Rack Design Research Articles

Laboratory Research on Hydraulic Losses on SHP Inlet Channel Trash Racks

There is currently a growing trend towards renewable energy sources, which are characterised by a guaranteed power supply and low failure rate. Hydropower plants (small or large) are an example of such a source. They supply a total of 16% of the world’s electricity. The advantages of a small hydropower plant include the relatively simple construction process and the lack of need for upstream water storage. SHPs are one of the most cost-effective and environmentally friendly energy technologies, which is why they are steadily increasing in popularity. One of the important components of SHPs are the trash racks in the inlet channels. Their main purpose is to catch debris and other elements carried downstream and to prevent these pollutants from reaching the turbine units. They can also protect migrating ichthyofauna such as larger fish. If trash racks are installed in the inlet channel, hydraulic losses are to be expected due to the reduction in the flow cross-section through the racks (bars) themselves and through the accumulation of debris and various types of trash on these racks. Energy losses on the trash racks affect the financial aspect of SHP investments. This paper presents the results of laboratory tests on trash racks for SHPs by taking into account the different shapes of the bars used, their number and spacing, and the angles of the trash racks to estimate the hydraulic losses on the trash racks. The measured values of hydraulic losses Δh on the trash racks varied according to the type of trash racks, the density of the bars in the cross-section, and the angle of the trash racks from the horizontal, reaching the highest values on the trash racks with angle bars (AB). They were almost eight times greater than those recorded on cylindrical-bar (CB) trash racks, although they involved different angles. It was shown that the discrepancy in the magnitude of losses on trash racks can be large, even for the same type of trash racks. It depends significantly on the design (shape and bar spacing) of the trash racks and the way the trash racks are installed. Depending on the inclination angle, the increase in energy losses reached 70% for angle bars, 60% for flat-bar trash racks, and almost 40% for cylindrical bars. The values of energy loss as well as the loss coefficient β varied non-linearly for the different bar types depending on the angle of inclination of the gratings, and the degree of this non-linearity depended on the type of bars and the blockage ratio of the section. The presented research results can be useful both during the design and the operation of an SHP.

PENGEMBANGAN DESAIN RAK DISPLAY PAKAIAN DISTRIBUTION STORE

The fashion industry is very quick to follow trends that match the lifestyle of this modern era. The concept of distribution began in the mid-1990s in Bandung. At that time Bandung independent bands were trying to sell their merchandise such as CD cassettes, t-shirts, and stickers other than where they performed. The initial form of the distribution was a home-based business with storefronts and shelves to sell clothes. One of the distributions that has developed at this time in the city of Surabaya, namely CasualCultureco, is a distribution that carries the concept of football supporters. The design of the display rack to show fashion products that will be sold in the distribution also has an effect on increasing sales of CasualCultureco distribution products. The research method used to design this display rack uses descriptive qualitative methods by searching for data in the field related to display racks and conducting interviews with the leadership of CasualCultureco, the method used aims to facilitate researchers in making products which are then analyzed using analysis and design requirements. , analysis of display product types, shape analysis, product placement analysis, ergonomics analysis, product dimension analysis, design style analysis, color analysis, systems analysis, information media technology analysis, structural material analysis and finishing material analysis. The final result is a product with an informative and minimalist concept, this display rack can be disassembled, which makes it easier for users and can also be carried anywhere, besides that on this display rack there are digital displays as information media that informs about products and social media CasualCultureco to consumers.

The Relationship between Critical Thinking Skills, Portfolio Models and Academic Achievement of Moroccan Midwifery Students

The present study investigates the relationship between critical thinking skills and portfolio models and academic achievement among midwifery students. Design: A mixed method was followed for this study. A cross-sectional study was used for reporting the results of the California critical thinking skills test (CCTST). In addition, a focus group while following the COREQ guideline to establish the categorization of portfolios. Method: the research sample consisted of 41 students, 48.78 % were registered in the third semester, and 51.21% were in the sixth semester. The CCTST was used to measure critical thinking skills (CTS). A focus group of six teachers was used to develop a classification of portfolio models. The data was analyzed using Chi-Square, and ANOVA. Results: The CCTST and all subscales are highly reliable. Age and educational level were significant variables for the portfolio models, and (CTS). Relationships were also found between the midwifery student’s portfolios models and their CCTST overall scores. Moreover, the students with the highest scores in (CTS) had portfolio Toast Rack design. Conclusion: CCTST showed good validity and reliability for Moroccan midwifery students, and can be used to inform on portfolios design. Validation with large and diverse samples is recommended. It is suggested that instructors consider the dominant portfolio design of each level and use appropriate teaching methods.
 
