Combination of baffling technique and high-thermal conductivity fluids to enhance the overall performances of solar chan
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ORIGINAL ARTICLE
Combination of baffling technique and high‑thermal conductivity fluids to enhance the overall performances of solar channels Younes Menni1 · Mahyar Ghazvini2 · Houari Ameur3 · Myeongsub Kim2 · Mohammad Hossein Ahmadi4 · Mohsen Sharifpur5,6 Received: 12 June 2020 / Accepted: 31 August 2020 © Springer-Verlag London Ltd., part of Springer Nature 2020
Abstract In the present study, two-phase flow and forced-convection heat transfer of hydrogen gas (H2) in a solar finned and baffled channel heat exchanger (SFBCHE) is studied numerically. The effect of different obstacles in the channel is addressed. A H2 heat transfer fluid (HTF) having a high thermal conductivity with the baffling technique is implemented to enhance the overall performance of a solar channel. In the initial step, the results from the proposed numerical model were compared with the experimental data of a smooth channel, and then against data with a baffled channel. After checking the validity of our model, the same numerical approach was used for studying thermal-fluid characteristics of the channel with the new fluid. A hydrothermal analysis is presented for a range of Reynolds number (Re) from 5000 to 25,000. At the lowest Re = 5000, the thermal enhancement factor (TEF) is about 1.25. This value increases to 2.16, or 73.46%, when Re = 10,000. This increase in the TEF values continues as Re increases. The largest Re = 25,000 gives the highest TEF value, as it is about 4.18, which is 2.75 times greater than that given for the case of using the conventional gaseous fluid (air). Therefore, our proposed structure for the SFBCHE with high H2 HTF flow velocity leads to improve the values of dynamic pressure (Pd) and heat transfer (Nu), while reducing the skin friction (f) values, which increases the overall TEF of the channel. In addition, all performance values are greater than unity (or 1.00). This reflects the importance of the H2 HTF baffling and finning technique in improving the hydrodynamic thermal-energy performance of solar heat exchangers. The suggested model of SFBCHE filled with an H2 HTF having a high thermal conductivity allows a considerable enhancement in the overall thermal performances which can be employed in various thermal types of equipment, such as solar energy receivers, automotive radiators, and cooling in chemical industries. Keywords Computational fluid dynamics · Hydrogen working fluid · Finning technology · Numerical analysis · Solar heat exchanger · Solar receivers List of symbols c1 Constant in k–ε model c2 Constant in k–ε model Cf Local coefficient of friction Cp Specific heat, J kg−1 K−1
Dh Hydraulic diameter, m f Average coefficient of friction f0 Friction Factor for smooth exchanger H Height of exchanger, m h Height of detached baffle, m
* Mahyar Ghazvini [email protected]
3
Department of Technology, University Centre of Naama (Ctr Univ Naama), PO Box 66, 45000 Naama, Algeria
* Mohsen Sharifpur [email protected]; [email protected]
4
Faculty of Mechanica
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