石蜡类相变材料的液相密度测量与表征OA

Phase change thermal storage technology utilizes the absorption and release of thermal energy during the phase change process of materials.It offers advantages such as high thermal storage density and precise temperature control,making it an important approach to addressing the mismatch between energy supply and demand,improving energy utilization efficiency,and achieving precise temperature control of equipment.Paraffinic phase change materials,represented by n-alkanes,are currently the most commonly used low-temperature(below 100℃)phase change materials.They possess advantages including high thermal storage density,great thermal stability,low supercooling degree,and non-toxicity,showing broad application prospects in thermal storage utilization,battery thermal management,and electronic device temperature control.Liquid-phase density is a key thermophysical property of phase change materials.Natural convection induced by differences in liquid-phase density is a critical factor affecting the heat transfer performance of the phase change process.Such differences also influence the temperature distribution and evolution of the phase interface,thereby affecting the formation and stability of the phase interface.In addition,phase change materials undergo volume changes during solid-liquid transition,which impose mechanical impacts on the structural stability of storage containers.However,for high-carbon-number paraffinic phase change materials,experimental measurement data on liquid-phase density remain scarce,and high-precision liquid-phase density prediction models applicable to wide temperature ranges have not yet been established,resulting in a significant restriction on the analysis of micro-scale flow and heat transfer characteristics,the accurate optimization of thermal storage devices,and the structural design and safety calibration of microelectronic devices based on paraffinic phase change materials.Wide-temperature-range liquid-phase density data of eight typical paraffinic phase change materials(eicosane,docosane,tetracosane,hexacosane,octacosane,triacontane,dotriacontane,and hexatriacontane)are experimentally measured by a thermostatic liquid density measurement instrument.The measured data are compared with published experimental data to verify their accuracy.Specialized high-precision prediction models for the liquid-phase density of the eight paraffinic phase change materials and a general prediction model applicable to paraffinic phase change materials are constructed,providing key data and model support for the application of paraffinic phase change materials in thermal storage and equipment temperature control.Results show that when the temperature changes by 30℃,the liquid-phase density variation of all eight paraffinic phase change materials exceeds 2.0％.At the same temperature,the maximum difference in liquid-phase density between eicosane and triacontane reaches 2.7％,demonstrating the importance of high-precision prediction of liquid-phase density.Established liquid-phase density prediction models exhibit good accuracy.Specifically,for the specialized prediction models,the relative root mean square deviation(RRMSD)is no more than 0.09％,and the maximum relative deviation(RD)is no more than 0.17％.For the general prediction model,the RRMSE is no more than 0.30％,and the maximum RD is no more than 0.41％.In addition,the general prediction model demonstrates strong extrapolation capability.It agrees well with experimental results reported in the literature,with a maximum RD not exceeding 1.83％.Reliable wide-temperature-range liquid-phase density data for eight typical paraffinic phase change materials,along with the high-accuracy specialized prediction models and general prediction model,are expected to facilitate the application of these materials and support the optimal design and safety assessment of thermal storage devices and temperature control equipment.