 Received: 21 June 2022 / Accepted: 16 August 2022 / Published: 2 September 2022

Estimating Energy Efficient Design Parameters for Trash Racks at Low Head Hydropower Stations

Trash racks are usually composed of an array of bars installed in a hydropower scheme to safeguard the turbines by collecting water-borne detritus. However, current design approaches for the design of trash racks focus on structural criteria. A little attention renders the proper evaluation of hydraulic criteria, which causes a significant hydraulic head loss in low head hydropower schemes with an integral intake. This study investigates the head loss through trash racks by employing computational fluid dynamics (CFD) for several design combinations. A three-dimensional model of trash racks using fractional area/volume obstacle representation (FAVOR) method in FLOW-3D is set up to define the effects of the meshing on the geometry and several simulations are carried out considering various approach velocities and different bar spacings, inclination angles, and blockage ratios. The results indicate that head loss increases with an increase in approach velocity, the inclination angle of the rack with channel bed, and blockage ratio. It is noticed that a clear spacing between vertical bars greater than or equal to 0.075 m has a minimum head loss before it becomes significantly high for lower spacing. In addition, the head loss coefficient increases for screen angles greater than 60°, which can be considered as an optimal parameter for design purpose.

FATIGUE ANALYSIS OF A RACK TOOL TO INCREASE MILLING PRODUCTIVITY

In recent years, the automotive industry has had remarkable technological growth. Organizations strive to have in their processes more advanced technologies that allow them to create a competitive advantage over others within the same field. The spline rolling and the threading process have evolved in line with the significant demand for quality products from major automakers in the automotive industry. Product consumers of the automotive industry demand quality at low prices, which results in the need to maximize resources for auto-parts manufacturing. In this work, an improvement in the performance of a spline forming rack from 5,000 to 25,000 pieces is reported. A conceptual design of such rack was developed in which the geometry of the tooth was modified; then, employing a finite element analysis, using ANSYS Version R19.2., the average fatigue life of 25,000 cycles was obtained. Finite element results were validated by on-site experimental tests using the Digital Image Correlation (DIC) technique. Finally, the tooling was manufactured and put into operation, reaching 32,785 rolled parts; with this performance, the initial goal of at least 25,000 parts was surpassed. Subsequently, three forming racks were fabricated, from which an average yield of 30,269 rolled parts was obtained. Keywords: Fatigue, Digital Image Correlation technique (DIC), Finite element analysis, Rolling process.

Research on Meshing Characteristics of Trochoidal Roller Pinion Rack Transmission

As a precision transmission mechanism, the trochoidal roller pinion rack has been paid more and more attention in recent years, but its meshing characteristics have not been deeply explored. In order to investigate the meshing characteristics of the trochoidal roller pinion rack transmission, it is particularly important to research its line of action and meshing stiffness. The equation of the line of action of the trochoidal roller pinion rack is deduced by using its tooth profile formation principle. The motion simulation of the trochoidal roller pinion rack transmission is carried out to verify the correctness of the theoretical derivation of the equation of the line of action, and the influence of the basic parameters on the line of action is summarized. The meshing stiffness of the trochoidal roller pinion rack is calculated based on the energy method used for gear meshing stiffness, and the meshing stiffness is defined considering the time-varying characteristics of its pressure angle, and the influence of each basic parameter on the meshing stiffness is studied. The results shows that the meshing stiffness increases first and then decreases in the double tooth meshing area, while the meshing stiffness gradually decreases in the single tooth meshing area. The basic parameters including number of roller pins, the module, the rack tooth profile offset coefficient, the diameter coefficient of roller pin, and the addendum coefficient of rack have different effects on the line of action and meshing stiffness. The research conclusion can provide reference for the parameter design of the trochoidal roller pinion rack, and provide the meshing stiffness calculation method for the dynamic analysis of the transmission.

