Device and Method for Measuring Heat Flux Density of Rotating Mirror Liquid Nitrogen Spray in Laser Cleaning Equipment

Abstract

The present invention relates to a device and method for measuring the heat flux density of liquid nitrogen spray for a rotating mirror of laser cleaning equipment. To solve the technical problems of the prior art in that the heat flux density of only one point is measured and heat leakage is not considered, the device comprises a three-dimensional displacement platform, an adapter, a box, a heat flux density measuring unit and a constant temperature unit located in the box; the heat flux density measuring unit comprises a first thermal insulation support, a heater, a second thermal insulation support, a metal block, a temperature sensor assembly and a third thermal insulation support; the first thermal insulation support is located in the box, its upper end is connected to the third thermal insulation support, and the box is mounted on the three-dimensional displacement platform via the adapter; the metal block and the second thermal insulation support are located in the third thermal insulation support, the heater is located on the second thermal insulation support and is in contact with the metal block; the input end of the temperature sensor assembly is embedded in a groove on the side wall of the metal block, and the output end is connected to an external data collector.

Description

Technical Field

[0001] The invention relates to measurement of liquid nitrogen spray heat flux density, and in particular to a device and method for measuring the heat flux density of liquid nitrogen spray of a rotating mirror of laser cleaning equipment. Background Art

[0002] When the laser light path inside a laser cleaning device passes through a rotating reflective lens, the spectral absorption rate of the rotating reflective lens surface in the laser band cannot reach 0%. Therefore, part of the laser radiation will be converted into heat on the lens surface. Due to the high laser power and the low thermal conductivity of the rotating reflective mirror, water cooling or air cooling cannot meet the heat dissipation requirements of the rotating reflective mirror lens. Therefore, the rotating reflective mirror lens needs to be cooled by liquid nitrogen spray. Because the lens material is quartz glass, if the heat flux density of the liquid nitrogen spray is unevenly distributed, it will cause a large temperature gradient on the lens surface, thereby causing thermal deformation and thermal stress of the lens. If the thermal stress exceeds the allowable stress, the lens is easily damaged. Therefore, it is necessary to measure the heat flux density of the liquid nitrogen spray. However, the existing technology measures the axial temperature gradient, the temperature measurement point is fixed, and can only measure the heat flux density of the liquid nitrogen spray at one point. Moreover, it does not take into account the problem of heat leakage, resulting in poor measurement effect. Summary of the Invention

[0003] The purpose of the present invention is to solve the technical problem that the existing technology can only measure the heat flux density of liquid nitrogen spray at one point and does not take into account the heat leakage problem, resulting in poor measurement effect, and to provide a device and method for measuring the heat flux density of liquid nitrogen spray of a rotating mirror in laser cleaning equipment.

[0004] In order to achieve the above object, the present invention adopts the following technical solutions:

[0005] A device for measuring the heat flux density of liquid nitrogen spray on a rotating mirror of a laser cleaning device, which is special in that it includes a three-dimensional displacement platform, an adapter, a box, a heat flux density measuring unit, and a constant temperature unit;

[0006] The heat flux density measuring unit includes a first thermal insulation support, a heater, a second thermal insulation support, a metal block, a temperature sensor assembly and a third thermal insulation support; the first thermal insulation support is arranged in the box, and the box is mounted on the three-dimensional displacement platform through the adapter, and the upper end of the first thermal insulation support is connected to the lower end of the third thermal insulation support; the third thermal insulation support is a hollow structure; the metal block and the second thermal insulation support are coaxially arranged in the hollow structure of the third thermal insulation support from top to bottom, and the upper end of the metal block is sealed and connected to the upper end of the hollow structure of the third thermal insulation support. and is located outside the box, with the end surface of the upper end of the metal block facing the nozzle of the liquid nitrogen spray; the heater is arranged on the second thermal insulation support member, its heating end is in contact with the lower end surface of the metal block, and the input end is connected to an external DC power supply; two grooves are provided on the side wall of the metal block; the temperature sensor assembly includes two first platinum resistors; the input ends of the two first platinum resistors are respectively embedded in the two grooves, and the output ends of the two first platinum resistors are respectively connected to an external data collector; the outer periphery of the middle section of the first thermal insulation support member and the outer periphery of the middle section of the third thermal insulation support member are both coated with thermal insulation material;

[0007] The constant temperature unit is arranged in the box body and is connected to an external temperature controller for controlling the temperature in the box body.

