Applied Mechanics and Materials Vols. 204-208

Abstract: A brief review on the respiratory aerosols transportation in ventilated built environment using CFD method was carried. Performs in-depth literature study about room model, manikin, respiratory aerosols, ventilation type and aerosol particulate matter model. Based on this study, summarizes the research status in quo and the main problem existed at home and abroad. The results showed that (1) recent studies mainly concerned on specific environment such as treatment room, aircraft cabin mock-up, office room, bus and high-speed rail cabin and based on the specific environment to simulate, (2) some studies put emphases only on droplet or droplet nuclei, and at the same time, evaporation, deposition and coagulation were neglected sometimes, (3) there were lack of studies on moving manikins (4) there was no finial conclusion about which ventilation pattern was better for reducing the risk of cross-infection from airborne transmission diseases in a certain place, (5) to choose the Lagrangian method or the Eulerian method for a certain problem generally depends on the subjects, targets, and the computer resources available.

Abstract: Ventilation is important for controlling the airborne transmission of infectious respiratory diseases, particularly in crowed and enclosed spaces, where exist higher risks of cross-infection. This paper studies the spatial concentration distribution and particle tracks of students talking continuously in a classroom with two air distribution methods, including mixing ventilation (MV) and displacement ventilation (DV) using CFD simulations. The classroom is occupied by 10 students with a seating arrangement of 5 rows and 2 columns. The objective of this study is to find out which ventilation mode is more effective in removing respiratory aerosols. The simulation results indicated that the displacement ventilation with the low air supply velocity magnitude and low turbulence could remove the respiratory aerosol droplets and minimize the risk of infectious effectively compared with mixing ventilation.

Abstract: A mathematical model of heat and mass transfer process in plate falling film absorber with wire-meshed fins was developed. The model could predict temperature and concentration distribution as well as the solution side heat transfer coefficient and the absorption rate. The results verify that heat and mass transfer performance of the plate falling film absorber with wire-meshed fins is better than the past absorber. Compared with the plate falling film absorber without fins, heat transfer coefficient of the absorber in this article increases 1.06 times and the absorption rate increases 2.32 times.

Abstract: The convolution-type Gurtin variational principle is known as the only variational principle that is, from mathematics point of view, totally equivalent to the initial value problem system. In this paper, the governing equation of bars is first transformed to a new equation containing initial conditions by using convolution method. Then, a convolution-type semi-analytical DQ approach, which involves differential quadrature (DQ) approximation in space domain and an analytical series expansion in time domain, is proposed to obtain the transient response solution. The transient heat transfer examples show the proposed method is a very useful and efficient tool in transient heat transfer problems.

Abstract: In order to study the distribution of indoor air from wind distributor, the velocity field and temperature field in the room are simulated with AIRPAK software which uses indoor zero-equation turbulent model. To simplify the physical model of wind distributor, five model methods have been used in the modeling process. The indoor temperature and velocity distribution characteristics were obtained and did a comparative study with the experiment. The results of the study show that the model can be simplified largely, simplified model consistent with the experimental data can also save computing resources and computing time in modeling process of wind distributor.

Abstract: kg-εg-kp-εp-kpg-θ turbulence model is proposed which considers particle-particle collision and gas-particle turbulence. This model includes turbulent kinetic energy equation, turbulent kinetic energy dissipation rate equation, particle pseudo-temperature transportation equation and the two-phase velocity correlation transport equation. To close the turbulence model, algebraic expressions of two-phase Reynolds stresses and two-phase velocity correlation variable are established which considered both gas-particle interaction and anisotropy. This model is used to simulate gas-particle in swirling sudden-expansion chamber. Comparing with kg-εg-kp-εp-θ model which is simply closed using a semi-empirical dimensional analysis, the present model has better predicted capability. It is shown that the present model gives simulation results in much better agreement with the experimental results than the kg-εg-kp-εp-θ model.

Abstract: The normal and safe supply of gas is one key of the urban operations. The risk comprehensive evaluation of gas supply companies is even more important. According to the actual work needs, to construct the application system is indispensable based on the rich internet applications(RIA) and web-based GIS(WebGIS). Therefore the application system of risk comprehensive evaluation was established by taking gas supply company as main study object after analysis the application requirements and functions. Based on the WebGIS and representational state transfer(REST), the application framework was designed and the procedure of the risk comprehensive evaluation was drafted according to the evaluation works and the index model was constructed by the main risk factors. The application system meets the normal evaluation work, which can also be more useful for the company and government manager or decision maker.

Abstract: The change of system performance caused by regenerative cycle in different operating conditions was analyzed in this paper, comparing the cycle with or without internal heat exchanger in a CO₂ trans-critical cycle. We analyzed theoretically the performance of CO₂ trans-critical cycle with the internal heat exchanger, and found that the coefficient increased with the decreasing of the high side pressure and the increasing of outlet temperature in gas cooler, in a certain range of the high side pressure and outlet temperature. The evaporation temperature could be raised when the system with internal heat exchanger and at the same time the coefficient of performance could be improved obviously. At lower high side pressure, the performance coefficient could be improved significantly by increasing the suction superheat. The higher the gas cooler outlet temperature was, the more obvious the increase was.

Abstract: Basing on 3 dimensional simulation of Airpak software, it studied the indoor thermal environment characteristics and influence factor of LGS house which provided with one air circulation system. It investigated the indoor air flow velocity field, temperature field, air age distribution and PMV-PPD distribution, and completed prediction and evaluation for air flow organization and air quality. The study shows that this air circulation system improves the air flow velocity and temperature distribution of LGS house indoor, provided a good thermal environment and air exchanging effect for indoor with low energy consumption, this has a significant meaning for improving comfort level of LGS house on the basis of meeting green energy saving.

Abstract: To solve the problem of enhancing the heat transfer capability of antifreeze mixture in a ground source heat pump system, the existing Transductive Support Vector Machine (TSVM) model was updated into an improved TSVM model. Also, a new method of mixed antifreeze heat transfer capability classification was given in the paper by analyzing antifreeze [1] heat transfer capability of the ground source heat pump system and applying the improved TSVM model.