Infrared and Laser Engineering, Volume. 54, Issue 7, 20250026(2025)

Design and optimisation of thermal protection systems for infrared thermal imager in high temperature environments

Zhiyuan XI1,2, Hailiang SHI2, Jiasheng CAO3, Xiongwei SUN2、*, Xianhua WANG2, and Jile WANG2
Author Affiliations
  • 1Institutes of Physical Science and Information Technology, Anhui University, Hefei 230601, China
  • 2Key Laboratory of Optical Calibration and Characterization, Anhui Institute of Optics and Fine Mechanics, Hefei Institutes of Physical Science, Chinese Academy of Sciences, Hefei 230031, China
  • 3Zhanjiang Cigarette Factory, China Tobacco Guangdong Industrial Company Limited, Zhanjiang 524033, China
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    ObjectiveThermal protection for infrared cameras is critical for maintaining their stability under complex operating conditions, such as high temperatures and high humidity. The elevated temperatures and humidity during the drying process pose significant challenges to the camera’s performance and lifespan, potentially causing deformation of the imaging window, damage to electronic components, and a loss of temperature measurement accuracy. To address these issues effectively, a thermal shield that combines thermal insulation with active cooling is essential to maintain the camera’s operating temperature within its acceptable range (10 ℃ to 50 ℃). This thermal protection device must provide efficient heat dissipation, reliable sealing, and compact design. However, conventional thermal protection methods relying solely on insulation or basic cooling are insufficient to meet the demands of such complex conditions. Therefore, this study proposes a thermal protection device for infrared thermal imager that integrates passive insulation with active cooling, enabling adaptation to high-temperature, high-humidity environments while optimizing the camera’s temperature measurement performance and operational stability.MethodsA thermal protection structure for an infrared thermal imager is proposed (Fig.3). The design integrates passive thermal insulation using a PTFE housing and active heat transfer optimization with a diffuser installed at the cooling air inlet (Fig.4). Numerical simulations were performed to determine the optimal structural parameters of the diffuser (Fig.5). The flow and heat transfer processes within the structure were analyzed using computational fluid dynamics (CFD), with the Realizable k-ε turbulence model selected as the computational approach. Grid-independence validation (Fig.6) was conducted to ensure that the numerical simulation results were unaffected by the grid density. In order to verify the validity of the numerical simulation results, experimental tests were carried out within the high temperature drying process section (Fig.14).Results and DiscussionsThe guide vane angle was increased from 35° to 55°, significantly improving convective heat transfer efficiency and optimizing temperature distribution (Fig.7). The cooling effect was optimal at 55°, where the average temperature of the thermal imaging camera was 36.55 ℃, and the maximum temperature was 36.7 ℃ (Fig.8). When the horizontal diffusion circle diameter D1=40 mm, the average temperature of the infrared thermal imager was further reduced to a minimum of 33.65 ℃ (Fig.10), and the convective heat transfer coefficient reached a maximum value of 78.07 W·m-2·K-1 (Table 5), achieving optimal airflow distribution and temperature uniformity. Under fixed guide vane angle and diffusion circle diameter conditions, the guide vane length L=10 mm, resulted in the lowest infrared thermal imager temperatures, with an average temperature of 33.65 ℃ and a maximum temperature of 33.75 ℃ (Fig.12). At this length, the convective heat transfer coefficient also reached its maximum value of 78.07 W·m-2·K-1 (Tab. 6), indicating optimal airflow disturbance and heat transfer efficiency. However, excessive guide vane length reduced cooling performance and caused a temperature rebound. The temperature of the cooling air varies with seasonal weather, requiring a higher flow rate to enhance convective heat transfer in hot conditions. At an air inlet temperature of 38 ℃, increasing the flow rate from 40 m/s to 140 m/s reduced the average temperature of the camera from nearly 50 ℃ to 42.35 ℃ (Fig.13), meeting its operational requirements. The influence of the thermal gradient on heat conduction was analyzed, with the calculated results presented in Tab.7. The maximum deformation observed was 0.11 mm, and the peak thermal stress reached 5.52 MPa, both within acceptable limits. Numerical simulations were conducted under the same boundary conditions as the experiments, and the results from both approaches were compared. Figure 15 illustrates the comparative analysis between experimental data and numerical simulation outcomes under varying air inlet temperatures. The findings indicate a high degree of correlation between the numerical simulations and experimental measurements, with the maximum relative error for peak temperatures at measurement points being 5.72%, and for average temperatures, 5.92%.ConclusionsA forced convection heat transfer protection structure was designed by integrating passive heat insulation and active convection technologies. The passive design utilizes low thermal conductivity materials to form a shell structure, minimizing heat transfer in high-temperature environments. For active cooling, high-pressure gas is introduced as a cooling source, with a circular diffuser and optimized air inlet structure enhancing convective heat transfer efficiency. Both numerical simulations and experimental tests confirm that the proposed structure can reliably protect infrared thermal imager in ambient temperatures up to 130 °C. The optimized design achieves uniform cooling gas distribution, lowering the maximum camera temperature from 42.6 ℃ to 33.75 ℃—a 20.78% reduction. Under extreme room temperatures of 38 ℃, increasing the air inlet velocity to 140 m/s reduces the camera temperature to 42.35 ℃, meeting operational requirements. This study provides a valuable reference for addressing thermal protection challenges of optical instruments in industrial high-temperature scenarios. The experimental validation ultimately confirmed the effectiveness of the thermal protection structure, with the experimental results demonstrating excellent agreement with the numerical simulation outcomes.

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    Zhiyuan XI, Hailiang SHI, Jiasheng CAO, Xiongwei SUN, Xianhua WANG, Jile WANG. Design and optimisation of thermal protection systems for infrared thermal imager in high temperature environments[J]. Infrared and Laser Engineering, 2025, 54(7): 20250026

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    Paper Information

    Category: Infrared

    Received: Jan. 10, 2025

    Accepted: --

    Published Online: Aug. 29, 2025

    The Author Email: Xiongwei SUN (xiongweisun@163.com)

    DOI:10.3788/IRLA20250026

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