[0008] Furthermore, in order to further reduce the downward heat leakage of the heater, a trimming pad and a gasket are coaxially arranged at the lower end of the second thermal insulation support member to press the heater and the metal block; a T-shaped channel is axially arranged at the upper end of the first thermal insulation support member, and the input end of the heater passes through the trimming pad, gasket, and T-shaped channel in sequence and is connected to the external DC power supply.

[0009] Furthermore, in order to better fix the metal block and reduce heat leakage between the side wall of the metal block and the third thermal insulation support, the metal block is a cylindrical structure, and its side wall is axially provided with multiple annular protrusions, and the annular protrusions are interference fit with the inner wall of the hollow structure of the third thermal insulation support; 5400 glue is provided at the position where the upper end of the metal block contacts the upper end surface of the third thermal insulation support, and the outside of the 5400 glue is coated with silicone rubber; the heater is arranged on the second thermal insulation support by coating with silicone rubber.

[0010] Furthermore, in order to facilitate disassembly and assembly and observation of the internal situation of the box, the box is composed of an aluminum profile frame and an acrylic plate detachably mounted on the aluminum profile frame.

[0011] Furthermore, to prevent the first platinum resistor from being pulled out during the wiring operation, two first through holes are provided on the side wall of the middle section of the third thermal insulation support member, and two second through holes are provided at the lower end of the third thermal insulation support member; two third through holes are provided at the upper end of the first thermal insulation support member; the output ends of the two first platinum resistors are connected to the external data collector after respectively passing through the two first through holes, the two second through holes, and the two third through holes in sequence;

[0012] The notches of the two grooves face opposite directions, and the two grooves correspond to the positions of the two first through holes respectively; the two second through holes are symmetrical to each other and coincide with the axes of the two third through holes respectively.

[0013] Furthermore, the constant temperature unit includes a constant temperature fan and a second platinum resistor arranged on the inner wall of the constant temperature fan; the second platinum resistor is connected to an external temperature controller for controlling the temperature inside the box.

[0014] Furthermore, the first thermal insulation support member, the second thermal insulation support member and the third thermal insulation support member are all made of tetrafluoroethylene material; the thermal insulation material is polyurethane foam, and the diameter of the polyurethane foam, the diameter of the upper end surface of the first thermal insulation support member and the diameter of the lower end surface of the third thermal insulation support member are the same; the metal block is 6061 aluminum; thermal conductive silicone grease is coated between the lower end surface of the 6061 aluminum and the heater, and the surface of the first platinum resistor is coated with thermal conductive silicone grease.

[0015] At the same time, the present invention also provides a method for measuring the heat flux density of liquid nitrogen spray for a rotating mirror of a laser cleaning device, based on a device for measuring the heat flux density of liquid nitrogen spray for a rotating mirror of a laser cleaning device, which is special in that it includes the following steps:

[0016] Step 1: Adjust the position of the three-dimensional displacement platform so that the center of the liquid nitrogen spray nozzle is aligned with the center point of the metal block, and adjust the nozzle to a preset height from the center point of the metal block;

[0017] Step 2: Adjust the temperature controller to set the temperature to the preset temperature T;

[0018] Step 3. Turn on the liquid nitrogen switch and adjust the DC power knob to keep the temperatures T1 and T2 at the two measuring points inside the metal block at T±ΔT;

