Fast calculation model for heat and mass transfer in a deep-buried underground air tunnel using Z-transfer coefficient method.

• A fast numerical model for deep-buried underground tunnel ventilation is proposed. • The model uses the Z-transfer coefficient method considering air condensation. • The model greatly improves the calculation efficiency and accuracy. • The influence of air humidity on the accuracy of thermal pressure in the calculation model is evaluated. Deep-buried tunnels are widely used in underground space for transportation and air ventilation. Accurately predicting the heat and mass transfer process of the ventilation in a tunnel is conducive to the design optimization of air conditioning and utilization of thermal pressure for underground buildings. The air condensation process has an important impact on the variation of air parameters in the tunnel. The Z-transfer coefficient method cannot accurately calculate the air parameters when the air condensation process occurs. To resolve this problem, in this study, the computational domain is redefined and a fast calculation model is proposed for heat and mass transfer in a deep-buried underground tunnel. The calculation results of this model are in good agreement with the field test results. Moreover, when calculating the hourly parameters of ventilation for a year, the running time of the new model is less than half of the finite difference method model. Considering the hourly parameters of ventilation for a certain number of days, the new model has a higher calculation efficiency. In addition, a case study was conducted to demonstrate the significance of considering the air condensation process in the model. If the calculation results of the model considering air humidity and condensation are taken as a reference, the absolute error of air temperature at the tunnel exit and the relative error of the thermal pressure, calculated by the model ignoring air humidity, can respectively reach 1.94 °C and 34%. [ABSTRACT FROM AUTHOR]