Giampietro Fabbri

A genetic algorithm for fin profile optimization

In the present work a genetic algorithm is proposed in order to optimize the thermal performances of finned surfaces. The bidimensional temperature distribution on the longitudinal section of the fin is calculated by resorting to the finite elements method. The heat flux dissipated by a generic profile fin is compared with the heat flux removed by the rectangular profile fin with the same length and volume. The genetic algorithm is then applied to the case of polynomial profile fins, in order to determine the polynomial parameter values which optimize the fin effectiveness. The optimum profile is finally shown for different polynomial orders.

Heat transfer optimization in corrugated wall channels

Abstract In this work, the heat transfer in a channel composed of a smooth and a corrugated wall is studied under laminar flow conditions. The velocity and temperature distributions are determined with the help of a finite element model. The heat transfer performance of the corrugated wall channel is compared with that of a smooth wall duct. The numerical model is utilized in a genetic algorithm to maximize the heat transfer by optimizing the corrugation profile, for given volume of the corrugated wall and pressure drop in the channel. Some optimum corrugation profiles are presented at the end.

Heat transfer optimization in internally finned tubes under laminar flow conditions

Abstract In the present work the problem of optimizing the geometry of internally finned tubes in order to enhance the heat transfer under laminar flow conditions is studied. The velocity and temperature distributions on the finned tube cross-section are determined with the help of a finite element model, and a global heat transfer coefficient is calculated. A polynomial lateral profile is proposed for the fins and the geometry is optimized in order to make the heat transferred per unit of tube length or surface as high as possible for a given weight and for a given hydraulic resistance. Finally, the optimum fin profiles obtained by means of a genetic algorithm are shown for different situations.

Optimum profiles for asymmetrical longitudinal fins in cylindrical ducts

Abstract In the present work the problem of optimizing the geometry of tubes with internal asymmetrical fins in order to enhance the heat transfer under laminar flow conditions is studied. The velocity and temperature distributions on the finned tube cross-section are determined with the help of a finite element model and a global heat transfer coefficient; an equivalent Nusselt number and a compared effectiveness are calculated. Polynomial profiles are assigned to the two lateral fin surfaces and the geometry is optimized in order to make the heat transferred per unit of tube length or surface as high as possible for a given weight and for a given hydraulic resistance. The optimum asymmetrical fins, obtained by means of a genetic algorithm, are finally shown for different situations and their performances are compared with those of optimum symmetrical fins.

Optimization of heat transfer through finned dissipators cooled by laminar flow

In the present work, the problem of optimizing the shape and the spacing of the fins of a thermal dissipator cooled by a fluid in laminar flow is studied. For a particular finned conduit, the velocity and temperature distributions on the transversal section are determined with the help of a finite element model and a global heat transfer coefficient is calculated. A polynomial lateral profile is proposed for the fins and the geometry is optimized in order to make the heat transfer coefficient as high as possible with the smallest dimensions or the lowest hydraulic resistance to the flow. The optimum fin profile and spacing, obtained by means of a genetic algorithm, are finally shown for different situations. Increases of 45% are obtained in the heat transfer coefficient referring to the maximum values which can be obtained with rectangular fin profiles.

Heat Transfer Optimization in Finned Annular Ducts under Laminar-Flow Conditions

In the present work the problem of optimizing the lateral profile of longitudinal fins in annular ducts in order to enhance the heat transfer under laminar coolant flow conditions is studied. The velocity and temperature distributions on the annular duct cross section are determined with the help of a finite-element model, and a global heat transfer coefficient is calculated. A polynomial lateral profile is proposed for the fins, and the geometry is optimized in order to make the transferred heat as high as possible for a given amount of material and for a given hydraulic resistance. Lastly, the optimum fin profiles obtained for different situations by means of a genetic algorithm are shown.

Optimum performances of longitudinal convective fins with symmetrical and asymmetrical profiles

Abstract In the present work, the heat transfer performance of optimized dissipators with longitudinal fins of asymmetrical cross section is investigated and compared with that of optimized dissipators with symmetrical fins. In particular, the problem of optimizing the shape and the spacing of the fins of a thermal dissipator cooled by a fluid in laminar flow is studied by assigning two different polynomial lateral profiles to the fins. A finite element model is proposed to determine velocity and temperature distributions and is employed in a genetic algorithm to find the dissipator geometries which make the heat transfer coefficient as high as possible under different conditions. Some examples of optimized geometries are finally shown and discussed.

Effect of disuniformities in vapor saturation pressure and coolant velocity on vapor back flow phenomena in single-pass air-cooled condensers

Abstract In the present work vapor back flow phenomena in single-pass, multiple-row, cross-flow air-cooled condensers are investigated. The condensation in this kind of heat exchangers is studied with the help of a mathematical model, which considers the effect of changes in the saturation temperature inside the tubes and changes in the air velocity in the direction transversal to the coolant flow. The model equations are solved with a new algorithm. The vapor distribution, the pressure drop between the inlet and outlet plena and the global effectiveness are determined under different working conditions.

Analysis of vapor back flow in single-pass air-cooled condensers

Abstract In the present work a mathematical model of the vapor distribution in single-pass, multiplerow, cross-flow condensers is proposed. An analysis of the performances of such condensers is carried out by varying both the row number and the effectiveness of each row. Some convenient configurations, which reduce the pressure drop between inlet and outlet plena or avoid the accumulation of noncondensable gases, are finally distinguished.

Analysis of the Noncondensable Contaminant Accumulation in Single-Pass Air-Cooled Condensers

In the present work a mathematical model of a single-pass, multiple-row, cross-flow, air-cooled condenser, supplied by vapor containing noncondensable contaminants, is presented. Moreover, a calculation algorithm is proposed which allows the vapor distribution in such a condenser to be found for as large a number of rows as desired. An analysis of the global effectiveness of single-pass, cross-flow condensers is performed by varying both the row number and the effectiveness. Finally, some convenient configurations are distinguished.