CN1474180A - Method and device for continuously detecting phase transformation material life - Google Patents
Method and device for continuously detecting phase transformation material life Download PDFInfo
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- CN1474180A CN1474180A CNA031297617A CN03129761A CN1474180A CN 1474180 A CN1474180 A CN 1474180A CN A031297617 A CNA031297617 A CN A031297617A CN 03129761 A CN03129761 A CN 03129761A CN 1474180 A CN1474180 A CN 1474180A
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Abstract
The method of detecting the life of phase transformation material includes setting the tested phase transformation material in molten pool and continuous repeated melting and freezing test with automatic circular melting and freezing system including cold melt and hot melt. During the detection, the temperature change data is detected continuously with some temperature measuring device and fed to data collector and temperature controlling device, so that the cold melt and hot melt are switched, the temperature change is recorded, calculated and curve drawn, the phase transformation point and phase transformation heat are determined and the life of the phase transformation material is measured. The corresponding detection device is designed. The present invention has the advantages of multiple sampling, automatic continuous measurement, accurate measurement, and other advantages.
Description
Technical Field
The invention relates to a technology for measuring the service life of a phase-change material, in particular to a method and a device for measuring the service life of the phase-change material according to a change curve of the temperature of the phase-change material along with time in a condensation process after multiple times of melting and freezing experiments, wherein the main classification number of the international patent is planned to be int.C17.G01N 25/06.
Background
In the using process of the phase-change material, the structure and the function of the phase-change material can be changed due to the repeated phase-change process, for example, the organic phase-change material can change the original properties due to aging; also for example, inorganic hydrated salt phase change materials, the phase change heat of the material will gradually decrease due to the unavoidable tendency of phase separation. Therefore, after repeated use, the function of the phase change material is changed or lost due to the influence of the environment and its own factors, and the number of times of use of the phase change material in which the phase change point shifts and the phase change heat decays to a certain extent is referred to as the lifetime thereof.
There is currently no uniform standard for the measurement of the lifetime of phase change materials. The general method is to examine the change size of the melting point of the phase-change material and the decay of the latent heat of phase change after a plurality of times of melting and freezing experiments to judge the service life of the phase-change material. The melting point is generally measured by two methods: the walking curve method and the melting point determinator method. The phase transition heat is generally measured by three methods: conventional kaometer method, Differential Thermal Analysis (DTA) and Differential Scanning Calorimetry (DSC).
The conventional methods for measuring the service life of the phase-change material need to manually perform a plurality of freezing experiments, the phase-change point and the phase-change heat of the phase-change material are measured after each freezing experiment, and then the decay rate of the phase-change material is calculated according to the following formula: eta ═ Hmi/Hm0In the formula, Hm0、HmiThe phase change latent heat of the phase change material initially and after i times of melting and freezing experiments is respectively.
The advantages of these measurement methods are a higher measurement accuracy, but the disadvantages are also apparent: firstly, the service life of the phase-change material can be obtained only after hundreds of times, even thousands of times of melting and freezing experiments; moreover, DSC test is required to be matched with freeze-thaw experiments, and the sample taken in each DSC measurement is only 2.0-10.0 mg, so that the experimental result cannot truly reflect the thermal physical properties of the measured material (especially bulk material); meanwhile, the measurement cannot be automatically carried out due to the limitation of a measurement method, and time and labor are wasted; in particular, the decay process of the phase change material cannot be systematically and continuously observed; in addition, the measuring method has high testing cost, and is not beneficial to practical application and popularization.
Disclosure of Invention
Aiming at the defects of the existing determination method, the invention mainly solves the technical problem of providing the method for continuously determining the service life of the phase-change material, and the method has the advantages of more samples, automatic and continuous measurement, accurate determination result, lower cost and the like; meanwhile, the device for continuously measuring the service life of the phase-change material by implementing the method of the invention is also designed, and has the advantages of simple structure, low manufacturing cost, simple and convenient operation, low use cost and the like.
