Study On Porous Media Model Of Air Distribution Simulation In Large Space Building

As is known, air conditioning system plays a very important part on indoor environment in large space industrial factory building, however, according to field measurement the environment in the plant is disappointment, which indicates that the traditional air conditioning system design pattern still need to be improved. A large space paper-making plant is selected for the physical model in this paper, combined with numerical simulation method the porous media model is applied to simplify the complex production equipment in the plant.Firstly characteristics and properties of porous media are introduced briefly in the paper and then give a review on the predecessors’ research work on large space air distribution simulation as well as the porous media research fields. Finally theory analysis, field measurement and numerical simulation are confirmed as the research method in the paper.The fluid flow region is divided into pure fluid region and porous media region in the paper. The flow control equations in pure fluid region are fluid mechanics equations that have been derived in many books, while the porous media region is treated as a special continuous fluid contains amounts of pores. Based on the pure fluid mechanics equations, the representative element volume is introduced, on which the on the pure fluid mechanics equations are averaged, to derive the porous media macroscopic flow equations. Previously, some macroscopic parameters such as porosity, specific area, coefficient of permeability and permeability ratio are defined. Besides the measure calculate method and model for these parameters are also introduced.The field measured large space industrial factory building is simplified firstly and then the simulation physical model is created in professional modeling software Gambit, hexahedron and tetrahedron cells are used to partition the calculation region to generate the grids. The boundary conditions and the source terms will be set according to the field measurement results in the calculation software Fluent, and in convenience of setting porous media model parameters, the production equipment in the plant is divided into five parts, namely wet part , front dry part, glue part, back dry part and complete part. And the porous media model is only imposed on the wet part in the paper, at first the porous media porosity and permeability are calculated using destiny method and capillary tube model respectively. After that iteration method is combined with the destiny method and capillary tube model to calculate the final porous media model parameters.In order to ensure the defined porous media model parameters is effective, the simulated cases are set the same with the production conditions in the plant. Temperature, relative humidity and velocity vector on typical sections and lines are calculated, further more the calculated temperature and relative humidity are compared with the measured temperature and relative humidity, which indicates the temperature and relative humidity calculated from the defined parameters coincide with the measured temperature and relative humidity every well. Therefore the defined porous media model parameters are effective. Besides, both velocity distribution difference and iterate time with porous media model and without porous media model are compared, and the reason for this difference is analyzed as well.