Band 14, Heft 3 -

In recent years, the permissible limits of engine exhaust emissions are reduced considerably. Hence a quick warm-up and high conversion efficiency of the catalyst system is essential to meet upcoming stringent emission regulations. In the present work, the transient thermal behavior of an oxidation catalyst is studied using a one-dimension mathematical modeling approach with the focus on CO oxidation for dual-fuel engine application. At first, the heat generation due to chemical reactions is considered negligible for studying the warm-up behavior. Upon obtaining a good agreement between predicted warm-up temperature profiles with available literature data, the effect of an electrical heater on the warm-up behavior is investigated. The model is then extended by incorporating heat generation due to CO oxidation. A simplified reaction rate model is considered in order to reduce the computational complexity. It is observed that the simplified model agrees well with the experimental data for both low and high levels of CO concentration at the inlet, typical in dual-fuel technology when an engine is operated under diesel and dual-fuel modes, respectively.

This paper addresses the control of integrating processes with time delay. Two different control structures, namely single feedback loop (SFBL) and double feedback loop (DFBL) have been considered. In the SFBL, the controller has been designed using direct synthesis approach for the desired regulatory performance. In the DFBL, the inner loop controller is the proportional only controller which stabilizes the inner loop. The outer loop controller of DFBL has been designed through direct synthesis approach to achieve desired servo performance. Both the proposed control scheme works satisfactorily for low order as well as high order integrating process which may have a time delay and inverse response dynamics. Simulation of various examples shows improved performance when compared with the recently reported method.

This study investigates the effect of ultrasound pretreatment on moisture content and oil uptake of hamburger slices during deep-fat frying. Samples received ultrasound pretreatment at two power modes: Normal (at 40 and 60 °C) and Boost (at 40 and 60 °C), both for 15 min. They were then deep fried at 150, 160 and 170 °C. Results showed that samples receiving the ultrasound pretreatment with Normal power had higher moisture contents than those from the Boost pretreatment, with a significant difference. The highest moisture content was obtained with Normal power mode at 40 °C and frying at 150 °C. On the other hand, the effective water diffusivity coefficient increased at higher fryer temperatures and higher power mode (the Boost system). The highest effective water diffusivity coefficient was obtained with Boost power mode at 60 °C and frying at 170 °C where its range was calculated to be 6.93 × 10 –8 - 8.77 × 10 –8 m 2 /s. At the same time, the highest activation energy belonged to higher power mode (the Boost system) and frying at 150 °C ranging from 13.20–17.29 kJ/mol. In addition, the lowest oil uptake was obtained with Boost power mode at 60 °C and frying at 170 °C. Multivariate regression analysis showed that the exponential model had the best fitness for predicting variations in moisture content and oil uptake of hamburger slices.

In this paper, the solution of the Lacher model describing the relationship between the Pressure – Composition, and Temperature (PCT diagrams) of AB 5 type metal-hydrides (LaNi 4.8 Sn 0.2 , LmNi 4.91 Sn 0.15 , LaNi 4.5 Al 0.5 ) for hydrogen storage using C ++ platform, with the help of a numerical method of nonlinear equation, Newton-Raphson method is presented. This study focuses on the development of a C ++ code to describe the iteration of Newton-Raphson for application in Hydrogen to Metal-Hydride systems.

The present study applied computational fluid dynamics (CFD) to investigate the heat transfer of Newtonian (water) and non-Newtonian (0.3 %wt. aqueous solution of carboxymethylcellulose (CMC)) fluids in the presence of Al 2 O 3 nanoparticles. To analyze the heat transfer rate, investigations were performed in a vertical helical coil as essential heat transfer equipment, at different inlet Reynolds numbers. To verify the accuracy of the simulation model, experimental data reported in the literature were employed. Comparisons showed the validity of simulation results. From the results, compared to the aqueous solution of CMC, water had a higher Nusselt number. In addition, it was observed that adding nanoparticles to a base fluid presented different results in which water/Al 2 O 3 nanofluid with nanoparticles’ volume fraction of 5 % was more effective than the same base fluid with a volume fraction of 10 %. In lower ranges of Reynolds number, adding nanoparticles was more effective. For CMC solution (10 %), increasing concentration of nanoparticles caused an increase in the apparent viscosity. Consequently, the Nusselt number was reduced. The findings reveal the important role of fluid type and nanoparticle concentration in the design and development of heat transfer equipment.