The technical scheme for solving the technical problem of the method is as follows: designing a method for continuously measuring the service life of a phase-change material: putting the phase-change material to be tested into a melting and freezing experiment pool, and carrying out continuous multiple melting and freezing experiments on the phase-change material by utilizing two liquid flow circulating devices of cold liquid and hot liquid connected with the phase-change material; the cold liquid and hot liquid circulating devices are respectively composed of respective liquid flow conveying equipment and flow metering equipment; the two groups of liquid circulation devices of cold liquid and hot liquid and the low and high temperature constant temperature bath tanks connected with the liquid circulation devices form an automatic circulation thawing system; in the experimental process, the temperature measuring device is used for continuously detecting the temperature change data from the experimental pool connected with the temperature measuring device, the collected data are simultaneously and respectively sent to the data collecting device and the temperature control switch device which are connected with the temperature measuring device, the latter automatically switches two groups of liquid flow circulating devices of cold liquid and hot liquid, the former records and calculates the change value of the temperature of the phase change material along with the time and draws the change curve, and then the phase change point and the relative size of the phase change heat of the phase change material are determined according to the change value and the relative size of the phase change heat, and the service life of the phase change material is measured.
The technical scheme for solving the technical problem of the device is that the device for continuously measuring the service life of the phase-change material is designed according to the method, and is characterized by comprising a melting and freezing experiment pool device for bearing the phase-change material to be measured and two independent liquid flow circulating devices which are connected with the melting and freezing experiment pool device and can continuously carry out melting and freezing experiments on the phase-change material for multiple times; one of the two groups of liquid circulation devices is a low-temperature liquid circulation device which is connected with the low-temperature constant-temperature bath; the other group is a high-temperature liquid flow circulating device which is connected with the high-temperature constant-temperature bath tank, and the low-temperature liquid flow circulating device and the high-temperature liquid flow circulating device are respectively connected with a temperature control switch device which can switch the conveying equipment to be switched on and off; the temperature control switch device is also connected with the temperature measuring device; the temperature measuring device is respectively connected with the melting and freezing experiment pool device and the data acquisition device.
The method of the invention uniquely designs an automatic circulating thawing system, can determine the service life of the phase-change material according to the curve rule of the temperature of the phase-change material changing along with time in the condensation process, and has the following advantages compared with the traditional determination method: DSC test and freeze thawing experiment are not required to be carried out; the number of test samples is large, and about 30g can be taken generally, so that the thermophysical properties and the like of a large block of material can be reflected more accurately, and the obtained data is closer to the actual situation of engineering application; the device for continuously measuring the service life of the phase-change material has simple structure, does not need a complete set of precision instruments, has low cost, further greatly reduces the test cost by more than 50 percent compared with the current universal method; meanwhile, the method for measuring the latent heat of phase change is simple and convenient, and the continuous service life measurement can be realized; in addition, the continuous determination of the service life of the phase-change material is applicable to both inorganic phase-change materials and organic phase-change materials, and is greatly beneficial to screening the service life of the phase-change materials.
Description of the drawings:
the present invention will be described in detail with reference to the following embodiments and the accompanying drawings.
Fig. 1-1 is a graph of a step cooling curve for determining a change in phase change temperature with time when a supercooling phenomenon does not occur in a phase change material. Since a phase change occurs in a substance with a certain thermal effect, the temperature corresponding to the first turning point is defined as the phase change temperature. Such as T in FIG. 1-1m；
Fig. 1-2 are graphs of a step cooling curve for determining a change in phase change temperature with time when a supercooling phenomenon occurs in a phase change material. As can be seen from fig. 1-2, when the first turning point of the step profile occurs, there is a certain temperature rise (i.e. supercooling phenomenon), and the highest temperature of the phase change material at which supercooling occurs and the temperature rise is generally defined as the phase change temperature. Such as T in FIGS. 1-2m。
FIG. 2 is a schematic diagram illustrating the method of determining the lifetime of a phase change material according to the present invention; wherein,
FIG. 2-1 is a graph of phase change temperature versus time recorded and processed by the data acquisition system during a first condensation of the phase change material;
fig. 2-2 is a graph of phase change temperature versus time recorded and processed by the data acquisition system during the ith condensation of the phase change material.
FIG. 3 is a schematic block diagram of an apparatus for continuously measuring the lifetime of a phase-change material according to an embodiment of the present invention;
FIG. 4 is a schematic structural diagram of an embodiment of an apparatus for measuring the lifetime of a phase-change material according to the present invention, which corresponds to the structural principle of the method illustrated in FIG. 3;
FIG. 5 is a graph showing the variation of the phase change point of the phase change material with the number of times of freezing in accordance with example 1 of the present invention;
FIG. 6-1 is a graph of temperature versus time recorded and processed by the data acquisition system during a first condensation of the phase change material of example 1;
fig. 6-2 is a graph of temperature versus time obtained during the 50 th condensation of the phase change material of example 1.
