Yükleniyor…
Yükleniyor…
Knowledge of the flow patterns in the upper respiratory tract is a key factor to the understanding of airway resistance and predicting the deposition of particles. Flow in this region is, however, complex and can be patient dependent, defying the ability of simple numerical models to predict particle deposition. Computational fluid dynamics (CFD) can be used, and is perhaps best suited for predicting flow in this region for a given respiratory pattern. In this study, first air, then 70/30 helium/oxygen (Heliox) flow and particle deposition in the human throat were numerically analyzed with CFD software, Fluent (Fluent 6.2.16, Fluent Inc.). Particle ranging between SMD=0.5 um and SMD=20 um were used both Heliox and air simulations. The throat model was constructed from MRI of a 25 year old female taken at 3 mm slices. The vertex data of throat obtained from MRI by means of the OSIRIS software. After that, a 3D human airway model was created with GAMBIT software (Fluent Inc.). Consequently, the computational model was imported into Fluent solver and the steady state conservation equations of mass, momentum and energy were solved using the finite volume method. The chosen inlet velocity was based on an approximate adult breathing condition with a steady flow rate of 18 liters per minute. Both heliox and air flows reached maximum velocities at larynx region because of the laryngeal jet flow. It has been observed that flow patterns of the gas flow are similar both Heliox and air. However, Heliox presented values that are higher than the air system. It has also been found that when smaller particles (SMD=0.5 um and SMD=2 um) were injected into the flow, the whole particles deposited around the larynx and could not reach to the throat exit. Keywords: Human throat, Computational Fluid Dynamics (CFD), Fluent CFD Software, Spray characteristics, SST k–ε model
This study, the annual performance of a new generation Trombe wall in which solar energy is stored as latent heat is experimentally investigated. For this purpose, a test room is built and the south wall of a test room is designed as Trombe wall having Phase Change Material (i.e., PCM wall). The PCM wall made of, from inside to outside, insulation, brick, plaster in which encapsulated PCM is buried, air gap and novel designed Transparent Insulation Material (TIM). Data such as solar radiation, temperature, flow rate of circulation air, electric consumption are measured and recorded via data acquisition system to analyses the thermal and optical performance of the PCM wall. After analyzing the experimental data, proper melting temperature for the PCM is determined, the diurnal, monthly and annual variation of the performance parameters such as, the ratio of the solar energy benefit to heat load of the room, overall efficiency of the wall, solar transmittance of the TIM are analyzed. The ratio of energy benefit of PCM wall to heat load of test room is determined as 70,4%, 40,8%, and 14,2% for October, November and December of the year 2008, respectively and 9,4%, 11,3% and 4,3% for January, February and March of the year 2009, respectively. The overall efficiency of the GR35 PCM wall is higher than that of GR41 PCM wall. It is concluded that higher melting temperature of PCM results in lower overall efficiency. It is determined that solar transmittance of TIM varies between 0,45 to 0,55 in the winter season and 0,18 to 0,2 in summer season.