Heat Transfer and Flow Analysis in a Circular Tube Equipped with Triangular Helical Strip Inserts Under Turbulent Flow Conditions for the Application of Boiler

• Published in: International journal of thermophysics 2023, Vol.44 (1), Article 1
• Main Authors: Adgale, Tushar, Zainith, Prabhakar, Mishra, Niraj Kumar, Sharma, Anshul
• Format: Article
• Language: English
• Subjects: Circular tubes; Classical Mechanics; Condensed Matter Physics; Experimentation; Fluid dynamics; Fluid flow; Friction; Friction factor; Geophysics; Heat transfer; Industrial Chemistry/Chemical Engineering; Inserts; Nusselt number; Physical Chemistry; Physics; Physics and Astronomy; Reynolds number; Strip; Thermodynamics
• ISSN: 0195-928X; 1572-9567
• DOI: 10.1007/s10765-022-03112-y

In the present study, an experimental investigation was carried out for the Nusselt number, friction factor and thermal performance factor using triangular helical strip inserts. For the experimentation air was considered as flowing fluid medium with Reynolds number ranging from 37 500 to 52 000. For present study helical strip inserts of widths 5 mm, 7.5 mm, and 10 mm were considered and varied with two pitches i.e., single pitch (i.e., w = P) and double pitch (i.e., w = 2P) i.e., 5 mm width strip with 5 mm and 10 mm pitch, 7.5 mm width strip with 7.5 mm and 15 mm pitch, 10 mm width strip with 10 mm and 20 mm pitch. In addition, the experimentation was carried out considering two passes of test section to analyze the thermo-hydraulic characteristics. Experimental results exhibited that heat transfer and thermal performance of the helical inserted tube were expressively improved compared to plain tube. The Nusselt number of helical strip inserts is more for inserts with lower width, tighter pitch for all geometries. Nusselt number ratio was 1.45–2.05 times for single pass and 1.55–2.45 times that of plain tube. The friction factor is lower for inserts with higher pitch. The friction factor is high insert with higher width. The friction factor enhancement ratio is high for strips with more significant number of passes, tighter pitch and more width. The thermo-hydraulic performance of the helical strip insert improves for high number of passes, lower width, lower pitch. Moreover, the thermal enhancement factor (TEF) was in the range of 1.01–2.03 and 1.08–2.41 for single pass and double pass, respectively.