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  • Author: P. Kumar, x
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In this paper, the influence of sample geometry and different solar drying conditions on mass transfer evaluation at food-air interface, hm obtained from different approaches is experimentally investigated. Two different approaches of hm estimation used in the analysis are based on the measurement of moisture loss rate data (direct method) and graphically computed values of drying parameters and moisture diffusion coefficient (indirect method). Drying experiments were performed with potato cylinders and slices of same thickness of 0.01 m with their respective length and diameter of 0.05 m using natural convection mixed-mode solar dryer and open air sun drying conditions. Results of analysis reveal that for each method of estimation, the cylinders vis-à-vis slices produce higher values of hm for both the solar drying conditions. It is also found that the mixed-mode solar drying enhances moisture transfer at food-air interface for each of the sample geometry as expected. Out of the two approaches investigated for hm estimation, the indirect method exhibits lower values of hm and these values are found to be more close to the results reported in the literature. The present analysis also indicates that Chilton-Colburn analogy for heat-mass convection does not hold well in the natural convection air drying of food product.

Abstract

Nonlinear dynamic behavior of fixed-fixed shallow and deep curved beams is studied experimentally using non-contact type of electromagnetic shaker and acceleration measurements. The frequency response obtained from acceleration measurements is found to be in fairly good agreement with the computational response. The travellingwave phenomenon along with participation of higher harmonics and softening nonlinearity are observed. The experimental results on the internal resonance of curved beams due to direct excitation of anti-symmetric mode are reported for the first time. The deep curved beam depicts chaotic response at higher excitation amplitude.

Abstract

The thermal instability of a layer of Rivlin-Ericksen elastico-viscous fluid acted on by a uniform rotation is considered. For stationary convection, a Rivlin-Ericksen elastico-viscous fluid behaves like a Newtonian fluid. It is found that rotation has a stabilizing effect and introduces oscillatory modes in the system. The visco-elasticity also introduces oscillatory modes in the system. A suffi-cient condition for the non-existence of overstability is also obtained.

Abstract

The stability of the plane interface separating two Rivlin-Ericksen elastico-viscous superposed fluids of uniform densities when the whole system is immersed in a uniform horizontal magnetic field has been studied. The stability analysis has been carried out, for mathematical simplicity, for two highly viscous fluids of equal kinematic viscosities and equal kinematic viscoelasticities. It is found that the stability criterion is independent of the effects of viscosity and viscoelasticity and is dependent on the orientation and magnitude of the magnetic field. The magnetic field is found to stabilize a certain wave-number range of the unstable configuration. The behaviour of growth rates with respect to kinematic viscosity and kinematic viscoelasticity parameters are examined numerically.

Abstract

The thermal instability of a layer of Rivlin-Ericksen elastico-viscous fluid acted on by a uniform vertical magnetic field is considered. For stationary convection, a Rivlin-Ericksen elastico-viscous fluid behaves like a Newtonian fluid. The magnetic field has a stabilizing effect. It is found that the presence of a magnetic field introduces oscillatory modes which were non-existent in its absence. The sufficient condition for the non-existence of overstability is also obtained.