CN106370312A - Absolute radiometer and absolute radiometer background space radiation and heat transfer measuring method - Google Patents

Abstract

The invention provides an absolute radiometer and absolute radiometer background space radiation and heat transfer measuring method, which belongs to the field of optical radiation and measurement to solve the problems in the prior art that in the process of using a conventional absolute radiometer to measure the total solar irradiance, radiation and heat transfer often suffer from correction loss and that the international radiation benchmark traceability is poor. The absolute radiometer comprises a field diaphragm, a main diaphragm and an internal thermal structure in the radiometer. The internal thermal structure in the radiometer includes a compression sheet, a polyimide gasket, a thermopile, a heat sink and an absorption cavity. The absorption cavity is of a positively conical cavity structure with brim; the upper face of the thermopile is connected with the brim of the absorption cavity and the lower face is connected with the heat sink. The compression sheet is fixed to the brim of the absorption cavity through the polyimide gasket. In this method, the radiometer is minimized through the use of a finite element method, and a corresponding radiation element is covered on the outer surface. The radiation element is used to solve the complex radiation and heat transfer relationship between the background space and the absorption cavity and to make up the lack of a correction system in the absolute radiometer.

Description

Absolute radiometer and absolute radiometer background space radiation heat transfer measurement method

technical field

The invention relates to the field of on-orbit optical radiation measurement of a remote sensor, in particular to a measurement method for measuring background space radiation heat transfer of an absolute radiometer.

Background technique

With the continuous deepening of solar irradiance research and the development of space spectrum remote sensing, people have higher and higher requirements for the measurement accuracy of total solar irradiance. Quantitatively measuring the background space radiation heat transfer of absolute radiometers to improve the measurement accuracy of absolute radiometers is a key issue in the development of solar irradiance science at this stage. Among them, the radiation heat transfer that affects the measurement of the absolute radiometer includes two parts: the radiation heat transfer from the background space to the absorption cavity and the radiation heat transfer between the radiometer cavity components. The radiation heat transfer inside the cavity component is usually neglected due to the small temperature difference of each component, and the radiation heat transfer in the background space is considered to be a key factor affecting the temperature of the cavity component. However, due to the complex cavity assembly structure of absolute radiometers, the radiation angle factor between the background space and the absorbing cavity is difficult to quantitatively evaluate. At the same time, since the absolute radiometer is enclosed in a precise internal space, this part of energy cannot be accurately obtained by experimental measurement or theoretical calculation.

In existing research, a radiation protection layer made of oxygen-free high-conductivity copper is generally covered outside the base and the absorbing cavity. The radiation energy in the background space is first transferred to the protective layer, and then the heat is quickly transferred to the base of the refrigerator through the characteristics of oxygen-free high-conductivity copper and high thermal conductivity, so as to achieve the purpose of shielding the radiation heat exchange in the background space. However, this method can only achieve the purpose of weakening the effect of background space radiation heat transfer on the temperature of the absorbing cavity components. That is, part of the energy is transferred to the base of the refrigerator through heat conduction, and part of the energy is still transferred to the absorption cavity assembly through the radiation protection layer through radiation heat exchange. In addition, the uncertainty and systematic error introduced by this method cannot be accurately assessed, which also affects the data processing of the absolute radiometer instrument.

Therefore, in order to meet the research needs of the Earth's climate observation, improve the accuracy of the absolute radiometer on-orbit measurement and trace the measurement data to the world radiation standard. Using a new measurement method to quantitatively evaluate the background space radiation heat transfer of an absolute radiometer is a new idea for on-orbit optical radiation measurement.

Contents of the invention

In order to solve the problem of lack of radiation heat transfer correction in the process of measuring the total solar irradiance of the existing absolute radiometer and poor traceability with the international radiation reference, the invention provides an absolute radiometer and an absolute radiometer background space radiation heat transfer method Measurement methods.