Impacts of Location on Designs and Economics of DIY Low-Cost Fixed-Tilt Open Source Wood Solar Photovoltaic Racking

Although small solar photovoltaic (PV) systems avoid most soft costs, they still have a relatively high $/W value due to racking costs. In order to fulfill the promise of small-scale plug-and-play solar, a do-it-yourself PV rack design is provided and analyzed here for six criteria: (1) made from locally-accessible renewable materials, (2) 25-year lifetime to match PV warranties, (3) able to be fabricated by average consumers, (4) able to meet Canadian structural building codes, (5) low cost and (6) that it is shared using an open-source license. The open-source wood-based fixed-tilt ground-mounted bifacial photovoltaic rack design evaluated here was found to be appropriate throughout North America. Economic analysis of the bill of materials showed the racking system ranges from 49% to 77% less expensive compared to commercial proprietary racking in Canada. The racking design, however, is highly dependent on the cost of lumber that varies widely throughout the world. Even for an absolute lower-cost design in Togo due to a lower fixed tilt angle and lower loads from lack of snow, it was not found to be economic because of the relatively high cost of wood. The recent volatile lumber market warrants local evaluation from those considering the use of the open-source design. This design, however, provides for a PV rack that can be manufactured with distributed means throughout most of the world enabling more equitable access to solar energy to support a circular bioeconomy.

Stiffness and resistance of brace-to-upright joints with lipped channel braces assembled flange-to-flange

Industrial cold-formed steel pallet racks are constructed of upright frames bolted to braces in the cross-aisle direction. The flexibility and resistance of these brace-to-upright joints play a key role in the structural behavior of pallet racks in the cross-aisle direction. In this paper, the behavior of these joints has been evaluated through monotonic and cyclic experimental tests to determine the dominant failure modes and the stiffness. The resultant cyclic structural response is pinched, which suggests that upright frame connections are non-dissipative. An analytical model based on the Component Method has been developed to evaluate the ultimate resistance and the flexibility of these bolted connections, with braces oriented flange-to-flange. The model is capable of identifying the influence of each component on the connection structural response. A comparison with results obtained by a Finite Element numerical model, typically used in common practice, in which members are modelled by elastic frame elements and connections are assumed rigid is conducted. The numerical model overestimates the effective stiffness by nearly 14 times. The same model, when modified with a linear link with a force-displacement response determined from the analytical model, provides reliable results in agreement with the experiments. The developed modelling approach is recommended for adoption by practitioners for the design of steel storage pallet racks.

Design and Husbandry Considerations for a Containment Level 2 Aquatic Facility.

The greatly increased use of aquatic species to study disease over the past 20 years necessitates understanding their husbandry and housing requirements to optimize research and welfare and to ensure compliance with regulations. To achieve these goals, aquatic systems have expanded from pet shop and home aquaria to research-grade systems incorporating designs and features to increase their robustness, practicality, and flexibility. Moreover, these last decades have seen the increasing use of aquatic animals for infectious disease research using containment level 2 (CL2)/biosafety level 2 pathogens. In this study, we discuss the facility design requirements and modifications, which must be considered for the planning, construction, and use of an aquatic facility for zebrafish infected with CL2 pathogens. These include decontamination of water and equipment, racking and filtration design, personal protective equipment, and husbandry procedures. This guidance is based on our experience in the design and ongoing management of such facilities.