Detailed Description
The method for continuously measuring the service life of the phase-change material (see figures 3 and 4) designed by the invention is as follows: putting the phase-change material to be tested into a melting and freezing experiment pool 1, and carrying out continuous multiple melting and freezing experiments on the phase-change material by utilizing two sets of liquid flow circulating devices 21 and 22 of cold liquid and hot liquid connected with the phase-change material; the cold liquid and hot liquid two groups of liquid circulation devices 21 and 22 respectively comprise respective known liquid flow conveying equipment and flow metering equipment; the two groups of liquid circulation devices 21 and 22 of cold liquid and hot liquid and the low and high temperature constant temperature baths 51 and 52 connected with the liquid circulation devices form an automatic circulation freezing system for the freezing experiment; in the experimental process, the temperature measuring device 3 is used for continuously detecting the temperature change data of the phase change material from the freezing experimental pool 1 connected with the temperature measuring device, the acquired data are simultaneously and respectively sent to the data acquisition device 4 and the temperature control switch device 6 connected with the temperature measuring device, the latter automatically switches two sets of liquid flow circulation devices 51 and 52 of cold liquid and hot liquid according to set process conditions, and the former records and calculates the change value of the temperature of the phase change material along with time and draws the change curve of the whole process, including the curve of the condensation process for further determining the phase change point of the phase change material and the relative magnitude of phase change heat, namely determining the service life of the phase change material.
The continuous measurement principle of the present invention (see FIGS. 1-1, 1-2, 2-1 and 2-2) is based on the following results of the inventors: the melting point of the phase change material and the relative magnitude of the change in latent heat of phase change are determined by the temperature profile of the phase change material over time during condensation (see fig. 2-1). Under the constant cold source, the liquid phase-change material is in the time t1Carrying out cooling treatment; before the phase change occurs, the cooling curve can be regarded as a straight line; when the phase change occurs, the temperature-lowering curve has a turning point (i.e. t on fig. 2-1)2，TmA point); when the phase transition is completely realized, the cooling curve has a second turning point (t)3，T3A dot). Assuming no phase change of the material occurs, then at t2-t3Within time, its cooling curve should be along t1-t2The extension line of the temperature-reducing curve (the dotted line in fig. 2-1) is still linearly changed during the development, but in the actual process, the temperature-reducing curve is turned due to the occurrence of phase change. Set at time t2-t3During the phase change, the temperature difference between the actual temperature reduction of the phase change material and the hypothetical phase-change-free temperature reduction is delta T, and can be obtained according to the principle that the thermodynamic state function is irrelevant to the process: hm0＝mcpΔT0，Hmi＝mcpΔTi(ii) a So η ═ Hmi/Hm0＝ΔTi/ΔT0Wherein m is the mass of the phase change material in the melting and freezing experiment pool; hm0、HmiRespectively phase change latent heat of the phase change material initially and after i times of melting and freezing experiments; c. CpIs the constant pressure heat capacity of the phase-change material in the liquid state. While maintaining multiple condensation of ambient temperature phaseMeanwhile, the temperature-decreasing curve in the phase-change time can be linearized (see fig. 2-1 and 2-2), and the expression is η ═ Hmi/Hm0＝Δti/Δt0＝(t3i-t2i)/(t30-t20). Therefore, the method can continuously measure the service life of the phase-change material according to the temperature change curve of the phase-change material in the condensation process along with the time.
The principle of the method for determining the lifetime of a phase change material according to the present invention is shown in FIG. 2 (see FIGS. 2-1 and 2-2). Wherein FIG. 2-1 is a graph of temperature versus time recorded and processed by the data acquisition system during a first condensation of the phase change material; fig. 2-2 is a graph of temperature versus time obtained during the ith condensation of a phase change material. And obtaining the decay rate of the phase change heat of the phase change material according to different values of the delta T in the two graphs.
