Rib Type Research Articles

Application of Analytical Solution for Extended Surfaces on Curved and Squared Ribs

Abstract The presented article discusses how to increase heat transfer through ribbed surfaces and it is oriented to the mathematical representation of temperature fields and the total thermal flow. The complexity of solving for some types of ribs with variable cross-section requires the application of numerical methods, which are applied consequently to the planar rib as well. In this case there was chosen the finite- difference method (FDM). During solution of the cylindrical ribs the FDM method is preferably used directly with regard to the complexity of solving for infinite sums and improper integrals in Bessel functions. In conclusion is assessed the application suitability of the calculation procedure applied to curved ribs. This procedure is usually used to planar ribs. At the same time it is pointed out the possibility of using this method for calculation of the total thermal flow through cylindrical ribs, which have got the squared form.

Heat transfer and friction characteristics of the microfluidic heat sink with variously-shaped ribs for chip cooling.

This paper experimentally and numerically investigated the heat transfer and friction characteristics of microfluidic heat sinks with variously-shaped micro-ribs, i.e., rectangular, triangular and semicircular ribs. The micro-ribs were fabricated on the sidewalls of microfluidic channels by a surface-micromachining micro-electro-mechanical system (MEMS) process and used as turbulators to improve the heat transfer rate of the microfluidic heat sink. The results indicate that the utilizing of micro-ribs provides a better heat transfer rate, but also increases the pressure drop penalty for microchannels. Furthermore, the heat transfer and friction characteristics of the microchannels are strongly affected by the rib shape. In comparison, the triangular ribbed microchannel possesses the highest Nusselt number and friction factor among the three rib types.

Exergy analysis and performance evaluation of flow and heat transfer in different micro heat sinks with complex structure

Simulations are conducted to investigate flow and heat transfer performance of de-ionized water flowing through different micro heat sinks with complex structure under uniform heat flux. Six new micro heat sinks with different types of cavities and ribs are proposed. Moreover, they are compared involving friction factor and Nusselt number relative to other micro heat sinks in the existed literature. Exergy analysis is also applied to investigate the physical mechanism of heat transfer enhancement. Different performance evaluation criteria, based on first and second law of thermodynamics, are proposed to assess the overall performance of micro heat sinks. The results clearly show that the micro heat sink with triangular cavities and triangular ribs (Tri.C–Tri.R for short) presents the best heat transfer performance over a Reynolds number range of 300–600. The performance of heat transfer can be enhanced by decreasing the net temperature gradient of fluid in micro heat sinks. New correlations of friction factor and Nusselt number are proposed based on numerical data, which relate with Reynolds number and relative cavity height and relative ribs height.

English

The wing rib of an aircraft is a very critical part. It provides airfoil contour to the wing. Its principal role in wing structure is that to transfer load from skin to stringers or other parts of wing. However, the objective is to determine stress and displacement of the wing rib with and without cutouts which have thickness 1mm in the application of 0.01 MPa air pressure. The tools used in this design and analysis are CATIA V5 and MSC NASTRANPATRAN. On above conclusion, displacement and von mises stress results for both types of wing ribs are studied

Relationship Study between Bolt Shape and Anchor Performance

Relationship between bolt rib type, rib height, rib spacing and anchor performance have been studied through laboratory drawing test method. Bolt rib type plays a significant impact on the bolt anchor performance. The bigger of the bolt rib height and higher of the drawing force, the better of the anchor performance, but when the rib reach a certain height, drawing force will not increase obvious with the continue increase of rib height. Drawing force will different if the rib spacing is different, and with the increase of rib spacing, drawing force will increase at first and then reduce. When the rib spacing is about 30mm, the drawing force will get the maximum and the best of the anchor performance.