Development of friction-damped seismic fuses for steel storage racks

This paper describes a study [1] on the behaviour and design of drive-in racks with fuses installed to reduce seismically imposed internal actions. Two different cross-aisle framing systems were tested using various earthquake signals and magnitudes. The first system featured cross-aisle frames fully braced from top to bottom using diagonal braces. In the second system, the cross-aisle frames were braced from the top down to the level of the first pallet runner. In the former system, the rack structure was found to be very stiff and hence, it attracted high base shear action causing severe damage to the uprights, braces and connections. The latter system was found to be significantly more flexible, attracting much lower base shears. However, due to the inherent flexibility of the latter system, second order effects due to excessive sway could cause instability especially when spatial plastic hinges develop in the uprights. Based on the outcomes of the study, a new bracing mechanism has been developed to improve the seismic behaviour of steel storage racks using friction-damped seismic fuses. This paper presents the new bracing system with integrated seismic fuses including tests of the components of the fuses. Full-scale tests of complete 3-bay drive-in racks are also presented featuring tests in the elastic range to determine the natural frequencies of the two systems and destructive tests of fully loaded racks subject to common earthquake time histories of increasing magnitude. The paper also discusses the opportunity the seismic fuses present to substantially enhance the seismic performance of steel storage racks.

Effect of reversing duration time and commutation meshing state on the elastohydrodynamic lubrication of reciprocating spur gear rack

AbstractReciprocating spur gear rack is prone to lubrication failure near the reversing dead center position. Ree‐Eyring lubrication fluid, multigrid method and multigrid integral method were used to calculate the pressure profile, film thickness and oil temperature rise. Compared with linear motion, the process of reciprocating commutative movement is more complicated and the lubrication state are more unstable. The effects of different reversing duration time and commutation meshing state on lubricant film were analysed. The results show that, the oil thickness during the gear reversing process is significantly reduced. While shortening the reversing time can improve the lubricating film thickness, it causes the instantaneous oil temperature to rise. Therefore, the gear tooth damage caused by high temperature can be avoided by prolonging the reversing duration time properly. The longer the reversing duration time, the minimum value of central film thickness and central pressure is closer to the meshing outlet area. No matter what the reversing time change, the minimum lubrication film thickness is in the reversing dead center position. So the reversing dead center is still the dangerous point for the lubrication failure of the spur gear rack mechanism. When the reversing dead center is in the leading tooth of double‐tooth meshing, the gear has the largest film thickness and the largest contact area. In addition, the synthetic radius of curvature and entrainment velocity become larger so the lubrication conditions have been improved. The results provide the theoretical basis and guidance for the reasonable design of the spur gear rack and the improvement of its lubricating performance.

Evaluation of trashrack replacement design for malalo intake of singkarak hydro power plant in west Sumatera

Singkarak hydro power plant (SHPP) with the capacity of 175 MW provide essential supply to Sumatera Interconnection System thus reliable and efficient operation of the hydro power plant component must be maintained. With the damaged experienced by the trash rack during Padang earthquake, the operation of the power plant was disturbed and replacement of trash rack need to be executed. This study evaluate the modification of trash rack replacement in terms of head loss, potential energy and revenue losses. This simple evaluation finds that the replacement design gives lower head loss which translated to lower energy and revenue losses. The potential energy and revenue losses also increase exponentially with the increase of trash rack blockage. This result amplify the importance of trash rack design and cleaning during operation of a hydro power plant.

PROTOTIPE PERANCANGAN ULANG RAK PENDINGIN ROTI DENGAN MENGGUNAKAN METODE VEREIN DEUTCHER INGENIEURE 2222

MSME AAA Bakery is a home industry produces white bread. This MSME produces every day to fulfil customer demand. However, there is waste in the production activities of MSME AAA Bakery, namely in the form of a relatively longer cooling time, cooling time for fresh bread between 120 minutes to 180 minutes, while at MSME AAA Bakery the cooling time for bread is 231 minutes on average. This is due to the initial rack design that hinders the cooling process. The purpose of this study was to minimize the cooling time of the bread with a prototype of a bread cooling rack redesign. The method used is Verein Deutcher Ingenieuer 2222, because it can provide a solution to the problem of long bread cooling time by redesigning the bread cooling rack. So that the relatively long cooling time of bread can be minimized and there is no long waiting time for bread production activities at MSME AAA Bakery. The results of the redesigned prototype of the bread cooling rack showed that there was a differences in the cooling time of the bread. In the experiment with the redesigned shelf prototype, the cooling time of the bread was around 90 minutes.

