Heat transfer performance in the longitudinal corrugated fin and oval tube compact heat exchangers
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Date
2017
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Publisher
Universiti Teknologi Malaysia
Abstract
Fin-and-tube compact heat exchangers (FTCHEs) are commonly used in various fields of industry and thermal engineering systems. Due to their extensive use, an increase in their efficiency would require smaller dimensions, lower weight, and reduced cost and materials. The main challenging task for researchers in FTCHEs is how to increase the thermal-hydraulic performance of compact heat exchangers. New designs of FTCHEs with longitudinal corrugated fin patterns and oval tubes have been conceptualized and developed. Based on these designs, three objectives were generated. The first one was to investigate the thermal-hydraulic characteristics in the FTCHEs with a new design of longitudinal corrugated fin patterns. The second one was to find the optimal thermal performance factors in the FTCHEs with corrugated fin patterns and oval tube geometry through a parametric study. Finally, the research compared numerical simulation with experimental results of flow pattern in the corrugated FTCHEs. A comprehensive analysis through parametric design explorations, numerical modeling, and experimental examinations of fluid flow characteristics were applied as a comprehensive methodology that included the design process of producing physical models to identify thermal-hydraulic characteristics of fluid flow in the FTCHEs. Parametric design exploration methodology was used to find the optimal configuration of FTCHEs with corrugated fins patterns and in-line oval tubes arrangements. The results showed that the model of FTCHEs with ONCF pattern (Corrugated fin with one fluted domain) was the best one in the terms of thermal and hydraulic characteristics and thermal performance factor. Compared to the plain fin at the range of Reynolds number between 500 and 5000, the optimal thermal performance factor (n-factor) of devices had increased by 3..0% in the case of ONCF design. The n-factor increased by 13.3% with regard to TWCF (Corrugated fin with two fluted domains) design whereas the n-factor increased by 20.9% in the case of THCF (Corrugated fin with three fluted domains) design. Experimental examination has shown that the corrugated fin pattern in the FTCHEs can limit the wake size after the tubes and prevent the rising of the boundary layer over tube surface in the FTCHEs. For analyzing flow pattern around the tubes, it was found that it is reliable to employ numerical simulation as a tool to predict fluid flow characteristics. As a conclusion, smaller dimensions, lower weight, and increase in performance criteria were accomplished in the new design of the FTCHEs. Furthermore, the design can produce substantially increased thermal efficiency and performance criteria of FTCHEs
Description
Thesis (PhD. (Mechanical Engineering))
Keywords
Heat exchangers