Parameterized Finite Element Modeling and Buckling Analysis of Six Typical Composite Grid Cylindrical Shells

Six typical composite grid cylindrical shells are constructed by superimposing three basic types of ribs. Then buckling behavior and structural efficiency of these shells are analyzed under axial compression, pure bending, torsion and transverse bending by finite element (FE) models. The FE models are created by a parametrical FE modeling approach that defines FE models with original natural twisted geometry and orients cross-sections of beam elements exactly. And the approach is parameterized and coded by Patran Command Language (PCL). The demonstrations of FE modeling indicate the program enables efficient generation of FE models and facilitates parametric studies and design of grid shells. Using the program, the effects of helical angles on the buckling behavior of six typical grid cylindrical shells are determined. The results of these studies indicate that the triangle grid and rotated triangle grid cylindrical shell are more efficient than others under axial compression and pure bending, whereas under torsion and transverse bending, the hexagon grid cylindrical shell is most efficient. Additionally, buckling mode shapes are compared and provide an understanding of composite grid cylindrical shells that is useful in preliminary design of such structures.

Effect of Rotation on Detailed Heat Transfer Distribution for Various Rib Geometries in Developing Channel Flow

The effects of Coriolis force and centrifugal buoyancy have a significant impact on heat transfer behavior inside rotating internal serpentine coolant channels for turbine blades. Due to the complexity of added rotation inside such channels, detailed knowledge of the heat transfer will greatly enhance the blade designer's ability to predict hot spots so coolant may be distributed more effectively. The effects of high rotation numbers are investigated on the heat transfer distributions for different rib types in near entrance and entrance region of the channels. It is important to determine the actual enhancement derived from turbulating channel entrances where heat transfer is already high due to entrance effects and boundary layer growth. A transient liquid crystal technique is used to measure detailed heat transfer coefficients (htc) for a rotating, short length, radially outward coolant channel with rib turbulators. Different rib types such as 90 deg, W, and M-shaped ribs are used to roughen the walls to enhance heat transfer. The channel Reynolds number is held constant at 12,000 while the rotation number is increased up to 0.5. Results show that in the near entrance region, the high performance W and M-shaped ribs are just as effective as the simple 90 deg ribs in enhancing heat transfer. The entrance effect in the developing region causes significantly high baseline heat transfer coefficients thus reducing the effective of the ribs to further enhance heat transfer. Rotation causes increase in heat transfer on the trailing side, while the leading side remains relatively constant limiting the decrement in leading side heat transfer. For all rotational cases, the W and M-shaped ribs show significant effect of rotation with large differences between leading and trailing side heat transfer.

Heat transfer in the microchannels with fan-shaped reentrant cavities and different ribs based on field synergy principle and entropy generation analysis

This study numerically investigates performance analysis of three types of microchannels and the results obtained are compared with the open literature. The results show that the effect of different types of ribs on the overall performance is evident. The thermal enhancement factor η of the microchannels F–R (with rectangular ribs) is always the lowest, depending on the range of Reynolds number. Furthermore, different comprehensive performance criteria, based on the first and second law of thermodynamics, are proposed to assess the relative merit of each microchannel. The microchannel F-Trp (with trapezoidal ribs) is appeared to be the most promising configuration when Re<300, while the microchannel F–C (with circular ribs) has the best performance when Re>300. According to field synergy principle, the heat transfer enhancement can be attributed to the good synergy between velocity vector and temperature gradient. Moreover, thermal boundary is disturbed after adding ribs and temperature different between the channel wall and fluid is small, thus the corresponding of irreversibility (entropy generation) reduces and heat transfer rate improves. The present study aims to provide alternative ways to evaluate the heat transfer performance of microchannels.

Exploration of Rotation Lowering with Building RC Box-Rib Arch Bridge

Arch rib construction of Zhenzhu Bridge on the road from Wuchuan to Pengshui in Guizhou uses construction technology of vertical casting in the first place, and then vertical rotation, and the total weight of which is 610t. This paper introduces technical points and process of vertical rotation construction, and has made beneficial exploration and summary of such kind of construction technology.OverviewBridge rotation construction has advantages including saving costs for hoisting and erecting frames, reducing risks of frames losing stability when casting arch rib concrete, convenient, flexible, safe, reliable and good integrated construction operation, structural line type and internal forces are easy to adjust and control, small range requirement of construction site, and low impact on surrounding environment. Bridge rotation construction would have a broad application prospect in the practice of bridge construction, especially in Chinas southwest area with wide distribution of deep groove and dangerous gully, such construction method is more advantageous. Therefore, practice and research on such construction technology are very practical and significant.Ordinary vertical rotation construction is to have low casting or arch rib assembling, and then lift upward to reach the designed location. Concrete arch rib construction of Zhenzhu Bridge on the road from Wuchuan to Pengshui in Guizhou uses the technology of negative-angle vertical rotation construction, vertical casting arch rib, and then lowering rotation with weight of 610t. Such construction technology is used in China for the first time, while current vertical rotation of the same type of RC arch rib in China has the maximum weight. Based on emphasis on introducing construction technology characteristics of this bridge, this paper also includes innovation and beneficial exploration on the new construction technology of negative-angle vertical rotation.