Absolute radiometer, including field diaphragm, main diaphragm and internal thermal structure of the radiometer; the field diaphragm is assembled in front of the internal thermal structure of the radiometer to limit the incident intensity of incident light and eliminate stray light, the main diaphragm Located behind the field diaphragm and installed at the entrance of the internal thermal structure of the radiometer, the heat sink is used to balance the temperature of the absorption cavity; the internal thermal structure of the radiometer includes a pressing plate, a polyimide gasket, a thermopile, and a heat sink and an absorption cavity; the absorption cavity is embedded with a heating wire for electric heating in the light radiation area, and the inside of the absorption cavity is coated with a specular reflective paint. The top surface is connected to the brim of the absorption cavity, and the bottom surface of the thermopile is connected to the heat sink; the pressure sheet is fixed to the brim of the absorption cavity by a polyimide gasket.

The measurement method of absolute radiometer background space radiation heat transfer, the method is realized by the following steps:

Step 1. Establish a finite element model;

According to the actual three-dimensional structure of the absolute radiometer, a finite element model corresponding to the actual three-dimensional structure of the absolute radiometer is established in the finite element system;

Step 2. Apply different incident powers sequentially to the finite element model described in step 1 and the actual three-dimensional structure, and compare the steady-state sensitivities of the finite element model and the actual three-dimensional structure when the incident power is the same, and judge the difference between the finite element model and the actual three-dimensional structure. Whether the relative error of the steady-state sensitivity of the actual three-dimensional structure is less than 1%, if yes, perform step three; if not, return to step one;

Step 3, background space heat transfer measurement;

At the far end of the finite element model described in step one, establish a space node that has no coordinate relationship with the finite element model, set the ambient temperature of the radiation cover of the radiometer as a constant, and attach the constant to the space node;

A layer of radiation units corresponding to the space nodes is covered on the outer surface of the radiometer, the shape factors between the space node radiation units are stored in a matrix relationship, and the ambient temperature and heat sink are obtained according to the matrix relationship. The radiation heat exchange between the ambient temperature and the heat sink is equivalent to the radiation heat exchange between the space node and the corresponding radiation unit;

Apply different incident powers to the absorbing cavity of the finite element model in sequence, and record the equilibrium temperature of the absorbing cavity under the state of radiative heat transfer and the state of no radiative heat transfer respectively; take the average value of the measured equilibrium temperature difference, and the average value is the corresponding Radiative heat transfer energy between the background space and the absorbing cavity.

Beneficial effects of the present invention:

One, the method described in the present invention is simple and easy to operate, and repeatability is strong, and the finite element system that is used for quantitative measurement is combined with the actual structure of absolute radiometer, and accuracy is high, is suitable for the different conical cavity structure of absolute radiometer Radiation heat transfer measurement;

Two, the absorption chamber structure and the equivalence of thermophysical properties in the present invention simplify the structure of each layer of the cone chamber, and include the deoxidized resin glue bonding the cone chamber, which is considered more comprehensive and accurate; the thermopile structure consists of 180 pairs of copper - Composed of constantan heating wire and polyimide matrix, the finite element system divides the thermopile into two structures, which is helpful to study the specific contribution of each component of the cone cavity to the time constant of the absolute radiometer;

3. The absorption cavity is divided into a heating wire layer and a black paint layer, corresponding to the light heating stage and the electric heating stage of the absolute radiometer; in addition, the heat sink is connected to the absorption cavity through a thermopile to maintain the components of the absolute radiometer at a constant temperature Under these conditions, the stability and controllability of the measurement are improved.

4. The method of the present invention has the advantages of simple and convenient operation and strong adaptability, and at the same time has the guarantee of accurate and stable measurement and calculation. The cavity structure for different radiometer cone cavities can be used as a standard for quantitative measurement. Combining the established finite element system with the actual model, the relative uncertainty is included in the measurement uncertainty of the absolute radiometer instrument for calculation, which effectively solves the problem of quantitative evaluation of the absolute radiometer background space radiation heat transfer.