The measuring device (see fig. 3 and 4) for continuously measuring the service life of the phase-change material mainly comprises a melting and freezing experiment pool device 1 for bearing the phase-change material to be measured, and two groups of liquid flow circulating devices 2 which are connected with the melting and freezing experiment pool device and can continuously carry out melting and freezing experiments on the phase-change material for multiple times; one of the two liquid circulation devices 2 is a low-temperature liquid circulation device 21 which is connected with a low-temperature constant-temperature bath 51; the other group is a high-temperature liquid flow circulating device 22 which is connected with the high-temperature constant-temperature bath 52, the low-temperature liquid flow circulating device 21 and the high-temperature liquid flow circulating device 22 are respectively connected with a temperature control switch device 6 (hereinafter referred to as a temperature control switch 6) which can switch the conveying equipment to be switched on and off, and the temperature control switch 6 is also connected with a temperature measuring device 3; the temperature control switch 6 can set the temperature, and when the input temperature signal is higher than the set upper limit of the temperature, the temperature control switch 6 is in a long-closed state; when the input temperature signal is lower than the set lower limit of the temperature, the temperature control switch 6 is in a long-open state; the temperature measuring device 3 is respectively connected with the melting and freezing experiment pool device 1 and the data acquisition device 4. The low-temperature and high-temperature constant-temperature bath tank devices 51 and 52 are used for storing liquid flow media for heating or cooling the phase-change materials so as to perform a melting and freezing experiment; the low-temperature and high-temperature liquid flow circulating devices 21 and 22 are used for liquid flow circulating flow of a phase-change material heating or freezing measurement experiment; the temperature measuring device 3 is used for measuring the instant detection of the temperature change of the phase-change material during the whole measuring period; the data acquisition device 4 is used for acquiring and recording the change of the temperature of the phase-change material along with the time in the whole continuous melting and freezing measurement experiment period; the temperature control switch 6 is used for controlling the switching of the melting or freezing measurement experiment of the phase-change material, namely, the automatic switching of the low-temperature liquid flow circulating device 21 and the high-temperature liquid flow circulating device 22.
FIG. 3 is a schematic block diagram of a phase change material life measuring device according to an embodiment of the present invention. The melting and freezing experiment pool device 1 is used as a main body part for bearing experiment determination phase-change materials, and a temperature sensing instrument platinum resistance thermometer for temperature determination is inserted inside the melting and freezing experiment pool device; signals measured by the platinum resistance thermometer are transmitted to two directions through the temperature measuring device 3, and are transmitted to the data acquisition device 4 for data storage; secondly, the measured temperature is transmitted to the temperature control switch device 6 to automatically open and close the conveying equipment, so as to achieve the automatic switching of the cold and hot circulating system, and when the measured temperature is higher than the upper limit temperature (such as T) set by the temperature control switch device 6mWhen the temperature is 10 ℃, an electric signal is sent to conveying equipment in a cold circulation system, the cold circulation system is started, the phase-change material is in a cooling and solidifying stage, and the temperature of the phase-change system is reduced; when the measured temperature is lower than the lower limit temperature (e.g. T) set by the temperature-controlled switch device 6mAt-10 ℃), the conveying equipment in the cold circulation system stops running, the cold circulation system is closed, the cold liquid in the outer sleeve C (see fig. 4) automatically flows back to the low-temperature constant-temperature bath 51, meanwhile, the conveying equipment in the hot circulation system starts running, the hot circulation system is started, the temperature of the phase-change system starts increasing, and the phase-change system enters a melting stage; when the measured temperature is higher than the set temperature (T) againmAt +10 ℃, the cold circulation system is automatically opened, the hot circulation system is automatically closed at the same time, meanwhile, the hot liquid in the inner sleeve B (see fig. 4) automatically flows back to the high-temperature constant-temperature bath 52, and the phase-change material is in the cooling and solidification stage. The temperature sensing instrument senses the temperature constantly and sends a signal, and the phase change material can realize multiple times of melting and freezing experiments. During the experiment, the temperature values of the liquid in the high-temperature constant-temperature bath 52 and the low-temperature constant-temperature bath 51 are adjusted and set in advance, so that the phase change is realizedThe temperature rising and reducing rate of the material is controlled at 2-5 ℃/min.
