CN102419343B - Multi-temperature stage measuring method of concrete thermal diffusivity - Google Patents
Multi-temperature stage measuring method of concrete thermal diffusivity Download PDFInfo
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Abstract
The invention provides a multi-temperature stage measuring method of concrete thermal diffusivity, characterized in that: the initial condition of a homothermic test piece comprises that the center of the test piece and the surface of the test piece form an uniformly distributed stable temperature gradient field with a temperature difference of less than 5 DEG C; when measuring, the error of the ambient water temperature relative to the thermal diffusion ambient temperature is controlled to be less than 1 % of the minimum permissible initial temperature difference of a measuring device; the termination condition of ending the measurement of the present stage is that the temperature difference between the center of the test piece and the thermal diffusion ambient temperature is less than 0.1 theta 0-0.2 theta 0; the state is the condition of subsequent measurement of the homothermic test piece, the ambient water temperature in each temperature stage measurement is controlled according to the three stages of rapid access, stable formation of thermal diffusion, and stable thermal diffusion, and the third stage is a temperature-time record stage. Compared with the prior art, the method realizes that the concrete thermal diffusivity of multiple temperature stages can be continuously measured by one measurement based on guaranteeing the measurement precision in the prior art, and greatly increases the efficiency of the measurement.
Description
Technical field
What the present invention relates to is a kind of Multi-temperature stage measuring method of concrete thermal diffusivity, belongs in physics by using the technical field of by the use of thermal means test material.
Background technology
publication number is that the Chinese invention patent application " assay method of thermal diffusivity of concrete and test unit " of CN101915776 discloses a kind of technical scheme (referred to as the BYR method) that is referred to as the reverse assay method of thermal diffusivity of concrete, the method is " to comprise the test specimen that first concrete for making is become the symmetric shape of rule, again this test specimen is made the consistent equality of temperature body test specimen of Temperature Distribution, then this equality of temperature body test specimen is placed in the mensuration environment of constant temperature, making test specimen be in its central temperature is equal in the temperature of measuring environment and the process that obtains the steady state thermal diffusion, measure and record test specimen central temperature and the corresponding time of this convergent process, again with the test specimen central temperature value that records with the test specimen center temperature difference of measuring that environment temperature calculates, be depicted as curve in natural logarithm and time take the test specimen center temperature difference in the rectangular coordinate system of two coordinate axis, choose two some formula on this curve cathetus part
Calculate the thermal diffusivity that obtains this test specimen, in formula:
α: thermal diffusivity, t
a: the corresponding time value of some a on straight line portion, t
b: the corresponding time value of some b on straight line portion, θ
a: the point corresponding test specimen of a center temperature approach on straight line portion, θ
b: the point corresponding test specimen of b center temperature approach on straight line portion, K is the shape coefficient of test specimen.
Wherein the temperature of said making equality of temperature body test specimen is local temperature or lower than the curing temperature of the concrete sample of 30 ℃, said local temperature is temperature or room temperature or the water temperature under the natural conditions of mensuration behavior location, curing temperature is the temperature that realizes according to curing requirements, and the thermostat temperature of measuring environment is higher than 50 ℃ of hot water temperatures.
Said with the test specimen central temperature value that records with the test specimen center temperature difference of measuring that environment temperature calculates, be depicted as curve in take the natural logarithm of the test specimen center temperature difference and time as the rectangular coordinate system of two coordinate axis after, the data that are used in this curve cathetus segment limit calculate the fitting a straight line equation with least square method, then use formula
α＝|k|·K
Calculate thermal diffusivity, in formula: α is thermal diffusivity, and k is the slope of fitting a straight line, and K is the shape coefficient of test specimen.
When said test specimen was right cylinder, when calculating thermal diffusivity, shape coefficient K used was:
In formula, R is the bottom surface radius of right cylinder test specimen, and L is the height of test specimen, and π is circular constant.
When said test specimen was rectangular parallelepiped, when calculating thermal diffusivity, shape coefficient K used was:
In formula, a, b, c are respectively the length of rectangular parallelepiped, and π is circular constant.”
Wherein the sign of said steady state thermal diffusion process is that natural logarithm and the variation of time of test specimen center and thermal diffusion ambient temperature differences presents the linear decrease Changing Pattern.
