J. Batina, M. Batchi, S. Blancher, R. Creff and C. Amrouche
The purpose of this paper is to analyse the convective heat transfer of an unsteady pulsed, laminar, incompressible flow in axisymmetric tubes with periodic sections. The flow is…
Abstract
Purpose
The purpose of this paper is to analyse the convective heat transfer of an unsteady pulsed, laminar, incompressible flow in axisymmetric tubes with periodic sections. The flow is supposed to be developing dynamically and thermally from the duct inlet. The wall is heated at constant and uniform temperature.
Design/methodology/approach
The problem is written with classical homogeneous boundary conditions. We use a shift operator to impose non‐homogeneous boundary conditions. Consequently, this method introduces source terms in the Galerkin formulation. The momentum equations and the energy equation which govern this problem are numerically solved in space by a spectral Galerkin method especially oriented to this situation. A Crank‐Nicolson scheme permits the resolution in time.
Findings
From the temperature field, the heat transfer phenomenon is presented, discussed and compared to those obtained in straight cylindrical pipes. This study showed the existence of zones of dead fluid that locally have a negative influence on heat transfer. Substantial modifications of the thermal convective heat transfer are highlighted at the entry and the minimum duct sections.
Practical implications
Pulsated flows in axisymmetric geometries can be applied to medical industries, mechanical engineering and technological processes.
Originality/value
One of the original features of this study is the choice of Chebyshev polynomials basis in both axial and radial directions for spectral methods, combined with the use of a shift operator to satisfy non‐homogeneous boundary conditions.
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Jean Batina, Serge Blancher and Tarik Kouskou
Mathematical and numerical models are developed to study the melting of a Phase Change Material (PCM) inside a 2D cavity. The bottom of the cell is heated at constant and uniform…
Abstract
Purpose
Mathematical and numerical models are developed to study the melting of a Phase Change Material (PCM) inside a 2D cavity. The bottom of the cell is heated at constant and uniform temperature or heat flux, assuming that the rest of the cavity is completely adiabatic. The paper used suitable numerical methods to follow the interface temporal evolution with a good accuracy. The purpose of this paper is to show how the evolution of the latent energy absorbed to melt the PCM depends on the temperature imposed on the lower wall of the cavity.
Design/methodology/approach
The problem is written with non-homogeneous boundary conditions. Momentum and energy equations are numerically solved in space by a spectral collocation method especially oriented to this situation. A Crank-Nicolson scheme permits the resolution in time.
Findings
The results clearly show the evolution of multicellular regime during the process of fusion and the kinetics of phase change depends on the boundary condition imposed on the bottom cell wall. Thus the charge and discharge processes in energy storage cells can be controlled by varying the temperature in the cell PCM. Substantial modifications of the thermal convective heat and mass transfer are highlighted during the transient regime. This model is particularly suitable to follow with a good accuracy the evolution of the solid/liquid interface in the process of storage/release energy.
Research limitations/implications
The time-dependent physical properties that induce non-linear coupled unsteady terms in Navier-Stokes and energy equations are not taken into account in the present model. The present model is actually extended to these coupled situations. This problem requires smoother geometries. One can try to palliate this disadvantage by constructing smoother approximations of non-smooth geometries. The augmentation of polynomials developments orders increases strongly the computing time. When the external heat flux or temperature imposed at the PCM is much greater than the temperature of the PCM fusion, one must choose carefully some data to assume the algorithms convergence.
Practical implications
Among the areas where this work can be used, are: buildings where the PCM are used in insulation and passive cooling; thermal energy storage, the PCM stores energy by changing phase, solid to liquid (fusion); cooling and transport of foodstuffs or pharmaceutical or medical sensitive products, the PCM is used in the food industry, pharmaceutical and medical, to minimize temperature variations of food, drug or sensitive materials; and the textile industry, PCM materials in the textile industry are used in microcapsules placed inside textile fibres. The PCM intervene to regulate heat transfer between the body and the outside.
Originality/value
The paper's originality is reflected in the precision of its results, due to the use of a high-accuracy numerical approximation based on collocation spectral methods, and the choice of Chebyshev polynomials basis in both axial and radial directions.
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The Institute for Scientific and Technical Information (INIST) is a service unit of the French National Centre for Scientific Research (CNRS). A leading integrated scientific and…
Abstract
The Institute for Scientific and Technical Information (INIST) is a service unit of the French National Centre for Scientific Research (CNRS). A leading integrated scientific and technical information center, INIST provides the major public research and academic institutions as well as the socio‐economic sector with resources and services designed to improve dissemination of and access to international scientific and technical information. Committed to the new information and communication technologies, INIST offers a whole range of access services to scientific and technical information on the Internet. The article highlights the place and the future of document supply in this context.
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Benjamin B. Dunford, Deidra J. Schleicher and Liang Zhu
This study used dominance analysis to examine the relative importance of psychological versus pecuniary approaches to the development of employee ownership attitudes and…
Abstract
This study used dominance analysis to examine the relative importance of psychological versus pecuniary approaches to the development of employee ownership attitudes and behaviors. In a sample of 409 non-unionized employees from a commercial real estate firm, we found that perceptions of information and control (i.e., psychological ownership) had a much stronger impact on ownership-related outcomes than did voluntary investment in company stock (i.e., pecuniary ownership), as hypothesized. These findings are consistent with the predictions of the employee ownership literature, suggesting that ownership culture initiatives should be directed at increasing employees’ perceptions of information and control.
Reviews emerging trends and new challenges in interlending, document delivery and resource sharing, as written up in the recent literature. Focuses on the balance of providing…
Abstract
Reviews emerging trends and new challenges in interlending, document delivery and resource sharing, as written up in the recent literature. Focuses on the balance of providing access to journal articles via commercial document supply, traditional interlibrary resource sharing and access to publisher full‐text databases. Reference linking, aggregator services and the challenges of providing effective access to material in less developed countries are also considered
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Reviews recently published literature in the field of resource sharing and e‐journal access. Considers recent articles on the value of consortial membership and licensed access to…
Abstract
Reviews recently published literature in the field of resource sharing and e‐journal access. Considers recent articles on the value of consortial membership and licensed access to electronic journals. Also looks at published articles in the area of aggregators, reference linking, performance measurement, document delivery in public libraries, and new trends and developments in a number of countries world‐wide.
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Abstract
Purpose
This paper aims to design and optimize the threaded fastener of leakage current particulate matter (PM) sensor. The corresponding air-tight test is conducted to ensure the reliability of the installation strategy with screw connection.
Design/methodology/approach
Research on the pressure-deformation curve of seal gasket was conducted and the vibration load of engine was considered for the calculation of the minimum installation pre-tightening force. Simultaneously, the danger threaded section area was calculated, and the carrying capacity was verified. The height of the welding line was studied to ensure the reliability of the application. FEA was carried out to acquire the relationship between local structure size and local stress for continuous improvement of thread connection. The installation torque range was acquired from the torque control principle for the pre-tightening force. The sealing reliability of the connector was proved with leakage.
Findings
The air tightness of the thread connector is proved to be fine. When the pre-tightening force is over 8,000 N, and its length reaches 2 mm, the connector has good reliability at ambient temperature. The tightening torque of 60-74 Nm can guarantee the reliable fixing ability of thread connector, and its plastic non-deformation ability in the process of repeated tearing down.
Originality/value
This paper provides an installation strategy and an optimization of PM sensor, which has a positive effect on the study and the manufacture of PM sensor. It is helpful to further develop PM sensor and after-treatment technology. This kind of real-time monitoring PM sensor needs to be studied further to achieve its commercial application.