Description of drawings

Fig. 1 is the structural representation of absolute radiometer described in the present invention;

Fig. 2 is a structural schematic diagram of the internal thermal structure of the radiometer in the absolute radiometer according to the present invention.

detailed description

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 1. This embodiment is described in conjunction with FIG. 1 and FIG. 2. The absolute radiometer includes a field diaphragm 2, a main diaphragm 3 and an internal thermal structure of the radiometer; the field diaphragm 2 is assembled inside the radiometer. The front of the thermal structure is used to limit the incident intensity of the incident light 1 and eliminate stray light, the main diaphragm 3 is located behind the field diaphragm 2 and installed at the entrance of the thermal structure inside the radiometer, and the heat sink 6 is used to balance the temperature of the absorption cavity 5 ; The internal thermal structure of the radiometer includes a pressing plate 7, a polyimide gasket 8, a thermopile 4, a heat sink 6 and an absorption cavity 5;

The absorption cavity 5 is embedded with a heating wire for electric heating in the light radiation area, and the inside of the absorption cavity 5 is coated with a specular reflective coating. The top surface is connected to the brim of the absorbing cavity, and the bottom surface of the thermopile 4 is connected to the heat sink 6; the pressing sheet 7 is fixed to the brim of the absorbing cavity through a polyimide gasket 8.

In photoelectric measurements the area of the main aperture is precisely measured to determine the irradiance intensity of the incident light. The pressing piece 7 in the cavity assembly is an aluminum ring that fixes the thermopile, and the polyimide gasket 8 insulates the side of the thermopile, so that the thermopile and the heat sink are only connected through the bottom surface and perform heat exchange. It is convenient for the simplified analysis of the heat transfer system of the absolute radiometer. The heat sink 6 is an aluminum cylindrical metal block with a large volume, which encapsulates the cavity assembly and the main aperture of the absolute radiometer. During the photoelectric measurement, the temperature of the heat sink is kept stable by thermal control to ensure the The background environment of heat exchange in the light heating and electric heating stages is the same.

During the photoelectric measurement process of the absolute radiometer, the temperature of the cavity components is affected by the radiation heat transfer, which is specifically manifested as the temperature difference caused by the radiation heat transfer in the background space. The temperature difference cannot be repeatedly measured by specific experimental methods. Measuring this difference requires repeated experiments and has an easy-to-adjust function. The specific steps are as follows:

1. Establish a finite element model. According to the actual three-dimensional structure of the absolute radiometer, the corresponding finite element model is established in the finite element system according to the principle of Boolean operation. The absorption cavity contains a multi-layer structure, the main body is silver, and the outer wall is coated with epoxy resin glue to bond with the thermopile. The complex three-dimensional structure and the uneven distribution of the adhesive need to be simplified. The simplified absorption chamber includes a black paint layer, a heating wire layer and the main body of the absorption chamber, and the resin glue is contained in the main body of the absorption chamber. The specific heat capacity and thermal conductivity of the absorption cavity are set to be adjustable, and other parameters are inherent properties. Apply a heating power of 1mW in the heating area. When the final equilibrium temperature and equilibrium time constant of the finite element model absorption cavity are the same as the actual structure, the specific heat capacity and thermal conductivity at this time are the selected values. This simplification ensures that the finite element model and the real structure have the same total heat fusion and total thermal conductivity.

Second, the finite element model is combined with the actual structure. The steady-state sensitivity of the absolute radiometer is an important parameter to evaluate the performance of the instrument, and determines the range of the temperature of the receiving cavity and the range of the measurement power. In the measurement process, it is defined as the ratio of the temperature difference between the receiving cavity and the heat sink to the input power. Apply incident powers of 60mW, 75mW and 90mW to the finite element model and the actual structure in turn, and compare the steady-state sensitivities of the two cases. When the relative error is less than 1% (meeting the accuracy requirements of the absolute radiometer instrument), the finite element model is considered Comply with the photoelectric inequality measurement standard.