The assay method of original thermal diffusivity of concrete, the assay method (referred to as the SL352 method) of (SL352-2006) stipulating as People's Republic of China's water conservancy industry standard " concrete for hydraulic structure testing regulations ", what carry out is that first high temperature obtains equality of temperature body test specimen, then realizes the route that the steady state thermal diffusion process is measured in normal temperature or cryogenic thermostat environment.And above-mentioned BYR method is to have for overcoming in original technology that water consumption is large or first normal temperature (or the concrete curing temperature) constant temperature that the deficiency that energy consumption is large proposes obtains equality of temperature body test specimen, then realizes the route that the steady state thermal diffusion process is measured in the high temperature constant temperature environment.
Studies show that, in the thermal diffusion process under different thermostat temperatures, concrete thermal diffusivity is different.Simultaneously, in certain temperature range in the thermal diffusion process of (10 ℃～70 ℃) thermal diffusivity and temperature can present linear relationship preferably.When therefore obtaining the thermal diffusivity of degree of precision for needs, the mensuration of just need to be under different thermostat temperatures, repeatedly carrying out thermal diffusion process is measured as repeat 3 times at 15 ℃, 30 ℃, 45 ℃, 60 ℃ 4 temperature spots, each temperature spot to obtain the thermal diffusivity characteristic of concrete application of temperature section (being generally 10 ℃～70 ℃).
Existing two kinds of assay methods, be that SL352 method and BYR method all require test specimen to keep the enough large start-stop temperature difference, when namely measuring beginning the temperature of equality of temperature body test specimen and when measuring the difference between the temperature of constant temp. heating diffusional environment want enough large, with the accuracy of assurance measurement result.Its reason is that test specimen center and the temperature difference of thermal diffusion environment of the error of test findings when stopping to test is relevant.
Can push away according to measuring principle and thermal diffusivity computing formula, the caused error to thermal diffusivity α measurement result of the error of the temperature difference θ of test specimen center and thermal diffusion isoperibol is:
Wherein: θ is the temperature difference of test specimen center and thermal diffusion environment temperature, and Δ θ is the error of the θ of proving installation; α is the thermal diffusivity of detected concrete.
By formula (1) can be by the relative error of the thermal diffusivity of the caused detected concrete of error delta θ of temperature difference θ:
That is: the relative error of measurement result is determined by Δ θ/θ.Accordingly as can be known, temperature approach when stopping due to test is the minimum temperature difference value in whole process of the test, at same test specimen under the condition determination of the thermostat temperature departure of identical thermometric error and thermal diffusion environment, the relation that is inversely proportional to of the temperature difference when caused relative error to measurement result stops with test.
The factor that causes Δ θ is mainly: the departure of the test specimen environment temperature of thermal diffusivity measuring system and the thermometric error of system.In prior art, stipulate as People's Republic of China's building trade product standard " concrete heat physical parameter measurement instrument " JG/T329-2011: the thermometric error of thermal diffusion determinator should be greater than ± 0.1 ℃; Steady heat diffusion phase water temperature change value: the SL352 method should be greater than ± 0.5 ℃, and the BYR method should be greater than ± 0.3 ℃.
Due to: (1) test specimen center temperature difference θ reduces in time, under the constant prerequisite of Δ θ, the maximum relative error of measurement result the temperature difference is determined when stopping by measuring; (2) according to the measuring principle of assay method, for same test specimen, it is put into the constant temp. heating diffusional environment from equality of temperature body test specimen and plays that to form the required time of steady heat disperse state identical, and irrelevant with the test temperature difference; And it is also basic identical for (the shortest) duration of satisfying the required steady heat disperse state of assay method; (3) calculating of measurement result relates to the calculating of the slope of the straight-line segment that the natural logarithm curve of the center temperature difference forms under the steady heat disperse state, and its enough computational accuracy of certain duration guarantee must be arranged; (4) and become to be similar to proportional relation for the termination temperature difference of identical its test of duration with the Initial Temperature Difference of test.Also namely, if keep thermometric error value and the constant temp. heating diffusion phase water temperature departure value of the determined thermal diffusion determinator of prior art, the Initial Temperature Difference of contract measurement, will reduce the measuring accuracy of measurement result.For these reasons, therefore poor all the requirement more than 30 ℃ of test initial temperature of existing two kinds of assay methods can not comprise the thermal diffusion environment temperature in the mensuration of 30 ℃～50 ℃ of temperature sections.
