Ahmet Sinan Oktem

Performance analysis of two stage combined heat pump system based on thermoeconomic optimization criterion

A thermoeconomic performance analysis based on a new kind of optimization criterion has been performed for a two stage endoreversible combined heat pump cycle model. The optimal performances and design parameters that maximize the objective function (heating load per unit total cost) are investigated. The optimal temperatures of the working fluids, the optimum performance coefficient, the optimum specific heating load and the optimal distribution of the heat exchanger areas are determined in terms of technical and economical parameters. The effects of the economical parameter on the global and optimal performances have been discussed.

Optimal performance analysis of irreversible regenerative MHD power cycles

A performance analysis of an irreversible regenerative magnetohydrodynamic (MHD) power cycle operating at maximum power for a constant-velocity and a constant-Mach-number type of MHD generator has been carried out. The obtained results are evaluated together with the results of performance analysis at maximum thermal efficiency, and thus the upper and lower bounds of the optimal operating region in terms of power and thermal efficiency are determined. The considered MHD power cycle model includes irreversibilities coming from the electrical losses at the MHD generator, frictions at the compressor and pressure losses in the heater, the cooler and the regenerator. The effects of these major irreversibilities and regeneration application on the general and optimal performance are investigated. The analysis presented in this study may provide a theoretical basis for the optimal design and operating conditions for regenerative MHD power cycles.

Analysis of the static response of cross-ply simply supported plates and shells based on a higher-order theory

The boundary-discontinuous double Fourier series-based solution methodology is used to solve the problem of higher-order shear deformation of cross-ply plates and doubly curved panels, which are characterized by a system of five highly coupled linear partial differential equations with mixed-type simply supported boundary conditions prescribed at all four their edges. The present solution is related to a number of unsolved boundary-value problems and can serve as a tool in particular for early design stages and for benchmark comparisons and verifications of numerical results. The analytical results obtained are compared with finite-element calculations, and a good agreement is found to exist between them.

Higher order theory based Fourier analysis of cross-ply plates and doubly curved panels

An analytical solution to the static analysis of a general cross-ply finite-dimensional doubly curved panel of rectangular plan-form, modeled using a higher order shear deformation theory, is presented. A solution methodology, based on boundary-discontinuous generalized double Fourier series approach is used to solve a system of five highly coupled linear partial differential equations, generated by the higher order-based laminated shell analysis, with the fully clamped type 4 (C4) boundary condition prescribed on two opposite edges, while the remaining two edges are subjected to the simply supported type 4 (SS4) constraint. The numerical accuracy of the solution is ascertained by studying the convergence characteristics of the deflection and moment of a cross-ply spherical panel, and also by comparison with the available results in literature. Additional comparisons were made with the finite element counterparts using commercially available software for distributed load. Hitherto unavailable important numerical results presented include sensitivity of the predicted response quantities of interest to shell geometry (cylindrical and spherical), lamination, lamina material property, thickness and membrane effects as well as their interactions.

Levy-Type Boundary Fourier Analysis of Thick Cross-Ply Panels with Negative Gaussian Curvature

A boundary-discontinuous generalized double Fourier-series-based solution to the problem of deformation of a finite-dimensional general cross-ply thick, doubly curved panel with negative Gaussian curvature and of rectangular planform, modeled using a higher-order shear deformation theory, is presented. This spectral method is used to solve a system of five highly coupled, linear partial differential equations, generated by the higher-order shear deformation theory-based laminated shell analysis, with the simply supported of type 2 boundary condition prescribed on two opposite edges, whereas the remaining two edges are subjected to the simply supported of type 3 constraint. The hitherto unavailable important numerical results presented include sensitivity of the predicted response quantities of interest to shell geometry (negative or positive Gaussian curvature), lamination and thickness effects, as well as their interactions.