Entropy generation due non-Newtonian fluid flow in an annular pipe with relative rotation is investigated. A third grade fluid with constant viscosity is accommodated in the analysis. Relative rotational motion is present between inner and outer cylinders, which induces the flow. Analytical solutions for velocity and temperature distributions are presented, and entropy generation number is computed for different dimensionless values of non-Newtonian viscosity, Brinkman’s number and velocity ratio. It is found that the increasing of dimensionless non-Newtonian viscosity lowers the number entropy generation. This is more pronounced in the region close to the annular pipe inner wall. The increasing of Brinkman’s number enhances the number entropy generation, particularly in the vicinity of the annular pipe inner wall.
PL
W pracy zbadano zagadnienie generacji entropii obserwowanej podczas przepływu nieniutonowskiej cieczy przez przewód pierścieniowy, którego ścianki obracają się względem siebie. Do analizy przyjęto płyn trzeciego stopnia o stałej lepkości. Przepływ czynnika jest indukowany względnym ruchem obrotowym zewnętrznego i wewnętrznego cylindra tworzącego ścianki przewodu. Rozwiązania analityczne zaprezentowano dla rozkładu prędkości i temperatury płynu, a liczbę generacyjną entropii wyznaczono dla różnych wartości lepkości nieniutonowskiej cieczy, liczby Birnkmana i stosunku prędkości obwodowej cylindrów. Potwierdzono, że zwiększenie bezwymiarowej lepkości obniża liczbę generacyjną entropii. Ten efekt jest szczególnie wyraźny w obszarze bliskim ściany wewnętrznego cylindra. Wzrost liczby Birnkmana powiększa liczbę generacyjną entropii, także w pobliżu ściany wewnętrznej przewodu.
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We investigate the unsteady, non-isothermal, pressure driven channel flow of a third grade liquid subject to exothermic reactions. We assume temperature dependent fluid viscosity and also that the flow is subjected to convective cooling at the channel walls. The exothermic reactions are modelled via Arrhenius kinetics and the convective heat exchange with the ambient at the channel walls follows Newton’s law of cooling. The time-dependent, coupled, and nonlinear partial differential equations governing the flow and heat transfer problem are solved numerically using efficient, semi-implicit finite difference algorithms. The sensitivity of the fluid flow and heat transfer system to the various embedded parameters is explored.
The steady-state magnetohydrodynamics (MHD) flow of a third-grade fluid with a variable viscosity parameter between concentric cylinders (annular pipe) with heat transfer is examined. The temperature of annular pipes is assumed to be higher than the temperature of the fluid. Three types of viscosity models were used, i.e., the constant viscosity model, space dependent viscosity model and the Reynolds viscosity model which is dependent on temperature in an exponential manner. Approximate analytical solutions are presented by using the perturbation technique. The variation of velocity and temperature profile in the fluid is analytically calculated. In addition, equations of motion are solved numerically. The numerical solutions obtained are compared with analytical solutions. Thus, the validity intervals of the analytical solutions are determined.
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This work concerns the study of the thin film flow problem arising in non–Newtonian fluid mechanics using analytical approach. The governing equations are reduced to ordinary nonlinear boundary value problem by applying the transformation method. Homotopy Perturbation Method (HPM) has been applied to obtain solution of reduced nonlinear boundary value problem. The analytical solutions of the flow velocity distributions for different cases have been presented. The effect of material constant has also discussed. Finally, analytical results have been compared with numerical one obtained by forth order Runge Kutta method. High accuracy and validity are the advantages of present study.
An analysis was carried out for an unsteady magnetohydrodynamic (MHD) flow of a generalized third grade fluid between two parallel plates. The fluid flow is a result of the plate oscillating, moving and pressure gradient. Three flow problems were investigated, namely: Couette, Poiseuille and Couette-Poiseuille flows and a number of nonlinear partial differential equations were obtained which were solved using the He-Laplace method. Expressions for the velocity field, temperature and concentration fields were given for each case and finally, effects of physical parameters on the fluid motion, temperature and concentration were plotted and discussed. It is found that an increase in the thermal radiation parameter increases the temperature of the fluid and hence reduces the viscosity of the fluid while the concentration of the fluid reduces as the chemical reaction parameter increases.
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