Mixed convection in a 90 Deg horizontal bend

The effect of a developing secondary flow, induced by both centrifugal and buoyancy forces, on heat transfer inside a horizontal curved pipe is studied. The governing equations are solved in a finite element formulation using tri-quadratic elements for the velocity as well as for the temp. field. Due to interaction of centrifugal, buoyancy and pressure forces, a complex secondary flow develops, consisting of two secondary longitudinal vortices, perpendicular to the axial flow. Heat transfer shows to be increased considerably as a result of the three-dimensional flow fiel

A model structure for product quality in processing agro-material for process control purposes

In this paper, a model structure is presented that captures product behaviour with respect to quality properties. Modelling product quality properties involves nominal (bulk) dynamic behaviour and the variation of these properties. Nominal behaviour is modelled using a limited number of basic reactions. To deal with the variation the presented model structure is extended with a three-step approximation procedure using discretised intervals. The model structure is suitable for control purposes and will contribute to closing the gap between product specialists and the system and control community. The applicability of the model structure and the possibility to describe quality properties is shown with existing models from the literature that show a good fit with the described model structure and by an industrial case study on potato storag

Mixed convection in a 90 Deg horizontal bend

The effect of a developing secondary flow, induced by both centrifugal and buoyancy forces, on heat transfer inside a horizontal curved pipe is studied. The governing equations are solved in a finite element formulation using tri-quadratic elements for the velocity as well as for the temp. field. Due to interaction of centrifugal, buoyancy and pressure forces, a complex secondary flow develops, consisting of two secondary longitudinal vortices, perpendicular to the axial flow. Heat transfer shows to be increased considerably as a result of the three-dimensional flow fiel

Developing mixed convection in a coiled heat exchanger

In this paper the development of mixed convection in a helically coiled heat exchanger for Re = 500, Pr = 5 and δ =114 is studied. The influence of buoyancy forces ¢(Gr = ¢O (105)) on heat transfer and secondary flow is analyzed. In the method used the parabolized equations are solved using a finite difference discretization. The code is tested on mixed convection flow in a 90° curved tube of which the results are compared to the results obtained with an elliptical code. For the helically coiled tube a constant wall temperature is considered. It appeared that heat transfer is highly influenced by secondary flow induced by centrifugal and buoyancy forces. For low Grashof numbers a splitting phenomenon of the temperature field is observed due to large secondary velocities, resulting in two separated areas of fluid. For high Grashof numbers the fluid in the coiled pipe becomes almost linearly startified which results in small secondary velocities. A wavy behaviour in the Nusselt number is observed for medium Grashof numbers

Mixed convection in a 90 Deg horizontal bend

The effect of a developing secondary flow, induced by both centrifugal and buoyancy forces, on heat transfer inside a horizontal curved pipe is studied. The governing equations are solved in a finite element formulation using tri-quadratic elements for the velocity as well as for the temp. field. Due to interaction of centrifugal, buoyancy and pressure forces, a complex secondary flow develops, consisting of two secondary longitudinal vortices, perpendicular to the axial flow. Heat transfer shows to be increased considerably as a result of the three-dimensional flow fiel

The influence of the wall temperature on the development of heat transfer and secondary flow in a coiled heat exchanger

In the present study the development of mixed convective flow is studied in a helically coiled heat exchanger with an axially varying wall temperature for Re = 500, Pr = 5 and d = 1/14 and compared to the constant wall temperature boundary condition. In the method used the parabolized equations are solved using a finite difference discretization scheme. The influence of buoyancy forces is analyzed on heat transfer and secondary flow. For all Grashof numbers studied it appears that both heat transfer, quantified by the Nusselt number, and secondary flow, quantified by the relative kinetic energy, exhibit a wavy behaviour in axial direction. For higher Grashof numbers, however, this phenomenon diminishes for the case with an axially varying wall temperature due to stabilizing stratification effects