Department of Mechanical Engineering

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IIT Jodhpur

In present experimental investigation, a modest attempt is made to study the influence of load density and size of food product on drying efficiency of solar dryer. In order to achieve this objective, the laboratory model of mixed-mode solar dryer is fabricated and tested under indoor simulated conditions. Experiments have been performed on dryer with cylindrical potato samples of different thicknesses (5, 8 10 and 18 mm) and loading density (1.08, 2.16, 3.24 and 4.33 kg/m2 of food sample tray area) under forced air circulation. The air mass flow through dryer system is kept constant at 0.011 kg/s (1.3 m/s). Experimental variation of food product moisture content with drying time data have been plotted and analyzed for a wide range of product size and loading density. Results of experimental investigation reveal that the load density and food product size have significant effect on drying efficiency. It is also found that load density has an increasing influence on efficiency whereas the opposite trend is observed for food product size. Sensitivity analysis results indicate that both the variables are equally sensitive to overall efficiency of the dryer. © 2011 IEEE.

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2011 World Congress on Sustainable Technologies, WCST 2011

Performance evaluation of forced convection mixed-mode solar dryer: Experimental investigation

In present study, the simple test procedure is proposed for thermal performance evaluation of solar dryers in general and mixed mode dryer in particular. Steady state heat balance concept has been applied to the absorber surface of collector-dryer assembly for identification of a dimensionless parameter called Dryer Performance Ratio (DPR) representing the effectiveness of a dryer. No-load experiments on mixed mode dryer have been performed for natural and forced air circulation under indoor controlled conditions. The dryer is tested for a wide range of operating conditions of absorbed thermal energy (300-800W/m2) and air mass flow rate (0.009-0.026 kg/s). Comparison of DPR values obtained for natural and forced air circulations indicates a significant performance improvement of 94% at the minimum air flow rate of 0.009 kg/s. It is also found that there is sharp rise in DPR by 31% is observed when airflow is increased from 0.009 to 0.017 kg/s and thereafter a marginal increase of 4% can be noticed for air flow enhancement of ∼ 53%. Another important finding of present study relates to invariable DPR values obtained for a wide range of absorbed energy and ambient air temperature data irrespective of air circulation mode adopted for a dryer. © 2011 IEEE.

Thermal test procedure for mixed mode solar dryer

This paper presents the development of nonlinear coupled electro-thermo-elastic constitutive relations applicable for piezo materials. These nonlinear constitutive relations model the experimentally observed hysteresis and butterfly loops accurately and, can be easily incorporated in structural analysis of smart structures. Using this nonlinear formulation, static analysis of smart composite plates has been carried out to bring out the effect of polarization-electric field nonlinearity on the deformation of composite plates. Results of static analysis are correlated with the experimental data and it is shown that nonlinear formulation provides a better correlation with the experimental results than the linear case. © 2010 Springer Science+Business Media B.V.

IUTAM Bookseries

A study on polarization-electric field nonlinearity in smart composite structures

Resonance

George K Batchelor (1920-2000)

Polarization-electric-field (P-E) interaction results in rendering the stress tensor non-symmetric and in a nonlinear force term in the equilibrium equation. In this paper, an attempt is made to study these (P-E) nonlinear effects on the static response of laminated composite plates with piezo actuators. Further, this paper also focuses on finding the most effective piezo lay-up and ply orientation which gives the maximum deflections. Four different piezo lay-up configurations and three ply orientations are considered. It has been observed from the study that width-wise strips show more transverse bending and twisting. However, full length piezo layers show maximum longitudinal bending. The results of nonlinear analysis show a more considerable softening trend in deformations than that of the linear analysis in the case of longitudinal bending and twisting. In the case of transverse bending this nonlinear effect shows a hardening trend. Further, it has been observed that the influence of P-E nonlinearity depends on the stiffness of the core material, the geometric arrangement of piezo patches, the boundary conditions and the actuation voltage. © 2010 IOP Publishing Ltd.

