Model Validation for the Heat Transfer in Gasket Plate Heat Exchangers Working with Vegetable Oils

Many models for accurately predicting the performance of gasket plate heat exchangers were developed in the last decades, grouped in three categories: empirical, semi-analytical or theoretical/numerical, with the view to saving materials and energy through correct design of industrial equipment. This work addresses one such model, namely Lévêque correlation modified by Martin and by Dović, which is promising due to the correct assumption of the flow in sine duct channels and the consideration of energy losses caused by flow reversal at plate edges and the flow path changing when entering the chevron angle. This model was validated by our own experimental data under industrial conditions for vegetable oils processing, both in laminar flow (Re = 8–42) and fully developed turbulent flow (Re = 446–1137). Moreover, in this study, particular values for constants/parameters of the model were determined for the corrugation inclination angle relative to vertical direction equal to 30°. Through statistical analysis, this study demonstrates that this particularized form of the generalized Lévêque correlation can be used with confidence.

Observation of a giant nonlinear wave-packet on the surface of the ocean

In many physical systems such as ocean waves, nonlinear optics, plasma physics etc., extreme events and rare fluctuations of a wave field have been widely observed and discussed. In the field of oceanography and naval architecture, their understanding is fundamental for a correct design of platforms and ships, and for performing safe operations at sea. Here, we report a measurement of an impressive and unique wave packet recorded in the Bay of Biscay in the North-East of the Atlantic Ocean. An analysis of the spatial extension of the packet that includes three large waves reveals that it extents for more than 1 km, with individual crests moving faster than 100 km/h. The central and largest wave in the packet was 27.8 m high in a sea with significant wave height of 11 m. A detailed analysis of the data using the nonlinear Fourier analysis reveals that the wave packet is characterized by a non trivial nonlinear content. This observation opens a new paradigm which requires new understanding of the dynamics of ocean waves and, more in general, of nonlinear and dispersive waves.

Evaluation of loading methods for determination of material and elastic constants of cement fiber board

Cement fiber boards (CFB) are special group that are used in a wide range of structural civil engineering. For the correct design of a cement fibre board structure, it is important to define their material and elastic constants, which are usually determined by destructive tests. The paper deals with a definition of a suitable method of loading for the determination of basic materials and elastic constants of cement fiber boards reinforced with organic fibers loaded in the mid-plane. The publication compares and evaluates load tests by three-point and four-point bend.

OPTIMUM WORKHOLDING CONDITIONS FOR PRECISION CYLINDRICAL GRINDING OPERATIONS

Grinding process is a very important process in machining industry being one of the most popular processes when high quality parts must be manufacture. Likewise, workholding is a critical issue on cylindrical grinding. The use of the driving dog is common when the workpiece is held between centers. However, one of the handicaps of this workholding is that the cylindrical workpiece cannot be ground along the complete length. In order to tackle this issue, in the present work the workpiece is held between centers avoiding the use of the driving dog. To this end, a methodology to obtain the grinding limit parameters that ensure that the transmitted torque is higher that the resistance torque is presented, being the aim of these tests is to avoid the sliding between the point and the workpiece. Finally, non-destructive tests are designed, which, using a safety coefficient of about 0.77, the tests allow the correct design of each specific grinding process. Keywords: cylindrical grinding, workholding, driving dog, sliding

Green Areas in the City as an Element of Noise Protection

From the dawn of history, humanity created communication routes in order to move efficiently. Trees were planted along the roads connecting towns and villages so that travellers could rest in their shade. The line of trees also played an informative, strategic and sometimes aesthetic role. Currently, a line of tall vegetation along the street provides shade and relief in cities during hot weather. It is also worth emphasizing that greenery reduces stress factors in large cities. One of the stressors in cities is noise. In an urbanized environment, noise is perceived as unpleasant and bothersome. Appropriate planting of greenery in the city can reduce this phenomenon. The article not only analyses the possibilities of reducing noise through appropriate planting of greenery, but also provides guidelines for the correct design of greenery along streets and at crossroads. It is worth emphasizing here that the correct design of greenery in the vicinity of communication arteries is not only a matter of ethics or landscape legibility, but also a matter of safe use of infrastructure. The article also deals with the issue of legal acts relating to the design of urban greenery. The former and current legal acts contain provisions related to the classification of green areas, their protection and shaping. These regulations apply to various fields (construction, spatial planning, environmental protection) and therefore there are discrepancies in the legal interpretation of this term. All these doubts will be clarified.

