T of the aluminum sheet in S2 is -4℃. In S3, the curve of s and temperature t is measured as shown in Figure 4 Table 1. In which, the measured data of time s and temperature t are shown in Table 1:

[0045] Table 1: Corresponding relationship between time s and temperature t

[0046]

[0047]

[0048] The calculated slope n is 0.1085 when the temperature is -4℃, and the calculated thermal conductivity of ice is about 2.4.

[0049] Based on the above ideal embodiments according to the present application, through the above description, relevant personnel can make various changes and modifications without deviating from the technical idea of the present application. The technical scope of the present application is not limited to the content of the specification, and must be determined according to the scope of the claims.

Claims

1. A testing device for determining the thermal conductivity of ice based on the steady-state method, characterized in that, The inner wall of the heat insulation cylinder is fixed with a semiconductor refrigerating sheet, and the upper surface wall of the semiconductor refrigerating sheet is fixed with an insulator; the insulator is provided with an experimental hole penetrating through the insulator in the vertical direction; the end surface of the experimental hole is circular; The test device further comprises a first metal film sensor and a second metal film sensor for measuring the temperature of the ice in the experimental hole and the temperature of the semiconductor refrigerating sheet, respectively; The test device further comprises a metal sheet, the projection of the metal sheet on a horizontal plane exactly covers the projection of the experimental hole on the horizontal plane; the test device further comprises a temperature sensor for monitoring the temperature of the metal sheet and a stopwatch for monitoring the cooling time of the metal sheet; The test device is further based on a calculation method for determining the thermal conductivity of ice based on the steady-state method, comprising: S1: pour water into the experimental hole, and use the semiconductor refrigerating sheet to cool the water to make ice; place the metal sheet above the ice, and the lower surface wall of the metal sheet is attached to the upper surface wall of the ice; S2: use the first metal film sensor and the second metal film sensor to monitor the temperature of the ice and the temperature of the semiconductor refrigerating sheet, respectively; when the temperature of the ice and the temperature of the semiconductor refrigerating sheet no longer change, use the first metal film sensor and the second metal film sensor to record the temperature T1 of the ice and the temperature T2 of the semiconductor refrigerating sheet, respectively; use the temperature sensor to record the temperature T of the metal sheet at this time; S3: take the metal sheet off the ice and place it on the upper surface wall of the semiconductor refrigerating sheet, use the temperature sensor to monitor the temperature t of the metal sheet again, and use the stopwatch to record the cooling time s, and establish a curve of time s and temperature t; S4: in the curve, calculate the slope n of the curve when the temperature is T; and substitute it into the calculation formula of the thermal conductivity of ice: ( ) wherein, Cp is the specific heat capacity of the metal sheet; m is the mass of the metal sheet; n is the thickness of the ice; n is the slope of the curve at temperature T; T2-T1; d is the diameter of the metal sheet.

2. The test apparatus for measuring the thermal conductivity of ice based on the steady-state method according to claim 1, characterized by The inner wall of the heat insulation cylinder is fixed with a layer of asbestos, and the semiconductor refrigerating sheet is fixed on the inner wall of the asbestos.

3. The test apparatus for measuring the thermal conductivity of ice based on the steady-state method according to claim 1, characterized by, The upper end surface wall of the heat insulation cylinder is above the semiconductor refrigerating sheet, and the upper end surface wall of the heat insulation cylinder is above the upper end surface wall of the insulator.

4. The test apparatus for measuring the thermal conductivity of ice based on the steady-state method according to claim 1, characterized by The metal sheet is an aluminum sheet with a thickness of 1 mm.

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