[0019] Step 4: When the fluctuation of the temperatures T1 and T2 at the two measuring points inside the metal block is less than ±0.2°C / min, calculate the cooling heat flux density q1 at the center point using the heating power Q and the diameter d of the lower end of the metal block:

[0020]

[0021] Based on the measured temperatures T1 and T2 of the two measuring points inside the metal block, the distance Δx between the two measuring points, and the thermal conductivity λ of the metal block, the cooling heat flux density q2 at the center point is calculated using the Fourier formula:

[0022]

[0023] Define error η = (q2-q1) / q1. If the error η is within the measurement accuracy requirement, the cooling heat flux density measurement result of the center point meets the requirement; otherwise, the cooling heat flux density measurement result of the center point does not meet the requirement.

[0024] Step 5: Turn off the DC power supply and the liquid nitrogen switch;

[0025] Step 6: Adjust the position of the three-dimensional displacement platform in the X and Y directions, and repeat steps 3 to 5 to obtain the cooling heat flux density distribution in the two-dimensional plane.

[0026] Furthermore, the T is 20°C; and the ΔT is 3°C.

[0027] Beneficial effects of the present invention:

[0028] 1. The present invention provides a device for measuring the heat flux density of liquid nitrogen spray on a rotating mirror in laser cleaning equipment. A three-dimensional displacement platform is used to measure the cooling heat flux density at different locations within a two-dimensional plane. The constant temperature unit in the present invention prevents low-temperature cold nitrogen from cooling the first, second, and third insulation supports, as well as the insulation material, thereby reducing downward heat dissipation from the heater. It also prevents cooling of the temperature sensor assembly, thereby avoiding heat leakage along the temperature sensor assembly, thereby significantly improving measurement accuracy. Furthermore, the housing in the present invention is easily disassembled and assembled, and the acrylic sheet comprising the housing is easy to process and transparent, facilitating observation of the interior.

[0029] 2. The trimming pad and gasket in the present invention can further reduce the downward heat leakage of the heater. The first insulation support and the second insulation support are used for wiring and insulation, which can reduce the heat leakage between the heater and the three-dimensional displacement platform.

[0030] 3. The metal block in the present invention is made of 6061 aluminum, and the annular protrusion on its side wall can reduce heat leakage between it and the third thermal insulation support member. In addition, since too small or too large a temperature difference will affect the cooling heat flux density measurement results, the temperature difference caused by the thermal conductivity of 6061 aluminum is about 10°C, which can reduce the impact on the cooling heat flux density measurement results; in addition, 5400 glue has high low-temperature resistance and strength, and its outer side is coated with silicone rubber to further achieve sealing, preventing liquid nitrogen or cold nitrogen from entering the side wall of the metal block through the gap.

[0031] 4. The present invention provides a method for measuring the heat flux density of liquid nitrogen spray on a rotating mirror of a laser cleaning device, which can measure the cooling heat flux density at different positions in the entire two-dimensional plane. The temperature controller is adjusted to set the temperature at the average temperature of the two measuring points to reduce heat leakage. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 This is a schematic structural diagram of an embodiment of a device for measuring the heat flux density of liquid nitrogen spray for a rotating mirror in laser cleaning equipment according to the present invention (the second platinum resistor is not shown);

[0033] Figure 2 Schematic diagram of the structure of the heat flux measurement unit in the present invention;

[0034] Figure 3 This is a schematic diagram of the connection structure of the measuring device in an embodiment of a method for measuring the heat flux density of liquid nitrogen spray on a rotating mirror of a laser cleaning device according to the present invention.

