Stability analysis on dual solutions of second- grade fluid flow with heat and mass transfers over a stretching sheet

Stability on dual solutions of second-grade fluid flow over a stretching surface with simultaneous thermal and mass diffusions has been studied. The fluid flow is governed by Lorentz force and energy dissipation due to viscosity. Lorentz force is generated due to the application of magnetic field along the transverse direction. In methodology, suitable similarity transformation and MATLAB built-in bvp4c solver technique have been adopted. Effects of some flow parameters are exhibited through figures and tables and a special emphasis is given on the existence of dual solutions. A stability analysis is executed to determine the stable and physically achievable solutions. For the laminar flow, the drag force on the surface for the time-independent case is reduced due to amplifying values of But, it enhances the drag force for the time-dependent case. This shows the effectiveness of the first solution (during steady case) over the unsteady case.

Investigation of optimization of solar energy refrigerator with natural humidifier

Cold chain processes of horticultural products in tropical countries is very urgent to maintain product quality. In Indonesia, the temperature and humidity are relatively high, so that the deterioration of horticultural products is very fast. Because of the high humidity, this condition can highly possibly use a natural humidifier for a cold room by purging humid ambient air to the refrigerator cabin with the best certain time. Meanwhile, as a tropical country, solar energy has good reliability to be developed. This study aims to determine the performance of the medium temperature refrigerator with a natural humidifier using solar energy as energy source. This research was conducted as an experimental investigation. The rig has been built completely with measurements and instrumentation for precise temperature and humidity control. The results showed that the system reached a quite good coefficient of performance (COP), with the thermodynamically COP of 3.6. However, humidifiers contribute a cooling load which can affect the temperature increase of 1o C - 1.5o C in the cooling system. Further studies will examine the optimization of the refrigerator system with natural humidifiers with low electricity consumption and eco-operating conditions with the best combination of temperature and humidity to keep the product of good quality in a long storage time.

Simultaneous impact of magnetic and Arrhenius activation energy on the flow of Casson hybrid nanofluid over a vertically moving plate

The present study deals with the Blasius and Sakiadis flow of Casson hybrid nanoliquid over a vertically moving plate under the influence of magnetic effect and Joule heating. Here, we considered Silver and Copper as nanoparticles suspended in 50% Ethylene-Glycol (EG) as base fluid. Further, the Arrhenius activation energy and convective boundary conditions are taken into the account. The set of PDEs of the current model are converted into ODEs by using suitable similarity variables. The reduced ODEs are numerically solved with the help of RKF-45 method by adopting shooting scheme. The impact of various pertinent parameters on the fluid fields is deliberated graphically. The result outcomes reveal that, rise in values of Casson parameter diminishes the velocity gradient. The escalated values of magnetic parameter decline the velocity profile but reverse trend is detected in thermal and concentration profiles. Moreover, the augmentation in the activation energy parameter elevates the concentration profile.

Effects of magnetic field on blood flow with suspended copper nanoparticles through an artery with overlapping stenosis

The flow of blood mixed with copper nanoparticles in an overlapping stenosed artery is reported in the presence of a magnetic field. The presence of stenosis is known to impede blood flow and to be the cause of different cardiac diseases. The governing nonlinear equations are rendered dimensionless and attempted under the conditions of mild stenosis. The analytical solutions for velocity, resistance to the flow, wall shear stress, temperature, and streamlines are obtained and analyzed through graphs. The obtained outcomes show that the temperature variation in copper nanoparticles concentrated blood is more and flow resistance is less when compared to pure blood. The investigations reveal that copper nanoparticles are effective to reduce the hemodynamics of stenosis and could be helpful in biomedical applications.

Combined effects of nonuniform temperature gradients and heat source on double diffusive Benard-Marangoni convection in a porous-fluid system in the presence of vertical magnetic field

The physical configuration of the problem is a porous-fluid layer which is horizontally unbounded, in the presence of uniform heat source/sink in the layers enclosed by adiabatic and isothermal boundaries. The problem of double diffusive Bènard-Marangoni convection in the presence of vertical magnetic field is investigated on this porous-fluid system for non-Darcian case and is subjected to uniform and nonuniform temperature gradients. The eigenvalue, thermal Marangoni number is obtained in the closed form for lower rigid and upper free with surface tension velocity boundary conditions. The influence of various parameters on the Marangoni number against thermal ratio is discussed. It is observed that the heat absorption in the fluid layer and the applied magnetic field play an important role in controlling Benard-Marangoni convection. The parameters which direct this convection are determined and the effect of porous parameter is relatively interesting.