Local Heat Transfer Dependency on Thermal Boundary Condition in Ribbed Cooling Channel Geometries

The present study is geared toward quantifying the effects of imposed thermal boundary condition in cooling channel applications. In this regard, tests are conducted in a generic passage, with evenly distributed rib type perturbators at 90 deg, with a 30% passage blockage ratio and pitch-to-height ratio of 10. Uniform heat-flux is imposed on the external side of the slab which provides Biot number and solid-to-fluid thermal conductivity ratio around 1 and 600, respectively. Through infrared thermometry measurements over the wetted surface and via an energy balance within the solid, conjugate heat transfer coefficients are calculated over a single rib-pitch. The local heat extraction is demonstrated to be a strong function of the conduction effects, observed more dominantly in the rib vicinity. Moreover, the aero-thermal effects are investigated by comparing the findings with analogous aerodynamic literature, enabling heat transfer distributions to be associated with distinct flow structures. Furthermore, the results are contrasted with the iso-heat-flux wetted boundary condition test case. Neglecting the thermal boundary condition dependence, and thus the true thermal history of the boundary layer, is demonstrated to produce large errors in heat transfer predictions.

Evaluation of moisture management properties on knitted fabrics

In order to determine the effect of raw material, weave type and tightness on liquid absorption and transmission which is an important factor in the perception of people’s clothing comfort, knitted fabrics made of cotton, viscose and polyester yarns, which had single jersey, 1 × 1 rib and single pique weave type, had three different tightness as tight, medium and loose, were produced. Moisture management tester (MMT) was used for multi-dimensional liquid transport of the fabrics produced. As a result of the study, it is observed that polyester fabrics had higher OMMC values than those of cellulosic-based fabrics. Regarding the effect of tightness, liquid transport has decreased with increasing tightness in general. Weave types examined in this study, were not as strong as raw materials and tightness and did not have such a significant effect.

재하 크기에 따른 개단면 리브 보강판의 국부 처짐과 국부 모멘트의 정형화

In this study, stiffened plates with open ribs are analyzed to estimate and formulate the local displacement and local moments according to square loading sizes. For the local behaviors of plates stiffened with rectangular and reverse T ribs, the ratio functions according to the dimensions of stiffened plates are obtained at each square loading size. Analytical results show that values of the basic stiffened plates are different but the ratio functions of each square loading size are similar and the difference of the ratio functions between rectangular ribs and reverse T ribs are small, so the ratio functions can be unified by integrating the loading sizes regardless of the rib type. The application of the unioned ratio functions to L type ribs and rectangular loading shows good accuracies. Therefore, the local behaviors of plates stiffened with open ribs can easily be obtained by using the unioned ratio functions proposed in this study.

평판형 태양열 집열기의 압력강하 및 열전달 성능 향상에 관한 수치해석적 연구

Abstract : The use of artificial roughness in various forms of shapes and sizes is the most common and effec-tive way to improve the performance of a flat-plate solar collector. In the present study, numerical analysis on heat transfer and pressure drop was performed in a rectangular channel with various rib arrays. The uni-form heat flux is applied to the channel from the upper side. The forms of ribs considered in this study were rib 90°, groove 90°, groove 60°, baffle 90°, baffle 60°, wave 90° and wave 60°. Air is the working fluid, and the Reynolds number ranges from 3200 to 17800. Nusselt number and friction factor were investigated to predict the performance of the system with various type of ribs. The average Nusselt number and pressure drop were increased with the increase of velocity in all types of ribs. The highest heat transfer and pressure drop occurred for the baffle 90°, but highest performance factor considering heat transfer and pressure drop together occurred for the groove 60°. Therefore, heat transfer and pressure drop should be considered together when a flat plate solar collector is designed.

