Numerical study of the possibility of improving the hydrothermal performance of an elliptical double-pipe heat exchanger
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Numerical study of the possibility of improving the hydrothermal performance of an elliptical double‑pipe heat exchanger through the simultaneous use of twisted tubes and non‑Newtonian nanofluid Amin Shahsavar1 · Mohammad Amin Bakhshizadeh1 · Müslüm Arici2 · Masoud Afrand3,4 · Sara Rostami5,6 Received: 11 July 2020 / Accepted: 19 August 2020 © Akadémiai Kiadó, Budapest, Hungary 2020
Abstract In this investigation, the combined use of twisted tubes and nanofluid (NF) to augment the performance of a double-pipe heat exchanger (DPHE) has been considered numerically. Steady-state laminar flow of the cold non-Newtonian CuO NF and hot water pass inside the tube side and annulus side, respectively. The base fluid is the aqueous solution of 0.5 mass% carboxymethyl cellulose. The effects of the Reynolds number ( Re ), the volume concentration of nanoparticles ( 𝜑 ) and twist pitch on the performance metrics are examined, and the outcomes are compared with those a plain DPHE. The outcomes showed that the increase in Re has desirable effects such as improved heat transfer and heat exchanger effectiveness, and unpleasant effects such as increased pressure drop and pumping power. Moreover, it was found that except for 𝜑 ≤ 1.5% and Re = 500, the NF performs better than the base fluid. In addition, it was reported that the variation pattern of overall hydrothermal performance of NF with twist pitch is ascending–descending. Furthermore, the outcomes illustrated that the overall hydrothermal performance of twisted DPHE is superior to that of the plain DPHE, and its highest value is 2.671, which belongs to case of Re = 2000, 𝜑 = 3% and twist pitch = 4 mm. Keywords Double-pipe heat exchanger · Twisted pipe · Non-Newtonian fluid · Nanoparticles · CFD simulation List of symbols A Heat transfer surface area (m2) cp Specific heat capacity (J kg−1 K−1) C Heat capacity rate (W K−1) Dh Hydraulic diameter (m) * Sara Rostami [email protected] 1
Department of Mechanical Engineering, Kermanshah University of Technology, Kermanshah, Iran
2
Department of Mechanical Engineering, Faculty of Engineering, Kocaeli University, Umuttepe Campus, 41001 Kocaeli, Turkey
3
Institute of Research and Development, Duy Tan University, Da Nang 550000, Vietnam
4
Faculty of Electrical – Electronic Engineering, Duy Tan University, Da Nang 550000, Vietnam
5
Laboratory of Magnetism and Magnetic Materials, Advanced Institute of Materials Science, Ton Duc Thang University, Ho Chi Minh City, Vietnam
6
Faculty of Applied Sciences, Ton Duc Thang University, Ho Chi Minh City, Vietnam
f Friction factor (–) FoM Figure of merit (–) h Convection coefficient (W m−2 K−1) k Thermal conductivity (W m−1 K−1) L Length of tube (m) m Consistency index (kg m−1 s−1) ṁ Mass flow rate (kg s−1) n Power-law index (–) P Pressure (Pa) PEC Performance evaluation criterion (–) q Heat transfer rate (W) Re Reynolds number (–) T Temperature (K) Tf Average temperature of fluid (K) Tw Average temperature of inner tube (K) u Fluid velocity (m
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