竖直地埋管换热器热作用半径的估算方法

为了在设计过程中合理布置换热器和估计它们之间的热干扰程度,提出估算竖直埋管换热器影响半径的方法.通过几种简单负荷条件下换热器周围土层中过余温度的分布特征分析了过余温度随距离衰减的一般性规律,指出土层对短周期冷热交替负荷具有“过滤”作用,即短周期冷热交替负荷引起的过余温度会随距离很快衰减,周期越短则衰减越快.基于该“过滤”作用,得到了离换热器一定距离处最大过余温度的估算公式和换热器热作用半径的估算方法.通过实际算例表明:该估算方法能快速和较准确地确定换热器的热作用半径,在设计过程中可利用其确定换热器的间距；换热器的热作用范围主要受两方面影响：一是土层的综合热扩散系数和导热系数，二是其负荷的冷热不平衡率和所包含的长周期冷热交替成分的大小.

Method for estimating thermal effect radius of vertical borehole heat exchangers

In order to evaluate the thermal disturbance between the vertical borehole heat exchangers (VBHEs) reasonably and to design an efficient heat exchanger system, an estimation method of the thermal effect radius (TER) of the VBHE was proposed. The general law of the temperature rise distribution in the soil caused by several typical and simple thermal loads applying on the VBHE was studied first. It is found that the soil has a filter effect on the short period cycle thermal load, meaning that the temperature rise caused by the short period cycle thermal load will attenuate quickly in the soil as the distance from the VBHE increases. The shorter the period, the more quickly the temperature attenuate. Based on the filter effect, a formula for estimating the temperature rise in the soil at the point far from the VBHE a certain distance was presented and the method for estimating the TER of VBHE was derived. The application of the method in an actual example displays that it can give a quick and reliable result and can be used for determining the span between the VBHEs in the practical design. This method shows that the TER is mainly influenced by the thermal diffusion coefficient and the thermal conductivity of the soil, and the unbalance rate of the thermal load and the long period component in it.