Some results on particle image velocimetry (PIV) in 2 D freely bubbling fluidized beds are presented. The PIV applications were used in order to determine the initial particle velocity of bubble eruptions. A two dimensional non reacting fluidized bed was constructed to measure the origin of the ejected particles and the initial particle velocity distribution, using coarse sand particles. The bubble ejection mechanism was observed taking into account the origin of particles ejected, the initial particle velocity distributions as well as the effect of other neighbor exploding bubbles. Our results show that the assumption of linear dependence of initial velocity with the angle predicts the velocity faithfully only for purely vertical ascent bubbles. Measurements of ejection velocities show that initial velocities in the combined layer are higher than those of the particles in the nose of the leading bubble. Avoiding coalescence of bubbles at the bed surface can lead to less particle entrainment out of the bed and consequently to shorter fluidized beds.

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a b s t r a c tThe problem of non isothermal absorption of vapour into freely expanding liquid sheets is addressed in this study. This is done in the context of four models that characterise the coupled heat and mass transfer in the liquid phase: a nonlinear model retaining the effect of sheet growth, an approximate model for slowly increasing mass flow rate in the sheet, a large Lewis number model and finally, a boundary layer model. These models have been numerically or analytically solved and applied to the comparative anal ysis of two different working pairs, LiBr H 2 O and LiNO 3 NH 3 , under conditions representative of adia batic absorption in refrigeration systems. The limits of applicability of each model have been assessed and the sensitivity of the results to the sheet aperture angle, heat of absorption and initial subcooling has also been tested. For equal initial mass fraction and subcooling, the models indicate that Sherwood number and the rate of absorption in laminar expanding sheets for the LiNO 3 NH 3 solution are always superior to those for the LiBr H 2 O solution.

In the braking system, the heat dissipation generated by the friction between the disc and pad should be evacuated as quickly as possible. In this work, five common different automotive disc brakes were studied through mathematical theories of heat transfer and numerical methods using the ANSYS software. In addition, a direct comparison between experimental, theoretical, and simulation values found in the open literature was performed to propose a disc brake with an improved geometry in terms of dissipation of heat transfer. The numerical results were considered to propose two possible solutions of disc brake geometries using N-38 ventilation blades used in aeronautic engineering. An improvement in temperature dissipation was achieved by approximately 23.8% compared to the five geometries analyzed with a simple type N-38 ventilation blade. The heat dissipation in the brakes strongly depends on the geometry of the disc, the geometry of the blades, the material from which it is manufactured, the material of the pad, the weight of the vehicle, and the operating conditions, as can be verified with mathematical calculations and experiments. The results obtained demonstrate that the discs can be used effectively in extreme working conditions (80 km/h and 33°C), without affecting the safety of the occupants and the braking system.

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This investigation analyzes the propagation of the uncertainty of the number of life cycles to fatigue failure, taking into account the strain life method, considering as random variables some parameters of the material and loading in a steel plate under fatigue, with constant and variable loading through multidimensional Hermite polynomials. The application of series of multidimensional Hermite polynomials allowed the prediction of the randomness of the output vector. This research has shown that a multidimensional Hermite polynomial adequately estimates the propagation of the uncertainty of the input random variables. The results showed that variations in material and loading parameters can generate important failure probabilities and allowed quantifying the variability in the number of life cycles for fatigue failure steel parts