CN111735840B - Concrete single-sided heat conduction test device and test method thereof - Google Patents
Concrete single-sided heat conduction test device and test method thereof Download PDFInfo
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- CN111735840B CN111735840B CN202010561569.0A CN202010561569A CN111735840B CN 111735840 B CN111735840 B CN 111735840B CN 202010561569 A CN202010561569 A CN 202010561569A CN 111735840 B CN111735840 B CN 111735840B
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N25/00—Investigating or analyzing materials by the use of thermal means
- G01N25/20—Investigating or analyzing materials by the use of thermal means by investigating the development of heat, i.e. calorimetry, e.g. by measuring specific heat, by measuring thermal conductivity
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- G01K—MEASURING TEMPERATURE; MEASURING QUANTITY OF HEAT; THERMALLY-SENSITIVE ELEMENTS NOT OTHERWISE PROVIDED FOR
- G01K7/00—Measuring temperature based on the use of electric or magnetic elements directly sensitive to heat ; Power supply therefor, e.g. using thermoelectric elements
- G01K7/16—Measuring temperature based on the use of electric or magnetic elements directly sensitive to heat ; Power supply therefor, e.g. using thermoelectric elements using resistive elements
- G01K7/18—Measuring temperature based on the use of electric or magnetic elements directly sensitive to heat ; Power supply therefor, e.g. using thermoelectric elements using resistive elements the element being a linear resistance, e.g. platinum resistance thermometer
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N1/00—Sampling; Preparing specimens for investigation
- G01N1/28—Preparing specimens for investigation including physical details of (bio-)chemical methods covered elsewhere, e.g. G01N33/50, C12Q
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N1/00—Sampling; Preparing specimens for investigation
- G01N1/28—Preparing specimens for investigation including physical details of (bio-)chemical methods covered elsewhere, e.g. G01N33/50, C12Q
- G01N1/44—Sample treatment involving radiation, e.g. heat
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Abstract
The invention provides a concrete single-sided heat conduction test device which comprises a heat preservation device, wherein the heat preservation device is provided with a sample hole, and a concrete sample is placed in the sample hole. The invention also provides a test method of the heat exchange coefficient of the concrete surface, which comprises the following steps: firstly, constructing a concrete single-sided heat conduction test device, and ensuring that a concrete single side exchanges heat with the environment; placing the concrete single-sided heat conduction test device in an environment box, measuring temperature data of a concrete surface layer, and calculating a concrete surface temperature gradient; step three, calculating the heat exchange coefficient of the concrete surface. The device and the method can realize single-sided heat conduction of the concrete, and facilitate research on influence factors of single-sided heat exchange coefficients.
Description
Technical Field
The invention belongs to the technical field of civil engineering test devices, and particularly relates to a concrete single-sided heat conduction test device and a test method thereof.
Background
Along with the acceleration of the urban process in China, the energy consumption is higher and higher, and the building industry is used as a national post industry, so that the social requirement is met, the national economic development is promoted, and a large amount of resources are consumed, and the negative effects of environmental pollution, climate warming and the like are caused. The building energy consumption is 29.74% of the total energy consumption in global terms, while in the building energy consumption, the heat dissipated through the outer wall is about 40% of the total heat of the building. Therefore, the heat insulation performance of the building material is particularly important, and the heat conductivity coefficient and the heat transfer coefficient related in the heat conduction process are important indexes for identifying the heat insulation performance of the material, and concrete is a main building material, so that the heat conduction test of the concrete is required. In order to study the influence of each factor on the heat conductivity coefficient and the heat transfer coefficient, a fine test is needed, but the traditional test method cannot meet the requirement or cannot exclude the influence of other factors, so that a concrete single-sided heat conduction test device is designed to meet the needs of related scientific researchers and test staff. The device is easy and simple to handle, but automatically regulated has greatly improved test efficiency and precision.
Disclosure of Invention
The invention provides a single-sided heat conduction test device and a test method for concrete, which realize single-sided heat conduction of the concrete and facilitate research on influencing factors of single-sided heat exchange coefficients.
In order to solve the technical problems, the invention adopts the following technical scheme: the utility model provides a concrete single face heat conduction test device, includes heat preservation device, heat preservation device is equipped with the sample hole, and the concrete test piece is placed in the sample hole.
In a preferred scheme, the heat preservation device is made of polyurethane.
In the preferred scheme, be equipped with electric heating wire in the heat preservation device, electric heating wire sets up around the concrete test piece, electric heating wire and heating temperature control equipment electric connection.
In the preferred scheme, a cooling liquid circulating pipe is arranged in the heat preservation device and is connected with liquid cooling temperature control equipment.
In the preferred scheme, a temperature probe is arranged in the heat preservation device and is connected with a temperature real-time collector through a data line.
In the preferred scheme, the intelligent temperature control system further comprises a controller, wherein the controller is electrically connected with the temperature real-time collector, the liquid cooling temperature control equipment and the heating temperature control equipment.