3. Background space radiation heat transfer measurement. A space node that has no coordinate relationship with the 3D model is established at the far end of the model, and the temperature of the second layer of the radiation shield of the low-temperature radiometer is set as a constant and stable at 77K, that is, the ambient temperature is 77K and is attached to the space node. Then, a layer of radiation elements corresponding to the space nodes is covered on the entire outer surface of the radiometer, and the shape factors between the space nodes and the radiation elements are stored in a matrix relationship. Using the matrix relationship and the corresponding radiation relationship when solving, the radiation heat transfer between the ambient temperature and the heat sink is equivalent to the radiation heat transfer between the space node and the corresponding radiation unit. The calculation of this radiation heat transfer energy will follow the thermal changes with sink temperature. The incident powers of 60mW, 75mW and 90mW were sequentially applied to the conical cavity of the finite element model, and the final equilibrium temperatures of the cavity components in the state of radiative heat transfer and the state of no radiative heat transfer were recorded respectively. Take the average value of the final equilibrium temperature difference of the three groups of measurements, and this value is the radiation heat transfer energy corresponding to the background space and the absorption cavity.

In this embodiment, the established model microns the actual structure of the absolute radiometer, and the finite element model closely matches the three-dimensional structure of the radiometer. The structure and thermophysical properties of the radiometer absorption cavity are equivalently simplified. The simplified absorption chamber includes a black paint layer, a heating wire layer, and the main body of the absorption chamber, and the structure includes deoxidizing resin glue for bonding the cone chamber.

The radiometer thermopile structure described in this embodiment is composed of 180 pairs of copper-constantan heating wires and a polyimide matrix. The thermopile structure in the finite element system is divided into a heating wire part and a matrix part.

The measurement method described in this embodiment has strong adaptability, and it can meet the measurement requirements for different types of absolute radiometers and cone cavities with different cavity structures.

In the space environment, affected by cosmic rays and space particles, the cavity components of the radiometer are severely attenuated, and the thermophysical properties of materials change significantly, which affects the calculation of background space radiation heat transfer. After the equivalent of the finite element method of the present invention is adopted, the thermal conductivity and specific heat capacity of the absorption cavity and other component materials are attached with corresponding attenuation functions, which not only improves the accuracy of the background space radiation heat transfer of the solar irradiance absolute radiometer, It can also take into account the attenuation of the physical properties of various materials when measuring in space.

Beginning in the 1980s, the National Physical Laboratory (NPL) and the National Institute of Standards and Technology (NIST) of the United States proposed to develop a low-temperature solar absolute radiometer, thereby establishing a new benchmark for absolute calibration measurement of optical radiation. Compared with the normal temperature radiometer, the measurement accuracy of the low temperature radiometer is increased from 0.1% to 1% to 0.01%. New precision requirements require more accurate error correction. The measurement method of the present invention uses the finite element element method to micronize the radiometer, which is conducive to obtaining high-precision radiation measurement results, and covers the outer surface with a layer of corresponding The radiative element is used to solve the complex radiative heat transfer relationship between the background space and the absorbing cavity. The measured radiative heat transfer is a quantitative effective value, not a qualitative evaluation. This can make up for the lack of the correction system of the absolute radiometer and meet the experimental measurement requirements of the low-temperature solar pyranometer. It is of great significance to improve the traceability between the absolute radiometer measurement value and the international radiation reference WRR (World Radiometric Reference).

To sum up, the finite element element method of the present invention for quantitatively measuring the radiation heat transfer in the background space of the absolute radiometer can solve the key problem that the radiation heat transfer between the background space and the absorption cavity cannot be accurately measured at present. This method has the characteristics of simple operation and strong adaptability, and the boundary conditions and initial conditions of the finite element system can be adjusted to meet the requirements for different situations. Especially for different types of absolute radiometers, the cavity structure of the cone cavity may be different, but this method is still applicable.

