地热井保温水泥导热系数影响因素研究

RESEARCH ON INFLUENCING FACTORS OF THERMAL CONDUCTIVITY OF THERMAL INSULATION CEMENT FOR GEOTHERMAL WELL

选择合适的测试方法探究不同因素对保温水泥导热系数的作用规律和方式。研究表明:随着保温材料加量和水灰比的增大,水泥石导热系数先迅速减小,随后下降速率降低并逐渐趋于稳定;随着养护温度的升高和时间的增长,导热系数逐渐减小,并在7 d后基本稳定;随着含水率的增大和测试温度的升高,导热系数显著增大;其中,含水率、测试温度、保温材料加量和水灰比等因素对导热系数的影响逐级递减。低密度和具有类蜂窝状结构的保温材料在降低导热系数和维持抗压强度等方面具有较大优势,且保温材料的推荐加量为15%~20%。

This paper reveals the variation law of thermal conductivity of thermal insulation cement under various factors and the corresponding changes of micro characteristics on the basis of selecting appropriate test methods.The experimental results show that the thermal conductivity first decreases rapidly,and then the decline rate tends to be stable with the increase of the amount of insulation materials and the water cement ratio.The extension of curing time and the increase of curing temperature help to reduce the heat transfer capacity of the skeleton,but the thermal conductivity is basically stable after the curing temperature exceeds 120℃in a same curing time and the curing time exceeds 7 d at a same temperature.And the increase of moisture content and test temperature can significantly improve the thermal conductivity by enhancing the heat transfer capacity of voids and skeletons.What’s more,the results of factor significance analysis show that the effect of moisture content is the most obvious,the test temperature and the amount of insulation material are the second,and the influence of water cement ratio is the lowest.The analysis results show that the low-density thermal insulation material can effectively reduce the thermal conductivity,and the honeycomb like structure has great advantages in maintaining the strength of cement.In addition,cement within 15%-20%thermal insulation material can get better thermal insulation effect on the basis of ensuring reasonable compressive strength and economy.