| Air conditioning system process of roof porous convection and radiation is a convective heat transfer and radiation heat transfer interaction. The biggest difference between roof porous radiation air conditioning and traditional radiation air conditioning system is the carrier of energy is air instead of water. Roof porous radiation air conditioning is energy saving and comfortable as well as traditional radiation air conditioning. At the same time, Roof porous radiation air conditioning known as noncondensing and convenient installation.Based on the heat transfer theory, this article analyses system model of traditional metal plate type heat radiation air conditioning. Through the establishment of radiation heat transfer model, we can combine with the characteristics of roof porous convection radiation air conditioning terminal equipment to analyze radiation heat transfer. Then according to basic CFD theory, FLUENT software are used to simulate the orifice plate heat transfer performance under the condition of different opening rate(2.14%, 3.14%, 4.14%)、aperture(1cm, 2cm, 3cm) 、air temperature(8℃, 10℃, 12℃) and air velocity(0.8m/s, 1.3m/s, 1.8m/s). According to the basic research,(1) With the orifice coefficient increases, air heat,getting into indoors through the orifice plate increases, however, radiation heat transfer and the heat flux decline.(2) Aperture effect of heat transfer is not obvious. On the contrary, it takes much effect on air evenness.(3)With the increasing of supplying air temperature, convection and radiation heat transfer of porous plate and indoor air heat transfer decrease.(4) Air speed causes little influence on indoors temperature field, as well as with the air speed increased, the heat changes of porous convection and radiation plate is not obvious. On the contrary, the convection heat transfer and indoor air heat transfer gradually increase.Paper uses the Fluent to investigate the different roof temperature(summer 16℃、18℃、20℃,winter 24℃,26℃,28℃),building envelope temperature(summer 26℃,29℃,32℃,winter 8℃,11℃ 14℃) on theinfluence of radiant ceiling heat transfer and indoor thermal environment. Research gets the variation curves of room temperature and velocity distribution and heat transfer in winter and summer. Article also designs a UDF programming to calculate the PMV-PPD index so as to obtain the human comfort condition. Research shows that:(1) the air conditioning system in the actual operation should be controlled through adjusting roof temperature(summer temperature controlled below 20℃)to increase the terminal equipment proportion of radiation heat transfer,so as to improve the system energy efficiency. In winter condition, system terminal radiation heat transfer accounts for a large proportion, but the roof temperature should be better not more than 28℃ for the sake of improving system energy saving ability. Therefore, porous convection radiation roof also has good heating capacity in winter.(2) In the practical application, air conditioning system should balance the cooling ability and indoor thermal load. When the roof temperature is 18℃, the most suitable building envelope temperature should not be greater than 32 ℃and not less than 26℃.In winter condition, when the roof temperature is26℃, the most suitable building envelope temperature is not greater than11℃ and not less than 8℃Finally, experiments are made in a reading room of the school library,which equipped with roof porous convection and radiation air conditioning in winter and summer. Comparing test data with simulation results eventually proves simulation is accurate and reasonable. The results of this study will be a certain reference and help for the researches,design and application of the future roof porous convection radiation air conditioning system. |
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