Research on the End-Face Distribution of Rotational Molding Heating Gun Based on Numerical Simulation Method

The distribution of heating gun ends plays a decisive role in the sidewall properties of finished rotomolded products. To obtain the optimal distribution of the end face of a rotational molding heating gun, the temperature response of the end-face mold under heating gun heating was investigated, and an analysis method based on numerical simulation is proposed. The FDS (fire dynamics simulator) was used to construct a heating model of the heating gun, simulate and obtain a heatmap of the temperature field distribution of a heating gun of Φ30–70 mm, and determine the optimal diameter and heating distance of the heating gun. ANSYS was used to establish the thermal response model of the heat-affected mold, which was combined with the mold structure and thermophysical properties of steel. A temperature field distribution on the inner wall surface of Φ30, Φ50, and Φ70 mm heating guns when heating at each diameter of the end face was obtained and the distribution position of the end face of each diameter heating gun was determined. ANSYS was used to establish the thermal response model of the end-face mold and obtain the temperature field distribution of the inner wall surface of the end-face mold. The size of the heat-affected area of each diameter heating gun was combined, the end-face heating gun distribution was optimized, and the optimal heating gun end-face distribution was obtained. An experimental platform was built, and a validation experiment was set up. Through the analysis and processing of the data of three experiments, the temperature variation curve of each diameter on the inner surface of the end-face mold was obtained. We compare and analyze the simulation and experimental results to determine the feasibility of the FDS + ANSYS method and the correctness and accuracy of the simulation model and the results.

Cooling holes with different structures effects on coolant cross flow and heat transfer at the outlet of the combustion chamber

The major effects of cylindrical and row trenched cooling holes with angles of alpha=30, beta=0, alpha=40, beta=0 and alpha=50, beta=0 at BR=3.18 on the effectiveness of film cooling near the combustor end wall surface is an important subject to study in detail. In the current study, researchers used a FLUENT package 16/11 to simulate a 3-D model of a Pratt and Whitney gas turbine engine. In this research, RNG turbulence model K-ε model was used to analyze the flow behavior on the passage ways of internal cooling. In the combustor simulator, the dilution jets and cooling flow staggered in the streamwise direction and aligned in the spanwise direction as well. In comparison with the baseline case of cooling holes, the application of trenched hole near the end wall surface increased the effectiveness of film cooling up to 100% for different trench cases.

Evaluation of surface processes in the PALM model system 6.0 for a real urban environment: a case study in Dejvice, Prague

<p>In recent years, the the Large-eddy simulation (LES) model PALM has been rapidly developed its capability to simulate physical processes within urban environments. For example, this includes energy-balance solvers for building and land surfaces, a radiative transfer model to account for multiple reflections and shading, a plant-canopy model to consider the effects of plants on flow (thermo-)dynamics, and a chemistry transport model, as well as nesting capabilities that enable “hot-spot” analysis, to name a few.</p> <p>This contribution provides an evaluation of modeled meteorological as well as ground and wall-surface quantities against dedicated in-situ measurements taken in an urban environment in Dejvice, Prague. Measurements included monitoring of surface temperature and wall heat fluxes. Simulations were performed for multiple days during several summer and winter episodes, characterized by different atmospheric conditions. To consider time-evolving synoptic conditions, boundary conditions were obtained from mesoscale WRF simulations.</p> <p>For the simulated episodes, the resulting temperature and wind speed within street canyons show a realistic representation of the observed state, except that the LES did not adequately capture night-time cooling near the surface in some scenarios. At most of the evaluation points, the simulated surface temperature reproduces the observed surface temperature reasonably well, for both, absolute and daily amplitude values. However, especially for the winter episodes and for modern buildings with multi-layer wall structure, the heat transfer through the walls is not well captured in some cases, leading to discrepancies between the modeled and observed wall-surface temperature. Moreover, we also show that the model performance with respect to the observations strongly depends on the accuracy of the input data. To name a few, this includes e.g. the prescribed initial soil moisture, the given leaf-area densities to account for correct shading, or if a facade is insulated or not. Additionally, we will point out current model limitations, particularly implications accompanied by the step-like topography on the Cartesian grid, or wide glass facades that are not fully represented in terms of radiative processes.</p> <p>With our findings we are able to evaluate the representation of physical processes in PALM, while also pointing out specific shortcomings.</p>

