Numerical Study Of Heat And Mass Transfer In Long Straight Tunnel With Water

In this paper, the technique of computational fluid dynamics(CFD)is adopted to simulate the heat and mass transfer in the tunnel with water under the air where the weather condition is similar to the Ya'an district Sichuan province. We analyze and compare the different output with different air inlet temperature, velocity, the volume fraction of the vapor, the different wall temperature and water temperature by reference to the air inlet tunnel in real hydropower statioa Get the expected outcome which suit to real engineering project The possibility of the air temperature distribution is discussed. Point out the fault of the computational model and the difference with the real situation.We use the average temperature and the humidity on the section plane to value the effect of the heat and mass transfer in tunnel.Multiphase fluid model-VOF was adopted to do the numerical simulation. In this paper, the standard three dimensional k-ε two equations turbulence model which modifies the item of buoyant effect and SIMPLEC algorithm are adopted. Body force weighed was used. And the volume fraction of the air, water and the vapor were defined at the initial stage. Stable VOF model's under relax factor was defined between 0.2~0.5.The outcome shows that the wall temperature, water temperature, air temperature and the air inlet velocity have the effect on the simulation. The effect of the heat and mass transfer will more better if the difference in temperature is more higher and the air velocity is more slower. Through the analysis we can draw the conclusion that the ideal air inlet velocity should be between 0.5-1.0m/s. the capability of the temperature reduction and dehumidification is different at the different position. This capability will decrease along the direction of the air flow.