石蜡/纳米石墨复合相变储热材料的换热与放热效率

The Heat Transfer and Heat Release Rate of Paraffin/nano Graphite Composite Phase Change Heat Storage Material

相变储热是提高能源利用率的重要手段之一,相变储热材料的换热系数与放热效率研究对太阳能高效利用具有重要意义。通过变换铝管管径、循环风速以及空气温度,计算出复合相变储热材料的换热系数及放热效率。结果表明:铝管管径不变,循环风速小于3m/s时,空气温度对换热系数影响很小,差值在1W/(m2·℃)左右;换热系数、放热效率都随风速的增大而有所提高,放热效率最大可达95.3%;随着管径增大,换热系数逐渐减少,放热效率却逐渐增大;适合石蜡/纳米石墨复合相变储热材料的最佳条件为管径30mm、循环风速3m/s以及空气温度90℃。

Phase change heat storage is one of the most important methods to improve energy efficiency. The research of heat transfer coefficient and heat release rate of phase change heat storage materials is significant to the use of solar energy efficiently. This study calculated the heat transfer coefficient and heat release rate of composite phase change heat storage material through changing aluminum tube diameter, wind speed and air temperature. The results indicated that-when the aluminum tube diameter unchanged, the wind speed was less than 3rn/s, the impact of air temperature on the actual measurement of heat transfer coefficient was very little, the difference was about 1W/（m^2.℃）; The heat transfer coefficient and heat release rate were improving with wind speed increasing, and the heat release rate can reach to 95.3%; The heat transfer coefficient was decreasing and the heat release rate was increasing with the increase of pipe diameter. The optimum condition for paraffin/nano graphite as composite phase change material was that： 30mm pipe diameter, 3m/s wind speed and 90℃ air temperature.