The invention also provides a test method of the heat exchange coefficient of the concrete surface, which comprises the following steps:
firstly, constructing a concrete single-sided heat conduction test device, and ensuring that a concrete single side exchanges heat with the environment;
placing the concrete single-sided heat conduction test device in an environment box, measuring temperature data of a concrete surface layer, and calculating a concrete surface temperature gradient;
and thirdly, calculating the heat exchange coefficient beta of the concrete surface.
In a preferred embodiment, in the second step, each set of temperature data is subjected to a quadratic polynomial y=a 0 +a 1 ·x+a 2 ·x 2 Fitting to obtain a 0 And a 1 Wherein a is 0 Namely the surface temperature of the concrete, a 1 The concrete surface temperature gradient is obtained.
In a preferred scheme, in the third step, the concrete surface heat exchange coefficient beta can be calculated according to the formula (1)
Wherein:
T w the surface temperature of the concrete;
T f is ambient temperature;
lambda is the coefficient of thermal conductivity of the concrete;
In the preferred scheme, in the third step, after the heat exchange coefficient of the concrete surface is calculated, the change relation between the heat exchange coefficient of the concrete surface and the temperature difference between the environment and the concrete sample is tested.
The concrete single-sided heat conduction test device and the test method thereof provided by the invention have the following beneficial effects:
1. according to the invention, the side surface and the bottom surface of the concrete test piece are in contact with the heat preservation device, and only the top surface is in heat exchange with the environment, so that single-sided heat conduction of concrete is realized.
2. The heat preservation device is made of polyurethane, and sample holes with different shapes can be dug, so that the heat preservation device can be applied to concrete samples with different shapes, such as cylinders, cuboids, cubes and the like, so as to meet the requirements of different tests.
3. The invention can realize automatic temperature rise and temperature reduction in the polyurethane heat preservation device and ensure the heat preservation effect of the polyurethane heat preservation device.
4. Through setting up the concrete single-sided heat conduction test device, the research on influence factors of the concrete single-sided heat exchange coefficient is realized.
Drawings
The invention is further illustrated by the following examples in conjunction with the accompanying drawings:
FIG. 1 is a schematic view showing the overall structure of an inventive single-sided heat conduction test apparatus;
FIG. 2 is a top view of a single-sided thermal conductivity test apparatus of the present invention;
FIG. 3 is a temperature fitting curve of a concrete sample;
FIG. 4 is a graph showing the relationship between the heat exchange coefficient of the concrete surface and the temperature difference;
in the figure: the device comprises a heat preservation device 1, a concrete test piece 2, a cooling liquid circulating pipe 3, an electric heating wire 4, a liquid cooling temperature control device 5, a heating temperature control device 6, a temperature real-time collector 7, a controller 8, a temperature probe 9 and a sample hole 101.
Detailed Description
As shown in fig. 1-2, a concrete single-sided heat conduction testing device comprises a heat preservation device, wherein the heat preservation device is provided with a sample hole, a concrete sample is placed in the sample hole, and the sample hole is in close contact with the concrete sample.
In this embodiment, the heat insulation device is made of polyurethane. The heat preservation device prepares sample holes according to the size and shape of the concrete sample.
An electric heating wire is arranged in the heat preservation device and surrounds the concrete test piece, the electric heating wire is buried in the heat preservation device and is connected with heating temperature control equipment, and the heating temperature control equipment adopts an intelligent digital display temperature control box ff300.
The electric heating wire is electrified to be opened and closed through the heating temperature control equipment, the heat preservation device is heated through the electric heating wire, the heat dissipated by the concrete sample through the heat preservation device is compensated, and the concrete sample and the environment can only perform single-sided heat exchange.
The heat preservation device is internally provided with a cooling liquid circulating pipe, and the cooling liquid circulating pipe is buried in the heat preservation device and is connected with liquid cooling temperature control equipment. The liquid cooling temperature control equipment selects liquid cooling temperature control equipment XMTD-818CPK.
The temperature probe is arranged in the heat preservation device and is connected with the temperature real-time collector through a data line. The temperature real-time collector adopts a 16-path PT100 collecting module, and the temperature real-time collector can automatically collect temperature data measured by the temperature probe and display the temperature data on the temperature real-time collector, so that test personnel can observe and know the real-time temperature condition inside the heat preservation device conveniently.
The device also comprises a controller, wherein the controller is a computer and is electrically connected with the temperature real-time collector, the liquid cooling temperature control device and the heating temperature control device.
Setting a control temperature value in the controller, when the temperature probe detects that the temperature data is higher than a set value, automatically powering on the liquid cooling temperature control equipment and reducing the temperature of circulating liquid, and continuously circulating the cooled circulating liquid through the cooling liquid circulating pipe, so that the internal temperature of the heat preservation device is reduced until the set value is reached; when the temperature probe detects that the temperature data is lower than the set value, the heating temperature control equipment controls the electric heating wire to be electrified to heat the heat preservation device until the temperature reaches the set value.
A test method for the heat exchange coefficient of the concrete surface comprises the following steps:
step one, constructing a concrete single-sided heat conduction test device, and ensuring that the concrete single-sided heat conduction test device exchanges heat with the environment.