Simultaneously, existing assay method requires the detected concrete test specimen to need to form the equality of temperature concrete conditions in the establishment of a specific crime before thermal diffusion process begins, and equality of temperature body test specimen needs to put at the utmost point isoperibol that thermal diffusion is measured in the short time.This requirement is that to be based upon the initial boundary condition of abundant necessity of finding the solution the thermal diffusion differential equation on the physics principle basis of existing method of testing drawn.Yet this strict equality of temperature body starting condition has limited the mensuration of carrying out immediately another temperature after the mensuration of completing certain thermal diffusion environment temperature, when its reason is off-test, the test specimen internal temperature is not consistent, as existing two kinds of methods all stipulated the mensuration final temperature poor be 3 ℃～6 ℃.
As after to adopt the BYR method to complete the thermal diffusion environment temperature be the mensuration of 60 ℃, can not carry out immediately SL352 method thermal diffusion environment temperature and be the mensuration of 20 ℃, reason is test specimen central temperature and due to the temperature difference that exists between test specimen center and surface more than 3 ℃, and not meeting existing test method is the regulation of isothermal (being that measured temperature equates) about the condition of equality of temperature body test specimen.And wait for that test specimen internal temperature balance forms strict equality of temperature concrete conditions in the establishment of a specific crime and still needs time of a few hours.
In sum, existing method can not be carried out the mensuration of many temperature sections continuously with an equality of temperature body test specimen, can not carry out the mensuration of equal accuracy under the less temperature difference with equality of temperature body test specimen temperature and thermal diffusion environment temperature, can not be that the 30 ℃～temperature section of 50 ℃ carries out the mensuration of equal accuracy in the thermal diffusion environment temperature, and can only single carry out mensuration to thermal diffusivity of concrete by the steady state thermal diffusion process of different start-stop temperature.
In determination of concrete thermal diffusivity, claim that the Pass Test method is equality of temperature body test specimen about the test specimen of the consistent test initial conditions of test specimen interior temperature distribution; Test specimen is residing take the predetermined environment water temperature of assay method as the thermal diffusion environment temperature, and the environment water temperature refers to the water temperature of the water environment take the thermal diffusion environment temperature as the equality of temperature body test specimen place of controlling target; Measured thermal diffusivity result is the thermal diffusivity measured value of test specimen under the thermal diffusion environment temperature; Temperature range between equality of temperature body test specimen temperature when " section " in multiple temperature sections refers to measure beginning under certain thermal diffusion environment temperature and this thermal diffusion environment temperature; Difference when measuring beginning between equality of temperature body test specimen temperature and thermal diffusion environment temperature is initial temperature differences; Central temperature and the difference between the thermal diffusion environment temperature of measuring test specimen when stopping are the termination temperature difference.
Summary of the invention
For above-mentioned deficiency, technical matters to be solved by this invention is how to adjust the assay method of thermal diffusivity of concrete, thereby propose an a kind of available test specimen and carry out continuously the determination efficiency that a plurality of temperature sections measure to improve the thermal diffusivity of concrete sample different temperatures, and the mensuration start-stop temperature difference of each temperature section is less, thereby realizes containing the thermal diffusion environment temperature at the Multi-temperature stage measuring method of concrete thermal diffusivity of 30 ℃～50 ℃ of temperature sections.
