Experimental Heat Transfer Analysis of Helical Coiled Tubes on the Basis of Variation in Curvature Ratio and Geometry

Autor: Susheel Madhavrao Magar, Gaurav Kumar Gugliani, Ravindra Rambhau Navthar
Jazyk: angličtina
Rok vydání: 2024
Předmět:
Zdroj: Journal of Heat and Mass Transfer Research, Vol 11, Iss 1, Pp 89-108 (2024)
Druh dokumentu: article
ISSN: 2345-508X
2383-3068
DOI: 10.22075/jhmtr.2024.32179.1491
Popis: The influence of curvature ratio (CR) within helical tubes on secondary flows and subsequent enhancement of heat transfer is well-established. Furthermore, the interaction between the shell fluid and the helical tube is recognized as pivotal in this regard. In this paper, the impact of varying CR and coil geometry on the performance of heat exchangers (HEs) through experimental heat transfer analysis conducted on five distinct coils viz., straight helical (ϴ= 90°), conical (ϴ= 70°,50°,30°), and spiral (ϴ= 0°) configurations have been studied. Moreover, correlations for modified effectiveness are proposed for all HEs. The Reynolds number range chosen for the analysis spans from 3700 to 20000, encompassing laminar and turbulent flow regimes of the coil hot water. The optimal HE is identified based on thermal and hydrodynamic parameters, including hot water temperature difference, effectiveness, modified effectiveness, rate of heat transfer, pressure drops of the coil, shell fluids, and pumping power. Observations reveal that helical cone coil heat exchangers (HCCHEs) demonstrate superior thermal and hydrodynamic characteristics when the fluid flow aligns with increasing CR. Notably, for both laminar and turbulent flows, the highest hot water temperature difference, effectiveness, and rate of heat transfer are observed for ϴ= 30° HCCHE, while the lowest values are attributed to ϴ= 90° HE. Tube side Nusselt numbers, pressure drops, and friction factors show agreement with the predictions of researchers. The analysis reveals that the coil fluid pressure drop is maximal for ϴ =0° HE, whereas the maximum shell fluid pressure drop is encountered for ϴ =90° HE. Furthermore, the highest pumping power per unit heat transfer area for coil and shell fluids are noted for ϴ= 0° HE and ϴ= 90°HE, respectively, while ϴ= 30° HCCHE exhibits comparable performance to the remaining HEs within the specified parameter range, establishing its optimality.
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