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In this paper, the challenge is to increasing of the heat exchanger performance by placing different size balls inside the tubes. the development of previous studies to enhance relatively bad case of heat transfer where the inserting (a large ball and then a small ball) to collide the water molecules in the ball and generate turbulent flow (Reynolds number range from 50,000 to 350,000) and thus increase the thermal performance due to collision of particles with the inner casing of the tube and reduce the stagnation near the wall. The usefulness of small ball, after the big ball, is Reduce of gets wake flow. A simulation was made when changing the diameter ratio of big to small ball (Dr = 3, 4, 5). Also, the distance between the big ball and the small ball was changed (X = 2, 3, 5) mm. It was concluded that the best ball diameter ratio and best Distance is (Dr= D_b/D_sb = 5), (X = 3 mm), respectively. The pressure drop acts as a side effect of enhancement. Therefore, the method of equal pumping was adopted. The average thermal performance factor (TPF=1.178) of tube with insert the balls enhanced by 17.8% at (x=3mm) and (Dr=5) when compared with smooth tube.

For semigroups of linear bounded operators on Hilbert spaces, the problem of being in Cp , 0 Keywords

The aerodynamic force coefficients of five linear cascade of existing film cooling turbine blades are evaluated numerically. The blade is geometrically identical to the first rotor blades of the high pressure (HP) turbine of the F-100-PW-220 military turbofan. Cascade turbine blade test rig has been designed, constructed, and calibrated to introduce experimental work for the same flow conditions of the numerical solution to validate correctness of the numerical results. The numerical simulation shows acceptable agreement with experimental. Also it was found experimentally that both lift and drag coefficients are increased slightly with add of film cooling. The local Mach number distributions outside the boundary layer on both blade sides of the cascade blade are evaluated numerically and compared with the results of well known CFD code (Fine/Turbo) for existing gas turbine rotor stage of identical blade. The computational results obtained for both cases show that the Mach number distributions trend along both blade sides for rotor stage and cascade are approximately the same, and the values of Mach number of rotor stage are higher than that for the corresponded cascade. Also it was found that the Mach number distributions on both blade sides are reduced in values by the addition of air cooling, and the local Mach numbers for the cascade case is reduced in values among the rotor stage for the two cases with and without film cooling on both blade sides.