Heat Transfer Enhancement in a Double Sequential Impingement Channel

Sequential impingement channels can reduce the adverse effect of crossflow in narrow impingement channels, as well as increase the cooling efficiency. In this work, sequential impingement channels are experimentally investigated using the transient liquid crystal technique to assess their thermal performances. A low heat transfer region is identified in the downstream part of the first channel where the flow is discharged into the second plenum. Various means of increasing the heat transfer at this location are investigated. Ribs on the target plate allow for an increase of the average heat transfer coefficient with small losses in pressure. Reducing the channel cross-section increases the mean flow velocity and, combined with the ribs, allows for a further increase of the heat transfer. Additionally, the geometrical changes of the channel caused by the addition of a ramp with a rounded corner, allow to decrease the pressure losses associated with the discharge into the second plenum, which is not optimal in the baseline configuration due to the sharp corner of the purge hole. Further reducing the cross-section to increase the heat transfer, however, increases the pressure losses due to the small open area in the transition zone.

Configurations of Fortified Settlements of the Sintashta-Petrovka Type: Forms, Sizes, Transformations

The article aims to analyze the configurations of fortified settlements of the Sintashta-Petrovka type (SPT settlements). Sources of information about the configurations are the results of remote research (aerial photographs, geomagnetic maps, topographic maps) and data from archaeological excavations. The study of configurations is one of the aspects of settlement archaeology at the level of research of the structure of the whole settlement. The article summarizes and compares the characteristics of forms, layouts, sizes, variants of transformations. The forms of SPT settlements can be divided into two types: rounded, with a radial arrangement of rows of dwellings, and subrectangular, with a linear arrangement. Eight sites are classified as rounded, sixteen are subrectangular. In the forms of many settlements there are mixed signs that emphasize the common architectural tradition: rounded settlements have separate straightened segments and straight rows of buildings, and subrectangular ones have rounded bends of building lines and rounded corner sections. In summarizing the size indicators, small, medium and large settlements were identified. The small ones have an area from 6 to 13 m2; thousand nine sites – subrectangular, with two rows of dwellings, and rounded, with one ring of buildings – are small. The small m2. settlements have about 20 to 30 buildings. The number of medium settlements is also nine, their area is from 15 to 21 thousand Most medium-sized sites are either subrectangular, with four rows of buildings, or rounded, with two rings of buildings. The medium m2. sized settlements have about 40 to 60 buildings. There are six large settlements; their area is 23 to 32 thousand Two of the large settlements are oval, four subrectangular, with traces of significant rearrangements. Due to the small volume of field research, it is difficult to estimate the number of dwellings in large settlements. The generalization of the remote data and the results of the excavations allows the author to propose a scheme of transformations of the SPT settlements. The structural component of their configurations is a row of closely spaced dwellings, enclosed by a line of fortifications. Several rows, most often two or four, oriented linearly or radially, form the inner space of the closed fortified settlement. While the fortified settlements functioned, they were restructured, with preservation of the general principles of regularity and isolation of the living environment. There are three main scenarios for rebuilding: the completion of rows to the early section, the overlapping of fortified villages, the reduction of the area of a fortified settlement. The final stage of the life of settlements is associated with the gradual abandonment of the cramped and closed configurations. The Srubnaya-Alakul settlements, successors of the SPT settlements, use more spacious, dispersed layouts, with partial preservation of the tradition of building rows of closely spaced dwellings and with refusal to build fortifications.

Improvement of thermal EHL by selecting bush-pin geometry based on an investigation for industrial chains

Purpose This study aims to investigate the influence of geometry of bush-pin pair from a perspective of optimal lubrication through a thermal elastohydrodynamic lubrication model for finite line contact. Design/methodology/approach A constitutive equation: Ree-Eyring fluid is used in the calculations. The real chain sizes, i.e. equivalent radius of curvature, bush length, length of the rounded corner area and rounded corner radius, are jointed investigated. Moreover, the effects of the length of the rounded corner area and the radius of rounded corner are investigated. Findings It is found that the current standard of the chain might not consider the importance of lubrication, and the lubrication state can be improved effectively by choosing an optimal radius of rounded corner and the length of the corner area. Originality/value By optimally selecting sizes, the occurrence of high pressure, high temperature rise and near zero film thickness at the ends of bush, especially under heavier load, can be effectively avoided. Peer review The peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-01-2020-0031/

Effect of Corner Shape on Hydraulic Performance of One-Cycle Rectangular Labyrinth Weirs