Numerical Study on the Rising Motion of Bubbles near the Wall

Based on the volume of fluid method (VOF), the rising characteristics of bubbles in near-wall static water are studied. In this study, the influence of the wall on the rising motion of the bubble was studied by changing the distance of the bubble wall, the diameter of the bubble, the arrangement of the bubble and the size ratio, etc. The influence is expressed as the average swing amplitude of the “Z”-shaped motion when the bubble rises. The study found that in the case of a single bubble, the wall surface has a certain influence on the rise of the bubble, and its degree is affected by the bubble wall distance and the bubble diameter. The influence of bubble wall distance is more obvious. The greater the bubble wall distance, the less the bubble is affected by the wall; in the case of double bubbles, the influence of the interaction force between the bubbles is significantly greater than the wall surface.

Masters and apprentices at the Chapel of Hatshepsut: towards an archaeology of ancient Egyptian reliefs

Ancient art is typically studied in terms of its aesthetic or historical value. This article presents an alternative approach, examining ancient Egyptian wall reliefs from a chaîne opératoire perspective. The reliefs assessed here adorn the walls of the Chapel of Hatshepsut at Deir el-Bahari in Thebes. The analysis reveals, for the first time, the sequence of the artists’ work, from the initial preparation of the wall surface to the master sculptor's final touches. This enables a reconstruction of the ergonomic organisation of the work, distinguishing the contributions of individual hands and revealing often intangible phenomena, such as master-apprentice interactions. A similar approach may be useful when examining carved reliefs in other parts of the world.

Cryptococcus neoformans capsule regrowth experiments reveal dynamics of enlargement and architecture

The polysaccharide capsule of fungal pathogen Cryptococcus neoformans is a critical virulence factor that has historically evaded characterization. Polysaccharides remain attached to the cell as capsular polysaccharide (CPS) or are shed into the surroundings in the form of exopolysaccharide (EPS). While a great deal of study has been done examining the properties of EPS, far less is known about CPS. In this work, we detail the development of new physical and enzymatic methods for the isolation of CPS which can be used to explore the architecture of the capsule and removed capsular material. Sonication and glucanex digestion yield soluble CPS preparations, while French Press and modified glucanex digestion plus vortexing remove the capsule and cell wall producing polysaccharide aggregates that we call capsule ghosts. The existence of capsule ghosts implies an inherent organization that allows it to exist independent of the cell wall surface. As sonication and glucanex digestion were noncytotoxic, it was possible to observe the cryptococcal cells rebuilding their capsule, revealing new insights into capsule architecture and synthesis consistent with a model in which the capsule is assembled from smaller polymers, which are then assemble into larger ones.

Heat Dissipation by Streams of Bifurcated Tubes

There is a need for solutions to provide sufficient cooling from power devices, which produce large amounts of heat. This paper focuses on the influence of design of bifurcated fluid streams to dissipate heat. In this study, a single Y-tubes, a double Y-tubes, and an X-tubes designs are studied numerically under space constraints. For a comprehensive and in-depth performance analysis, both heat dissipation and hydraulic performances are analyzed. The distributions of velocity and temperature in the fluid streams is simulated, also the flow resistances and dissipated heat are calculated. Based on the results obtained, a thermo-hydraulic performance factor is introduced for the designs under study. In addition, the accumulation of undesired substances on the wall surface (fouling) that may influence the heat exchanging capability is studied.

Development of an automated milling system for the decontamination of the wall surface in a nuclear power plant

Nowadays, concrete decontamination is done by, e.g., grinding, milling, etc., always combined with labor resources. In order to relieve employees from the monotonous and physically stressful decontamination work, a novel milling system for automated surface decontamination has been developed and assembled. The current work presents this new concept for a milling tool that could automatically position itself to the wall surface and subsequently remove surface contamination. A process chain (Fig. 1) defined in the German Federal Ministry of Education and Research (BMBF)-funded project ROBDEKON was introduced first. The chain consists of a total of five steps for a compact process, from environmental exploration to the transportation of waste. This automated decontamination is the third step in the process chain for decontamination of building structures in nuclear facilities. The structure (Fig. 2) of the milling system and the function of each component are then explained in detail. With the assembled sensors, such as a laser distance sensor, a force sensor etc., the various physical quantities can be measured in real time, thus enabling automation of the milling process during decontamination.