[0035] Figure numbers: 1-three-dimensional displacement platform, 2-adapter, 3-box, 31-aluminum profile frame, 32-acrylic plate, 4-heat flux density measurement unit, 41-first thermal insulation support, 411-third through hole, 412-T-shaped channel, 42-heater, 43-second thermal insulation support, 431-trimming pad, 432-gasket, 44-metal block, 441-groove, 45-temperature sensor assembly, 451-first platinum resistance, 46-third thermal insulation support, 461-first through hole, 462-second through hole, 47-thermal insulation material, 5-constant temperature unit, 51-constant temperature fan, 6-data acquisition device, 7-DC power supply, 8-24V power supply, 9-temperature controller, 10-laptop computer. DETAILED DESCRIPTION

[0036] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0037] like Figure 1-2As shown, a device for measuring the heat flux density of liquid nitrogen spray for rotating mirrors of laser cleaning equipment includes a three-dimensional displacement platform 1, an adapter 2, a box 3, a heat flux density measuring unit 4, and a constant temperature unit 5. Specifically, the heat flux density measuring unit 4 includes a first thermal insulation support 41, a heater 42, a second thermal insulation support 43, a metal block 44, a temperature sensor assembly 45, and a third thermal insulation support 46. The metal block 44 in this embodiment is made of 6061 aluminum; the first thermal insulation support 41 is arranged in the box 3, and the box 3 is installed on the three-dimensional displacement platform 1 through the adapter 2. The upper end of the first thermal insulation support 41 is connected to the lower end of the third thermal insulation support 46; the third thermal insulation support 46 is a hollow structure with an I-shaped axial section; 6061 aluminum and the second thermal insulation support 43 are coaxially arranged in the hollow structure of the third thermal insulation support 46 from top to bottom, wherein 6061 aluminum It is a cylindrical structure, and its side wall is provided with multiple annular protrusions along the axial direction. The annular protrusions are interference-fitted with the inner wall of the hollow structure of the third thermal insulation support 46. The upper end of the 6061 aluminum is sealed and connected to the upper end of the hollow structure of the third thermal insulation support 46, and is located outside the box body 3. The end face of the upper end of the 6061 aluminum is used to face the nozzle of the liquid nitrogen spray. In this embodiment, 5400 glue is provided at the position where the upper end of the 6061 aluminum contacts the upper end face of the third thermal insulation support 46, and the outer side of the 5400 glue is coated with silicone rubber to prevent liquid nitrogen or cold nitrogen from entering the 6061 aluminum side wall through the gap; the lower end of the second thermal insulation support 43 is coaxially provided with a trimming pad 431 and a gasket 432 in sequence for pressing the heater 4 2 and 6061 aluminum; the heater 42 is arranged on the second thermal insulation support member 43 by coating with silicone rubber, the heating end of the heater 42 is in contact with the lower end surface of the 6061 aluminum, the upper end of the first thermal insulation support member 41 is axially provided with a T-shaped channel 412, the input end of the heater 42 passes through the trimming pad 431, the gasket 432, the T-shaped channel 412 in sequence and is connected to the external DC power supply 7; in addition, thermal conductive silicone grease is coated between the lower end surface of the 6061 aluminum and the heater 42, and two grooves 441 are provided on the side wall of the 6061 aluminum, and the notches of the two grooves 441 face oppositely; the side wall of the middle section of the third thermal insulation support member 46 is provided with two first through holes 461, and the two first through holes 461 are respectively The third thermal insulation support member 46 is provided with two second through holes 462 at the lower end; the first thermal insulation support member 41 is provided with two third through holes 411 at the upper end, the two second through holes 462 are symmetrical to each other, and respectively coincide with the axes of the two third through holes 411; the temperature sensor assembly 45 includes two first platinum resistors 451, and the surfaces of the two first platinum resistors 451 are coated with thermal conductive silicone grease; the input ends of the two first platinum resistors 451 are respectively embedded in the two grooves 441, and the output ends of the two first platinum resistors 451 respectively pass through the two first through holes 461, the two second through holes 462, and the two third through holes 411 in sequence and are connected to the external data collector 6;The first insulating support member 41 has an I-shaped axial cross-section. The outer periphery of the middle section of the first insulating support member 41 and the outer periphery of the middle section of the third insulating support member 46 are both coated with an insulating material 47. In this embodiment, the insulating material 47 is polyurethane foam, and the diameter of the polyurethane foam, the diameter of the upper end surface of the first insulating support member 41, and the diameter of the lower end surface of the third insulating support member 46 are the same. In this embodiment, the first insulating support member 41, the second insulating support member 43, the third insulating support member 46, and the gasket 432 are all made of tetrafluoroethylene.