Smart Materials and Structures

A study of the polarization-electric-field nonlinear effect on the response of smart composite plates

Euler angles are generally used for representing rigid body rotation in three dimensions. In this paper we introduce a concept of Euler-angle-joints (EAJs) which are nothing but three revolute joints so connected by imaginary links with zero length to represent particular Euler angle set. These EAJs can be represented using the well-known Denavit-Hartenberg (DH) parameters. The proposed EAJs are useful in representing a spherical joint present in any multibody system. One can then derive a corresponding decoupled natural orthogonal complement (DeNOC) matrices used in dynamic formulation to obtain the analytical expressions of the generalized inertia matrix elements in scalar form. These expressions are used to develop an 0(n) - n being the number of degree-of- freedom of a serial chain - recursive forward dynamics algorithm. The methodology suggested is illustrated with a numerical example. Copyright © 2009 by ASME.

Proceedings of the ASME International Design Engineering Technical Conferences and Computers and Information in Engineering Conference 2009, DETC2009

Denavit-Hartenberg parameters of Euler-angle-joints for order (N) recursive forward dynamics

Identification and Classification of Coating Defects using Machine Vision

Machining of thin-walled tubular geometries poses interesting problems from a process planning perspective. In machining of such geometries by milling, cutting force-induced tool and workpiece deflections have to be overcome in order to realize part accuracies without compromising productivity. This calls for a systematic study of surface errors on machined parts due to both tool and workpiece deflections. The present paper investigates the effect of cutter and workpiece flexibilities on surface error during peripheral milling of thin-walled tubular geometries. Unlike previous attempts to study milling of thin-walled straight geometries, the present work focuses mainly on machining of tubular geometries. Tubular geometries need to be treated differently from a process planning perspective by exploiting the workpiece rigidity they offer. The process planner has an option of synclastic and anticlastic machining possibilities during machining of tubular geometries which needs to be explored and understood. More importantly, the complex and varying profile of surface error with cutting conditions has to be accounted for. From the outcomes of the present work it can be summarized that surface errors in machining of closed tubular geometries are due to multiple factors which include workpiece rigidity, tool overhang, curvature effects, thinning effects, and nature of tool and workpiece engagements. All of these parameters are affected by process parameters chosen during machining. The present study also demonstrates that the understanding of surface error profiles due to cutter and workpiece deflections not only helps in realizing dimensional accuracy, but geometric tolerances as well.

Proceedings of the Institution of Mechanical Engineers, Part B: Journal of Engineering Manufacture

On milling of thin-walled tubular geometries

The coupled electrothermoelastic constitutive relations, representing the behaviorof piezo materials, are shown to be nonlinear when the polarization-electric field interaction effects are properly accounted for. Under static condition, the polarization-electric field nonlinearities correspond to a distributed body force and body moment. For time varying situations, polarization-electric field interaction exhibits a hysteresis effect. Using the nonlinear constitutive relations, alayer-by-layerfinite element formulation is developed for both static and dynamic analyses of smart plates including hysteresis effects. Linear and nonlinear analyses are carried out to study the effect of nonlinearity due to polarization-electric field interaction on the response of the smart plates. To validate the present formulation, the results of static analysis of a smart plate are compared with experimental data available in literature. It is observed that the P-E hysteresis effects show a friction-type damping in the dynamic response of the smart plate. Copyright © 2010.

AIAA Journal

Nonlinear analysis of smart composite plates including hysteresis effects

With the application of the WRSIS (wetland-reservior-subirrigation system) concept in the Midwest USA and recently in China, an improved design and evaluation approach is needed. An experimental WRSIS site established in Guilin, China, consists of a wetland constructed within an existing paddy scheme. In this paper, we present a simulation analysis approach on the hydraulics of the Guilin constructed basin design, and alternatives to the original design focused on basin shape, flow barriers within the basin, vegetation density and distribution, etc. A SST k-ω model is applied to simulate the flow hydraulics within the constructed basin. Variables influencing hydraulic characteristics have been used to predict flow characteristics within the basin, with particular interest in inlet and outlet conditions, flow barrier presence and placement, and vegetation density and distribution. Flow analysis results are further analyzed using a multi-parameter probabilistic model, which helps us infer individual correlations existing between the variables. Modeling results have led to proposed changes in constructed wetland basin designs, based on alternative placement of flow barriers, vegetative resistance, and other design parameters influencing the overall mass flow rate. This approach has been developed to serve as research, engineering design and evaluation methodologies.