Claims (7)

1. absolute radiometer, including field stop (2), key light door screen (3) and the internal heat structure of radiometer；Described field stop (2) It is used for limiting the incident intensity of incident illumination (1) before being assemblied in the internal heat structure of radiometer and eliminate veiling glare, key light door screen (3) position After field stop (2) and be arranged on the internal heat structure porch of radiometer, heat sink (6) are used for the temperature in Balance Absorption chamber (5) Degree；It is characterized in that, the internal heat structure of described radiometer includes tabletting (7), polyimides pad (8), thermoelectric pile (4), heat sink (6) With absorbing cavity (5)；

Described absorbing cavity (5) is imbedded inside for electrically heated heater strip, absorbing cavity (5) in light radiation region and is scribbled direct reflection Coating, described absorbing cavity (5) is the normal cone cavity configuration with the brim of a hat, and the upper top surface of described thermoelectric pile (4) connects the absorbing cavity the brim of a hat, The bottom surface of thermoelectric pile (4) is connected with heat sink (6)；It is solid with the absorbing cavity the brim of a hat that described tabletting (7) passes through polyimides pad (8) Fixed.

2. absolute radiometer according to claim 1 is it is characterised in that in step one, the absorbing cavity of FEM (finite element) model Outer wall scribbles epoxide-resin glue, and is bonded with thermoelectric pile (4) by described epoxide-resin glue.

3. absolute radiometer according to claim 1 is it is characterised in that described thermoelectric pile (4) structure is by 180 pairs of copper-health Copper heater strip and polyimide matrix composition.

4. the measuring method of absolute radiometer spatial context radiant heat transfer, the method is realized by following steps:

Step one, set up FEM (finite element) model；

According to the actual three dimensional structure of absolute radiometer, finite element system is set up the actual three-dimensional with described absolute radiometer The corresponding FEM (finite element) model of structure；

Step 2, different incident powers are applied successively to the FEM (finite element) model described in step one and actual three dimensional structure, and right Ratio when incident power is identical, the steady state sensitivity of FEM (finite element) model and actual three dimensional structure, judge described FEM (finite element) model and Whether the relative error of the steady state sensitivity of actual three dimensional structure is less than 1%, if it is, execution step three；If not, returning step Rapid one；

Step 3, spatial context heat exchange measurement；

The far-end of the FEM (finite element) model described in step one sets up the space nodes not having coordinate relation with described FEM (finite element) model, The ambient temperature of radiation shield setting radiometer is as constant, and described constant is attached to space nodes；

Cover one layer of radiating element corresponding with described space nodes in described radiometer outer surface, described space nodes are radiated Form factor between unit is stored in a matrix relationship, according to described matrix relationship obtain ambient temperature and heat sink between Radiation heat transfer, described ambient temperature with heat sink between radiation heat transfer be equivalent to the spoke of space nodes and corresponding radiating element Penetrate heat exchange；

Different incident powers are applied successively to the absorbing cavity of FEM (finite element) model, record has radiant heat transfer state and radiationless respectively The equilibrium temperature of absorbing cavity under heat transfer conditions；The equilibrium temperature difference of measurement is averaged, this meansigma methods is corresponding background Space and the radiant heat transfer energy of absorbing cavity.

5. the measuring method of absolute radiometer spatial context radiant heat transfer according to claim 4 is it is characterised in that step In two, FEM (finite element) model and actual three dimensional structure are applied successively with different incident powers is 60mw, 75mw and 90mw；Step 3 In, different incident powers are applied successively for 60mw, 75mw and 90mw to the absorbing cavity of FEM (finite element) model.

6. the measuring method of absolute radiometer spatial context radiant heat transfer according to claim 4 is it is characterised in that step In one, the absorption intracavity of FEM (finite element) model comprises reflectance coating, heater strip layer and absorbs cavity main body, and described absorption cavity main body includes Resin glue, the specific heat capacity of absorbing cavity and thermal conductivity is had to be set to adjustable state.

7. the measuring method of absolute radiometer spatial context radiant heat transfer according to claim 4 is it is characterised in that step In one, ambient temperature is constant, and constant value is 77k.