• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.23 no.5
• /
• pp.678-686
• /
• 1999

The purpose of this work is to Investigate the pressure drop and the heat transfer characteristics in the channel of plate heat exchanger with crossed-discrete ribs. The flow is assumed to be three-dimensional, laminar and periodically fully developed. Computations have been carried out for angles of attack from $0^{\circ}$ to $90^{\circ}$ and ratios of rib height from 0.15 to 0.46 for various values of Reynolds and Prandtl numbers. The heat transfer was improved by inclined ribs generating helical vortices and secondary flows. The results show that the pressure drop has a maximum value at $70^{\circ}$ and the heat transfer has a maximum value at $45^{\circ}$. As the rib height increases, the pressure drop and the heat transfer increase quadratically, and the increasing rate of pressure drop is higher than that of the heat transfer. As Reynolds number increases, the pressure drop increases in proportion to the square of Reynolds number and the heat transfer increases linearly.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
• /
• v.29 no.8
• /
• pp.401-407
• /
• 2017

The effect of different rib geometries such as V-shaped continuous (case A), parallel broken (case B), and V-shaped broken (case C) ribs on local heat transfer distributions and pressure drops in a divergent channel with $30^{\circ}$ inclined ribs on one wall or two walls was investigated for Reynolds numbers from 22,000 to 75,000. Top and bottom walls were insulated; two side walls were uniformly heated in the divergent channel. Heated walls were composed of 10 isolated coper sections and length-to-outlet hydraulic diameter ratio of 10. Rib height-to-outlet hydraulic diameter ratio was 0.1, and rib pitch-to-height ratio equaled 10. Results revealed that V-shaped continuous rib (case A) produced approximately 1.4 times higher average Nussselt number than in the parallel broken rib (case B), and V-shaped broken rib (case C) in the channel with two ribbed walls at Re = 54,000.

• Korean Journal of Computational Design and Engineering
• /
• v.11 no.4
• /
• pp.246-255
• /
• 2006

Ribs and fans are interesting geometric entities that are derived from an ordinary $B\'{e}zier$ curve or surface. A rib itself is a $B\'{e}zier$ curve or surface with a lower degree than the given curve or surface. A fan is a vector field whose degree is also lower than its origin. First, we present methods to transform the control points of a $B\'{e}zier$ curve or surface into the control points and vectors of its ribs and fans. Then, we show that a $B\'{e}zier$ curve of degree n is decomposed into a rib of degree (n-1), a fan of degree (n-2), and a scalar function of degree 2. We also show that a $B\'{e}zier$ surface of degree (m, n) is decomposed into a rib of degree (m-1, n-1) and three fans of degrees (m-1, n-2), (m-2, n-1), and (m-2, n-2), respectively. In addition, the lengths of the fans are further controlled by scalar functions of degree 2 and (2, 2). We present relevant notations and definitions, introduce theories, and present some of design examples.

• Structural Engineering and Mechanics
• /
• v.48 no.3
• /
• pp.395-414
• /
• 2013

The present study fundamentally investigated the mechanical performance of the rib-stiffened super-wide bridge deck with twin box girders in concrete, which is a very popular application to efficiently widen the bridges with normal span. The shear lag effects of the specific cross-sections were firstly studied. The spatial stress distribution and local stiffness of the bridge deck with twin box girders were then investigated under several typical wheel load conditions. Meanwhile, a comparative study for the bridge deck with and without stiffening ribs was also carried out during the investigation; thereby, a design optimization for the stiffening ribs was further suggested. Finally, aiming at the preliminary design, an approximate methodology to manually calculate the bending moments of the rib-stiffened bridge deck was analytically proposed for engineers to quickly assess its performance. This rib-stiffened bridge deck with twin box girders can be widely applied for concrete (especially concrete cable-stayed) bridges with normal span, however, requiring a super-wide bridge width due to the traffic flow.

• The Journal of Engineering Geology
• /
• v.18 no.2
• /
• pp.137-144
• /
• 2008

The stand-off errors due to the different separations between the sonde and the borehole wall were measured and analyzed in 4 physical borehole models located in Kangwon National University having different densities with cylindrical and half cylindrical PVC and/or acrylic casings. The analysis of the stand-off error data based on the "spine and ribs" technique suggests a well defined rib line for each model irrespectively of the types and thicknesses of the casing, and that the gradients of the ribs are proportional to the densities of the models. By using these characteristics successful density correction could be made for the plastic casings in NX sized boreholes.

• Journal of Chest Surgery
• /
• v.55 no.2
• /
• pp.183-187
• /
• 2022

Flail chest is a critical medical condition in which multiple segmentally fractured adjacent ribs cause paradoxical movement of the thoracic cage in patients with severe blunt trauma injury. Surgical stabilization is considered essential in patients who require mechanical ventilation. However, there is no consensus on which surgical procedure to choose among the various available techniques or when to perform surgery. We report the case of a patient with traumatic anterior flail chest due to bilateral multiple fractures of the ribs requiring surgical stabilization in whom weaning from mechanical ventilation had failed. The Nuss procedure using double bars with the bridge technique was performed for chest wall stabilization. The patient was weaned from mechanical ventilation on postoperative day 44 and she underwent bar removal on postoperative day 71. After extensive rehabilitation for multiple trauma, she was discharged successfully. The patient currently shows no recurrence of chest wall depression in outpatient follow-up.