Multi-temperature stage measuring method of concrete thermal diffusivity provided by the invention is first made equality of temperature body test specimen; Again equality of temperature body test specimen is placed in the water environment that design temperature is the thermal diffusion environment temperature, and controls this environment water temperature and keep constant temperature in default thermal diffusion environment temperature, so that test specimen inside forms the steady heat diffusion process under this thermal diffusion environment temperature; Measure and record the test specimen center at the temperature-time-varying relationship of this steady heat diffusion process, calculate thermal diffusivity by existing formula at last; Wherein
The condition that said equality of temperature body test specimen is set up is that surface temperature is identical, and the distribution of test specimen internal temperature is and take on test specimen center and test specimen surface as the steady heat diffusion temperature gradient fields of extreme value, and the temperature difference on test specimen center and test specimen surface is less than 5 ℃ simultaneously; The temperature difference of said test specimen surface temperature and central temperature and the thermal diffusion environment temperature that will measure therein all allows Initial Temperature Difference greater than the minimum of test unit regulation;
The said thermal diffusion environment temperature of measuring has multistage, be equality of temperature body test specimen when measure finishing under present segment thermal diffusion environment temperature at the equality of temperature body test specimen of measuring under subsequent segment thermal diffusion environment temperature, finish end condition that present segment measures and be the temperature difference of test specimen center and thermal diffusion environment temperature less than 0.1 θ
0～0.2 θ
0, θ wherein
0Be the initial temperature differences that present segment is measured, the smaller value in two temperature difference when getting this temperature section mensuration beginning between test specimen surface and test specimen central temperature and thermal diffusion environment temperature;
In the mensuration process of each temperature section, the Environmental Water temperature control divides three phases to carry out:
Phase one---enter the stage fast, the water temperature that controls environment reaches thermal diffusion environment temperature ± 0.3 ℃ in 5min, makes equality of temperature body test specimen surface enter fast the thermal diffusion environment;
Subordinate phase---steady heat diffuses to form the stage, and the error of the water temperature that controls environment and thermal diffusion environment temperature spreads the inner steady heat that forms of test specimen less than ± 0.3 ℃;
Phase III---steady heat diffusion phase, the error of the water temperature that controls environment and thermal diffusion environment temperature allows 1% of Initial Temperature Difference less than the minimum of determinator, namely meets relational expression:
ΔT
max≤0.011θ
0，min
Wherein: θ
0, minBe the minimum Initial Temperature Difference of determinator, Δ T
maxMeasure the limits of error of environment temperature for thermal diffusion, make the test specimen interior temperature distribution remain on steady heat diffusion temperature gradient fields state.
Usually, after all temperature sections are done repeatedly to measure, can draw the measurement result of two types, one is by each thermal diffusion temperature, the mean value calculation of the data measured at this temperature to be obtained thermal diffusivity of concrete on each temperature spot, another is after calculating thermal diffusivity measured value on each temperature spot by each data measured, be that the sample data group is carried out linear fit with each thermal diffusion environment temperature with corresponding thermal diffusivity, finally draw the fitting a straight line equation of detected concrete thermal diffusivity and thermal diffusion environment temperature relation.
The minimum Initial Temperature Difference θ of said determinator
0, minThat under existing assay method, determinator guarantees that the minimum of measuring relative error allows to stop temperature difference θ
E, minCorresponding mensuration initial temperature differences, θ
E, minThe maximum error Δ θ of the test specimen center temperature difference θ that is formed by thermometric error and the thermal diffusion environment thermostatic control error of determinator, and the design relative error Δ α/α of determinator determined by formula 2, that is:
Multi-temperature stage measuring method of concrete thermal diffusivity provided by the invention, control the isoperibol temperature and control the present segment test temperature difference at test specimen center and thermal diffusion environment temperature when stopping by syllogic, meet this test method about the needed state of equality of temperature body test specimen so that the state of temperature of the test specimen inside of present segment when measuring termination still is in.The main points that are the inventive method are exactly: the starting condition of equality of temperature body test specimen used is the test specimen center and the poor equally distributed equilibrium temperature gradient fields less than 5 ℃ of the surperficial formation temperature of test specimen, the error of surveying timing controlled environment water temperature relatively hot diffusional environment temperature allows 1% of Initial Temperature Difference less than the minimum of determinator, finishes end condition that present segment measures and be the temperature difference of test specimen center and thermal diffusion environment temperature less than 0.1 θ
0～0.2 θ
0, this state and the equality of temperature body test specimen condition of measuring for subsequent segment, in each temperature section test said environment water temperature by enter fast, steady heat diffuses to form, steady heat spreads three phases and controls.Compared with prior art, the inventive method has realized once measuring the thermal diffusivity of a plurality of temperature sections of process energy METHOD FOR CONTINUOUS DETERMINATION concrete on the basis that guarantees prior art measuring accuracy level, greatly improve the efficient of determination test.In addition, determining of the starting condition of equality of temperature body test specimen shortened the time of making equality of temperature body test specimen greatly, also improved the efficient of test specimen.