Fig. 4 is a schematic structural diagram of an embodiment of the apparatus for continuously determining the lifetime of a phase-change material according to the present invention, which corresponds to the structural principle of the method illustrated in fig. 3. The device is characterized in that the melting and freezing experiment pool device 1 for bearing the tested phase change material comprises (see figure 4): a crystallized glass tube A for placing phase-change materials, and an inner sleeve B and an outer sleeve C which are closed and provided with liquid flow inlets and outlets; the length of the crystallized glass tube A is 150-200mm, the outer diameter is 25mm, and the wall thickness is 2 mm; an inner sleeve B for heating the phase change material in a liquid bath outside the crystallized glass tube A and simultaneously serving as a protective sleeve of the crystallized glass tube A, wherein the inner sleeve B is made of glass, the length of the inner sleeve B is 180mm, the inner diameter of the inner sleeve B is 45mm, the wall thickness of the inner sleeve B is 2mm, a hydrothermal inlet of the inner sleeve B is positioned at the bottom a of the inner sleeve B (the protective sleeve, the lower part of the inner sleeve B is the same), and an outlet of the inner sleeve B is positioned; an outer sleeve C which is made of glass and used for carrying out liquid bath cooling on the phase-change material and is arranged outside the inner sleeve B, the height of the outer sleeve C is 200-250mm, the thickness of an interlayer between the inner sleeve C and the outer sleeve B, C is 30mm, a cold liquid inlet of the outer sleeve C is positioned at the position C at the bottom of the outer sleeve C, and an outlet of the outer sleeve C is positioned at the position d at the top of the outer sleeve C; the liquid inlet a of the inner sleeve B passes through the outer sleeve C. Although the described embodiments have been given specific data values, the present invention is not limited by the numerical values given in the embodiments. The low-temperature constant-temperature bath device D (51 in fig. 3) and the high-temperature constant-temperature bath device E (52 in fig. 3) are a well-known super thermostat device; the liquid circulation device comprises a cold liquid or low-temperature liquid circulation device and a hot liquid high-temperature liquid circulation device. The lines of the two liquid flow circulating systems are mutually locked, namely when one liquid flow circulating system is opened, the other liquid flow circulating system is closed; the two liquid flow circulating systems respectively comprise a conveying device K, L and a flow metering device (such as a rotary flowmeter); the temperature measuring device F (3 in fig. 3) contains a well-known platinum resistance thermometer G for measuring the change in temperature of the phase change material during the entire experimental measurement; the data acquisition device H (4 in fig. 3) is also prior art and can automatically record the data signal from the temperature measuring device F; the function of the known thermostat I (6 in fig. 3) is to determine when the measured temperature is above its set upper limit temperature (e.g. T)mAt +10 deg.C, an electrical signal is sent to the cold cycleConveying equipment in the system starts a cold circulation system; when the measured temperature is below a predetermined lower limit temperature (e.g. T)mWhen the temperature is minus 10 ℃), the cold circulation system is closed, the hot circulation system is opened, namely the automatic circulation thawing system can receive a signal from the temperature control switch I and execute corresponding actions; meanwhile, the temperature control switch I is also controlled by the temperature measuring device F. The upper and lower temperature limit values are set according to the property of the measured material. When the hydrothermal circulation system is closed, the hydrothermal in the inner sleeve B automatically flows back to the high-temperature constant-temperature bath tank E; similarly, when the cold liquid circulating system is closed, the cold liquid in the outer sleeve C automatically flows back to the low-temperature constant-temperature bath D. J is a support for the freezing experimental tank device 1, which should make the level of the freezing experimental tank device 1 higher than the level of the cold and hot bath D, E, so as to facilitate the liquid flow in the inner and outer sleeves B, C to automatically and smoothly flow back into the cold and hot bath D, E by gravity after the circulation device is closed. During the experiment, the temperature rise and the temperature drop rate of the phase change material are controlled at 2-5 ℃/min by adjusting the preset temperature values of the liquid in the high-temperature constant-temperature bath tank and the low-temperature constant-temperature bath tank. If the temperature rising and reducing speed is too fast, the phase change process of the phase change material is too fast, so that the phase change is incomplete; if the temperature rising and reducing rate is too slow, the experiment time is too long, which is not favorable for the continuous determination of the experiment.
