成层土界面接触热阻试验研究与分析

    EXPERIMENTAL INSIGHTS: UNVEILING AND ANALYZING THERMAL RESISTANCE AT STRATIFIED SOIL INTERFACES

    • 摘要: 成层土中的界面热阻影响热量传输,产生界面温差,阻碍热传导工程的分析。采用自制的一维土柱热阻试验装置,首先,测试了50 ℃、60 ℃、70 ℃和80 ℃下黏土与砂土的导热系数;然后,基于稳态热流法,对黏土-黏土、砂土-砂土、黏土(受热端)-砂土、黏土-砂土(受热端)这4种类型的接触界面,在单向温度梯度条件下研究接触热阻随接触界面及加热温度变化的发展规律。结果表明,随着加热时间的增加,界面温差与接触热阻先迅速上升后下降,最终在特定区间内持续波动。随着温度提高,界面温差的差异性增大,而接触热阻视接触类型而定上升或下降。温度从50 ℃升至80 ℃时,对于远离受热端为黏土层的成层土,热阻值降低约0.002 K ·m2 ·W-1;而对于远离受热端为砂土层的成层土,热阻值升高约0.001 K ·m2 ·W-1。其次,通过有限元数值法进行含湿多孔介质的层热阻的温度模拟,验证实测温度结果。最后,结合热阻变化规律,建议工程中应在供能与热损耗间取得平衡。

       

      Abstract: Thermal contact resistance(TCR)in stratified soil media significantly affects heat transfer, generating interfacial temperature differences and complicating the analysis of heat conduction processes. This study employed a self-developed one-dimensional soil column thermal resistance testing apparatus. Initially, the thermal conductivities of clay and sand were measured at temperatures of 50 ℃, 60 ℃, 70 ℃, and 80 ℃. Subsequently, based on the steady-state heat flow method, TCR experiments were conducted for four types of soil interfaces(clay-clay, sand-sand, heated clay-sand, and heated sand-clay)under unidirectional temperature gradients to investigate the influence of interface type and heating temperature on TCR evolution. The results indicate that with prolonged heating, the interface temperature difference and TCR initially rise rapidly, then decline, and eventually oscillate within a stable range. As temperature increases, the variability of interfacial temperature differences grows, while TCR trends vary with interface type: as temperature rose from 50 ℃ to 80 ℃, the TCR of stratified soil with a clay layer distal to the heating end decreased by approximately 0.002 K·m2 ·W-1, whereas that with a sand layer distal to the heating end increased by about 0.001 K·m2 ·W-1. Furthermore, finite element numerical simulations of temperature distribution in wet porous media were performed to validate the experimental temperature measurements. Based on the observed thermal resistance variation patterns, it is recommended that engineering designs balance energy supply and heat loss to optimize system performance.

       

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