RICERCA ITALIANA     

Robust Design of Heat Exchangers

Università degli Studi di Trieste

Abstract

In this project new numerical methods will be developed both in the field of simulation of heat transfer as well as in the field of optimisation techniques.
In the frame of heat transfer simulation industrial codes (CFX) will be used to handle complex geometries but at the same time a highly innovative code based on SFEM+IBM (Spectral Finite Element + Immerse Boundary Methods) will be developed for conductive problems.
In the frame of optimisation techniques a new methodology for robust design will be developed in order to face design optimisation problems with uncertainity sources.
The developed technologies then integrated under the design optimisation framework modeFRONTIER will be used to optimise a regenerative heat exchanger for a micro gas turbine.
Some elements (the flow passages)of the optimal geometry found will be used for experimental validation of the methodology.

The project is made of six phases: two under the responsability of the first reserch unit, four under the responsability of the second reserch unit.
Targets and phases of the first reserch unit are:
- the development of an innovative simulation method
- the numerical validation of optimisation techniques applicable to heat transfer problems
Targets and phases of the second reserch unit are:
- the definition of a concrete design problem related to a regenerative heat exchanger for a micro-gas turbine
- the development >>>

Principal Investigator

Carlo POLONI Università degli Studi di TRIESTE

Research Objectives

The utilization of enhanced surface design is a very effective strategy to improve the heat transfer in many industrial applications, such as cooling of gas turbines, compact heat exchangers and cooling of electronic packages. All the applications share the common goal of achieving good ratio of heat transfer to pressure drop. Nevertheless, other aspects such as resistance against fouling and easy manufacturing are also important criteria. In this context the Computational Fluid Dynamics (CFD) is nowadays a consolidated tool for predicting the behavior of heat transfer devices and for testing different designs, avoiding the deployment of costly tests.
The research program objectives are related to the development of an integrated and innovative methodology for the detailed design of compact heat exchangers and the application of the metodology to the design of components of industrial relevance.
Traditional mechanical design mainly aims at the definition of a "feasible" component that meets the specification but it is clear that this approach would not necessarily produce "optimal" components.
More recently the use of optimisation procedures have made possible to automate the serch for feasible solutions and therefore parctical the optimisation of the component. However this approach has also highlighted the limitation of numerical simulation models and in some cases the optimisation procedure it self: an optimiser will infact easyly exploit unphysical >>>

First Results

In this phase the main result will be the feasibility demonstration of an innovative numerical sover based on SFEM+IBM methods on 2D problemsThe main result in this phase will be the development of an optimisation methodology applied to 2D cases using SFEM+IBM methods and modeFRONTIERDuring this phase the operating conditions for the preliminary design of the heat exchanger will be determined , with the definitions of the possible stochastic fluctuations.During this phase the numerical algorithms and strategies for Robust Design will be presented, for the development of a new methodology of optimization.During this phase the definition of the parametric model of the flowpath of the heat exchanger will be defined. Then the global optimization, using the Robust Design theory, will be performed.During the last phase the experimental validation of the developed methodology will be performed, to prove the effective performances of the heat exchanger.

Timescale

24 months

National and international background

The utilization of enhanced surface design is a very effective strategy to improve the heat transfer in many industrial applications, such as cooling of gas turbines, compact heat exchangers and cooling of electronic packages. All the applications share the common goal of achieving good ratio of heat transfer to pressure drop. Nevertheless, other aspects such as resistance against fouling and easy manufacturing are also important criteria. In this context the Computational Fluid Dynamics (CFD) is nowadays a consolidated tool for predicting the behavior of heat transfer devices and for testing different designs, avoiding the deployment of costly tests. A number of papers in literature demonstrates the need of a correct shape design; for instance in [1] a plate heat exchanger consisting of wavy plates has been considered; wave length, distance between plates, angle of inclination between the wave directions and Reynolds number were the parameters varied throughout the analysis to find the "best" configuration. The heat transfer enhancement between fluid and surface can also be obtained by adding vortex generators [2,3], this is a common tool utilized in tube and fin heat exchangers to help mixing the fluid behind the tubes. However, the consolidated approach is to prescribe the geometry, boundary conditions and thermophysical properties, and solving the governing equations iterating the process until a satisfactory performance is obtained. The success of this approach relies >>>