A Methodology to Analyze and Evaluate the Uncertainty Propagation Due to Temperature and Frequency and Design Optimization for EMC Testing Instrumentation

This paper presents a study and proposes a new methodology to analyze, evaluate and reduce the overall uncertainty of instrumentations for EMC measurements. For the scope of this work, the front end of a commercial EMI receiver is chosen and variations due to tolerances, temperature and frequency response of the system are evaluated. This paper illustrates in detail how to treat each block composing the model by analyzing each discrete component, and how to evaluate their influence on the measurand. Since a model can have hundreds or even thousands of parameters, the probability distribution functions (PDFs) of some variable might be unknown. So, a method that allows to obtain in a fast and easy way the uncertainty of the measurement despite having so many variables, to then being able to evaluate the influence of each component on the measurand, is necessary for a correct design. In this way, it will be possible to indicate which discrete components have the most influence on the measurand and thus set the maximum tolerances allowed and being able to design a cost-effective solution. Furthermore, this works presents a methodology which can easily be extended and applied to estimate and compute the uncertainty for electromagnetic interferences, energy storage systems (ESS), energy production, electric machines, electric transports and power plants in general.

Operads for complex system design specification, analysis and synthesis

As the complexity and heterogeneity of a system grows, the challenge of specifying, documenting and synthesizing correct, machine-readable designs increases dramatically. Separation of the system into manageable parts is needed to support analysis at various levels of granularity so that the system is maintainable and adaptable over its life cycle. In this paper, we argue that operads provide an effective knowledge representation to address these challenges. Formal documentation of a syntactically correct design is built up during design synthesis, guided by semantic reasoning about design effectiveness. Throughout, the ability to decompose the system into parts and reconstitute the whole is maintained. We describe recent progress in effective modelling under this paradigm and directions for future work to systematically address scalability challenges for complex system design.

BRT omnibus : how bus rapid transit enhances mobility

Bus Rapid Transit (BRT) has emerged in the 21st century as a leading form of building rapid transit in urban environs due to their ability as a rapidly implementable, relatively low-cost, flexible, and high-quality transit mode. While the popularity of the BRT mode continues to grow worldwide, there remains a degree of uncertainty over what designing for success looks like for BRT systems. This paper sought to determine whether there was a "correct" design approach for BRT implementation through literature review and case study. The case study revealed that despite differences in design and implementation, the cases successfully attained their respective planning and performance objectives. The inherent flexibility of the BRT mode allowed for BRT systems to be scaled to a wide array of operating and ridership contexts, as well as allow for incremental enhancements to the system as the passenger demands, available financing, and political will for upgrades arise. Key Words: bus rapid transit; BRT; BRT Lite; service package; system design.

BRT omnibus : how bus rapid transit enhances mobility

Bus Rapid Transit (BRT) has emerged in the 21st century as a leading form of building rapid transit in urban environs due to their ability as a rapidly implementable, relatively low-cost, flexible, and high-quality transit mode. While the popularity of the BRT mode continues to grow worldwide, there remains a degree of uncertainty over what designing for success looks like for BRT systems. This paper sought to determine whether there was a "correct" design approach for BRT implementation through literature review and case study. The case study revealed that despite differences in design and implementation, the cases successfully attained their respective planning and performance objectives. The inherent flexibility of the BRT mode allowed for BRT systems to be scaled to a wide array of operating and ridership contexts, as well as allow for incremental enhancements to the system as the passenger demands, available financing, and political will for upgrades arise. Key Words: bus rapid transit; BRT; BRT Lite; service package; system design.

A Random Forest Model for the Prediction of FOG Content in Inlet Wastewater from Urban WWTPs

The content of fats, oils, and greases (FOG) in wastewater, as a result of food preparation, both in homes and in different commercial and industrial activities, is a growing problem. In addition to the blockages generated in the sanitary networks, it also represents a difficulty for the performance of wastewater treatment plants (WWTP), increasing energy and maintenance costs and worsening the performance of downstream treatment processes. The pretreatment stage of these facilities is responsible for removing most of the FOG to avoid these problems. However, so far, optimization has been limited to the correct design and initial installation dimensioning. Proper management of this initial stage is left to the experience of the operators to adjust the process when changes occur in the characteristics of the wastewater inlet. The main difficulty is the large number of factors influencing these changes. In this work, a prediction model of the FOG content in the inlet water is presented. The model is capable of correctly predicting 98.45% of the cases in training and 72.73% in testing, with a relative error of 10%. It was developed using random forest (RF) and the good results obtained (R2 = 0.9348 and RMSE = 0.089 in test) will make it possible to improve operations in this initial stage. The good features of this machine learning algorithm had not been used, so far, in the modeling of pretreatment parameters. This novel approach will result in a global improvement in the performance of this type of facility allowing early adoption of adjustments to the pretreatment process to remove the maximum amount of FOG.