[0038] The constant temperature unit 5 is disposed within the housing 3 and includes a constant temperature fan 51 and a second platinum resistor disposed on the inner side wall of the constant temperature fan 51. The second platinum resistor is connected to an external temperature controller 9 for controlling the temperature within the housing 3. The housing 3 in this embodiment is composed of an aluminum profile frame 31 and an acrylic plate 32 that is detachably mounted on the aluminum profile frame 31.

[0039] like Figure 3 FIG. 1 shows the connection structure of the above-mentioned device for measuring the heat flux density of liquid nitrogen spray of a rotating mirror of a laser cleaning device in a measurement system. Based on this, the present invention also provides a method for measuring the heat flux density of liquid nitrogen spray of a rotating mirror of a laser cleaning device, comprising the following steps:

[0040] Step 1: Adjust the position of the three-dimensional displacement platform 1 so that the center of the liquid nitrogen spray nozzle is aligned with the center point of the metal block 44, and adjust the nozzle to a preset height from the center point of the metal block 44; in this embodiment, the metal block 44 is 6061 aluminum;

[0041] Step 2: Check whether the line connection is correct, adjust the temperature controller 9 and set the temperature to 20°C;

[0042] Step 3. Turn on the liquid nitrogen switch and adjust the DC power supply 7 knob to maintain the temperatures of the two measuring points T1 and T2 inside the 6061 aluminum at 20±3℃;

[0043] Step 4: When the fluctuation of the temperature T1 and T2 at the two measuring points inside the 6061 aluminum is less than ±0.2°C / min, calculate the cooling heat flux density q1 at the center point using the heating power Q and the diameter d of the lower end of the 6061 aluminum:

[0044]

[0045] Based on the measured temperatures T1 and T2 of the two measuring points inside the 6061 aluminum, the distance Δx between the two measuring points, and the thermal conductivity λ of the 6061 aluminum, the cooling heat flux density q2 at the center point is calculated using the Fourier formula:

[0046]

[0047] Define error η = (q2-q1) / q1. If the error η is within the measurement accuracy requirement, the cooling heat flux density measurement result of the center point meets the requirement; otherwise, the cooling heat flux density measurement result of the center point does not meet the requirement.

[0048] Step 5: Turn off the DC power supply 7 and the liquid nitrogen switch;

[0049] Step 6: Adjust the X and Y positions of the three-dimensional displacement platform 1 and repeat steps 3 to 5 to obtain the cooling heat flux density q2 at different positions on the upper end surface of the metal block 44, thereby obtaining the distribution of the cooling heat flux density q2 in the two-dimensional plane.

[0050] In step 2, the circuit connection is specifically checked as follows: laptop computer 10 is connected to data collector 6 for reading temperature values; first and second platinum resistors 451 and 452 are both connected to data collector 6, which is used to collect the temperatures T1 and T2 at two measuring points, as well as the temperature within chamber 3; 24V power supply 8, temperature controller 9, and thermostatic fan 51 are connected in series; temperature controller 9 controls the power supply to thermostatic fan 51 and sets the temperature to 20°C. Furthermore, the 6061 aluminum alloy in this embodiment is disposed within the hollow I-shaped structure of third thermal insulation support member 46. Due to its small diameter, the cooling heat flux density of a specific point in the liquid nitrogen spray can be approximately measured, thereby measuring the cooling heat flux density distribution field of the liquid nitrogen spray.