The process of determining the service life of the phase-change material by using the method and the device of the invention is as follows: the phase change material has a known phase change point TmFirstly, the temperature of the high-temperature constant-temperature bath E, D and the temperature of the low-temperature constant-temperature bath E, D are respectively adjusted to be Tm+15℃、Tm15 ℃ below zero and the upper temperature limit of the temperature-controlled switching device I is set to Tm+10 ℃ with a lower limit of Tm-10 ℃ and then raising the temperature of a certain amount (generally 30g optionally) of the phase change material to Tm+15, it is placed in a crystallized glass tube A, inside which a platinum resistance thermometer G will measure its temperature. At the moment, the temperature of the phase-change material is higher than the set upper limit temperature of the temperature control switch device I, so that the conveying device K in the cold liquid circulating system is started, and the flow of the cold liquid is controlled by adjusting the size of the flow meter. At this time, the outer sleeve C is filled with cold fluid, and the phase change system enters a solidification stageA segment; due to condensation, the temperature of the phase change system will gradually decrease until the temperature of the phase change system decreases to the set lower limit temperature of the temperature control switch device I, the cold and hot circulation systems are automatically switched, namely, the conveying equipment K in the cold liquid circulation system is closed, and the conveying equipment L in the hot liquid circulation system starts to operate. At the moment, the cold fluid in the outer sleeve C flows back to the low-temperature constant-temperature bath D by virtue of gravity, the inner sleeve B is gradually filled with the hot fluid, and the phase-change system starts to enter a melting stage. When the temperature rises to Tm +10 ℃ again, the conveying device K is started, the conveying device L is closed, and the phase change system starts to enter the next freezing and melting process. The temperature change of the phase change system was measured by a platinum resistance thermometer G and recorded and stored by a data acquisition device H throughout the experiment, and the whole measurement experiment was continuously performed. And finally, determining the service life of the phase-change material by using the formula according to the temperature change curve of the phase-change material in the whole condensation process along with the time.
One specific example is given below:
the formula of the phase-change material for the life measurement experiment is as follows: 85% of a phase change working medium material mirabilite, 9% of filler sepiolite, 2% of a thickening agent sodium alginate, 1% of a crystal form regulator sodium hexametaphosphate and 3% of a nucleating agent borax.
The initial transformation point of the phase change material is known to be 32.0 ℃. Firstly, the temperature of the aqueous solution in a high-temperature constant-temperature bath E, D and a low-temperature constant-temperature bath E, D (a super constant-temperature bath is selected here) is regulated to 47.0 ℃ and 17 ℃, the upper limit of the temperature of a temperature control switch device I is set to 42 ℃, the lower limit of the temperature control switch device I is set to 22 ℃, then 30G of phase change material is heated to 47.0 ℃ and placed in a glass tube crystal A, a platinum resistance thermometer G measures that the temperature of the platinum resistance thermometer G is higher than the set upper limit temperature of the temperature control switch device I, a signal is transmitted to the temperature control switch I, a conveying equipment centrifugal pump K in a cold liquid circulating system is instructed to be started, and the. At the moment, the outer sleeve C is filled with cold liquid, and the phase change system enters a solidification stage; due to condensation, the temperature of the phase change system is gradually reduced until the temperature of the system is reduced to the set lower limit temperature of 22 ℃ of the temperature control switch device I, the cold and hot circulating systems are automatically switched, namely the centrifugal pump K is closed, and the conveying equipment of the hot liquid circulating system, namely the centrifugal pump L, starts to operate. At the moment, water flow in the outer sleeve C flows back to the low-temperature constant-temperature bath tank D by means of gravity; and the inner sleeve B is filled with hydrothermal liquid, the phase change system starts to enter a melting stage, when the temperature rises to 42 ℃ again, the centrifugal pump K is started, the centrifugal pump L is closed, and the phase change system starts to enter the next freezing and melting experimental determination process. In the experimental process, the temperature rising and reducing rates of the phase-change material are controlled at 2 ℃/min. In the experimental process, the temperature change of the phase change system is measured by a platinum resistance thermometer and recorded and stored by a data acquisition device H, for example, a graph of the temperature recorded and processed by the data acquisition system in the first condensation process of the phase change material and the time relationship is drawn in fig. 6-1; fig. 6-2 is a graph of the temperature of the phase change material obtained in the 50 th condensation process as a function of time, and all the experimental tests (i.e., 1 st to 50 th) were performed continuously, and fig. 5 is a graph showing the change point of the phase change material as a function of the number of times of freezing. The figure shows that after 50 times of thawing experiments, the phase change point of the phase change system does not drift, and meanwhile, the phase change system is reflected to have better anti-aging property.
