CN103983363A - Optimal refrigerating plate for low-temperature infrared target source - Google Patents

Abstract

The invention relates to an optimal refrigeration plate for a low-temperature infrared target source, which belongs to the field of low-temperature and infrared technology. A groove (1), a liquid nitrogen inlet (2) and a liquid nitrogen outlet (3) are provided on the surface of the refrigeration plate in contact with the liquid nitrogen, and the liquid nitrogen inlet (2) and the liquid nitrogen outlet (3) are located in the groove The two sides of (1) are connected with the groove (1), and several baffles (4) parallel to the left and right side walls of the groove (1) are arranged in the groove (1), and the adjacent baffles (4) Staggered arrangement to form a rotary corridor type. The refrigeration plate designed in the present invention can reduce the cooling time to 1260s while ensuring the temperature uniformity of the black body surface source, and the cooling time is very short; it can ensure that the temperature field distribution of the black body surface source is very uniform, and the temperature uniformity is less than 0.02K; Make the variable temperature low temperature infrared target source reach the temperature control range of the wide temperature range of 80K～300K.

Description

Optimum Cooling Plate for Low Temperature Infrared Target Source

technical field

The invention belongs to the field of low temperature and infrared technology, and relates to a refrigeration plate model of key testing equipment for testing and calibrating the response linearity and non-uniformity of low temperature infrared sensors.

Background technique

Infrared technology and products have been increasingly widely used in various fields such as national defense, aerospace, medical treatment, environmental engineering, and resource exploration. In particular, the optical detection system in the spaceflight field mainly adopts the infrared optical system at present. Therefore, the performance of infrared sensors directly affects the signal acquisition and processing capabilities in space exploration. In order to test and calibrate the performance of the sensor, the functional relationship between the output signal of the detector within the working temperature range and the standard radiation source is determined, and the target information obtained during the flight of the detection system is retrieved to obtain the spectral reflectance characteristics and For the spectral radiation characteristics, the linear responsivity and non-uniformity must be calibrated and corrected by using a low-temperature blackbody target source with a simulated space infrared radiation source.

At present, the temperature uniformity of the working area of the commonly used blackbody surface source is ±0.5K, and the mature low-temperature blackbody target source generally can only reach the low temperature of 220K.

Contents of the invention

The object of the present invention is to provide an optimal cooling plate for low-temperature infrared target source, which can control the temperature of the black body to be variable between 80-300K, and the temperature uniformity is less than 0.02K.

The purpose of the present invention is achieved through the following technical solutions:

An optimal refrigeration plate for a low-temperature infrared target source, which is a single-input-single-out structure. The surface of the refrigeration plate in contact with liquid nitrogen is provided with grooves, a liquid nitrogen inlet and a liquid nitrogen outlet, and the liquid nitrogen inlet and liquid nitrogen outlet are located at Both sides of the groove are in communication with the groove. Several baffles parallel to the left and right side walls of the groove are arranged in the groove, and adjacent baffles are arranged in a staggered manner to form a revolving corridor.

In the present invention, the liquid nitrogen inlet and the liquid nitrogen outlet are located at the upper end of the refrigeration plate, which can ensure that the liquid nitrogen can fully contact the refrigeration plate in each groove to achieve the uniformity of refrigeration.

The low-temperature infrared target source system consists of three parts: a blackbody, a heating plate, and a cooling plate. The cooling plate is a square structure with grooves. Different structures of the cooling plate directly lead to the cooling time and temperature uniformity of the blackbody surface source. The structure of the refrigeration plate of the present invention is a single-input-single-out model. Liquid nitrogen flows in from the liquid nitrogen inlet side of the refrigeration plate, flows through the entire refrigeration plate along the groove, and finally flows out at the liquid nitrogen outlet on the other side of the refrigeration plate. , The design of single-in and single-out structure can greatly shorten the refrigeration time and greatly improve the temperature uniformity.