피로손상된 용접이음의 피로수명 향상을 위한 햄머피닝 처리법의 적용

본 연구에서는 피로 손상된 용접이음의 피로수명 향상을 위한 방법으로 햄머피닝 처리법의 적용성을 검토하기 위하여 면외거셋 필렛 용접이음과 하중비전달형 리브 필렛 용접이음의 피로실험을 실시하였다. 본 실험에서는 면외거셋과 리브를 필렛 용접한 후 햄머피닝 처리를 하지 않은 용접그대로의 시험편, 용접후 햄머피닝 처리한 시험편, 그리고 용접그대로 시험편의 피로수명의 50% 시점에 햄머피닝 처리를 한 시험편의 피로실험을 실시하였다. 그리고 햄머피닝 처리에 의한 면외거셋과 리브 용접토우부의 형상 및 표면응력의 변화를 측정하였다. 그 결과, 햄머피닝처리에 의해 30~83MPa의 압축잔류응력이 도입 되었으며, 이로 인하여 강구조물의 제작시 용접후에 햄머피닝 처리를 실시하면 피로수명을 크게 향상 시킬 수 있을 뿐만 아니라, 이를 공용기간이 예상 피로수명의 50% 이하인 강구조물의 용접이음에 적용하여도 최소 1.3배 이상의 피로수명과 피로한계 향상효과를 기대할 수 있음을 제시하였다. In this study, fatigue tests were performed on longitudinal out-of-plane gusset fillet welded joints and transverse non-load-carrying cruciform rib fillet welded joints, and then applicability of hammer-peening treatment on improvement of fatigue life for fatigue damaged weld joints were investigated. Fatigue tests were carried out on three types of gusset and rib welded specimens: as-welded specimens, post-weld hammer peened specimens and hammer peened specimens at 50% of as-welded specimen's fatigue life. Before and after hammer peening treatment, the geometry of weld toes and surface stresses near weld toes were measured. As a result of hammer peening treatment, compressive residual stresses of 30-83MPa were introduced near weld toes of the gusset and rib welded joints, and 130% increase in fatigue life and fatigue limit of the welded joints could be realized by hammer peening treatment at 50% fatigue life of as-welded conditions.

Flow and heat transfer investigation behind trapezoidal rib using PIV and LCT measurements

The present work is an experimental investigation inside a rectangular duct for flow behind a trapezoidal type of rib with chamfering angle α (toward the direction of flow) at different Reynolds numbers. Chamfering angle α has been varied in between 0° and 20° with an increment of 5° and subsequently detailed fluid flow and heat transfer experiments have been performed at four different Reynolds numbers, that is, 9,400, 27,120, 44,600, and 61,480 (based on hydraulic diameter of the duct). In order to investigate the detailed fluid flow and heat transfer characteristics together, a distinct experimental setup has been designed while using 2-D particle image velocimetry and liquid crystal thermography, respectively. Flow investigations have been restricted within the streamwise location of x/e ≤ 11, while the region of interest for heat transfer measurement goes up to x/e ≤ 50. The emphasis is toward assessing and analyzing the potential impact of varying chamfering angle over the flow structures, and its subsequent effect on far downstream heat transfer enhancement, as well as its role in obviating the hot spots in the adjacent vicinity behind the chamfered rib turbulators. Transient heat transfer investigation has been performed for evaluating the surface heat transfer enhancement. Results are documented in terms of stream traces, mean and rms velocity fields, streamwise Reynolds stresses and vorticity distribution, and surface and spanwise averaged augmentation Nusselt numbers. The reattachment length has been identified for all of the configurations, and the turbulent characteristics have been discussed in reference to the reattaching shearing layer and its potential impact on the size of the recirculation bubble for different configurations and conditions. The result showed the successful impact of changing the trapezoidal angle α by manipulating the small-scale vortices at the leeward corner of the rib which helps in obviating the hot spots. Furthermore, the presence of large scale unsteady vortical structure within the shear layer has been confirmed, and it has been subsequently associated with heat transfer enhancement in the far downstream region.

