Method for measuring heat conductivity of active heat-protection type calorimeter by virtue of quasi-steady-state method and correction method of active heat-protection type calorimeter

Abstract

The invention discloses a technical scheme and a high-precision measuring method of a measuring device for measuring low-heat-conduction thermal insulation materials, provides a device and a method for measuring the heat conductivity of an active heat-protection type calorimeter by virtue of a quasi-steady-state method as well as a calorimeter correction method and technical scheme based on ASTME2584. Aiming at the shapes and types of different testing materials, an active heat-protection type structural design of a measuring device including a single panel sample, a dual-panel sample and a cylindrical sample is provided. According to the technical scheme, the lateral heat loss can be effectively eliminated, one-dimensional heat flow can be effectively guaranteed, the low heat conductivity measurement and the ultralow heat conductivity measurement on the thermal insulation materials can be realized under high-temperature and ultrahigh-temperature conditions, the continuous dynamic measurement on the heat conductivity in the whole temperature range can be realized, and meanwhile, the measurement accuracy is relatively high.

Description

technical field [0001] The invention belongs to the field of thermal physical property detection of materials, and relates to the measurement of thermal conductivity, thermal diffusivity and specific heat capacity of heat insulation materials in the form of various powders, solids and structural parts, and specifically relates to the thermal conductivity of quasi-steady-state calorimeter method The test principle and the measuring device and test method involved in ASTM E2584, especially a high-precision quasi-steady-state calorimeter method thermal conductivity measuring device with an active protective heat device and a calibrated calorimeter device and the corresponding test method . Background technique [0002] Thermophysical performance parameters such as thermal conductivity, thermal diffusivity, specific heat capacity, etc. are important performance parameters for the design, manufacture, use and quality control of various heat insulation materials and fireproof mat...

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Problems solved by technology

[0005] (3) For the steady-state measurement of thermal conductivity of anti-insulation materials, the classic steady-state guarded hot plate method and heat flow meter method are generally used at home and abroad. Although the highest test temperature does not exceed 1000 ° C, the measurement accuracy can be obtained. ensure

[0016] Disadvantages: Although the test model is simple, it is difficult to realize the boundary conditions required by the test model, so the outstanding disadvantage is that the measurement error is large. This is the calorimeter quasi-steady-state thermal conductivity test method Bottlenecks that can only be measured qualitatively but not quantitatively

It can be seen that ASTM E2584 adopts a typical passive heat protection technology. This 0.02 W / mK heat insulation material is far from meeting the adiabatic boundary conditions in the test model. During the temperature rise and fall test of the actual calorimeter , this means of heat insulation will bring a large lateral heat loss to the calorimeter, which is the biggest error source of this test method at present

At the same time, at present, thermal insulation materials with a thermal conductivity of 0.02 W / mK at home and abroad generally have low density and poor strength, and the material cost is also high. As a result, the measuring device using this type of thermal insulation material as a heat protection form is easily damaged. , it is necessary to change the heat protection material frequently, which is extremely inconvenient to use in engineering, which is the economic reason why this test method cannot be popularized and applied.

[0018] (2) The heat capacity of the calorimeter cannot be accurately determined.

[0019] (3) The influence of the uneven heating temperature of the sample: In the calorimeter-type quasi-steady-state thermal conductivity test practice ASTM E2584, the uniformity of the sample surface temperature distribution is not clearly stipulated, while the quasi-steady-state thermal conductivity The test model and boundary conditions of the conductivity test method are a typical one-dimensional heat flow problem. The non-uniform heating of the sample will seriously destroy the one-dimensional heat flow process and bring errors to the measurement.

However, the actual situation is that for the measurement of thermophysical parameters of phase change heat storage materials, the American Society for Testing and Materials (ASTM) did not adopt this characteristic calorimeter quasi-steady-state test method, but re-established a method based on The test method ASTM C1784 (Standard Test Method for Using a Heat Flow Meter Apparatus for Measuring Thermal Storage Properties of Phase Change Materials and Products) on the heat flow meter method, but this method and the corresponding measuring device are far more accurate than the calorimeter type steady state method

[0021] Through the above analysis of the advantages and disadvantages of the calorimeter-type quasi-steady-state thermal conductivity test method, we can clearly see the bottleneck of this test method. This is why ASTM E2584 has always been classified as a standard practice "Standard Practice" and cannot become a standard. The reason for the "Standard Test Method" test method is also the main reason why this very convenient quasi-steady-state test method has not been well promoted in applications.

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