Research On The Ventilation Usage Of The Access Tunnel In Deep Buried Underground Works

The using of underground air flue to introduce fresh air for buildings are takenseriously by people, because the effects of cooling, dehumidifying or heating thatunderground air flue has on fresh air can save a lot of air conditioning energyconsumption, the application is gradually increasing in engineering. Usually, there is atraffic tunnel to contact with the ground in buried deep underground engineering, wecan use the traffic tunnel to introduce outdoor fresh air directly in practical engineering,because of the larger depth and length, this treatment effect to fresh air is superior togeneral underground air flue. The correct use of processing power to air of the accesstunnel will effectively reduce the fresh air load of air conditioning unit, so as to achievethe purpose of "one tunnel, two uses" and fully energy conservation. However, in theengineering practical operation, we found that at the time of the access tunnel coolingand dehumidifying the fresh air, the phenomenon of condensation and fog will appear,its visibility was reduced, and have impact on traffic security. Therefore, further studythe problem of using the access tunnel to introduce air in buried deep undergroundengineering, is helpful for the energy conservation research of underground engineering,and also has important guiding significance to solve practical engineering problems.This paper is one of the major project topics "deep underground hydropower stationhot wet environment formation mechanism and saving energy control" which isbelong to major project topics of the national natural science funds (51178482).Firstly, this paper site measured the air condition into the access tunnels in threeburied deep underground hydropower stations in summer. Then using the measured data,analyze the heat and moisture processing power of the access tunnels, change law of airstate parameters and its influencing factors, and expound the cause of the dew and fogof air in the access tunnels. Through the analysis of three kinds of defogging technicalmeasures taken in current practical engineering, such as setting dehumidifier, attachingwith a thermal insulation layer and increasing ventilation rate, we found that thesetechnical measures ease the fog, at the same time, exist problems or limitations ofincreasing energy consumption, reducing the heat and moisture processing power of theaccess tunnel to air, and influencing internal heat and moisture environment ofunderground engineering, can’t satisfy the basic technical requirements of using thetraffic tunnel to introduce air, and be popularized to engineering. Based on the site measure and the theoretical analysis, this paper puts forward to new structure of the"double deck type access tunnel, which is fit for the buried deep undergroundengineering.Then, in allusion to the double layer access tunnel, establish mathematical physicalmodel of the heat and moisture exchange of tunnel and air, transform the section ofdouble layer access tunnel through the method of equivalent circular column modeltransformation, discrete differential form of the mathematical model, establish theairflow parameter calculation model and develop the corresponding calculationprogram.Using the developed program, in three different for wind modes, such as accesstunnel ventilation only, the interlayer space ventilation only and both of themventilation, calculate the heat and moisture exchange condition of double deck typeaccess tunnel and dynamic changes of the air state parameters respectively. Accordingto the calculated results, the mode of access tunnel ventilation only can solve theproblem of fog to some extent, but the heat and moisture processing power of it is farless than that of the original access tunnel; the heat and moisture processing power ofthe mode of the interlayer space ventilation only is far greater than that of the originalaccess tunnel, and solves the problem of fog; it’s the mode of both of them ventilationthat the heat and moisture processing power and the defogging effect is between thefirst two ventilation mode. Thus obtain the best for wind model is the interlayer spaceventilation, while the access tunnel no ventilation.Finally, contrast and analyze the engineering investment and energy efficiency ofthe double layer access tunnel in the best for wind mode and the original access tunnel,obtain the cost investment payoff period, so as to confirm the feasibility in engineeringapplication.