A comparative study of the process industry pipe racks using Indian and American standards

For any process industries like Power plant, Refineries, Food industries it is vital that the project must be backed by approved designs which must be economical. In any process industry, pipe racks are the most significant element as they transfer the materials between equipment and storage areas. Pipe racks play an important role in the proper functioning of the process industry plants. Their main function is to offer support to power cables, instrument cable trays and pipes in general. Sometimes pipe racks can also be used for offering support to mechanical equipment and vessels apart from valve control access platforms. One of the most important areas of design focuses on pipe racks and how diverse designing concepts can influence the end results that can be generated. As a general practice in pipe racks moment-resisting frames are provided in transverse directions which can cater for both the lateral loads as well as gravity loads. The lateral loads might as well be produced by seismic loads, pipe loads or wind loads. Longitudinal struts with a single braced bay are used for connecting the transverse frames. The purpose of this study is to find out the factors that influence the analysis of pipe racks along with estimating and analyzing the various design factors involved in the design of pipe racks. To achieve the purpose of this study, a pipe rack was modelled using STAAD.Pro and analyzed as per Indian and American standards. This study concluded a suitable design approach by establishing a conservative approach while designing the pipe racks by comparing Indian and American standards. As a result of the study, it is found that the members auto assigned by STAAD.Pro as per American code are comparatively lesser in weight against the members assigned as per Indian code. The findings of this study will serve as a guideline to choose the standards that can be followed for optimal analysis and design of pipe racks.

Industrial storage system continuous perforated uprights: a combined design proposal

Brazilian standards for design of cold-formed steel (ABNT NBR 14762:2010, 2010) and design of pallet racks (ABNT NBR 15524-2:2007, 2007) have different procedures to determine the strength of columns under axial compression, using different buckling curves. This paper aims to evaluate the efficiency of using cold-formed Brazilian standard buckling design curve instead of the formulations of the pallet-rack design standard to study the use viability of the equations in the calculation procedure for computing the uprights compressive strength. This strength was calculated in four ways: one using the original equations of pallet-rack Brazilian standard, and the other three using adaptations of the buckling curve from the cold-formed steel design standard. A theoretical and numerical procedure based on finite element analysis concerning local, global, and distortional buckling and imperfections was performed. Furthermore, experimental results were also consulted to determine the effective area of studied cross-sections considering the effects of local buckling and the presence of continuous perforations. The results show that the proposed modifications are consistently correlated to the results obtained using the original equations of ABNT NBR 15524, indicating the viability of using the buckling curve of ABNT NBR 14762.

Rack and Pinion Steering System Design for a Passenger Car

The steering system plays a crucial role in the stability of the automobile, especially in the safety of the passengers and pedestrians. The aim of this work is to design a rack and pinion steering system that could equip a passenger car. In this process, many parameters are considered for the correct and effective directional response behavior of the vehicle. 2D models were sketched to validate the kinematic algorithm calculus used to optimize and refine the dimensions of the components of the steering system. After a satisfactory Ackermann percentage was achieved, steering system is designed and analysed in one of the most used CAD and CAE software in automotive, CATIA.

Characterization of Existing Steel Racks via Dynamic Identification

Steel storage racks are widely used in logistics for storing materials and goods. Rack design is carried out by adopting the so-called design-assisted-by-testing procedure. In particular, experimental analyses must be carried out by rack producers on the key structural components in order to adopt the design approach proposed for the more traditional carpentry frames. For existing racks, i.e., those in-service for decades, it is required to evaluate the load carrying capacity in accordance with the design provisions currently in use. The main problem in several cases should be the appraisal of the key component performance, owing to the impossibility to obtain specimens from in-service racks without reduction or interruption of the logistic flows. To overcome this problem, a quite innovative procedure for the identification of the structural unknowns of existing racks has been proposed in the paper. The method is based on in-situ modal identification tests combined with extensive numerical analyses. To develop the procedure, cheap measurement systems are required, and they could be immediately applied to existing racks. A real case study is discussed, showing the efficiency of the procedure in the evaluation of the effective elastic stiffness of beam-to-column joints and base plate connections, that are parameters which remarkably affect the rack performance. The structural unknowns have been determined based on four sets of modal tests (two configurations on the longitudinal direction and two in the transversal direction) plus 9079 iterative structural analyses. The results obtained were then directly compared with experimental component tests, showing differences lower than 9%.

