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

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.