In practical operation, the error of control environment water temperature and thermal diffusion environment temperature that the control of said environment water temperature begins from subordinate phase allows 1% of Initial Temperature Difference among 15mins to complete to the error of control environment water temperature and the thermal diffusion environment temperature that enter the phase III less than the minimum of determinator less than ± 0.3 ℃.Namely before the diffusion of the inner formation of test specimen steady heat, the error of environment water temperature and thermal diffusion environment temperature is less than θ
0, minDegree.And whether equality of temperature body test specimen inside forms whether the steady heat diffusion met the difference of test specimen central temperature and thermal diffusion environment temperature by the test specimen central temperature-time relationship under the thermal diffusion environment temperature that records natural logarithm and the variation of time and presents the determination flag that this steady heat of linear decrease Changing Pattern spreads.
Multi-temperature stage measuring method of concrete thermal diffusivity provided by the invention, the variation of the thermal diffusion environment temperature of each section of front and back in said multiple temperature sections be that rise progressively successively or that fall progressively successively or lifting staggered.That is: compare with measuring thermal diffusion environment temperature used the last period, the change direction of the thermal diffusion environment temperature that subsequent segment is measured can be to heat up, and can be also cooling, can also be repetition and/or the combination of intensification, cooling.
Embodiment
1: one Multi-temperature stage measuring method of concrete thermal diffusivity of example,
First make equality of temperature body test specimen, process is first to make at normal temperatures test specimen, install temperature sensor at the center after the maintenance drying again in 19.5 ℃, form equality of temperature body test specimen after putting into again 24.5 ℃ of thermostatted water 30min, its surface temperature is all 24.5 ℃ everywhere mutually, and central temperature is 20 ℃ through temperature sensor measurement.Owing to maintaining in the more stable temperature of test specimen, substantially reached the requirement of equality of temperature body, the distribution of inferring the test specimen internal temperature in 24.5 ℃ of thermostatted waters after in 30min has been and has taken on test specimen center and test specimen surface as the steady heat diffusion temperature gradient fields of extreme value.
Thermal diffusivity default in this example is measured temperature, and instant heating diffusional environment temperature has 30 ℃, 40 ℃, 55 ℃, 70 ℃ 4, namely makes to measure according to 20 ℃-30 ℃, 30 ℃-40 ℃, 40 ℃-55 ℃, 55 ℃-70 ℃ 4 temperature sections the initial temperature differences θ of each temperature section
010 ℃, 10 ℃, 15 ℃, 15 ℃ successively.
After equality of temperature body test specimen forms, then equality of temperature body test specimen is placed in the water of first paragraph constant temp. heating diffusional environment temperature, so that test specimen inside forms the steady heat diffusion process under this thermal diffusion environment temperature; Put into water beginning test constantly test specimen central temperature, environment water temperature and by Measuring Time, measured value processed from test specimen, represent when linear decrease changes that test specimen is inner and form new steady heat diffusion process when the natural logarithm of the difference of the temperature of test specimen center and thermal diffusion environment and the variation of time present, be recorded in the temperature-time-varying relationship of this steady heat diffusion process, until the temperature difference of test specimen center and thermal diffusion environment temperature is less than 0.1 θ
0～0.2 θ
0
The Environmental Water temperature control divides three phases to carry out in the mensuration process of above-mentioned equality of temperature body test specimen at each temperature section:
Phase one---enter the stage fast, the water temperature that controls environment reaches thermal diffusion environment temperature ± 0.3 ℃ in 5min, makes equality of temperature body test specimen surface enter fast the thermal diffusion environment;
Subordinate phase---steady heat diffuses to form the stage, and the error of the water temperature that controls environment and thermal diffusion environment temperature spreads the inner steady heat that forms of test specimen less than ± 0.3 ℃;
Phase III---steady heat diffusion phase, the error of the water temperature that controls environment and thermal diffusion environment temperature allows 1% of Initial Temperature Difference less than the minimum of determinator, namely meets relational expression:
Δ T
max≤ 0.01 θ
0, min, θ
0, min=10 ℃, controlling value Δ T
max=0.1 ℃.Make the test specimen interior temperature distribution remain on steady heat diffusion temperature gradient fields state.