The present invention has following advantage:

1. Using the refrigeration plate designed by the present invention for the low-temperature infrared target source system can make the variable-temperature low-temperature infrared target source reach the temperature control range of a wide temperature range of 80K to 300K, and the temperature range has been greatly increased. The detection of the sensor in the low temperature environment provides a calibration benchmark, improves the accuracy of the detector in space, and provides a reliable technical quality assurance for the development and application of infrared detectors.

2. The materials used in the present invention are all red copper, which has good electric conduction, heat conduction, corrosion resistance and processability, and can be welded and brazed.

3. The refrigerating plate model designed by the present invention can reduce the refrigerating time to 1260s while ensuring the temperature uniformity of the black body surface source, and the cooling time is very short.

4. The refrigeration plate model designed in the present invention can ensure that the temperature field distribution of the black body surface source is very uniform, and the temperature uniformity is less than 0.02K.

5. The low-temperature infrared target source system using the refrigeration plate designed by the present invention can not only solve the detection problem of response linearity and non-uniformity of low-temperature infrared products (sensors), but also satisfies the calibration and correction of aerospace infrared detection systems need.

Description of drawings

Figure 1 is a schematic structural diagram of a low-temperature infrared target source system;

Fig. 2 is a schematic structural diagram of a single-in, single-out refrigeration plate;

Fig. 3 is the A-A direction view of Fig. 2;

Figure 4 is a structural diagram of a single-input-single-out model;

Fig. 5 is the distribution diagram of the overall cloud map of the single-input-single-out refrigeration plate;

Fig. 6 is a distribution diagram of the cloud image on the single-input single-out blackbody surface source;

Figure 7 is a single-in single-out cooling curve;

Fig. 8 is a structural diagram of a cylindrical model;

Fig. 9 is a cylinder model cloud map distribution diagram;

Fig. 10 is the distribution diagram of the cloud map of the black face of the cylindrical model;

Fig. 11 is a cooling curve of the cylindrical model;

In the figure, 1-vacuum tank; 2-liquid nitrogen tank; 3-tank support; 4-liquid nitrogen inlet/outlet; 5-cooling plate; 6-heating plate; 7-black body; 8-infrared window; 9-vacuum tank base; 10-vacuum unit.

Detailed ways

The technical solution of the present invention will be further described below in conjunction with the accompanying drawings, but it is not limited thereto. Any modification or equivalent replacement of the technical solution of the present invention without departing from the spirit and scope of the technical solution of the present invention should be covered by the present invention. within the scope of protection.

The structural principle of the low-temperature infrared target source system designed according to the existing technical performance index requirements is shown in Figure 1. The low-temperature infrared target system is mainly composed of three parts: low-temperature target source system, temperature measurement and control system, and vacuum system. Cryogenic Infrared Target Source System

As the key and core of the low-temperature infrared target system, the low-temperature infrared target source system is mainly composed of a low-temperature infrared target source system and a liquid nitrogen tank. The low-temperature infrared target source system is composed of three parts: a black body, a heating plate, and a cooling plate. The refrigeration plate provides a uniform cooling source for the black body surface source. In order to obtain a low temperature and uniform temperature effect of ≤80K, the system adopts a large-area direct cooling refrigeration method with liquid nitrogen (77K). The heating plate provides a uniform heating heat source for the black body surface source. Under the joint action of the cooling plate and the heating plate, the blackbody surface source can realize the adjustment and temperature control of the blackbody surface source by adjusting the heating power (heat source). Then the radiation at different temperatures is transmitted to the infrared sensor through the infrared window, and the infrared sensor is calibrated and corrected. In order to ensure that the black body surface source has better temperature uniformity and higher heat transfer efficiency, the above parts are made of copper material with higher thermal conductivity.

