Eventos Anais de eventos
ENCIT 2018
Brazilian Congress of Thermal Sciences and Engineering
Thermal-Hydraulic Evaluation of the Augmentation of Heat Transfer in a Solar Water Heater Through Longitudinal Vortex Generator
Submission Author:
Felipe Augusto Santos da Silva , SP , Brazil
Co-Authors:
Felipe Augusto Santos da Silva, Leandro Salviano
Presenter: Leandro Salviano
doi://10.26678/ABCM.ENCIT2018.CIT18-0279
Abstract
The direct conversion of solar energy into thermal energy is an interesting alternative for heating a fluid. The use of the solar water heater can represent an average savings of electricity of up to 48% in some regions. Flat plate solar collector is used to transfer the solar energy for a working fluid. However, provide the increase of the heat transfer in such devices is remains as a great challenge. Longitudinal vortex generator for enhancement of the heat transfer is a passive technique which increases the amount of free movement into the boundary layer to provide a better mixture between the hot and cold streams near to the wall. This paper analyzes the application of the delta-winglet vortex generators for three different positions of an idealized plate in y-axis, which could be symmetrical or asymmetrical, for two different attack angles of 30° and 45°. The Reynolds number 600 and 900 were evaluated. The main result show that the delta-winglet vortex generator is an effective passive technique to provide heat transfer enhancement, resulting in 2.2 times the increase of heat transfer compared to the smooth tube, with pressure drop penalty of 4.4 times. The best ration between the heat transfer and the pressure drop penalty is reached for the attack angle of 30º and for the flat plate with eccentricity 0. Regarding to PEC, the best result is also obtained for the same setup of flat plate, for both attack angle of the vortex generators and for both Reynolds number.
Keywords
thermal solar energy, Heat transfer enhancement, Passive technique, Delta-winglet vortex generators
