Two- and three-dimensional CFD applied to vertical display cabinets simulation

A commercial CFD code has been employed to simulate the air flow pattern and the temperature distribution in a frozen food vertical display cabinet. At first the choice of solver parameters has been investigated in a 2D modelisation. 3D simulations have been then performed, and the effects of the cabinet length, of the warm air curtain and of longitudinal ambient air movement have been investigated. The results show that, in short cabinets, 3D secondary vortices at the side walls provide the most important mechanism for hot air entrainment. Comparison with experimental results shows that a 2D simulation is totally inadequate for such configurations, while 3D computations predict refrigeration power within engineering accuracy. Furthermore, the computed refrigerating power shows that even low room air velocity, due to its interaction with the end-wall vortices, has a significant impact on cabinet performance.     

Comparison of CFD analysis to empirical data in a commercial vortex tube

This paper presents a comparison between the performance predicted by a computational fluid dynamic (CFD) model and experimental measurements taken using a commercially available vortex tube. Specifically, the measured exit temperatures into and out of the vortex tube are compared with the CFD model. The data and the model are both verified using global mass and energy balances. The CFD model is a two-dimensional (2D) steady axisymmetric model (with swirl) that utilizes both the standard and renormalization group (RNG) k-epsilon turbulence models. While CFD has been used previously to understand the fluid behavior internal to the vortex tube, it has not been applied as a predictive model of the vortex tube in order to develop a design tool that can be used with confidence over a range of operating conditions and geometries. The objective of this paper is the demonstration of the successful use of CFD in this regard, thereby providing a powerful tool that can be used to optimize vortex tube design as well as assess its utility in the context of new applications.     

Grid deformation strategies for CFD analysis of screw compressors

Customized grid generation of twin screw machines for CFD analysis is widely used by the refrigeration and air-conditioning industry today, but is currently not suitable for topologies such as those of single screw, variable pitch or tri screw rotors. This paper investigates a technique called key-frame re-meshing that supplies pre-generated unstructured grids to the CFD solver at different time steps. To evaluate its accuracy, the results of an isentropic compression-expansion process in a reciprocating piston cylinder arrangement have been compared. Three strategies of grid deformation; diffusion equation mesh smoothing, user defined nodal displacement and key-frame remeshing have been assessed. There are many limitations to key-frame re-meshing. It requires time consuming pre-processing, has limited applicability to complex meshes and leads to inaccuracies in conservation of calculated variables. It was concluded that customized tools for generation of CFD grids are required for complex screw machines.     

A nonintrusive flow measurement technique to validate the simulated laminar fluid flow in a packed container with vented walls

A nonintrusive flow measurement technique (particle image velocimetry) was used to determine the airflow field in a package with a container-to-product diameter ratio of less than 10. The complexity and uneven distribution of the measured flow field supported the requirement of a geometrical and mathematical model capable of describing the geometry and physics of flow within the package. Using novel computational fluid dynamics (CFD) codes, an accurate model of the packed structure was developed and the 3D Navier–Stokes equations were solved. A good agreement was obtained between experimental and predicted velocities. The detailed insight on the airflow pattern provided by the CFD analysis makes this approach an ideal tool to analyze the effect of different vent designs in the airflow field distribution in complex packaging systems.     

Un détail de ce qui change: Function of a Function

Why should computation be leading to a bifurcation in architectural detailing, resulting in a simultaneous, and opposing, tendency towards either greater precision in fabrication or increasing plasticity? Architectural designer and theorist Peter Macapia asks what is driving these propensities in computation, and what in turn historically might be the relation between the detail and force. What comes into play now, though, when architectural style is no longer identified by a taxonomy of parts, or a vocabulary of orders, but rather by a network of forces and functions correlating actions? How might economic and political power be interacting with force, the diagram and function in contemporary design?     

连续油管缺陷综合检测传感器的磁路设计

为了在现场能同时检测连续油管金属截面损耗缺陷 (LMA)和连续油管局部缺陷 (LF)两类磁特性完全不同的缺陷 ,做了连续油管缺陷综合检测传感器的磁路设计。传感器的励磁源选择具有较高性价比的钕铁硼永磁体NdFeB ,选用多回路励磁方式。为了获得较好的缺陷检测信号的信噪比 ,经过对磁路的理论计算和磁化曲线的分析 ,提出连续油管检测时磁场强度应选在磁化曲线的近饱和区。磁路尺寸参数设计时 ,磁轭和极靴的尺寸应尽量小 ,但又不能进入饱和区