In order to prevent the low temperature of the liquid nitrogen tank from being transferred to the vacuum tank and cause heat leakage, the direct contact between the liquid nitrogen tank and the vacuum tank should be avoided. For this reason, the liquid nitrogen tank can generally be installed by hanging or wedge-shaped tripod support. The device in the present invention adopts a wedge-shaped tripod support made of heat-insulating material for installation and fixation.

The core component of the present invention is a low-temperature surface source blackbody refrigeration plate model, the size of which is 250mm×250mm, and the thickness is 15mm. In order to improve the emissivity of the surface source blackbody and eliminate the influence of stray light, the surface of the blackbody is evenly distributed with a certain angle of quadrangular pyramid structure, and coated with low-temperature blackbody paint.

In order to investigate the overall temperature distribution of a blackbody surface source, the dimensionless characteristic number-Bivot number _Bi is generally used for analysis. When B _i ≤ 0.1, it can be considered that the overall temperature distribution of the blackbody is uniform. The formula for calculating the Biot number is as follows:

${\mathrm{<span\; class="notranslate">\; B</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; \&delta;h</span>}}{\mathrm{<span\; class="notranslate">\; \&lambda;</span>}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; ;</span>$

Among them, δ is the thickness of the black body; h is the surface heat transfer coefficient; λ is the thermal conductivity.

(1) Effect of black body radiation on temperature distribution

The thickness δ of the blackbody surface source is 15mm; the equivalent radiation heat transfer heat resistance 1/h of the blackbody surface is taken as 3; λ=400W/m·K.

Then B _i =1.125×10 ^-4 is calculated from formula (1).

At this time, B _i <<0.1, therefore, the radiation heat transfer between the blackbody and the infrared window has very little influence on the uniformity of the temperature distribution of the blackbody.

(2) Effect of heat conduction on temperature distribution

Here, only the blackbody temperature distribution under cooling conditions is considered. At this time, 1/h is the heat transfer resistance of heat conduction between the black body and the heating plate, and the size is taken as 0.1.

Then B _i =3.75×10 ^-6 is calculated from formula (1).

Similarly, at this time, B _i <<0.1, therefore, the heat conduction between the black body and the heating plate has very little influence on the temperature uniformity of the black body.

From the above analysis, it can be seen that the overall temperature distribution of the black body in the thermal equilibrium state is uniform.

In the present invention, several models are designed and simulated and analyzed. Through comparative analysis of several refrigeration plate models, the model with the best refrigeration time and blackbody surface source temperature uniformity is obtained. The single-input-single-out model structure is emphasized here.

The existing known structural model is a cylindrical model, and the refrigeration time of this structural model is too long and the temperature uniformity is not good enough. The best model for designing the refrigeration panel structure in this invention is the single-in, single-out model.

In the single-input-single-out structural model, the front cube is a blackbody surface source, the middle cube is a heating plate, and the rear cube is a cooling plate. Among them: the surface of the refrigeration plate in contact with liquid nitrogen is provided with a groove 1, and the groove 1 is provided with several baffles 4 parallel to the left and right side walls of the groove 1, and the adjacent baffles 4 are staggered to form a rotation Corridor type. On the refrigeration plate, the width of the baffle plate 4 is 2mm, the width of the groove is 10mm, and the depth of the groove is 10mm. Two conduits are drawn from the upper part of the refrigeration plate, which are the liquid nitrogen inlet 2 and the liquid nitrogen outlet 3 respectively. The inlet enters, fills the chamber, and is discharged from the outlet. The liquid nitrogen contacts the cooling plate in the chamber to provide a cold source for the blackbody. The single-in-single-out model allows liquid nitrogen to flow in from the groove at the left liquid nitrogen inlet 2, flow into the adjacent right groove after flowing to the bottom, and then flow into the adjacent right groove after reaching the top. Reciprocating in this way, the liquid nitrogen flows through the entire refrigeration plate, and finally flows out from the liquid nitrogen outlet 3 on the right. The liquid nitrogen flows in one direction in the groove on the refrigeration plate, and the refrigeration can be more uniform. Its structure is shown in Figure 2- 4. The material of all parts in this model is copper with good thermal conductivity. The initial temperature of the model is set as room temperature 300K, the analysis time is 1260s, and the time step is 20s, and a transient analysis (Transient) is performed on the process.