Investigation of the convective heat transfer and friction factor of magnetic Ni nanofluids within cylindrical pipes

The current paper reports the results of numerical research on the magnetic Ni nanofluid flowing in a tube, developing turbulent flows under constant heat flux conditions. The numerical investigations are conducted for a Reynolds number range from 3,000 to 22,000, and a particle concentration range of 0% to 0.6%. The effects of the Reynolds number on the friction factor and Nusselt number are computed and compared satisfactorily with the experimental results of the literature. The classical correlations of Gnielinski, Notter – Rouse, and Pak and Cho are verified by predicting the Nusselt number of the Ni nanofluid. The obtained results revealed an enhancement in the heat transfer with the increase of magnetic Ni particle volume fraction and Reynolds number.

Managing the energy of the air conditioning systems using a modified multi-variable control technique

This research is a continuation of our previous work [19], in which, I’ve investigated many control techniques for the multi-input multi-output (MIMO) control systems for air conditioners. In the present work, I’ve suggested another control technique which exhibited better performance in the cases where permanent disturbances are present. I’ve applied the technique to a model room that simulates a computer room and is conditioned by a simple, less expensive, and energy-saver HVAC system. The two control inputs are; the opening angle of a fresh air gate and the steam flow rate from a humidifier. The two controlled outputs are the temperature and humidity. The control technique and the in-door conditions are simulated using a written program that works along with a commercial code. The sampling interval for each controlled variable is modified to allow more accuracy for measured data. When applying accidental and permanent disturbances in both controlled variables, the suggested technique exhibited accepted performance. The controlled variables that are affected with permanent disturbances achieved their set-point values after longer time intervals than those of the cases where only accidental disturbances are present. Two comparisons were made between the controlled and uncontrolled system by operating the system for a certain period, and fixing the fresh air opening at 25% and 50% of the full opening area. The consumed energy in the two cases was compared with that of the case when applying the control technique for the same period. An energy-saving of about 15.3% was recorded in the first case and about 37.6% for the second case. The present technique is a case-independent and may be applied to any MIMO control system with little modifications.

MHD Natural Convective Flow of Cu-Water Nanofluid over a Past Infinite Vertical Plate with the Presence of Time Dependent Boundary Condition

In this paper, unsteady electrically conducting, incompressible, heat and mass transfer Magnetohydrodynamic free convective fluid flow with Cu-nanoparticles over a vertical plate embedded in a porous medium and variable boundary conditions are considered. The governing PDE's have been converted to non-dimensional equations then solved by FET for velocity, temperature and concentration profiles with the influence of buoyancy force due to heat and mass transfer, Prandtl and Schmidt number , time, magnetic and chemical reaction parameter in case of pure fluid and Cu-water nanofluid. The Cu-water nanofluid velocity is low than pure fluid, these are presented through graphical form . Also presented the local Skin-friction coefficient, rate of heat and mass transfer and code of validation through tabular forms.

Entropy Generation and Bejan Number Analysis of MHD Casson Fluid Flow in a Micro-Channel with Navier Slip and Convective Boundary Conditions

The analysis of MHD flow has been a concern of consideration for research scientists and engineers. In this treatise, the steady MHD flow of an incompressible and electrically conducting Casson fluid in a micro-channel with heat generation and viscous dissipation, in the presence of hydrodynamic slip and convective boundary conditions, is examined. Exact solutions of non-dimensional steady governing equations are obtained in closed form. Transient fluid velocity, temperature, entropy generation, and Bejan number are depicted by the line graphs whereas rate of heat transfer and skin-friction coefficient are computed in tabular form for pertinent flow parameters. It is established that the entropy generation rate and Bejan number increases for increasing values of the Casson parameter and heat generation parameter. In particular, the Casson parameter accelerates the skin-friction coefficient while it provides resistance to the rate of heat transfer near the channel walls. Casson fluid finds significant applications in biomechanics, polymer processing industries, and food processing.

Hall and induced magnetic field effects on convective flow of viscoelastic fluid within an inclined channel with periodic surface conditions

This paper is concerned with the analytical study of the convective flow of a viscoelastic electrically conducting fluid within an inclined channel bounding a porous regime with Hall and induced magnetic field effects. An external magnetic field of high intensity is applied in the direction normal to the inclined surface. The left inclined surface of the channel is considered to be non-magnetic while the right inclined surface is assumed to be magnetized. Suitable non-dimensional transformations are used to reduce the problem to a similar non-dimensional problem. The resulting flow governing equations are solved analytically. The consequences of various flow influencing parameters to the flow variables are numerically computed and presented in graphical and tabular form. It is interesting to note that the growth in angle of inclination reduces the induced magnetic field in the left half of the channel while this effect is opposite in the vicinity of the right inclined surface due to magnetization of this surface.