An approximated solution [Eq.(24)] to estimate rock surface temperature of underground airway with partly wet conditions has been provided. It is much simple and practical compared with previous methods or solutions. The solution is applicable to the range of airflow temperature from 0 to 32° or 10 to 40°(see appendix) and practical ranges of humidity, ventilation time, heat transfer rate, wetness, virgin rock temperature and rock thermal properties. Furthermore, an explicit function for the rock surface temperature is derived, then the rock surface temperature can be calculated by simple procedures without any iterative calculations. The short subroutine program in FORTRAN 77 to calculate the rock surface temperature is shown in the appendix.
The estimated value of rock surface temperature have been compared with Amano et al's numerical calculation results using two dimensional finite difference method.
Finally, a practical calculation system to predict airflow temperature and humidity along underground airways have been proposed using the practical solution of rock surface temperature. The system can consider the effects of airway inclination and wetness or wet area ratio upon airway surface. The calculation results of temperature and humidity along a single airway shows good agreement with the results of Uchino et al. using finite deference method for analysis of rock temperature distribution and some simulation codes reported by Danko et al.
Furthermore, it is pointed out that differences between calculation results of the simulation codes suggested by Danko et al. is probably caused by the difference between wetness and wet area-ratio (see Table 2).
The present prediction method for temperature and humidity in underground airways have been successfully applied to a general ventilation simulator named MIVENA run on the Microsoft WindowsTM which has been further developed and released by authors.
