Laminar heat transfer to Newtonian and Non-Newtonian fluids in tubes. Temperature and velocity profiles were determined experimentally for heating and cooling of Newtonian and non-Newtonian fluids in tubes and the results compared with theoretical predictions incorporating a temperature-dependent viscosity.
Flow in tubes
Newtonian and Non-Newtonian fluids
Heating and cooling
The University of Bradford theses are licenced under a Creative Commons Licence.
InstitutionUniversity of Bradford
DepartmentPostgraduate School of Studies in Chemical Engineering.
MetadataShow full item record
AbstractThis thesis is concerned with a theoretical and experimental study of the hydrodynamics and heat transfer characteristics of viscous fluids flowing in tubes under laminar conditions. Particular attention has been given to the effects of the rheological properties and their variation with temperature. A review of problems of this type showed that in spite of the many potential applications of the results in a wide range of industries the subject had not been well developed and further work is justified in order to fill some of the gaps in our knowledge. The early part of the thesis considers the justification of the work in this way and sets down the scope and objectives. A computer progracune was then developed to allow the governing equations of the problem to be solved numerically to give the velocity and temperature profiles and pressure drop for both heating and cooling conditions. The results were also presented in the form of Nusselt numbers as a function of the Graetz numberp since this form is useful for engineering design purposes. The validity of the predictions were then checked by a programme of experimental work. Temperature and velocity profiles have been measured in order to provide a more severe test of the theory than could be imposed by the measurement of overall heat transfer rates. A combined thermocouple probe/Pitot tube was developed to allow simultaneous measurements of velocity and temperature to be made. A Newtonian oil and two non-Newtonian Carbopol solutions were studied. This is the first time that velocity and temperature profiles have been measured for non-Newtonian fluids in this type of situation. The results of the work heve shown that (a) the velocity and temperature profiles and pressure drops are greatly affected by the temperature dependence of the rheological properties and since real viscous fluids are normally very temperature-sensitive it is important that this effect is properly taken into account. (b) the engineering design correlations commonly used for the prediction of heat transfer coefficients can be seriously in error, especially for cooling conditions and when non-Nevitonian fluids are being considered. (c) a mathematical model can be developed which accurately describes all the phenomena and gives predictions which are very close to those observed experimentally. An important objective was to develop more accurate engineering design correlations for non-isothermal pressure drop and heat transfer rates.
Showing items related by title, author, creator and subject.
Heat transfer in mixing vessels at low Reynolds numbers. An experimental study of temperature profiles heat transfer rates and power requirements for mechanically agitated vessels operating at low Reynolds numbers.Edwards, M.F.; Shamlou, Parviz Ayazi (University of BradfordPostgraduate School of Studies in Chemical Engineering, 2010-08-04)The present study investigates experimentally the laminar mixing and heat transfer of a range of helical ribbon and anchor impellers for both Newtonian and inelastic non-Newtonian fluids. The work also correlates the experimental data empirically in the form of dimensionless groups. In order to estimate the relative importance and the effect of all the geometrical parameters on the mixing power and heat transfer, data from the published literature sources will be utilized and combined with the results from this study. Thus, reliable empirical correlations will be obtained which are applicable over the widest range of operating conditions. The study also investigates the ablity of the various impellers to level out temerature distributions. The measurement of these temperature gradients and the impeller power requirements gives a measure of the mixing efficiency of the impeller used.
Computer simulation studies of dense suspension rheology. Computational studies of model sheared fluids; elucidation, interpretation and description of the observed rheological behaviour of simple colloidal suspensions in the granulo-viscous domain by Non-Equilibrium Particulate Dynamics.Woodcock, L.V.; Hopkins , Alan John (University of BradfordDepartment of Chemical Engineering, 2010-08-04)Rheological properties of idealised models which exhibit all the non-Newtonian flow phenomenology commonly seen in dense suspensions are investigated by particulate-dynamics computer-simulations. The objectives of these investigations are: (i) to establish the origins of various aspects of dense suspension rheology such as shear-thinning, shear thickening and dilatancy; (ii) to elucidate the different regions of a typical dense suspension rheogram by examining underlying structures and shear induced anisotropies in kinetic energy, diffusivity and pressure; (iii) to investigate the scaling of the simplest idealised model suspension; i.e. the hard-sphere model in Newtonian media and its relationship to the isokinetic flow curves obtained through non-equilibrium molecular dynamics (NEMD) simulations; (iv) to preliminarily determine the effect of perturbations present in all real colloidal suspensions, namely particle size polydispersity and a slight 'softness' of the interparticle potential. Non-equilibrium isokinetic simulations have been performed upon ;systems of particles interacting through the classical hard-sphere potential and a perturbation thereof, in which the hard-core is surrounded by a 'slightly soft' repulsive skin. The decision to base the present work upon isokinetic studies was made in order to obtain a better under- standing of suspension rheology by making a direct connection with previous NEMD studies of thermal systemst(93). These studies have shown that the non-linear behaviour exhibited by these systems under shear is atttributable to a shear-induced perturbation of the equilibrium phase behaviour. The present study shows this behaviour to correspond to the high shear region of the generalised suspension flow curve.
Water assisted injection moulding: development of insights and predictive capabilities through experiments on instrumented process in parallel with computer simulations.Polynkin, A.; Bai, L.; Pittman, J.F.T.; Sienz, J.; Mulvaney-Johnson, Leigh; Brown, Elaine C.; Dawson, A.; Coates, Philip D.; Brookshaw, B.; Vinning, K.; et al. (Maney Publishing, 2008)An idealised model of core-out in water assisted injection moulding (WAIM) is set up to isolate the effect of cooling by the water on the deposited layer thickness. Based on simulations, this is investigated for a specific case as a function of Pearson number and power law index. It is found that cooling significantly reduces the layer thickness to the extent that a change in the flow regime ahead of the bubble, from bypass to recirculating flow, is possible. For shear thinning melts with high temperature coefficient of viscosity, the simulations show very low layer thickness, which may indicate unfavourable conditions for WAIM. Although in the real moulding situation, other effects will be superimposed on those found here, the results provide new insights into the fundamentals of WAIM. Investigation of other effects characterised by Fourier and Reynolds numbers will be reported subsequently. Some early process measurement results from an experimental WAIM mould are presented. Reductions in residual wall thickness are observed as the water injection set pressure is increased and the duration of water bubble penetration through the melt is determined experimentally. The formation of voids within the residual wall is noted and observed to reduce in severity with increasing water injection pressure. The presence of such voids can be detected by the signature from an infrared temperatures sensor.