Heat transfer and exergy analysis of solar air heater tube with helical corrugation and perforated circular disc inserts
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Heat transfer and exergy analysis of solar air heater tube with helical corrugation and perforated circular disc inserts Suvanjan Bhattacharyya1 · Manabendra Pathak2 · Mohsen Sharifpur3 · Sunil Chamoli4 · Daniel R. E. Ewim5 Received: 18 June 2020 / Accepted: 27 August 2020 © Akadémiai Kiadó, Budapest, Hungary 2020
Abstract The effects of perforated circular disc swirl generator on heat transfer (HT) and flow fields in a solar air heater helical cor‑ rugated tube have been investigated experimentally. Thermal energy transport coefficient at different values of the corruga‑ tion angle (θ), the corrugation pitch ratio (y), the perforation ratio (k), and the perforation disc pitch ratio (s) is studied for Reynolds numbers (Re) ranging from 10,000 to 52,000. Isothermal pressure drop tests and heat transfer experiments under a uniform heat flux conditions have been carried out. The results indicate that in the presence of a perforated circular disc inside the helically corrugated tube, heat transfer is augmented by around 50–60%. Entropy generation in the form of irreversibility is reported. Exergy analysis, in terms of exergy efficiency, is presented. The corrugated tube with swirl generator inserts aug‑ ments the thermal energy transport coefficient mostly, which is accompanied by a minimum pressure penalty. The combined geometry augments more thermal energy transport coefficient than those of acting alone. A predictive Nusselt number and friction factor correlation are also developed. A large data set has been created for thermal energy transport coefficient and thermal–hydraulic performance, which is beneficial for the design of solar thermal air heaters and heat exchangers. Keywords Fluid flow · Heat transfer · Perforated disc · Corrugated helical tube · Heat exchanger · Entropy · Exergy List of symbols A Tube inner wall surface area (m2) b Breadth of baffle (m) cp Mean isobaric heat capacity (J kg−1 K−1) * Suvanjan Bhattacharyya [email protected]‑pilani.ac.in * Mohsen Sharifpur [email protected]; [email protected] 1
Center for Renewable Energy and Environment Development, Department of Mechanical Engineering, Birla Institute of Technology & Science, Pilani, Pilani Campus, Vidya Vihar, Pilani, Rajasthan, India
2
Department of Mechanical Engineering, Indian Institute of Technology Patna, Bihta, Patna 801103, India
3
Clean Energy Research Group, Department of Mechanical and Aeronautical Engineering, University of Pretoria, Hatfield, South Africa
4
Department of Mechanical Engineering, Govind Ballabh Pant Institute of Engineering & Technology, Pauri Garhwal, Uttarakhand, India
5
Department of Mechanical Engineering, Mechatronics and Industrial Design, Tshwane University of Technology, Private Bag X860, Pretoria 0001, South Africa
d Perforation diameter (m) D Inner diameter of test tube (m) f Darcy friction factor h Convective heat transfer coefficient (W m−2 K−1) H Perforation ratio HT Heat transfer HE Heat exchanger I Current (A) k Fluid th
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