Finally, according to the temperature change curve of the phase change material in 50 times of condensation processes along with time, the service life of the phase change material can be determined by the formula: that is, according to the different values of the key value Δ T in the two graphs of fig. 6-1, 6-2, the decay rate of the phase change material phase change heat can be calculated, wherein η ═ Hmi/Hm0＝ΔTi/ΔT0＝[29.0-(-14.4)]/[29.3-(-31.3)]71.6%. Such calculation can be simply done by a computer or calculator.
Claims (5)
1. A method for continuously measuring the service life of a phase-change material comprises the steps of putting the phase-change material to be measured into a melting and freezing experiment pool, and carrying out continuous multiple melting and freezing experiments on the phase-change material by utilizing two liquid flow circulating devices of cold liquid and hot liquid connected with the phase-change material; the cold liquid and hot liquid circulating devices are respectively composed of respective liquid flow conveying equipment and flow metering equipment; the two groups of liquid circulation devices of cold liquid and hot liquid and the low and high temperature constant temperature bath tanks connected with the liquid circulation devices form an automatic circulation thawing system; in the experimental process, the temperature measuring device is used for continuously detecting the temperature change data from the experimental pool connected with the temperature measuring device, the collected data are simultaneously and respectively sent to the data collecting device and the temperature control switch device which are connected with the temperature measuring device, the latter automatically switches two groups of liquid flow circulating devices of cold liquid and hot liquid, the former records and calculates the change value of the temperature of the phase change material along with the time and draws the change curve, and then the phase change point and the relative size of the phase change heat of the phase change material are determined according to the change value and the relative size of the phase change heat, and the service life of the phase change material is measured.
2. The method of claim 1, wherein the phase change point and the phase change heat change of the phase change material are determined by a temperature profile of the phase change material during condensation.
3. Method for continuously determining the lifetime of a phase change material according to claim 1, wherein the temperature determined by the temperature determining means is higher than the upper limit temperature (T) set by the temperature-dependent switching devicemAt 10 ℃, the conveying equipment in the cold circulating system starts to operate, and the cold circulating system is started; when the measured temperature is lower than the lower limit temperature (T) set by the temperature-controlled switch devicemAt-10 ℃), the conveying equipment in the heat circulation system starts to operate, and the heat circulation system is started; during the measurement, the temperature values of the liquid in the high-temperature constant-temperature bath and the low-temperature constant-temperature bath are adjusted and set in advance, so that the temperature rising and reducing rates of the phase change material are controlled to be 2-5 ℃/min.
4. An apparatus for continuously measuring the life of a phase change material for carrying out the method according to claim 1, 2 or the method, characterized in that it comprises a freezing experiment pool device (1) for carrying the phase change material to be measured, two independent liquid circulation devices (2) connected with the freezing experiment pool device for continuously carrying out a plurality of times of freezing experiments on the phase change material; one of the two groups of liquid flow circulating devices (2) is a low-temperature liquid flow circulating device (21) which is connected with a low-temperature constant-temperature bath (51); the other group is a high-temperature liquid flow circulating device (22) which is connected with a high-temperature constant-temperature bath (52), and the low-temperature liquid flow circulating device (21) and the high-temperature liquid flow circulating device (22) are respectively connected with a temperature control switch device (6) which can switch the conveying equipment to open and close; the temperature control switch device (6) is also connected with the temperature measuring device (3); the temperature measuring device (3) is respectively connected with the melting and freezing experiment pool device (1) and the data acquisition device (4).
5. The apparatus for continuous determination of the lifetime of a phase change material according to claim 6, wherein the freeze laboratory tank apparatus (1) carrying the phase change material to be measured comprises: a crystallized glass tube (A) for placing a phase-change material to be detected and two inner sleeves (B) and two outer sleeves (C) which are closed and provided with liquid flow inlets and outlets; the length of the crystallized glass tube (A) is 150-200mm, the outer diameter is 25mm, the wall thickness is 2mm, and a feeding port is arranged at the top; the length of the inner sleeve (B) is 130-180mm, the inner diameter is 45mm, the wall thickness is 2mm, the liquid inlet a is positioned at the lower part of the inner sleeve (B), and the liquid outlet B is positioned at the upper part of the inner sleeve; the height of the outer sleeve (C) is 200-250mm, and the thickness of the interlayer is 30 mm; the liquid inlet C is positioned at the lower part of the outer sleeve (C), and the liquid outlet d is positioned at the upper part of the outer sleeve; the liquid inlet a of the inner sleeve (B) passes through the outer sleeve (C).
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