Repeat the environment water temperature is carried out the control of three phases after this section measure to finish, controlling the thermal diffusion environment temperature that target is replaced by next section mensuration has multistage, and equality of temperature body test specimen is next section mensuration equality of temperature body test specimen used when the preceding paragraph greenhouse finishes.
Example 2, a Multi-temperature stage measuring method of concrete thermal diffusivity, its process is:
(1) be ready to test specimen, test specimen takes out from standard curing room, and the test specimen surface temperature is 20 ℃; Place temperature sensor in the preformed hole of test specimen center after, test specimen is put into the test bucket;
(2) to the test bucket water filling of determinator, water level exceeds approximately 5cm of test specimen, forms to measure environment water;
(3) in 5min, the temperature of measuring environment water in the test bucket is heated to 35 ℃, and controls this environment water temperature in 35 ± 0.3 ℃ of scopes;
(4) will test the temperature of measuring environment water in bucket in 15min controls in 35 ± 0.1 ℃ of scopes from 35 ± 0.3 ℃;
(5) keep this temperature controlling range and begin test constantly and record test specimen central temperature, environment water temperature, time after the temperature of measuring environment water is controlled in 35 ± 0.1 ℃ of scopes, until in test specimen central temperature and test bucket, the temperature difference of environment water less than 2 ℃, is completed first temperature section and is measured;
(6) in 5min, the temperature of measuring environment water in the test bucket is heated to 50 ℃, and controls this environment water temperature in 50 ± 0.3 ℃ of scopes;
(7) will test the temperature of measuring environment water in bucket in 15min controls in 50 ± 0.1 ℃ of scopes from 50 ± 0.3 ℃;
(8) keep this temperature controlling range and begin test constantly and record test specimen central temperature, environment water temperature, time after the temperature of measuring environment water is controlled in 50 ± 0.1 ℃ of scopes, until in test specimen central temperature and test bucket, the temperature difference of environment water less than 2 ℃, is completed second temperature section and is measured;
(9) in 5min, the temperature of measuring environment water in the test bucket is heated to 65 ℃, and controls this environment water temperature in 65 ± 0.3 ℃ of scopes;
(10) will test the temperature of measuring environment water in bucket in 15min controls in 65 ± 0.1 ℃ of scopes from 65 ± 0.3 ℃;
(11) keep this temperature controlling range and begin test constantly and record test specimen central temperature, environment water temperature, time after the temperature of measuring environment water reaches in 50 ± 0.1 ℃ of scopes, until in test specimen central temperature and test bucket, the temperature difference of environment water less than 2 ℃, is completed the 3rd temperature section and is measured;
(12) repeat (1) to (11) twice, get the steady state thermal diffusion process, i.e. the natural logarithm of the difference of test specimen center and thermal diffusion environment temperature and the variation of time presents linear decrease Changing Pattern three groups of data partly;
(13) calculate respectively 35 ℃, 50 ℃, thermal diffusivity measured value during 65 ℃ of three thermal diffusion environment temperatures according to three groups of data by the computing method of BYR method;
(14) thermal diffusivity and the thermal diffusion environment temperature with these measured 3 temperature spots is that parameter is carried out linear fit, draws the fitting a straight line equation of detected concrete thermal diffusivity and thermal diffusion environment temperature;
(15) maximum relative error of this measurement result is ± 5%.
