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Natural convection heat transfer from an isothermal horizontal fin attached to a cylinder, confined between two adiabatic walls of constant height is investigated by the Mach-Zehnder interferometry technique. This study is focused on the effect of a perforated fin attached to the bottom of a cylinder while the vertical position of the cylinder (Y) changes between two walls with a constant distance of W measuring 1.5 times the cylinder diameter. The cylinder's average Nusselt numbers are determined for three ratios of vertical position to its diameter, Y/D = 0.5, 1.5, 2, and 3. The Rayleigh number ranges from 4.5 × 10 3 to 1.2 × 10 4 . The distance between the walls is chosen to be 1.5 D, that is, an optimum distance at which the Nusselt number is maximum. The effect of the perforated fin on free convection heat transfer is investigated and compared with other works. Results show outstanding enhancement in heat transfer, with a minimum result of 40% and maximum of 90%.

Steady state and two-dimensional natural convection heat transfer flow around a horizontal and isothermal cylinder with a longitudinal fin attached to it that is located between two tilt and very low conductive plates is studied experimentally by using a Mach-Zehnder interferometer. Effects of the plates slope angel (θ) on heat transfer from the tube is investigated for Rayleigh number ranging from 1000 to 15500. Experiments are done for a fin attached cylinder placed between two low conductive plates. Two different diameter tubes with diameters of D=10 and 20mm are utilized for broad Rayleigh number range. Results specify that, heat transfer experience differs for special Rayleigh numbers. For Rayleigh numbers ranging less than 5500, rate of heat transfer amount from the cylinder surface is less than that of a lone cylinder and it’s the result of no slip boundary condition on the fin surface. For this range of Rayleigh number by the use of plates, heat transfer from the cylinder surface decreases slightly and plates leaning does not alter heat transfer speed from the cylinder surface. For Rayleigh number ranging from 5500 to 15500, heat transfer rate from the cylinder surface is lower than the heat transfer rate from the surface of an individual cylinder. Though, by adding placing the low conductive plates as plates to experimental model, heat transfer system differs and chimney effect between fin and the plates increases the heat transfer from the cylinder surface. By increasing the plates slope angel from 0° to 20°, the chimney effect between plates and fin weakens and heat transfer rate from the tube surface is going to the amount of heat transfer rate from a fin attached cylinder which is not placed between plates.

Simulation and prediction of gas turbine performance is a very important issue in design process or in actual behavior analysis. In these models physical behavior of components such as compressors, combustion chambers and turbines are simulated related to each other. The compressor is the most important part of simulation. This paper presents a model for simulating a compressor using stage stacking procedure with the aid of a genetic algorithm. The most important feature of the proposed method is that qualitative and quantitative rules based on turbo-machinery knowledge of compressors are used as constraints to the genetic algorithm to find the corrected situations of design. This knowledge is evaluated with both industrial and aero gas turbine engines (501F & CF6 (LM2500)). The model is based on an analytical solution and provides an insight into the effects of choices made during the compressor design process on performance and off-design stage matching. The results of the model highlight the capability of the method which accurately reproduces the available data. In addition to obtaining design conditions, this model can find and calculate stages that are highly loaded and this information is vital to control the compressor.