Isolated bifid rib: Clinical and radiological findings in children

Bifid rib is usually asymptomatic but sometimes occurs associated with other pathological conditions. The aim of this study was to investigate clinical and radiological characteristics in children with bifid rib. Nine children with the diagnosis of bifid rib between 2005 and 2010 were reviewed. Chest radiography and computed tomography (CT) were performed in all patients, and 3-D images were additionally reconstructed in six patients. Five girls and four boys with a mean age at presentation of 4.2 years had various types of unilateral bifid rib. Seven patients complained of a chest wall mass, whereas two patients whose costal abnormalities were incidentally detected on chest radiography were asymptomatic. Bifid ribs were confirmed on plain radiographs in six patients, while the other three patients were finally diagnosed on reconstruction 3D-CT. One patient with a flared rib on a radiograph showed bifurcation of the costal cartilage on 3D-CT. The other two patients with upper rib abnormalities on radiography had downward extension of the cervical or first rib articulating with the upper branch of the bifid first or second rib, respectively. Reconstruction 3D-CT can demonstrate complicated thoracic abnormalities in patients with atypical appearance of the rib on plain radiographs. An isolated bifid rib may require no further intervention.

Dielectric based resonant guided wave networks

Resonant guided wave networks (RGWNs) are demonstrated to operate based on dielectric waveguides, broadening the scope of this optical design approach beyond plasmonics. The intersection of two dielectric waveguides that is modified by a tuned scattering particle is shown to function as an equal power splitting element, a key enabler of resonant guided wave networks. We describe structures composed of two types of waveguides, Si slabs and SOI ribs, at the telecom frequencies using both, Au and etch, based scatterers.

Thermal visualization on surface with transverse perforated ribs

This paper presents the heat transfer and flow characteristics in a channel with different types of transverse perforated ribs. The effects of perforation/hole inclination angle (θ=0°, 15° and 30°) and a location of hole on the rib (h=0.2H, 0.5H and 0.8H), have been examined. The investigation was performed at constant Reynolds number (Re) of 60,000. The experimental heat transfer results via Thermochromic liquid crystal sheet are reported along with the numerical flow characteristics. The results reveal that due to jet-like flows impinging on the surface, the inclined perforated rib considerably improve the heat transfer immediately downstream from the ribs, compared to straight perforated and solid ones, resulting in superior overall heat transfer performance.

NUMERICAL PREDICTIONS OF PRESSURE DROP AND HEAT TRANSFER IN A BLADE INTERNAL COOLING PASSAGE WITH CONTINUOUS/TRUNCATED RIBS

Ribs are often used in the mid-section of internal turbine blades to augment heat transfer from the blade wall to a coolant, but most research works are concerned only with continuous ribs attached to the side walls. In this paper, a turbulent flow and heat transfer of a rectangular passage with continuous and truncated ribs on opposite walls have been predicted numerically. Two types of ribs are studied: 90-deg ribs and 45-deg V-shaped ribs. The inlet Reynolds numbers range from 12,000 to 60,000. The complex three-dimensional turbulent flows inside the blade internal coolant passage and heat transfer between the rib-walls and side-walls are presented. The overall performances of six different ribbed passages are evaluated and compared. Numerical results show that the passage with truncated V-shaped ribs is very effective in improving the heat transfer performance with a low pressure drop. (Less)

Performance of solar air heater ducts with different types of ribs on the absorber plate

Repeated ribs are considered an effective technique to enhance forced convection heat transfer in channels. In order to establish the performance of rib-roughened channels, both heat transfer and friction characteristics have to be accounted for. In the present paper, heat transfer coefficients and friction factors have been experimentally investigated for a rectangular channel having one wall roughened by repeated ribs and heated at uniform flux, while the remaining three walls were smooth and insulated. Angled continuous ribs, transverse continuous and broken ribs, and discrete V-shaped ribs were considered as rib configurations. Different performance evaluation criteria, based on energy balance or entropy generation analysis, were proposed to assess the relative merit of each rib configuration. All the rib-roughened channels performed better than the reference smooth channel in the medium-low range of the investigated Reynolds number values, which is that typically encountered in solar air heater applications.