In the present paper, a variable gas properties Eulerian model is employed to model the gas-solid heat transfer in a three-dimensional horizontal pipe, subjected to an adiabatic wall. The numerical model has been validated with the benchmark experimental data and other theoretical results available in the literature, and found satisfactory agreements. Moreover, the numerical heat transfer results considering the variable gas properties (i. e. density, dynamic viscosity, thermal conductivity, and specific heat) and constant gas properties are compared. It is noticed that the variable gas properties significantly affect the heat transfer, when compared to the constant gas properties. Therefore, the consideration of constant gas properties for the prediction of heat transfer may not be suitable in gas-solid flows, subjected to an adiabatic wall. Moreover, the temperature profiles, solid volume fraction profiles, and gas-solid Nusselt number are discussed. Finally, the pressure drop prediction with respect to the solid loading ratio is studied, and found that the pressure drop slightly decreases with increasing the solid loading ratio.

A tuning method is developed for the stabilization of the non-minimum phase second order plus time delay systems. It is well known that the presence of positive zeros pose fundamental limitations on the achievable control performance. In the present method, the coefficients of corresponding powers of s, s 2 and s 3 in the numerator are equated to α, β and γ times those of the denominator of the closed-loop system. The method gives three simple linear equations to get the PID parameter. The optimal tuning parameters α, β and γ are estimated by minimizing the Integral Time weighted Absolute Error (ITAE) for servo problem using fminsearch MATLAB solver aimed at providing lower maximum sensitivity function and keeping in check with the stability. The performance under model uncertainty is also analysed considering perturbation in one model parameter at a time using Kharitonov’s theorem. The closed loop performance of the proposed method is compared with the methods reported in the literature. It is observed that the proposed method successfully stabilizes and improves the performance of the uncertain system under consideration. The simulation results of three case studies show that the proposed method provides enhanced performance for the set-point tracking and disturbance rejection with improved time domain specifications.

In this work, fractional order PI λ D µ (FOPID) controller designed to enhance the dynamic performance of the Proton Exchange Membrane (PEM) fuel cell. The control objective is to regulate the supply manifold pressure on cathode side to maintain oxygen excess ratio of the PEM fuel cell. The higher order PEM fuel cell model is approximated to First order plus time delay (FOPTD) model for controller design and analysis. The proposed FOPID controller is designed based on minimization of Integral Absolute Error (IAE) with pre specified maximum sensitivity (M s ) as a constraint. Uncertainty and measurement noise analysis is carried out to verify the robustness of the designed controller. The simulation results of proposed FOPID controller is compared with other designing methods. Based on minimization of IAE value, the SP 1.4 FOPID controller produces IAE value of 0.255 where as AMIGO 1.4 tuning method and ZN based FOPID tuning methods produces 0.263 and 3.817 respectively for perfect case. Based on maximum sensitivity M s is 1.4, the SP 1.4 FOPID controller produces M s of 1.4 where as AMIGO 1.4 PID and ZN based FOPID tuning methods produces Ms of 1.5 and 1.25 respectively for perfect case, which indicates that the proposed SP 1.4 FOPID controller is robust. The proposed SP 1.4 FOPID provides better values (rise time of 0.331 sec, settling time of 0.692 sec and percentage of peak overshoot of 0.797 for perfect case) when compared with other methods. From simulation results, for the control of supply manifold pressure of PEM fuel cell, the proposed fractional-order PID controllers improves the closed loop performance in terms of rise time, settling time and percentage of peak overshoot when compared to the integer-order PID controllers.