Mathematical modelling of underground railway systems to inform design decisions hasrnbeen common place and a well proven technique for many years. However, during thernfeasibility design stage the time and expense of building a full representation of therntunnels and stations can prove impractical. Simpler approaches, using empirical methodsrnand steady-state theory, are often more beneficial at early project stages.rnSuch simple analyses are often unable to provide useful outputs of heat transfer andrnsystem temperatures owing to this relying on time varying effects such as thermalrncapacitance. This can limit the true assessment of the potential of some conceptsrnresulting in more costly analysis at a later stage or even to abortive design work. Equally, it could lead to a less cost effective solution being implemented owing to a more favourable solution being rejected too early. This paper explores an improvement to steady-state theory that results in more detailed assessment of heat transfer and the effect upon cooling options. The alternative uses simple calculations that only require Excel or equivalent software and not a full 1D network model. The paper focuses on the transient heat transfer provided by the ground surrounding a tunnel which provides significant capacitance to the system that needs to be accounted for in year-round analysis. This is achieved by identifying empirical relationships between ambient and wall surface temperatures in a variety of methods. The paper considers the use of analytic relationships, numerical options and the use of genuine data from a metro. The paper finally concludes where this system can provide significant benefits, and where existing approaches are still considered to be morernadvantageous.
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