[0051] Before the liquid nitrogen spray cools the rotating reflector lens, the liquid nitrogen spray heat flux density measuring device of the rotating mirror of the above-mentioned laser cleaning equipment can be used to measure the cooling heat flux density of the liquid nitrogen spray at different positions. The liquid nitrogen spray cooling heat flux density distribution and the laser radiation heat load are substituted into the rotating reflector lens model to analyze the thermal stress distribution on the surface of the rotating reflector lens. If the thermal stress is greater than the allowable stress of the quartz glass, it is necessary to optimize the various parameters of the liquid nitrogen spray. When the thermal stress is less than the allowable stress of the quartz glass, the liquid nitrogen spray at this time can be used to dissipate heat from the rotating reflector lens inside the laser cleaning equipment.

[0052] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions within the technical scope disclosed in the present invention shall be covered by the scope of protection of the present invention. Therefore, the scope of protection of the present invention shall be subject to the scope of protection of the claims.

Claims

1. A device for measuring the heat flux density of liquid nitrogen spray for rotating mirrors in laser cleaning equipment, characterized by: It comprises a three-dimensional displacement platform (1), an adapter (2), a box (3), a heat flux density measurement unit (4) and a constant temperature unit (5); The heat flux density measuring unit (4) comprises a first heat-insulating support member (41), a heater (42), a second heat-insulating support member (43), a metal block (44), a temperature sensor assembly (45) and a third heat-insulating support member (46); the first heat-insulating support member (41) is arranged in the box (3), the box (3) is mounted on the three-dimensional displacement platform (1) through the adapter (2), the upper end of the first heat-insulating support member (41) is connected to the lower end of the third heat-insulating support member (46); the third heat-insulating support member (46) is a hollow structure; the metal block (44) and the second heat-insulating support member (43) are coaxially arranged in the hollow structure of the third heat-insulating support member (46) from top to bottom, and the upper end of the metal block (44) is sealed and connected to the upper end of the hollow structure of the third heat-insulating support member (46). end, and is located outside the box (3), and the end surface of the upper end of the metal block (44) is used to face the nozzle of the liquid nitrogen spray; the heater (42) is arranged on the second thermal insulation support member (43), the heating end of which is in contact with the lower end surface of the metal block (44), and the input end is connected to the external DC power supply (7); two grooves (441) are provided on the side wall of the metal block (44); the temperature sensor assembly (45) includes two first platinum resistors (451); the input ends of the two first platinum resistors (451) are respectively embedded in the two grooves (441), and the output ends of the two first platinum resistors (451) are respectively connected to the external data collector (6); the outer periphery of the middle section of the first thermal insulation support member (41) and the outer periphery of the middle section of the third thermal insulation support member (46) are both covered with thermal insulation material (47); The lower end of the second heat-insulating support member (43) is coaxially provided with a trimming pad (431) and a gasket (432) for pressing the heater (42) and the metal block (44); the upper end of the first heat-insulating support member (41) is axially provided with a T-shaped channel (412); the input end of the heater (42) passes through the trimming pad (431), the gasket (432), and the T-shaped channel (412) in sequence and is connected to the external DC power supply (7); The metal block (44) is a cylindrical structure, and a plurality of annular protrusions are provided on its side wall along the axial direction, and the annular protrusions are interference-fitted with the inner wall of the hollow structure of the third thermal insulation support (46); 5400 glue is provided at the position where the upper end of the metal block (44) contacts the upper end surface of the third thermal insulation support (46), and the outer side of the 5400 glue is coated with silicone rubber; the heater (42) is provided on the second thermal insulation support (43) by coating with silicone rubber; The constant temperature unit (5) is arranged in the box (3) and is connected to an external temperature controller (9) for controlling the temperature in the box (3).

