Papers by Keyword: Second Law

Abstract: Laser cutting of ceramics offers considerable advantages over the conventional cutting methods. Some of these advantages include precision of operation, high speed processing and low cost. In addition, cutting process is independent of the mechanical properties of the ceramic material such as hardness and fracture toughness. Alumina is one of the widely used ceramics in industry due to their resistance to harsh environments. Laser cutting of alumina requires high laser power due to high latent heat of melting and elevated melting temperature. In efficient laser cutting process, the low laser power is required. Consequently, for optimum laser cutting conditions of alumina tiles, the thermal efficiency of the cutting process may not be a maximum. The optimum laser cutting parameters provide crack free and parallel edge cuts. Therefore, investigation into laser cutting of alumina ties and the efficiency analysis becomes essential. In the present study, laser cutting of alumina tiles with 3 mm thickness is carried out and thermodynamic analysis associated with the efficiency analysis is introduced. The lump parameter method is incorporated in the thermodynamic analysis. The optimum cutting conditions are then related to the first and second law efficiencies.

Abstract: This paper presents an overview of the concept of second law applications to all processes of thermofluid systems. The presentation is motivated by the need for engineers to be familiar with the new concept of exergy and entropy generation minimization, EGM which are used to design industrial production plants or individual components to maximize their energetic efficiency, and to minimize their environmental impact. It is essential for understanding to what extent resource and energy scarcities, nature’s capacity to assimilate loss as well as the irreversibility of transformation processes, constrain economic action. With these techniques and computational fluid dynamics, CFD, which is used for the conversion of the differential equations of flow to algebraic equations, designers can use the second law to focus on particular regions where design modifications can be made to improve and optimize thermofluid systems performance. Two case studies of exergy/EGM computations are presented for the design of open cycle simple gas turbine and vapour compression refrigeration.