土壤—空气换热系统流动与供冷性能的计算模拟

NUMERICAL SIMULATION OF FLOW AND COOLING PERFORMANCE OF THE EARTH-AIR HEAT EXCHANGERS

以土壤热传导方程和K_1—ζ湍流模型为基础,采用温度场叠加法对土壤—空气埋管换热系统进行了三维动态数值模拟,计算了埋管出口温度随时间的动态变化。研究了埋管管长、管径、风速等对换热器出口温度的影响。模拟结果表明：①换热器出口温度随外界气温和土壤表面获得的辐射能的周期性变化而呈周期性变化；②随着管长增加和管径减小,出口温度降低,而且受气温和太阳辐射的影响减小；③随着人口风速减小,出口温度降低且变化幅度减小,供冷性能提高。并进行了实验验证,实测数据与模拟结果之差不超过0.8℃。

A three-dimensional transtit numerical model is presented to predict the cooling performance of the earth-air heat exchanger with the superposition technology incorprating the undisturbed variation of the soil and cooling effect of the buried heat exchanger. The transit temperature variation at the heat exchanger outlet is calculated and the effects of pipe length, pipe radius and air velocity on the pipe outlet temperature were also studied. The numerical s＇imulations showed that： ①Qutlet temperature of the earth-air heat exchanger changers periodically with the periodical changers of ambient temperature and solar radiation. ②The impact on the outlet temperature posed by inlet temperature and solar radiation decreases with the increasing of pipe length and decreasing of pipe radius. Accordingly, the mean value and amplitude of outlet temperature decreases and the cooling performance of the earth-air heat exchanger increases. ③When the mean air velocity in the heat exchanger is high, the outlet temperature increases and the cooling performance decreases in despite of the higher heat transfer coefficient. The proposed model is validated against the experimental data in South China region, and the outlet temperature differences between measured data and simulated results rarely exceed 0.8 ℃.