Abstract Extracting heat from a sewage pipe through a typical horizontal ground heat exchanger has recently been introduced as a renewable energy alternative to reduce fossil fuel usage. This paper presents a novel design for a ground heat exchanger that extracts heat from the surrounding soil and sewage within the pipe while simultaneously being carried to a wastewater treatment plant. This research focuses on the long-term efficiency of the system under transient conditions in a cold climate. A numerical model using COMSOL Multiphysics was developed to verify the sustainability of the system for over 25 years. The model used constant inlet fluid temperatures to evaluate heat transfer with convective pipe flow and conductive phase change within the soil. The results showed a maximum temperature change in the surrounding soil adjacent to the heat extraction system over 25 years was 0.10 °C during the heating season in Winnipeg, Manitoba. The distance at which the heat extraction system did not show an impact on temperature change of adjacent soil was determined at 4 m. Critical parameters in this evaluation were system depth, sewage level, and the high-density polyethylene pipe thermal properties. The sustainability of the system was not affected by the system depth due to thermal balancing between climatic, subsurface and sewage heat fluxes. Sustainable behavior was achieved at 50 % and 75 % of sewage pipe capacity. The effect on thermal performance from the high-density polyethylene pipe thermal properties was deemed insignificant.

中文翻译：

---

用于长期效率估算的带有地热交换器的集成污水管的评估

摘要 通过典型的水平地面换热器从污水管道中提取热量最近被引入作为可再生能源的替代品，以减少化石燃料的使用。本文介绍了一种新型地埋换热器设计，该换热器从管道内的周围土壤和污水中提取热量，同时将热量输送到废水处理厂。这项研究的重点是系统在寒冷气候瞬态条件下的长期效率。开发了一个使用 COMSOL Multiphysics 的数值模型，以验证该系统超过 25 年的可持续性。该模型使用恒定的入口流体温度来评估对流管道流动和土壤内传导相变的热传递。结果表明，在马尼托巴省温尼伯的采暖季节，25 年来，与排热系统相邻的周围土壤的最大温度变化为 0.10 °C。排热系统对相邻土壤温度变化没有影响的距离确定为4 m。此评估中的关键参数是系统深度、污水水平和高密度聚乙烯管的热性能。由于气候、地下和污水热通量之间的热平衡，系统的可持续性不受系统深度的影响。在污水管道容量的 50% 和 75% 下实现了可持续行为。高密度聚乙烯管的热性能对热性能的影响被认为是微不足道的。马尼托巴省温尼伯的采暖季节气温为 10 °C。排热系统对相邻土壤温度变化没有影响的距离确定为4 m。此评估中的关键参数是系统深度、污水水平和高密度聚乙烯管的热性能。由于气候、地下和污水热通量之间的热平衡，系统的可持续性不受系统深度的影响。在污水管道容量的 50% 和 75% 下实现了可持续行为。高密度聚乙烯管的热性能对热性能的影响被认为是微不足道的。马尼托巴省温尼伯的采暖季节气温为 10 °C。排热系统对相邻土壤温度变化没有影响的距离确定为4 m。此评估中的关键参数是系统深度、污水水平和高密度聚乙烯管的热性能。由于气候、地下和污水热通量之间的热平衡，系统的可持续性不受系统深度的影响。在污水管道容量的 50% 和 75% 下实现了可持续行为。高密度聚乙烯管的热性能对热性能的影响被认为是微不足道的。此评估中的关键参数是系统深度、污水水平和高密度聚乙烯管的热性能。由于气候、地下和污水热通量之间的热平衡，系统的可持续性不受系统深度的影响。在污水管道容量的 50% 和 75% 下实现了可持续行为。高密度聚乙烯管的热性能对热性能的影响被认为是微不足道的。此评估中的关键参数是系统深度、污水水平和高密度聚乙烯管的热性能。由于气候、地下和污水热通量之间的热平衡，系统的可持续性不受系统深度的影响。在污水管道容量的 50% 和 75% 下实现了可持续行为。高密度聚乙烯管的热性能对热性能的影响被认为是微不足道的。