Freezing of central drainage ditches is a major cause of freeze damage in tunnels built in frigid climates, and traditional passive insulation such as thermal insulation layers is often inadequate in these harsh environments. A new study, published in the journal Geothermal Energy, examines whether ground-source heat pump based active heating systems can improve frost resistance for tunnel central drainage ditches in cold regions. The research combined laboratory tests with numerical simulations to evaluate how such systems perform under a range of operating conditions.
The team, led by Tantan Zhu and Fuwang Ma with colleagues including Chao Yang, Huanhuan Zhu and Bin Zeng, analyzed the effects of several parameters on system behavior. These included the volumetric flow rate of the circulating medium, the supply water temperature of the heating system, the linear density of the heating pipes, and the layout of the pipes themselves. The outcomes they tracked were the temperature differential between the supply and return water, the heat exchange power, and the temperature field of the central drainage ditch.
The results reveal clear patterns in how the system responds to changing conditions. The temperature differential between supply and return water diminishes as the volumetric flow rate of the circulating medium increases, but it escalates with higher supply water temperatures and with a greater linear density of heating pipe. The heating power of the ground-source heat pump system follows a different pattern: it initially rises and then declines as the volumetric flow rate grows, while it consistently increases with elevated supply water temperatures and greater heating pipe linear density.
Pipe layout also mattered. According to the study, helical heating pipes in the ground-source heat pump system outperform U-shaped heating pipes.
The study went beyond steady operating conditions to consider the tunnel environment itself. The researchers explored how wind speed inside the tunnel affects the temperature field of the central drainage ditch, the annual running time of the sectional heating system, the heating power of the system, and its energy consumption under active heating conditions. These factors connect the performance of the heating system directly to the airflow conditions that tunnels experience in practice.
The wind-related findings show a consistent directional relationship. The annual operating time of the heating system lengthens with higher tunnel wind speeds and shortens with increased distance from the tunnel inlet. Likewise, the average annual energy consumption of the heating system rises with increased tunnel wind speeds and declines as the distance from the tunnel inlet increases.
The study proposed a novel sectional layout method for heating pipes within the central drainage ditch, although the published abstract does not report quantitative savings figures for this arrangement.
For engineers working on tunnels in cold regions, the study offers a set of design levers: adjusting flow rate, supply temperature, pipe density and pipe layout changes both the heat delivered to the ditch and the energy required to deliver it. The work is presented as a laboratory and simulation study, so its conclusions describe modeled and tested system behavior rather than long-term field performance data from an operating tunnel.
The research is available as an open access article, published on 9 September 2026, and is currently shared as a peer-reviewed accepted manuscript that remains subject to further editorial edits before the final version of record appears. Readers should therefore treat the reported figures as part of a citable but still provisional version of the study.
Subject of Research: Ground-source heat pump active heating systems for preventing freezing of tunnel central drainage ditches in cold regions.
Article Title: Temperature field and system efficiency of a ground source heat pump heated tunnel drainage ditch
Article References: Zhu, T., Ma, F., Qin, Z., Yang, C., Zhu, H., & Zeng, B. (2026). Temperature field and system efficiency of a ground source heat pump heated tunnel drainage ditch. Geothermal Energy. https://doi.org/10.1186/s40517-026-00407-3
Image Credits: AI Generated
DOI: 10.1186/s40517-026-00407-3
Keywords: ground source heat pump, tunnel drainage ditch, freezing damage, cold regions, temperature field, heating pipe layout, supply water temperature, volumetric flow rate, energy consumption, tunnel wind speed, numerical simulation, frost resistance
News Source: Denise Maddox. (October 29, 2026). Research report: Temperature field and system efficiency of a ground source heat pump heated tunnel drainage ditch. Scienmag.
