CFD analysis for thermo-hydraulic properties in a tubular heat exchanger using curved circular rings
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CFD analysis for thermo‑hydraulic properties in a tubular heat exchanger using curved circular rings Satyendra Singh1 · Himanshi Kharkwal1 · Abhishek Gautam2 · Ashutosh Pandey1 Received: 24 October 2019 / Accepted: 6 April 2020 © Akadémiai Kiadó, Budapest, Hungary 2020
Abstract The never-ending demands of humans have led researchers to find more efficient energy conversion technologies. Enhancing heat transfer rate in a tubular heat exchanger through curved circular rings is one type of passive method that is studied in this work. The computational analysis has been done using “FLUENT” module of ANSYS 16.0. The tubular heat exchanger has internal diameter of 68.1 mm, length of 1.5 m and constant heat flux of 1000 W m−2. Air is the working fluid, which flows in Re varying from 3000 to 21,000. After reaching steady state conditions, the Nusselt number and friction factor are calculated for CCR rings. Furthermore, perforation has been done on these rings with perforation index 8, 12 and 16% and thermo-hydraulic properties are investigated. Computational results show that perforating the rings have a significant effect on heat transfer and friction factor. Greater the perforation index, greater is the Nu and TPF. The maximum enhancements obtained in Nu and TPF are 7.4 and 1.56 times, respectively (as compared to that of smooth tube), for PCCR-16%. Keywords Heat transfer rate · Friction factor · Thermal performance factor · Perforation index List of symbols Re Reynolds number v Velocity of air (ms−1) D Test section diameter (m) D1 Internal diameter of insert (m) Nu Nusselt number Nus Nusselt number for smooth tube h Average convective heat transfer coefficient (W m−2 K−1) k Thermal conductivity of air (W m−1 k−1) Pr Prandtl number m Air flow rate (kg s−1) ΔP Pressure difference between inlet and outlet of the test section (Pa) Ti Inlet air temperature (K) To Outlet air temperature (K) Twm Wall mean temperature (K) Tfm Fluid mean temperature (K) * Satyendra Singh [email protected] 1
Department of Mechanical Engineering, B.T. Kumaon Institute of Technology, Dwarahat 263653, Uttarakhand, India
Alternate Hydro Energy Centre, IIT Roorkee, Roorkee 247667, India
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Q Heat flux (W) Qair Heat carried by air (W) Qconv Heat transfer by convection (W) Cp Specific heat of air (J kg−1 K−1) A Area of the pipe (m2) f Friction factor fs Friction factor for smooth tube L Test section length (m) l Distance between two consecutive inserts (m) PA Perforated area of insert (m2) TA Total area of insert (m2) Abbreviations TPF Thermal performance factor CCR Curved circular rings PCCR Perforated curved circular rings PI Perforation index (PA/TA) ANN Artificial neural network
Introduction The increased demands of efficient thermal systems in industry have drove researchers to find new alternative method of enhancing convective heat transfer such that the energy savings could also be promoted. The heat transfer augmentation could be done through two techniques: active and passive
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