THERMAL EFFECTS OF BUILDING′S EXTERNAL SURFACES IN CITY——Characteristics of Heat Flux into and out of External Wall Surfaces

This study examined the thermal effects of building′s external wall surfaces, using observational data of spatial-temporal distribution of surface temperature, air temperature, and heat flux into and out of external surface. Results indicate that external wall surface temperature and nearby air temperature vary with the change of orientation, height and season. In general, the external wall surface temperature is lower near the ground, and is higher near the roof, than nearby air temperature. But north wall surface temperature is mostly lower than nearby air temperature at the same height; south wall surface temperature during the daytime in December, and west wall surface temperature all day in August, is respectively higher than nearby air temperature. The heat fluxes into and out of external wall surfaces show the differences that exist in the various orientations, heights and seasons. In December, south wall surface at the lower sites emits heat and north wall surface at the higher sites absorbs heat. In April, all external wall surfaces, emit heat near the ground and absorb heat near the roof. In August, west wall surface all day emits heat, and other wall surfaces just show the commensurate behavior with that in April.

Molecular Dynamics Study on the Mechanism of Nanoparticle Phase Change Caused by Collision with Wall Surface

The collision between the nanoparticle and wall surface is supposed to cause the escape of nanoparticle molecules which indicates the potential phase change of the nanoparticle.It is significant to understand the mechanism of the collision process involved with phase change for applications of nanoparticles in energy and mass transfer.In this study,the collision process between nanoparticle made of monatomic argon molecule and wall surface made of nickel metal crystal is simulated by molecular dynamics method.The travelling behavior and energy transformation of escaped molecules are respectively analyzed.The effects of the intermolecular force and initial temperature on the collision process are further discussed.The results show that the nanoparticle can be accelerated by the wall surface with the intermolecular force and finally collide with it.The molecules escape from the nanoparticle either by bouncing off the wall surface or the intermolecular energy exchange with the energy transformation between the potential energy and kinetic energy.The molecules far from the nanoparticle center are more likely to escape,while the velocity distributions of the escaped molecules follow the Maxwell distribution.More escaped molecules,namely higher phase change potential,are observed with lower intermolecular force and higher initial temperature.As a fundamental study on nanoparticle phase change in the vicinity of wall surface,the present investigation will be helpful for further study on the heat transfer characteristics and phase change mechanisms of nanoparticles.

On the Effect of the Rotating Chamber Reverse Speed on the Mixing of SiC Ceramic Particles in a Dry Granulation Process

In order to control the accumulation of SiC ceramic particles on the wall of the rotating chamber in the frame of a dry granulation process,the effect of the wall reverse speed on the mixing process is investigated.In particular,an Euler-Euler two-phase flow model is used to analyze the dynamics of both SiC particles and air.The numerical results show that by setting a certain reverse rotating speed of the rotating chamber,the accumulation of SiC particles on the wall can be improved,i.e.,their direction of motion in proximity to the wall can be changed and particles can be forced to re-join the granulation process.Experimental tests conducted to verify the reliability of the numerical findings,demonstrate that when the reverse rotating speed of the rotating chamber is 4 r/min,the sphericity of SiC particles in the rotating chamber is the highest and the fluidity is the best possible one.

Numerical Simulation of Proppant Dynamics in a Rough Inclined Fracture

Although the dynamics of proppant(small ceramic balls used to prevent opened fractures from closing on the release of pressure)have been the subject of several numerical studies over recent years,large-scale inclined fractures exist in unconventional reservoirs for which relevant information is still missing.In the present study,this problem is investigated numerically considering the influence of several relevant factors such as the fracture roughness,inclination,the proppant particle size,the injection rate and the fluid viscosity.The results show that a rough wall enables the proppant to travel farther and cover larger areas.The inclination angle has little effect on the dune but a significant influence on the suspension zone.The area of this zone increases with a decrease in the inclination angle,and its value for an inclination of 15°is 20 times that at 90°.Small particle size,high injection rate,and high fracturing fluid viscosity have a beneficial influence on proppant transport;vice versa they hinder settling phenomena.

Identification of Model Parameters of Vaporized Hydrogen Peroxide Decomposi-tion Flux on Building Materials for Compu-tational Fluid Dynamics

To maintain healthy and sanitary indoor air quality, development of effective decontamination measures for the indoor environment is important and hydrogen peroxide is often used as decontamination agent in healthcare environment. In this study, we focused on the decomposition phenomena of vaporized hydrogen peroxide on wall surfaces in indoor environment and discussed a wall surface decomposition model for vaporized hydrogen peroxide using computational fluid dynamics to simulate the concentration distributions of vaporized hydrogen peroxide. A major drawback to using numerical simulations is the lack of sufficient data on boundary conditions for various types of building materials and hence. We also conducted the fundamental chamber experiment to identify the model parameters of wall surface decomposition model for targeting five types of building materials.

碳当量对热模法大口径球铁管内壁翘皮的影响

介绍了球铁铸管内壁龟纹、翘皮缺陷及其产生的影响因素、解决的方法。分析了碳当量对龟纹翘皮的影响。

Distribution Characteristics of Transmitted Diffuse Solar Radiation on the Indoor Surface

The transparent envelope structure has huge energy-saving potential, which is the key point to reduce building energy consumption and improve the thermal building environment. The solar radiation transmitted through the transparent envelope structure(transmitted solar radiation) is reflected, scattered and absorbed by the indoor surface, which has a significant impact on the heat gain of the building. In this paper, firstly, the diffuse radiation received by different depths of various indoor surfaces is measured by experimental tests, and the distribution function of transmitted diffuse solar radiation(TDSR) on the indoor surface is established. Secondly, the diffuse solar radiation received by the indoor and outdoor surfaces in different seasons is continuously monitored;the variation of TDSR with time is analyzed, and the distribution function of TDSR on indoor surface with time is proposed. Finally, based on the temporal and spatial distribution characteristics of diffuse radiation under different weather conditions, the variation of TDSR with the weather is studied, and the distribution function of TDSR on the indoor surface with weather changes is established. The distribution function of the TDSR on the indoor surface under different depths, time and weather conditions obtained in this study can supplement and improve the theory of building heat gain and load, and help accurate simulation of building energy consumption.