SIMPLIFIED CFD MODELING METHOD AND ACCURACY VERIFICATION OF AIRFLOW FROM CEILING-MOUNTED PERSONALIZED AIR SUPPLY TERMINAL

Personal air conditioning system is an air distribution method to provide a satisfactory thermal environment. The purpose of this study is to propose a CFD modeling method of the airflow from personal air supply terminal. As the first step, a full-scale experiment was conducted under the isothermal condition, where a personal air supply terminal was installed on the ceiling. The supply airflow rate was regulated at 28 m3/h. In the experiment, 2-D velocity was measured using a X-type hot-wire probe, and turbulent statistics were measured using an I-type hot-wire probe. The experiment was conducted to obtain boundary conditions for CFD and to obtain true value for accuracy verification. Second, CFD analyses using Standard k-ε Model (SKE), SST k-ω Model (SST) and Reynolds Stress Model (RSM) were performed, and SKE and SST showed good agreement with experimental result as shown in Fig. 9. To perform this Detailed CFD analysis, a large number of grids is required, which leads to large computational load and difficulty in analysing a large space. Therefore, to decrease the number of grids without loosing accuracy, two CFD modeling methods were applied in this paper, i.e., momentum method and P.V. method. The analysis using these two methods was performed, and the accuracy was verified by comparing the result with that of above-mentioned detailed analysis. As the result, in the case of 50mm-mesh, the decrease of the accuracy was not significant because the number of grids is relatively large. On the other hand, in the case of 100mm-mesh, the accuracy was greatly decreased if no modeling method was applied. However, the accuracy was obviously improved by using the momentum method and P.V. method as shown in Fig. 12 and 13. The conclusions obtained in this paper are summarized as follows. (1) In the accuracy verification where the experiment was compared with CFD, both SKE and SST showed good agreement with the experimental result regarding average 2-D velocity distribution on the central section. However, RSM overestimated the diffusion of momentum, and consequently showed the tendency to underestimate the reach of air flow compared to the experimental value. (2) In the CFD analysis using the Momentum method, the accuracy is not sufficient if compared to the detailed analysis. However, the tendency of the velocity distribution was quite similar to that of the detailed analysis. In the case of a 100-mm mesh, the improvement of accuracy by CFD modeling becomes large if compa