Design analysis and Work load characteristics of a Micro data Center

Data centers are large-scale data storage and processing systems. It is made up of a number of servers that must be capable of handling large amount of data. As a result, data centers generate a significant quantity of heat, which must be cooled and kept at an optimal temperature to avoid overheating. To address this problem, thermal analysis of the data center is carried out using numerical methods. The CFD model consists of a micro data center, where conjugate heat transfer effects are studied. A micro data center consists of servers aligned with air gaps alternatively and cooling air is passed between the air gaps to remove heat. In the present work, the design of data center rack is made in such a way that the cold air is in close proximity to servers. The temperature and airflow in the data center are estimated using the model. The air gap is optimally designed for the cooling unit. Temperature distribution of various load configurations is studied. The objective of the study is to find a favorable loading configuration of the micro data center for various loads and effectiveness of distribution of load among the servers.

Structural analysis of the diagnostic rack locking in ITER lower port #8

ITER (International Thermonuclear Experimental Reactor) is a nuclear fusion research and engineering project. It is supposed to be the first fusion device to test the integrated technologies, materials and operational regimes necessary for the commercial production of fusion-based electricity. Front (explored in this paper) and Back diagnostic racks are used as supporting structures of the so-called ITER Divertor Thomson Scattering (DTS) Diagnostic System that is created to measure plasma characteristics. They will be attached to the lower port walls (ITER ports are used to locate diagnostic equipment and its supporting structures) through the so-called Divertor Rails. The developed design of the Front (Diagnostic) Rack locking (e.g. Rack attachment to the rails mechanism) was analyzed in this research to be consistent with thermal stresses, electromagnetic and seismic loads taking into account some specific assembly and maintenance loads including preloading under installation. The analysis of the rack locking design's resistance to the mentioned loads should prove correspondence of the suggested common rack design with the structure integrity criterions. Construction strength under the most severe loading scenario was estimated in this research and appropriate conclusions were made. It was found out that the stress criterion was not fully satisfied, so a new rack locking design concept was proposed. Its main details are also described at the end of this article.

The fluid-structure interaction effect on seismic response of double CAP1400 spent fuel storage racks

The spent fuel storage racks (racks) are immersed in the spent fuel pool to storage the spent fuels temporarily. The safe and reliable operation of racks is crucial to the safety of nuclear power plants. The free-standing rack's design gradually replaces the traditional bottom-fixed design because the free-standing design uses friction and water to decrease the seismic load transfer. The fluid–structure interaction (FSI) effect, which is the key phenomenon for racks under earthquake, can be simplified as an added mass matrix among the racks and the spent fuel pool. The added mass matrix is strongly associated with the rack’s distribution and the rack’s geometry. CAP1400 (a newly designed reactor type designed by China) racks adopt end-tube-connection construction and abandon outer plates, significantly changing the FSI effect. The end-tube-connection construction’s influence on double-rack seismic response hasn’t be studied numerically. Moreover, the large uncertainties in the previous experimental response bring some difficulties in model validation. To solve the above two problems, we built two CFD models to study the influence of the rack’s outer plates on the added mass matrix. Then double-rack seismic models with /without the FSI effect are validated by the experiments of sine waves and seismic waves input. The validated model is then used to study the influence of the friction coefficient and the outer plates on the rack’s seismic response. Results show the previous experimental large uncertainties in racks’ displacement response are mainly caused by the extremely low-frequency components. Moreover, the seismic displacement response of racks without outer plates is much larger compared to racks with outer plates, which means racks’ seismic performance may be improved if an outer plate is added to CAP1400 racks.