Cu含量对高温相变材料Al-Cu合金热特性的影响

Influence of Cu content on thermal characteristics of high-temperature phase change material Al-Cu alloy

高温相变材料Al-Cu合金是蓄热性能最好的太阳能储存材料之一,而Cu含量对其热特性影响的相关研究未见报道。采用差示扫描量热法(DSC)和激光脉冲法(LFA)研究了Cu含量在7.4%~51.7%范围内的Al-Cu合金相变材料的相变温度、相变潜热、比热容、热扩散系数和热导率,并结合其金相组织对热力学性能变化规律的内在机理进行了分析。结果显示,当Cu含量在7.4%~51.7%范围内时,Al-Cu合金的相变温度在524.4~645.9℃范围内;随Cu含量的增加,Al-Cu合金的质量潜热呈递减趋势,而体积潜热却呈上升趋势。Al-7.4%Cu在熔化和凝固过程具有最大的质量潜热,分别为339.6、343.5 kJ·kg^(-1)。Al-51.7%Cu在熔化和凝固过程具有最大的体积潜热,分别为1179、1143 MJ·m^(-3)。当Cu含量在7.4%~51.7%范围内时,Al-Cu合金的比热容随Cu含量的增加呈递减趋势;当温度在25~500℃范围内时,Al-Cu合金的比热容随温度升高呈递增趋势。Al-7.4%Cu的比热容在25℃时为0.85 J·g^(-1)·K^(-1),在500℃时达到最高值1.08 J·g^(-1)·K^(-1)。此外,Al-Cu合金的热导率随Cu含量的升高而降低,但即使Cu含量达到51.7%,其常温下的热导率仍然高达104 W·m^(-1)·K^(-1)。综合研究结果表明,Al-Cu合金作为高温相变材料具有在太阳能蓄热领域中应用的巨大潜力。

High-temperature phase change material（PCM） Al-Cu alloy is one kind of solar thermal energy storage material which has the best heat storage characteristics, but the study about influence of Cu content on its thermal characteristics has not yet been reported. The thermal characteristics of Al-Cu alloy with Cu content of 7.4%-51.7% including phase change temperature, phase change latent heat, specific heat, thermal diffusivity and thermal conductivity are investigated by differential scanning calorimetry（DSC） and laser flash apparatus（LFA）. The internal mechanism of Al-Cu alloy thermophysical properties is also analyzed from the perspective of metallurgical structure. The results indicate that when Cu content is in the range of 7.4%-51.7%, the phase transition temperature of Al-Cu alloy is within 524.4℃ to 645.9℃. With the growth of Cu content, the mass latent heat of Al-Cu alloy decreases and the volume latent heat increases. Al-7.4% Cu has the maximum melting/freezing mass latent heat, which are 339.6 and 343.5 kJ·kg-1 respectively. Al-51.7% Cu has the maximum melting/freezing volumetric latent heat with 1179 and 1143 MJ·m-3, respectively. When the temperature rises from 25℃ to 500℃, the specific heat of Al-Cu alloy keeps increasing. On the other hand, when Cu content rising from 7.4% to 51.7%, the specific heat of Al-Cu alloy decreases. The specific heat of Al-7.4% Cu is 0.85 J·g-1·K-1 at 25℃ and reaches the maximum 1.08 J·g-1·K-1 at 500℃. Besides, the thermal conductivity of Al-Cu alloy decreases with the increase of Cu content, but its thermal conductivity is still as high as 104 W·m-1·K-1 even if Cu content reaches 51.7%. The results reveal that Al-Cu alloy, as high-temperature phase change material, has great potential of application in the field of solar thermal energy storage.