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| Author(s): |
Juan José González Bayón
Total Authors: 1
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| Document type: | Doctoral Thesis |
| Press: | São Paulo. |
| Institution: | Universidade de São Paulo (USP). Escola Politécnica (EP/BC) |
| Defense date: | 1999-11-22 |
| Examining board members: |
Jurandir Itizo Yanagihara;
Carlos Alberto Carrasco Altemani;
Luis Fernando Alzuguir Azevedo;
Silvio de Oliveira Junior;
Marcos de Mattos Pimenta
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| Advisor: | Jurandir Itizo Yanagihara |
| Abstract | |
This work presents an experimental study of the influence of Delta Winglets longitudinal vortex generators on the heat transfer enhancement and flow losses in fin tube heat exchangers with two rows of tubes in alternate arrangement. The naphthalene sublimation technique was used to determine the global heat transfer coefficient based on the heat-mass transfer analogy. The local heat transfer coefficients were determined by using an evaporation technique based on the relation between the humidity content and the tonality (color) of the surface. This technique was developed specially for this work. The flow losses were determined by mean of a drag force measurement system. A parametric study of the longitudinal vortex generators mounted on the surface of the fins was carried out. The position, attack angle and aspect ratio of vortex generators were considered. The study was conducted for different longitudinal and transversal tube spacings and for values of the Reynolds number between 300 and 1000. Reasonable values of heat transfer enhancement (20,5%) for some vortex generators parameters sets were achieved. The flow losses of the enhanced surface were also increased, when compared to the smooth surface. This increase was higher for smaller Reynolds numbers. The analysis based on the Second Law of Thermodynamics showed that the destroyed exergy on surfaces with longitudinal vortex generator was smaller than on smooth surfaces, The results indicate that the use of vortex generators in fin tube configurations is advantageous, leading to a heat transfer augmentation with the reduction of exergy consumption. (AU) | |