3: one Multi-temperature stage measuring method of concrete thermal diffusivities of example, its process is:
(1) be ready to test specimen, test specimen takes out from standard curing room, and the test specimen temperature is 20 ℃; Place temperature sensor in the preformed hole of test specimen center after, test specimen is put into the test bucket;
(2) be the water of 40 ℃ from circulating water chennel to test bucket implantation temperature, water level exceeds approximately 5cm of test specimen, forms to measure environment water;
(3) in 5min, the temperature of measuring environment water in the test bucket is controlled in 40 ± 0.3 ℃ of scopes;
(4) will test the temperature of measuring environment water in bucket in 15min controls in 40 ± 0.2 ℃ of scopes from 40 ± 0.3 ℃;
(5) keep this temperature controlling range and begin test constantly and record test specimen central temperature, environment water temperature, time after the temperature of measuring environment water reaches in 40 ± 0.2 ℃ of scopes, until in test specimen central temperature and test bucket, the temperature difference of environment water less than 4 ℃, is completed first temperature section and is measured;
(6) get rid of in the test bucket water and be the water of 60 ℃ from another circulating water chennel to test bucket implantation temperature, water level exceeds approximately 5cm of test specimen, forms new mensuration environment water;
(7) in 5min, the temperature of measuring environment water in the test bucket is controlled in 60 ± 0.3 ℃ of scopes;
(8) will test the temperature of measuring environment water in bucket in 15min controls in 60 ± 0.2 ℃ of scopes from 60 ± 0.3 ℃;
(9) keep this temperature controlling range and begin test constantly and record test specimen central temperature, environment water temperature, time in the time of after the temperature of measuring environment water reaches 60 ± 0.2 ℃ of scopes, until in test specimen central temperature and test bucket, the temperature difference of environment water less than 4 ℃, is completed second temperature section and is measured;
(10) get rid of in the test bucket water and be the water of 20 ℃ from another circulating water chennel to test bucket implantation temperature, water level exceeds approximately 5cm of test specimen, forms new mensuration environment water;
(11) in 5min, the temperature of measuring environment water in the test bucket is controlled in 20 ± 0.3 ℃ of scopes;
(12) will test the temperature of measuring environment water in bucket in 15min controls in 20 ± 0.2 ℃ of scopes from 20 ± 0.3 ℃;
(13) keep this temperature controlling range and begin test constantly and record test specimen central temperature, environment water temperature, time in the time of after the temperature of measuring environment water reaches 20 ± 0.2 ℃ of scopes, until in test specimen central temperature and test bucket, the temperature difference of environment water less than 6 ℃, is completed the 3rd temperature section and is measured;
(14) repeat (2) to (13) twice, get the steady state thermal diffusion process, i.e. the natural logarithm of the difference of test specimen center and thermal diffusion environment temperature and the variation of time presents linear decrease Changing Pattern three groups of data partly;
(15) according to the Mean Test Number certificate of three temperature sections of three groups of data acquisitions, calculate respectively the thermal diffusivity measured value of 40 ℃, 60 ℃, 20 ℃ three thermal diffusion environment temperatures by the computing method of BYR method.
Example 4, thermal diffusion environment temperature are set as 15 ℃, 30 ℃, 45 ℃, 60 ℃ 4 thermal diffusion temperature spots, each temperature spot repeats 5 times and measures, and the fitting a straight line equation of detected concrete thermal diffusivity and thermal diffusion environment temperature is that the sample data group is carried out linear fit and drawn by measured 20 thermal diffusivities and corresponding thermal diffusion environment temperature.Process of the test the step of each temperature spot with on two examples with, the temperature spot segmentation designs for order by 45 ℃, 60 ℃, 15 ℃, 30 ℃, provide the mensuration environment water by a recirculated water feeding mechanism in conjunction with BYR method and SL352 subtraction unit feature, the configuration of recirculated water feeding mechanism meets to be observed two Environmental Water temperature controls between temperature section to reach in 5min in subsequent segment thermal diffusion temperature ± 0.3 ℃ scope, reaches the requirement of subsequent segment thermal diffusion temperature ± 0.1 ℃ in follow-up 15min.