Placing the concrete single-sided heat conduction test device in an environment box, measuring temperature data of a concrete surface layer, calculating a concrete surface temperature gradient, and performing quadratic polynomial y=a on each group of temperature data 0 +a 1 ·x+a 2 ·x 2 Fitting to obtain a 0 And a 1 Wherein a is 0 Namely the surface temperature of the concrete, a 1 The concrete surface temperature gradient is obtained.
Calculating the heat exchange coefficient beta of the concrete surface, and calculating the heat exchange coefficient beta of the concrete surface according to the formula (1)
Wherein:
T w the surface temperature of the concrete;
T f is ambient temperature;
lambda is the coefficient of thermal conductivity of the concrete;
And after calculating the heat exchange coefficient of the concrete surface, drawing a change relation diagram of the heat exchange coefficient of the concrete surface and the temperature difference between the environment and the concrete sample.
The environmental temperature of this example was-20℃and the initial temperature of the concrete was 20 ℃. And (3) measuring by a thermal conductivity tester, and obtaining the concrete thermal conductivity of 1.61W/(m.K) after taking an average value through multiple measurements.
The temperature data of the surface layer of the concrete sample is measured by a high-precision temperature probe, and a quadratic polynomial is applied for fitting, and a fitting curve is shown in fig. 3.
Correlation coefficient (R) 0.999186826456288, square of correlation coefficient (R) 2 ):0.998374314163788。
The concrete surface temperature gradient was calculated to be 157 c/mm.
According to the formula (1), the heat exchange coefficient beta of the concrete surface can be calculated
The heat exchange coefficient is calculated to be 39.8 kJ/(h.m) 2 ·℃)。
Thereby calculating the unidirectional heat exchange coefficient of the concrete under certain conditions.
The influence of the ambient temperature on the heat exchange coefficient was further investigated, in this example, the concrete temperature was set to 20 ℃, the ambient temperature was-10 ℃, 5 ℃, 0 ℃, 5 ℃, 10 ℃, 15 ℃, 25 ℃, 30 ℃, 35 ℃, 40 ℃, 45 ℃, 50 ℃ respectively, and the heat exchange coefficient of the concrete surface was monitored at the time of the test.
The change relation of the heat exchange coefficient of the concrete surface along with the temperature difference is shown in fig. 4, the heat exchange coefficient is increased along with the increase of the temperature difference, and when the ambient temperature is higher than the concrete temperature, the rate of increasing the heat exchange coefficient along with the increase of the temperature difference is gradually reduced. When the ambient temperature is less than the concrete temperature, the rate at which the heat exchange coefficient increases with increasing temperature difference becomes progressively greater.
Claims (8)
1. The utility model provides a concrete single face heat conduction test device, its characterized in that, includes heat preservation device, heat preservation device is equipped with the sample hole, and the concrete test piece is placed in the sample hole, and the side and the bottom surface of concrete test piece all contact with heat preservation device, and only the top surface carries out the heat exchange with the environment, realizes the single face heat conduction of concrete, be equipped with electric heating wire in the heat preservation device, electric heating wire sets up around the concrete test piece, electric heating wire and heating control by temperature change equipment electric connection, is equipped with the coolant circulation pipe in the heat preservation device, and the coolant circulation pipe is connected with liquid cooling control by temperature change equipment.
2. The concrete single-sided thermal conduction testing apparatus according to claim 1, wherein the heat preservation device is made of polyurethane.
3. The concrete single-sided heat conduction test device according to claim 1, wherein a temperature probe is arranged in the heat preservation device and is connected with a temperature real-time collector through a data line.
4. The concrete single-sided thermal conduction testing apparatus of claim 3, further comprising a controller electrically connected to the temperature real-time collector, the liquid cooling temperature control device and the heating temperature control device.
5. A method for testing the heat exchange coefficient of the concrete surface by using the single-sided heat conduction testing device for concrete according to any one of claims 1 to 4, which is characterized by comprising the following steps:
firstly, constructing a concrete single-sided heat conduction test device, and ensuring that a concrete single side exchanges heat with the environment;
placing the concrete single-sided heat conduction test device in an environment box, measuring temperature data of a concrete surface layer, and calculating a concrete surface temperature gradient;
and thirdly, calculating the heat exchange coefficient beta of the concrete surface.
6. The method according to claim 5, wherein in the second step, each set of temperature data is subjected to a quadratic polynomial y=a 0 +a 1 ·x+a 2 ·x 2 Fitting to obtain a 0 And a 1 Wherein a is 0 Namely the surface temperature of the concrete, a 1 The concrete surface temperature gradient is obtained.
7. The method according to claim 5, wherein in the third step, the concrete surface heat exchange coefficient β is calculated according to the formula (1)
Wherein:
T w the surface temperature of the concrete;
T f is ambient temperature;
lambda is the coefficient of thermal conductivity of the concrete;
8. The method according to claim 5, wherein in the third step, after calculating the heat transfer coefficient of the concrete surface, the change relation between the heat transfer coefficient of the concrete surface and the temperature difference between the environment and the concrete sample is plotted.
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