• Journal of Korean Society of Steel Construction
• /
• v.16 no.2 s.69
• /
• pp.191-200
• /
• 2004

In this paper, the modified method of orthotropic rigidities for stiffened plates with open ribs is proposed to solve the problem of the inaccurate results of the orthotropic plate analysis according to the dimensions of stiffened plates. In analyzing various types of stiffened plates with open ribs using the isotropic and orthotropic plate element, orthotropic plates are found to gave smaller maximum displacements compared to isotropic plates in a range that is smaller than the special rigidity ratio and reversely. Therefore, obtaining a more accurate solution of the orthotropic plate analysis requires modifying the orthotropic rigidities of stiffened plates according to the rigidity ratio. This study presents two modified methods using the displacement function and the displacement ratio. The application of the two methods improves the accuracy of the results of the orthotropic plate analysis, although the modified method using the displacement ratio is better than the method using the displacement function in terms of serviceability and safety. The comparison with the experimental example shows that the proposed modified method improves accuracy. Therefore, the orthotropic plate analysis of stiffened plates with open ribs can achieve more accurate results using the proposed method in this study.

• Journal of Korean Society of Steel Construction
• /
• v.17 no.1 s.74
• /
• pp.23-32
• /
• 2005

In this paper, the modified coefficient of the orthotropic rigidity for stiffened plates with open ribs is proposed to improve the inaccurate results of the orthotropic plate analysis. For stiffened plates with rectangular and angle ribs having various aspect ratios and boundary conditions, the aspect ratio and the rigidity ratio are selected as parameters and the parametric study on the modified coefficient is performed. Analyzed results of stiffened plates modeling with the isotropic and orthotropic plate element show that the modified coefficient can be expressed as a function of the rigidity ratio for each rib space regardless of the aspect ratio in case of the aspect ratio under 1 and can be represented as a single union function without regard to rib spaces and aspect ratios in the other case. The results also shows that the effects of the boundary condition on the modified coefficient is small and coefficient functions have different values according to rib shapes. The application to examples shows that the modified coefficient of the orthotropic rigidity improves accuracy. Therefore, the orthotropic plate analysis of stiffened plates with open ribs can easily achieve more accurate results using the coefficient function proposed in this study

• Journal of Trauma and Injury
• /
• v.24 no.1
• /
• pp.12-17
• /
• 2011

Purpose: A rib fracture secondary to blunt thoracic trauma continues to be an important injury with significant complications. Unfortunately, there are no definite treatment guidelines for severe multiple rib fractures. The purpose of this study was to evaluate the result of early operative stabilization and to find the risk factors of surgical fixation in patients with bilateral multiple rib fractures or flail segments. Methods: From December 2005 to December 2008, the medical records of all patients who underwent operative stabilization of ribs for severe multiple rib fractures were reviewed. We investigated patients' demographics, preoperative comorbidities, underlying lung disease, chest trauma, other associated injuries, number of surgical rib fixation, combined operations, perioperative ventilator support, and postoperative complications to find the factors affecting the mortality after surgical treatment. Results: The mean age of the 96 patients who underwent surgical stabilization for bilateral multiple rib fractures or flail segments was 56.7 years (range: 22 to 82 years), and the male-to-female ratio was 3.6:1. Among the 96 patients, 16 patients (16.7%) underwent reoperation under general or epidural anesthesia due to remaining fracture with severe displacement. The surgical mortality of severe multiple rib fractures was 8.3% (8/96), 7 of those 8 patients (87.5%) dying from acute respiratory distress syndrome or sepsis. And the other one patient expired from acute myocardial infarction. The risk factors affecting mortality were liver cirrhosis, chronic obstructive pulmonary disease, concomitant severe head or abdominal injuries, perioperative ventilator care, postoperative bleeding or pneumonia, and tracheostomy. However, age, number of fractured ribs, lung parenchymal injury, pulmonary contusion and combined operations were not significantly related to mortality. Conclusion: In the present study, surgical fixation of ribs could be carried out as a first-line therapeutic option for bilateral rib fractures or flail segments without significant complications if the risk factors associated with mortality were carefully considered. Furthermore, with a view of restoring pulmonary function, as well as chest wall configuration, early operative stabilization of the ribs is more helpful than conventional treatment for patients with severe multiple rib fractures.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.19 no.9
• /
• pp.69-76
• /
• 2018

The present study analyzed the effect of film hole position of 45 degree ribbed cooling channel on film cooling performance of gas turbine blades. We also investigated the influence of the ribs under the fixed blowing ratio. Three-dimensional numerical model was constructed and extensive simulation was conducted using the commercial code (Fluent ver. 17.0) under steady-state condition. Base on the simulation results, We investigated the cooling effectiveness, flow velocity, streamline, and pressure coefficient. Moreover, We analyzed the effect of cooling hole position on ejection of the secondary flow caused by the rib structure. From the results, It was found that internal flow of the cooling channel forms a vortex pair in the counterclockwise from the top side, and clockwise from the bottom side. For the channels with ribs, the vortex flow generated by the ribs caused a higher pressure difference near the hole outlet, resulting in at least 12% higher cooling effectiveness than the channel without ribs. Additionally, when the hole is located on the left side of the ribbed channel (Rib-Left), it can be found that the secondary flow generated by the ribs hits against wall surface near the hole to form a flow in the direction of the hole inclination angle. Therefore, It is considered that the region where the cooling gas discharged to the blade surface stays in the main flow boundary layer is wider than the other cases. In this case, The largest pressure coefficient difference was observed near the outlet of the hole, and as a result, the discharge of the cooling gas was accelerated and the cooling efficiency was slightly increased.