Claims (3)
1. a Multi-temperature stage measuring method of concrete thermal diffusivity, first make equality of temperature body test specimen; Again equality of temperature body test specimen is placed in the water environment that design temperature is the thermal diffusion environment temperature, and controls this water environment water temperature and keep constant temperature in default thermal diffusion environment temperature, so that test specimen inside forms the steady heat diffusion process under this thermal diffusion environment temperature; Measure and record the test specimen center at the temperature-time-varying relationship of this steady heat diffusion process, calculate thermal diffusivity by existing formula at last; It is characterized in that
The condition that said equality of temperature body test specimen is set up is that surface temperature is identical, and the distribution of test specimen internal temperature is and take on test specimen center and test specimen surface as the steady heat diffusion temperature gradient fields of extreme value, and the temperature difference on test specimen center and test specimen surface is less than 5 ℃ simultaneously; The temperature difference of said test specimen surface temperature and central temperature and the thermal diffusion environment temperature that will measure therein all allows Initial Temperature Difference greater than the minimum of test unit regulation;
The said thermal diffusion environment temperature of measuring has multistage, be equality of temperature body test specimen when measure finishing under present segment thermal diffusion environment temperature at the equality of temperature body test specimen of measuring under subsequent segment thermal diffusion environment temperature, finish end condition that present segment measures and be the temperature difference of test specimen center and thermal diffusion environment temperature less than 0.1 θ
0～0.2 θ
0, θ wherein
0Be the initial temperature differences that present segment is measured, the smaller value in two temperature difference when getting this present segment mensuration beginning between test specimen surface and test specimen central temperature and thermal diffusion environment temperature;
In the mensuration process of each temperature section, the water environment water temperature is controlled and is divided a three phases to carry out:
Phase one---enter the stage fast, control the water environment water temperature and reach thermal diffusion environment temperature ± 0.3 ℃ in 5min, make equality of temperature body test specimen surface enter fast the thermal diffusion environment;
Subordinate phase---steady heat diffuses to form the stage, controls the error of water environment water temperature and thermal diffusion environment temperature less than ± 0.3 ℃, and the inner steady heat that forms of test specimen is spread;
Phase III---steady heat diffusion phase, the error of control water environment water temperature and thermal diffusion environment temperature allows 1% of Initial Temperature Difference less than or equal to the minimum of test unit, namely meets relational expression:
ΔT
max≤0.01θ
0，min
Wherein: θ
0, minBe the minimum permission Initial Temperature Difference of test unit, Δ T
maxBe that thermal diffusion measures the limits of error of environment temperature, make the Temperature Distribution of test specimen inside remain on steady heat diffusion temperature gradient fields state.
2. the control water environment water temperature that Multi-temperature stage measuring method of concrete thermal diffusivity as claimed in claim 1, the control that it is characterized in that said water environment water temperature begin from subordinate phase and the error of thermal diffusion environment temperature allow 1% of Initial Temperature Difference among 15mins to complete to the error of the control water environment water temperature that enters the phase III and thermal diffusion environment temperature less than or equal to the minimum of test unit less than ± 0.3 ℃.
3. Multi-temperature stage measuring method of concrete thermal diffusivity as claimed in claim 1 or 2, the variation that it is characterized in that the thermal diffusion environment temperature of each section of front and back in said multiple temperature sections be that rise progressively successively or that fall progressively successively or lifting staggered.
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Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN101915776A (en) * | 2010-07-06 | 2010-12-15 | 舟山市博远科技开发有限公司 | Measuring method for thermal diffusivity of concrete and testing device |
| CN201754152U (en) * | 2010-08-04 | 2011-03-02 | 舟山市博远科技开发有限公司 | Testing device for determination of concrete thermal diffusivity |
| CN102033080A (en) * | 2010-12-27 | 2011-04-27 | 舟山市博远科技开发有限公司 | Method for measuring specific heat capacity of concrete |
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Patent Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN101915776A (en) * | 2010-07-06 | 2010-12-15 | 舟山市博远科技开发有限公司 | Measuring method for thermal diffusivity of concrete and testing device |
| CN201754152U (en) * | 2010-08-04 | 2011-03-02 | 舟山市博远科技开发有限公司 | Testing device for determination of concrete thermal diffusivity |
| CN102033080A (en) * | 2010-12-27 | 2011-04-27 | 舟山市博远科技开发有限公司 | Method for measuring specific heat capacity of concrete |
Non-Patent Citations (2)
| Title |
|---|
| 一种测定混凝土热扩散率的新方法;诸华丰等;《"全国混凝土新技术、新标准及工程应用"学术交流会暨混凝土质量委员会和建筑材料测试技术委员会2010年年会论文集》;20101231;第390-396页 * |
| 诸华丰等.一种测定混凝土热扩散率的新方法.《"全国混凝土新技术、新标准及工程应用"学术交流会暨混凝土质量委员会和建筑材料测试技术委员会2010年年会论文集》.2010,第390-396页. |
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