| How to accurately predicate the airflow temperature in high temperature mine is always a difficult problem that puzzles the mine air-conditioning design. And the heat emitting from surrounding rock is main heat source in mine. So, study on accurately calculation of heat emitting from surrounding rock and predicate the airflow temperature is very important. Two methods of calculate heat transfer of surrounding rock will be used. Then two methods of predicate the airflow temperature were obtained. Based on the heat transfer model of semi-infinite plate, considered the heat and moisture transfer between the surrounding rock and the ventilating air, built up thermal conduction differential equation of surrounding rock in airway. In order to solve this unsteady conduction equation, it put forward a simplified method,which is the relationship between saturated moisture content of air temperature was fitted into a liner curve. Additionally introduced correction air temperature, correction convective heat transfer coefficient and excess temperature. Wetness factor was adopted to calculate latent heat exchange between ventilation air and surface rock. It obtained a non-stable solution of temperature to surrounding rock in mine airway by using the method of Laplace transform. Then, it also put forward that the practical surface temperature would be weighted calculated with the temperature of perfectly dry surface and thoroughly wet surface. Based on the principle of heat and humidity balance, developed a heat and moisture transfer model between the ventilating air and surface rock. Deduced the non-station solution of airflow temperature and humidity in mine airway with central difference scheme. Based on the calculation example, according to the solution contrast, it analyzed space-time change laws of surface temperature, airflow temperature and humidity in mine airway. And it also analyzed the influence law of airflow temperature and humidity, surrounding rock temperature, surface temperature by the ventilation time, wetness factor and air volume. The result shows that,(1) airflow temperature increases with the growth of airway distance, and the rate of increase is reduce. Airflow humidity linear increase with the growth of airway distances,(2) airflow temperature decreases with the increase of wetness factor, but airflow humidity and enthalpy increases with wetness factor,(3) when wetness facor is exorbitant, surface temperature may less than airflow temperature because of evaporation of water, but the heat transfer direction between surrounding rock and airflow is surrounding rock release heat to airflow,(4) airflow temperature reduce with the growth of airflow quantity, but the bigger the airflow quantity is, the smaller range decrease is,(5) ventilation time has a significant influence on airflow temperature, humidity and rock temperature than wetness factor and airflow quantity.Another method to calculate heat transfer of surrounding rock is unsteady heat transfer coefficient between surrounding rock of the mine wells or lanes and airflow. It divided the variation range of temperature and humidity ratio into 9 intervals in mine. Then, a simplified method has been put forward, which the humidity ratio is represented in a linear function of 2 variables that are temperature and relative humidity. According to the heat transmission features between the tunnel periphery rock and airflow, the roadway can be divided into 2 types depends on whether the ventilation time of roadway is longer than 1 year. Next, it also deduced 2 new formulas for calculating the airflow temperature manually in mine. And, last of all, it also make a comparison and analysis of own forecast method and other related formulas. The results indicate that the method we have innovated enjoys the advantages of high precision and great convenience for engineering calculation. The calculate forlum of airflow temperature is more easy than the former method. It especially suitable for engineer. Thus, it can be seen that it can provide a theoretical reference to the high temperature mine cooling system design. |
PDF Full Text Request