2. The device for measuring the heat flux density of liquid nitrogen spray for rotating mirrors of laser cleaning equipment according to claim 1, characterized in that: The box body (3) is composed of an aluminum profile frame (31) and an acrylic plate (32) detachably mounted on the aluminum profile frame (31).

3. The device for measuring the heat flux density of liquid nitrogen spray for rotating mirrors of laser cleaning equipment according to claim 2, characterized in that: The side wall of the middle section of the third thermal insulation support member (46) is provided with two first through holes (461), and the lower end of the third thermal insulation support member (46) is provided with two second through holes (462); the upper end of the first thermal insulation support member (41) is provided with two third through holes (411); the output ends of the two first platinum resistors (451) pass through the two first through holes (461), the two second through holes (462), and the two third through holes (411) in sequence, and are then connected to the external data collector (6); The notches of the two grooves (441) face opposite directions, and the two grooves (441) respectively correspond to the positions of the two first through holes (461); the two second through holes (462) are symmetrical to each other and respectively coincide with the axes of the two third through holes (411).

4. The device for measuring the heat flux density of liquid nitrogen spray for rotating mirrors in laser cleaning equipment according to claim 3, characterized in that: The constant temperature unit (5) comprises a constant temperature fan (51) and a second platinum resistor arranged on the inner side wall of the constant temperature fan (51); the second platinum resistor is connected to an external temperature controller (9) and is used to control the temperature inside the box (3).

5. The device for measuring the heat flux density of liquid nitrogen spray for rotating mirrors of laser cleaning equipment according to claim 4, characterized in that: The first thermal insulation support member (41), the second thermal insulation support member (43) and the third thermal insulation support member (46) are all made of tetrafluoroethylene material; the thermal insulation material (47) is made of polyurethane foam, and the diameter of the polyurethane foam, the diameter of the upper end surface of the first thermal insulation support member (41) and the diameter of the lower end surface of the third thermal insulation support member (46) are the same; the metal block (44) is 6061 aluminum; thermal conductive silicone grease is coated between the lower end surface of the 6061 aluminum and the heater (42); and the surface of the first platinum resistor (451) is coated with thermal conductive silicone grease.

6. A method for measuring the heat flux density of liquid nitrogen spray for rotating mirrors in laser cleaning equipment, based on the device for measuring the heat flux density of liquid nitrogen spray for rotating mirrors in laser cleaning equipment according to any one of claims 1 to 5, characterized in that: The following steps are involved: Step 1: Adjust the position of the three-dimensional displacement platform (1) so that the center of the liquid nitrogen spray nozzle is aligned with the center point of the metal block (44), and adjust the nozzle to a preset height from the center point of the metal block (44); Step 2: Adjust the temperature controller (9) to set the temperature to a preset temperature T; Step 3: Turn on the liquid nitrogen switch and adjust the DC power supply (7) knob to maintain the temperatures T1 and T2 of the two measuring points inside the metal block (44) at T±ΔT; Step 4: When the fluctuation of the temperatures T1 and T2 at the two measuring points inside the metal block (44) is less than ±0.2°C / min, the cooling heat flux density q1 at the center point is calculated by the heating power Q and the diameter d of the lower end of the metal block (44): Based on the measured temperatures T1 and T2 of two measuring points inside the metal block (44), the distance Δx between the two measuring points, and the thermal conductivity λ of the metal block (44), the cooling heat flux density q2 at the center point is calculated using the Fourier formula: Define error η = (q2-q1) / q1. If the error η is within the measurement accuracy requirement, the cooling heat flux density measurement result of the center point meets the requirement; otherwise, the cooling heat flux density measurement result of the center point does not meet the requirement. Step 5: Turn off the DC power supply (7) and the liquid nitrogen switch; Step 6: Adjust the position of the three-dimensional displacement platform (1) in the X and Y directions, and repeat steps 3 to 5 to obtain the cooling heat flux density distribution in the two-dimensional plane.

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