Band 12, Heft 2 -

An overnight dry hard alkyd resin has been designed from non-drying gmelina seed oil (GSO). The study was enhanced through pseudo combined array (PCA) and a dynamic data processor (DDP). The GSO modified alkyd resin was synthesized through a two stage alcoholysis-esterification method using glycerol, phthalic and maleic anhydride. The DDP was designed for the conversion of the GSO acid functional group in the alkyd reactor on the basis of the third order kinetic model and sinusoidal function. Models describing the molecular properties (conversion, viscosity and molecular weight average) in terms of the process parameters were derived from multiple regression by integrating a 2 5–1 fractional factorial array (FFA) in a central composite design (CCD) implemented with design expert. The fatty acid profile of the raw GSO was determined using GC-MS while structural elucidation of the raw GSO, chemically modified GSO and GSO based alkyd resins were determined using FTIR spectrometry. The synthesized alkyds show very good physic-chemico-mechanical properties. Specifically, the drying schedule shows that the GSO alkyd resin achieved a dry hard time of 8.3 h in presence of nano-ZnO pigment. The designed kinetic model was able to track the trajectory of the reaction motion such that the molecular properties falls within specification. The Optimum responses of 89.66 % conversion, viscosity of 293 cP and molecular weight average of 5,481 predicted, fall within the range suggested from the kinetic model. Correspondent experiments conducted with the predicted optimum conditions were in reasonable agreement with the predicted values.

The refrigeration process involves complex systems exhibiting nonlinearities and coupled behavior, so this paper aims to evaluate the comparative performance of a multivariable fuzzy logic-based control system and a classic multi loop PID. The process variables were the temperature of the secondary fluid (propylene glycol) outlet and the evaporating temperature. The manipulated variables were the compressor frequency speed and the pump frequency speed. Aspen Plus and Aspen Dynamics simulators were used to simulate the experimental prototype. The model was previously validated and linked with MATLAB software, where the controllers were implemented. Tuning of the fuzzy controller was performed through the membership functions and gains adjustments. The tuning of the multi loop PID controller was performed using the Ziegler-Nichols method and then a fine tuning was carried out. In order to fairly compare energy consumption and control effort, the tune of PID-based strategy was finished when similar values of Integral of Squared Error were achieved. Thus, very similar behavior for the process variables in both controllers. On the other hand, a great improvement in the control effort and energy saving was observed when the multivariable fuzzy controller was used in comparison to classic PID. The energy consumption was reduced by 25 % and the control effort by 96 % when the proposed strategy was used.

Moisture diffusivity (D em ), mass transfer coefficient (h m ), activation energy and drying kinetics of the dill leaves were studied and modeled as a function of temperature (40–70 °C) and moisture content (0.20–5.67 kg water/kg dry matter). Results showed that the D em and h m significantly depend on the temperature and moisture content ( p < 0.05). The average of D em and h m varied between 4.02 × 10 –9 to 9.65 × 10 –9 m 2 /s, and 2.38 × 10 –7 to 6.33 × 10 –7 m/s, respectively. Activation energy showed a significant dependence on the moisture content and estimated as 16.84 kJ/mol for diffusion model and 28.70 kJ/mol for mass transfer model. Out of the six models considered, the logarithmic model showed the best fit to drying behavior of the dill leaves.

Palladium membranes are considered ideal for high purity hydrogen separation owing to their infinite selectivity to hydrogen. The key to such selectivity depends on the dense surface of the membrane that suggests absolute non-porous surface morphology. However, preparation of dense palladium membranes irrespective of any deposition technique leads to pit formation which makes synthesis of dense palladium membrane challenging. The current study illustrates the application of electroless plating assisted with novel catalytic sol pre-coating to prepare dense Pd membranes. The surface characterization using field emission scanning electron microscope (FESEM) and atomic force microscopy (AFM) were performed to identify the gaps between dip coating and electroless plating. It was observed that with the use of a dip coated catalytic sol, thinner and well dispersed Pd deposits could be prepared. The porosity of deposited Pd layers does not affect the essential densification property as sol surface underneath dispersed Pd remains dense.

Viscosities of binary mixtures of polyethylene glycol-1000 (PEG-1000) and water were measured precisely in the temperature range 293.15–343.15 K at atmospheric pressure using a high precision viscometer. Viscosity data were used to calculate the activation energy of viscous flow. The activation energy was observed to increase with increase in the concentration of aqueous solutions of PEG which indicated that more energy is required to move the molecule inside the structure with increase in concentration. The measured data provided better understanding to explain the behaviour of macromolecules with respect to change in concentration and temperature. The results were discussed in the light of polymer-solvent interactions. At lower concentration range, the molecules exhibit weak interaction due to dominant repulsive force and at higher concentration the entanglement of polymer chain increases. In view of greater force of interaction between solute and solvent molecules forming hydrogen bonding, there will be an increase in interaction with temperature and concentration.

Exact analytical solutions for the temperature profile and the efficiency of a nonlinear rectangular fin model have been obtained in the forms of well-known algebraic/non-algebraic functions. In the considered nonlinear fin model, the thermal conductivity and the heat transfer coefficient have been assumed to vary as distinct power-law functions of temperature thereby yielding a nonlinear BVP in a 2 nd order ODE (ordinary differential equation). These exact solutions have been obtained by employing the derivative substitution method which not only include the solutions of previously studied simplified cases of the same problem but also the solutions of a similar problem of reaction-diffusion process occurring in a porous catalyst slab. These exact solutions have been successfully validated against their numerical counterparts. Besides, effects of various parameters on the obtained solutions have been studied, and the conditions for their existence, uniqueness/multiplicity and stability/instability are analyzed and discussed in detail.