Application Research Of Direct Evaporative Cooling Air-Conditioning Technique In Lahore Subway Station

In recent years, China’s subway technology is developing rapidly, not only major domestic cities are planning line, and the output of the subway technology raises more and more attention. Currently, China’s subway design projects extend all over the world, the problem is caused by the less design data for reference, especially for the metro design project in less developed areas. This problem leads to the design of a certain unreliability that means subway station design conditions can not meet local design requirements. More prominent point is the environmental control system design of the subway station, subway station ventilation system design must be done according to local conditions, weather conditions in different regions has its own peculiarities, and only for a specific analysis of meteorological data, then the design can meet the design requirements as well save energy.Investment and operating costs of subway station is huge and energy consumption is serious. In recent years, energy issues began to let scholars focus on energy efficiency measures on metro station. Ventilation and air conditioning energy consumption accounts for a large proportion in subway station operation consumption. Therefore, Chinese scholars are looking for a new air-conditioning treatment of subway station actively. Evaporative cooling technology eliminates the need of energy consumption for artificial refrigerant cooling, compared with the traditional mechanical refrigeration, this technology can not only saving energy but also protect the environment effectively, therefore, application of evaporative cooling technology has been rapid development.This topic is based on designed project of metro station of Pakistan in Lahore. At first, In accordance with the domestic design experience combined with relevant national norms subway station load value is calculated, then discussion and analysis of Pakistan outdoor air conditioning calculation parameters is conducted, and compared with applicable conditions of direct evaporative cooling air conditioning technology, in addition design subway station model is analyzed, respectively, air supply of the platform and station level is estimated.This article studies two kinds of direct evaporative cooling mathematical models, whose accuracy has been experimentally verified, calculates export air state parameters under different contact form, while accounting the value of the air supply. According to metro station designed model, equal proportions of a three dimensional model of the platform layer and the station level are built, with the application of Fluent simulation software, the airflow has been researched. At the same time, this article analyses the temperature field and velocity field in public areas. For the moisture problems of evaporative cooling process, humidity field is analysed in public areas. According to simulated value, some advice are given about the wid-gap of actual design of location and related equipment recommendations. According to the relevant project examples, energy-saving effect of direct evaporative cooling process and traditional mechanical refrigeration is discussed, the result is that direct evaporative cooling technology has great potential for energy savings than traditional mechanical refrigeration.For the existing problems of simulation results in platform layer original model, we propose two ways to improve the airflow. First, the arrangement position of the outlet and the exhaust vents is adjusted, after comparison we find that the temperature distribution and velocity field improves significantly. And in order to solve the high relative humidity problem of public area in platform, we choose a way reducing the moisture content of the air blowing through the mixing method, the simulation results show that the relative humidity is lower than design requirements of 60% in public areas, at the same time the distribution of temperature can still satisfy the design requirements, both methods can be valid reference for the application of direct evaporative cooling technology in Lahore metro station.