冷热负荷不平衡对地埋管换热性能的影响及相关措施的比较分析

Influence of heat imbalance on heat transfer performance of ground heat exchangers and countermeasures

基于无限长线热源模型,推导了以年为周期的逐时负荷作用下地埋管周围土壤逐时温度分布的计算公式。以某典型建筑为例,采用该方法计算了负荷不平衡条件下系统运行50a期间地埋管钻孔壁的温度变化,分别比较了不同地埋管间距和数量及不同负荷不平衡率下地埋管的换热效率。结果表明,冷热负荷不平衡对单根地埋管换热性能的影响不大,但使地埋管对周围土壤的影响范围变大,由此带来的后果是多根地埋管组成的地下换热系统通常只能有效运行若干年;增大地埋管间距和数量对降低冷热负荷不平衡影响的作用有限,降低冷热负荷不平衡率是最直接和有效的方法。

Based on the infinite-length linear source model, deduces a formula for calculating the hourly temperature distribution in the soil around the ground heat exchanger under hourly load with a-year period. Taking a typical building as example, using this method, calculates the temperature variation on the borehole sidewall surface of the ground heat exchanger under heat imbalance conditions during 50 years. Compares the heat transfer efficiency separately under different spans between the ground heat exchangers, numbers and heat imbalance ratios conditions. The results show that the influence of the heat imbalance on a single ground heat exchanger is much small, but it enlarges the influenced range of the ground heat exchanger. As a result, the heat exchanger system composed of more ground heat exchangers can be easily influenced by the heat imbalance, which normally can operate for only several years. The countermeasures of enlarging the span between ground heat exchangers and increasing the number seem to have little effect on diminishing the influence of the heat imbalance, therefore the effective way is to reduce the imbalance ratio of the heat.