Heat transfer enhancement and optimization of flat-tube multilouvered fin compact heat exchangers with delta-winglet vortex generators

Author(s): 
Daniel Jonas Dezan, Leandro Oliveira Salviano, Jurandir Itizo Yanagihara (University of Sao Paulo)

CHALLENGE - The subject of heat transfer enhancement is of significant interest in developing compact heat exchangers to meet the need for high efficiency and low cost, which are as small as possible and as light as possible. The combination of multilouvered fins and delta-winglet vortex generators has shown to be a promising strategy to enhance heat transfer in compact heat exchangers. 

SOLUTION - Surrogate-based optimization procedure is used to maximize the heat transfer of multilouvered fin compact heat exchangers with delta-winglet vortex generators (DWL). Five input parameters, such as louver angle and DWL angles of attack and positions, were chosen. The heat transfer enhancement performance of two distinct geometries, GEO1 and GEO2, with two rows of delta-winglets were considered on this research. Reynolds numbers of 120 and 240, based on hydraulic diameter, were investigated. The surrogate-based optimization procedure uses the NSGA-II (Non-Dominated Sorting Genetic Algorithm) in modeFRONTIER combined with artificial neural networks. 

 

 

 

 

 

 

 

BENEFITS - Compared with the respective baseline geometry, results show that GEO1 optimized solutions increased the heat transfer by 21.27% and 23.52% with associated pressure loss increasing of 24.66% and 36.67% for the lower and the higher Reynolds numbers, respectively. For GEO2 optimized solutions, the heat transfer was increased by 13.48% and 15.67% with an increase of the pressure drop by 20.33% and 23.70%, for the lower and the higher Reynolds numbers, respectively. Solutions show that heat transfer behind the second row of delta-winglets are as high as behind the first row for both Reynolds numbers. The flow patterns and heat transfer characteristics from optimized solutions presented some particular behavior, differently from the findings when louvered fin and DWLs are applied separately. 

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