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To study the relation between cold-hot-water mixing ratio and outlet-water temperature of a mixer, the geometrical model of the mixer was built. On the basis of theoretical analysis, the outlet-water temperature with different mixing ratio of cold and hot water was simulated by FLUENT software. The results show that: flow field in mixer can be divided into recirculation zone and convection zone, in which there are different thermal resistances individually, and it result in the nonlinear relation in outlet average temperature and mixing ratio; there is a linear relation between outlet average velocity and mixing ratio, which accords to the mass conservation principle of non-compressible and continuous fluid flow.

In the present work, we focus on computational investigations of the Reynolds number effect and the wall heat transfer on the performance of axial compressor during its miniaturization. The NASA stage 35 compressor is selected as the configuration in this study and computational fluid dynamics (CFD) is used to carry out the miniaturization process and simulations. We perform parameter studies on the effect of Reynolds number and wall thermal conditions. Our results indicate a decrease of efficiency, if the compressor is miniaturized based on its original geometry due to the increase of viscous effects. The increased heat transfer through wall has only a small effect and will actually benefit compressor performance based on our study.

COVID-19 is a serious respiratory disease caused by a devastating coronavirus family (2019-nCoV) that has become a global epidemic. It is an infectious virus transmitted by inhalation or contact with the droplet core produced by infected people when they sneeze, cough, and speak. SARS-COV-2 transmission in the air is possible even in a confined space near the infected person. This study examines air conditioners’ effect on the mixed virus and droplets with aerosol disinfectant and gets throughout the elevator to detect the SARS-COV-2, which helps protect passengers’ lives. This study uses fluent 2019R3 software to simulate the virus transmission to model the transient flows numerically. The analysis found that the ventilation system’s turbulent fields can be an effective method of protecting the space from being saturated by the coronavirus.

A 3-D Eulerian-Eulerian multiphase Computational Fluid Dynamics (CFD) model combined with Population Balance Modeling (PBM) were presented for two phase bubbly flow in vertical pipes. The discrete bubble sizes prescribed in the dispersed phase were tracked by solving an additional set of transport equations, which these equations were progressively coupled with the flow equations during the simulations. Important flow quantities such as local void fraction, liquid velocity and normal turbulent stresses were calculated and compared against experimental data from literature. Good agreement with the experimental data was obtained. It was found that void fraction profile exhibited a sharp peak near the wall. The liquid velocity profile was flattened by the presence of the vapor phase (i.e. the bubbles), and all three normal fluctuations were affected by the presence of the vapor phase. These fluctuations do not increase monotonically as the void fraction increases. Thus this CFD-PBM modeling can be used for prediction of wall peaking and coring phenomena, and radial void distribution.