Abstract:

Many saturated cultural relics unearthed in the south need dehydration. The application of freeze-drying technology can effectively eliminate the cracking caused by the surface tension of liquid water. The material temperature is a process parameter that needs to be strictly controlled during the freeze-drying process. Due to the indivisible and irregular shape of cultural relics, the temperature in the different area of cultural relics is not uniform, resulting in inconsistent freeze-drying progress. In order to guarantee the success of the freeze-drying process of large-scale and multitudinous cultural relics, saturated woody cultural relic is taken as sample, infrared temperature sensor and thermal imager are combined together to monitor temperature of the freezing process of cultural relics. The results show that the infrared temperature sensor is very sensitive to the change of surface temperature of the sample, and can effectively track the dynamic process of temperature, but the accuracy of temperature measurement will be affected by the change of sample emissivity and environmental fluctuation. The infrared camera can achieve high measurement accuracy by calibrating the emissivity, and the temperature distribution map can be used to screen the highest/lowest temperature region on the entire surface of the sample. After the analysis of the temperature data, the surface temperature is low when the sample is close to the heat exchanger end of the chamber, and the surface temperature is high near the position of the door, besides, the upper surface temperature of the sample is slightly lower than the side temperature of the sample. The infrared temperature measurements are anticipated to give hints for the control of freeze-drying equipment, thus to reduce the risk of freezing drying failure, and relieve the workload of cultural relics protection staffs.

Key words: infrared, temperature distribution, imaging, measurement, cultural relics, freeze drying

摘要：

为了给大型、大批量文物的冷冻干燥保驾护航，以饱水木质文物为样品，结合红外温度传感器和红外热像仪，对文物的冷冻过程进行温度监控。结果表明，红外温度传感器对样品表面温度变化十分灵敏，能有效跟踪温度的动态变化过程，但测量准确性会受样品发射率、环境波动等因素的影响。红外热像仪经发射率标定后可达到较高的测量精度，利用热成像得到的图像，可直观地筛查样品表面的最高/最低温度区。经过分析，样品在靠近仓内换热器端的位置，表面温度较低，靠近仓门的位置，表面温度较高，且样品上表面温度略低于侧面温度。根据红外测温结果，预期能给出冷冻干燥设备控制的建议，降低文物冻干失败的风险，减轻文保工作者的工作负担。

关键词: 红外, 温度分布, 成像, 测量, 文物, 冷冻干燥