It can be seen from the cloud map distribution in Figure 5-6 that the blackbody surface source of this model has three temperature distributions, which are distributed in a ring shape with the center of the blackbody surface source as the center. The temperature in the red area of the four corners is the highest at 79.893K, and the temperature in the center of the surface source is the lowest. It is 79.8706K. The temperature difference of the black body surface source temperature field is 0.0224K. In the actual application process, what is actually needed is a radiation surface with a diameter of Ф=250mm. After analysis and calculation, only the orange area and the yellow area are actually used, so the two areas The temperature difference is 0.0112K. In the refrigeration process of this model, the contact between liquid nitrogen and the refrigeration plate is very uniform, and the cooling effect is very good. It can be seen from the cloud map distribution that the temperature difference is small.

Take three characteristic points on the black body surface source, and give the temperature change curve with time, as shown in Figure 7, in this graph, TEMP2 is the center point of the yellow region of the surface source, TEM3 is the characteristic point of the orange region of the surface source, and TEMP4 is the feature point of the area source red area. It can be seen from the curve that the blackbody surface source temperature can reach equilibrium at 1260s, and the equilibrium time is relatively fast. At this time, the temperatures of these three characteristic points are 79.8706K, 79.8818K, and 79.893K, respectively.

The following briefly introduces the cloud image distribution and cooling curve of the cylindrical model, as shown in Figure 8-11. The cooling time and temperature uniformity of the two refrigeration plate models are compared in Table 1.

Table 1 Comparison of cooling time and temperature uniformity of two refrigeration plate models

Parameter Type Cylindrical model One-in-one-out model Cooling time (s) 3100 1260 Temperature Uniformity (K) 0.0232 0.0112

To sum up, in the two models analyzed above, through the comparative analysis of the cooling time and temperature uniformity, it can be seen that for the cooling of the black body radiation surface of the same size and the same material, the temperature uniformity is the best and the cooling time is the shortest. The fast, one-in, one-out cooling model is the optimal model.

It can be seen that the present invention adopts a single-input-single-out model design structure, thereby greatly improving temperature uniformity and refrigeration time.

(1) Through the comparison of the refrigeration plate model, the temperature uniformity obtained by adopting the single-input-single-out model of the present invention can reach the precision of 0.0112K.

(2) Utilize the cold plate model of the low-temperature infrared target source designed by the present invention, the groove width, the baffle width and the groove depth of the cold plate model are the optimal dimensions under the same environment.

Claims (5)

1. The best refrigeration plate for low-temperature infrared target source, characterized in that the surface of the refrigeration plate in contact with liquid nitrogen is provided with a groove (1), a liquid nitrogen inlet (2) and a liquid nitrogen outlet (3), and the liquid nitrogen The inlet (2) and the liquid nitrogen outlet (3) are located on both sides of the groove (1) and communicated with the groove (1), and there are several holes parallel to the groove (1) in the groove (1). The baffles (4) on the side walls are arranged in a staggered manner adjacent to the baffles (4) to form a revolving corridor. 2. The optimal refrigeration plate for low-temperature infrared target source according to claim 1, characterized in that said liquid nitrogen inlet (2) and liquid nitrogen outlet (3) are located at the top of the refrigeration plate. 3. The optimal cooling plate for low-temperature infrared target source according to claim 1, characterized in that the width of the baffle plate (4) is 2mm. 4. The optimal refrigeration plate for low-temperature infrared target source according to claim 1, characterized in that the width of the groove (1) is 10mm, and the groove depth is 10mm. 5. The optimal cooling plate for low-temperature infrared target source according to claim 1, characterized in that the material of the cooling plate is red copper.