RICERCA ITALIANA     

Research program

Innovative techniques for the enhancement of forced convection

University Co-ordinator

Università degli Studi di BOLOGNA - INGEGNERIA ENERGETICA,NUCLEARE E DEL CONTROLLO AMBIENTALE - ()

Research Unit Leader

Giampietro Fabbri

Description

The Research Program is divided in two phases, each of one year, described as follows.
First phase
In this phase many experiments will be performed in the wind tunnel. In this phase, the same measurements as those described in the previous section, will be performed. The apparatus, set up for the study of heat transfer and condensation on smooth tubes, will be used for the study of heat transfer and water condensation on finned tubes.
A particular attention will be devoted then to the influence of fin geometry on heat transfer and water condensation.
The local heat transfer coefficient, local temperatures and water condensation mass flow will be measured for different finned tubes geometries. The 3d velocity patterns will be obtained by means of 3d PIV, recently added to our Laboratory equipment.
The results will be used for numerical code validations. A camera recording of the two-phase patterns will be obtained and compared with numerical results.
Experimental results will be also interpolated with the finite element results. The validated numerical results will be used for optimization procedures based on genetic algorithms.

Second phase
Transient behaviour of compact heat exchangers will be studied. This analysis will be focused to the simultaneous heat and mass exchange during the transient regime. Finite element codes developed in the last years by our Research Unit will be extended for this study. A part of air-cooled finned tube heat exchanger with different geometries for fins will be considered.
Simmtery planes or periodical flow and thermal conditions will be considered. Numerical simulations will be compared with Fluent results. Global an local thermal coefficient will be obtained for different transient boundary conditions. Temperature distribution, local relative humidity and condensed water mass flow will be obtained as a function of boundary conditions. Genetic algorthms (Matlab) will be used together with numerical codes (Fluent) for geometry optimization. The optimal distance between tubes, fins and fin shapes will be obtained. In these genetic algorthms different selection and reproduction techniques will be considered and compared. The configurations with higest thermal efficiency will be obtained with respect to overall heat transfer coefficient and pressure drop.

Synergies
From collaboration with Research Units of Udine, Milano, Ancona and Parma important results on heat transfer with vapor condensation will be obtained.
In particular, the synergies expected are the following.
-results and tests for numerical codes validation will be obtained from Udine RU,
- a comparison of experimental measurements on heat transfer coefficient on fins will be performed with Parma RU, with a particular attention to IR measurements,
- the fin optimization procedure will be tested with Milano RU,
- the PIV 3d measurements will be discussed with Ancona RU.