City Research Online

Abstract

Internal developing laminar flow is described by the full partial differential equations in two-dimensional cylindrical co-ordinates. Making assumptions only about property variations, these are expressed as finite-difference equations, which are treated by a computer program in Fortran. This involves a marching procedure and Gaussian elimination. A feature of the approach is that the energy balance at any axial position is guaranteed by using it as a constituent equation, rather than as a check.

The predictive ability of this treatment has been demonstrated firstly in adiabatic flow. ‘then it has been rigorously tested in a number of forced and combined convection situations against both analytical and experimental data. ‘these cover a range of thermal (constant heat flux and constant temperature) and fluid (undeveloped, partially - or fully - developed entry flow) boundary conditions; they involve working fluids which include air, water, and oils. In general, agreement is consistently good.

In combined convection, the phenomenon of transition from laminar flow is studied, for the differing cases of natural convection assisting or opposing the forced flow. The various processes accompanying transition are identified, and comparison made with published data.

The-complete nature of the equations used means it should be possible to use the model as a check on more approximate analyses. This has been carried out successfully in an instance involving heat transfer to transformer oil.

The problem of viscous dissipation demonstrates the flexibility of this approach, in its ability to treat the complete relevant terms in the energy equation. A study of this problem shows that viscous dissipation is usually a minor effect, tending to retard heat transfer.

Flexibility is also apparent in the application of the treatment to a concentric annulus. Initial results are for adiabatic developing flow.

Care has been taken to maintain the accuracy of the results for the wide range of situations reported. ‘to this end, a number of improvements have been made in the original program.

Publication Type:	Thesis (Doctoral)
Subjects:	T Technology > TJ Mechanical engineering and machinery
Departments:	School of Science & Technology > Department of Engineering School of Science & Technology > School of Science & Technology Doctoral Theses Doctoral Theses

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