Thermal accumulation in laser systems causes wavelength shift, reduction in optical power and conversion efficiency, and thermal stress generation, seriously affecting laser performance and safety. Traditional cooling methods are bulky and heavy, making it difficult to meet the development requirements for miniaturization and lightweight laser designs. In phase change energy storage technology, phase change materials (PCMs) absorb or release large amounts of heat during phase transitions while maintaining constant temperature, making them the best thermal management solution to meet laser development needs.
Starting from the fundamental materials of solid-liquid phase change energy storage technology, this paper summarizes and organizes organic, inorganic, and eutectic phase change materials suitable for the temperature requirements of lasers (Table 1–Table 4). It introduces the characteristics and defects of different types of materials, among which organic PCMs are widely used in laser thermal management systems due to their advantages of low price, high latent heat of phase change, and strong stability. Considering the conflicts between high-power laser thermal dissipation demands and low thermal conductivity of PCMs, various types of thermal conductivity enhancement technologies for phase change materials and their effects are analyzed (Table 5). All enhancement methods require adding additional thermal conductivity enhancement materials, whose effect depends heavily on their proportion. However, introducing these materials inevitably reduces energy storage density, weakening the advantages of solid-liquid phase change energy storage technology. Therefore, in practical applications, heat transfer enhancement designs must be carried out based on the corresponding constraints. For different laser power levels, the study reviews the current status of solid-liquid phase change energy storage technology application in thermal management for both low-power device-level lasers and high-power system-level lasers, both domestically and internationally. It discusses structural characteristics, system design, and heat transfer features of thermal management systems for kilowatt-level laser components (Table 6) and megawatt-level high-power laser systems (Table 7). Initially, solid-liquid phase change energy storage technology was applied to control thermal distortion of optical elements by suppressing operational temperature rise in low-power device-level laser thermal management. Through technological evolution, it has gradually expanded to thermal management of kilowatt-level lasers such as pump sources. Taking advantage of the properties of all-solid-state working media and passive thermal regulation mechanisms, solid-liquid phase change energy storage technology is widely used in aerospace to solve thermal shock problems of lasers in microgravity. In high-power system-level laser thermal management, the laser thermal loads increase sharply to the megawatt level. Phase change energy storage technology must be combined with other cooling methods such as forced convection, spray cooling, loop heat pipes, and mechanically pumped two-phase flow systems to form a complete thermal management system. Furthermore, limited by the low thermal conductivity of PCMs, optimization of the thermal management system and key heat exchange components of solid-liquid phase change energy storage is necessary. Existing research mainly focuses on thermal management processes, with most studies being confined to conceptual design stages and numerical simulations. There is a lack of corresponding component-level and system-level experimental verification. Although China has conducted research on high-power laser phase change energy storage thermal management systems since the early 21st century, follow-up studies and related academic reports are limited. Furthermore, the thermal loads addressed by these developed systems have been relatively low. Therefore, more design, simulations, and experimental research must be systematically conducted in this field to support large-scale industrial applications of high-power lasers in domestic industry and national defense.
Studies have shown that solid-liquid phase change energy storage technology can effectively control laser operating temperature, extend laser operation time, and increase the energy storage and power densities of the system. Currently, it meets the cooling requirements of kilowatt-level device-scale lasers. For megawatt-level high-power system-scale laser applications, solid-liquid phase change energy storage technology is usually combined with various active cooling methods to achieve laser system thermal management. High-efficiency heat transfer structures, including plate-type and plate-fin configurations, are employed to fulfill high-power thermal dissipation requirements, effectively reducing system power consumption, volume, and weight, and meeting the installation requirements of high-power lasers on different mobile platforms. The technology shows good application prospects. However, most research predominantly focuses on the thermal dissipation capacity and heat transfer characteristics during a single operation, while experimental studies on thermal management systems for high-power lasers remain insufficient. The heat transfer mechanisms of solid-liquid phase change under laser load impact are still unclear. The reliability of phase change thermal management systems under multi-cycle, long-term operation requires further investigation. Current research is insufficient to provide scientific support for the engineering application of solid-liquid phase change energy storage technology. Future work should emphasize the mechanism and reliability of phase change energy storage technology to provide scientific support for engineering applications and promote its large-scale use in laser thermal management.
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