The hydraulic performance of rectangular labyrinth weirs has been investigated by many researchers, however, the effects of the corner shape on the hydraulic performance of rectangular labyrinth weirs have not been addressed in the current literature. Accordingly, this experimental study aims to explore the effect of the corner shape of on discharge efficiency of rectangular labyrinth weirs. Five flat-crested rectangular labyrinth weirs, with five different corner shapes, were made of High-Density Polyethylene Plastic (HDPE) and tested in a rectangular flume. Under different overflow discharges, the discharge coefficients for the rectangular labyrinth weirs were determined. The results showed that the shape of corners for rectangular labyrinth weirs was an effective factor. For example, rounding or beveling the corners can significantly increase the discharge capacity of the rectangular labyrinth weirs. However, the rounded corner shape was slightly better than the beveled corner shape. Among all labyrinth weir models tested in this study, the rectangular labyrinth weir with a semi-circular apex showed the highest hydraulic efficiency, while the one with an acute-angle corner shape showed the lowest hydraulic efficiency. For the rectangular labyrinth weir having a semi-circular shape, although the original effective length reduced by about 14%, the discharge coefficient, CL, increased by 16.7% on average. For the rectangular labyrinth weir that has an acute-angle corner shape, although the effective length (LC) of the weir increased by 23%, its discharge capacity decreased by 35.2% on average. Accordingly, improper folding of the side-walls of the rectangular labyrinth weir led to a significant reduction in the weir’s hydraulic performance.

Regularities of formation of thickening in the rounded corner of parts made of composites molded by vacuum infusion on negative-type tooling

In this work, the regularities of the formation of a thickening in the zone of the rounded corner of composite parts made on the basis of aramid and carbon fi bers are established. The infl uence of the radius zone geometry and the type of reinforcing material on the mass and dimensions of the forming thickening is shown.

Effects of Different Staircase Design Factors on Evacuation of Children from Kindergarten Buildings Analyzed via Agent-Based Simulation

Staircase design is critical to the evacuation of children. Through an agent-based simulation, this study focused on the relationship between staircase design factors and evacuation efficiency in a multi-story kindergarten. A quantitative study was conducted on three critical architectural design factors: stair flight width, positional relationship, and design pattern of the juncture between the staircase and the corridor. The findings were as follows. (1) When the stair flight width ranges from 0.7 to 1.0 m, an increase in this width can improve evacuation efficiency significantly; when the width ranges from 1.1 to 1.4 m, evacuation efficiency is improved continuously, but an increase in this width range has a diminishing effect on evacuation efficiency; when the width is greater than 1.7 m, a further increase has an adverse effect on evacuation efficiency, because such a staircase space allows overtaking behaviors. (2) Under the same stair flight width conditions, evacuation efficiency is higher when the staircase and corridor are perpendicular to each other than when they are parallel, because the natural steering angle of the children was preserved during their evacuation. (3) The cut corner and rounded corner designs between the staircase and corridor improved evacuation efficiency and alleviated the congestion at bottleneck positions; the evacuation efficiency continued to rise with an increase in the cutting angle. These findings are expected to provide a useful reference for the evacuation design of kindergarten buildings and for emergency evacuation management.

A Note on the Comparative Analysis Between Rectangular and Modified Duct Heat Exchanger

The plate fin heat exchangers usually have either rectangular or triangular shaped flow passage. In comparison to triangular flow passage, rectangular flow passage gives comparatively higher heat transfer at the cost of higher pumping power. In the present investigation, flow passage is modified by rounding the corner of triangular passage to investigate the heat and flow characteristics of air flowing through it. Comparison of performance between modified and rectangular flow passage has also been presented and discussed. The radius of curvature of the rounded corner has been kept constant with value of 0.49 times duct height (H). The dimple was also fabricated at the inner side of the flow passage and arranged in rectangular array. Distance between them was defined by two different dimensionless parameters, relative transverse width (x/h), and relative streamwise length (z/h), whereas, dimensionless height of the protrusion is defined by relative dimple height (h/D). Noticeable increment in both heat transfer and friction factor has been observed by modifying the duct corners and 2.98 times increment in Nusselt number resulted due to dimples in modified duct for h/D, x/h, and y/h value of 0.44, 10, and 10, respectively, in comparison to smooth duct at Reynolds number of 19,500. For similar combination of roughness parameters, highest frictional penalty was estimated with value of 4.46 times that of the smooth duct at Reynolds number of 4400. Additionally, the comparative assessment of heat transfer enhancement (Nuenh), frictional penalty (fpenalty), and thermohydraulic performance index (THPi) has also been carried out to understand the suitability of round cornered duct. In comparison to protruded rectangular duct, 28% higher THPi is obtained in modified duct under similar conditions.