TJ414 : Analytical Solution to Forced Convection Heat Transfer of non-Newtonian Fluid Flow through Straight Pipes
Thesis > Central Library of Shahrood University > Mechanical Engineering > MSc > 2016
Authors:
Abstarct: In the present study the heat convection of non-Newtonian fluids in the straight pipes is investigated analytically and by the Modal analysis. The non-Newtonian fluids are namely, time independent non-Newtonian Power-law fluid, Viscoelastic non-Newtonian fluids following LPTT and FENE-P models. In Power-law fluid by assumption of thermally developing flow, the temperature distribution is solved in the closed form solutions for two special values of Power-law indeces. An analytical relation for Nusselt number versus longitudinal coordinate of pipe is derived. The comparison of the resulted local Nusselt numbers in this work with the previous results, reveals the good precise of this work. the temperature distribution of Viscoelastic fluids considered in this research, is derived by Frobenius series Method. By affecting of Viscous Dissipation term on Energy equation, the effects of dimensionless Brinkman number is discussed. It is revealed that by increasing of the level of elasticity of the fluid, dimensionless Debora number, the Nusselt number and so the heat transfer in the pipe are increased because of the enhancement of velocity gradient and shear rate in the wall region, and then reduction of fluid viscosity.It is shown that in the FENE-P Viscoelastic fluid, by increasing of extensibility parameter, L, the Nusselt number and so the heat transfer are decreased. But in the LPTT Viscoelastic fluids, by increasing of the corresponding extesion parameter, the heat transfer and the Nusselt numbers are increased. As we know the Brinkman number is because of considering of viscous dissipation term in the pipe.In deed by considering the viscous dissiaption term the dimensionless Brinkman number is resulted. The viscous dissipation term is defined as the tensor production of shear stress and velocity gradient. So the viscous dissipation term and Brinkman number have direct relatin with velocity gradient. By increasing the positive Brinkman numbers, more heat is produced in the pipe. Since the velocity gradient at any cross section of the pipe, is maximum in the wall region, so the highest values of heat generation is there. The results reveal that by increasing of the Brinkman number, the Nusselt number and so the heat transfer are decreased.
Keywords:
#Forced convection #Viscoelastic Fluid #Isothermal Pipe #Brinkman number #Modal Analysis Link
Keeping place: Central Library of Shahrood University
Visitor:
Keeping place: Central Library of Shahrood University
Visitor:
