Use of sinusoidal surface profile in the absorber tube of a parabolic trough solar collector to enhance its thermal perf
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Use of sinusoidal surface profile in the absorber tube of a parabolic trough solar collector to enhance its thermal performance Ashish Babarao Khelkar1 · Biplab Kumar Debnath1 · Kishore Debnath1 Received: 7 November 2019 / Accepted: 9 June 2020 © Akadémiai Kiadó, Budapest, Hungary 2020
Abstract In this work, the primary objective is to develop a sinusoidal wave profile at the inner surface of an absorber tube, study with different working fluids for its possible application in a parabolic trough solar collector. The thermo-hydraulic characteristics of the absorber tube with the sinusoidal profile are investigated for 4000 Reynolds number and accordingly the velocity of the working fluids, namely water and Therminol VP-1 are calculated. The absorber tube has a length of 2 m, with inner and outer diameters of 19 mm and 25 mm, respectively. The heat flux of 818.5 W m −2 is supplied at the bottom face, which is oriented towards the reflector of the parabolic trough solar collector. The RNG k-ɛ turbulence model is applied in the study, by considering the finite volume based software ANSYS FLUENT 18.0. The thermo-hydraulic characteristics of the absorber tube with sinusoidal wave profile are reported to enhanced performance to that of the other type of absorber tube. Keywords Absorber tube · Nusselt number · Therminol VP-1 · Thermal performance · Friction factor List of symbols Cp Specific heat of the fluid (J kg−1 K−1) Dh Hydraulic diameter of the tube (mm) f Friction factor h Convective heat transfer coefficient (W m−2 K−1) k Thermal conductivity of the fluid (W m−1 K−1) L Length of the tube (mm) Nu Nusselt number Δp Pressure drop across the absorber tube (Pa) Q Total heat supply (W m−2) ρ Density of the fluid (kg m−3) Re Reynolds number ΔT Temperature difference (K) U Inlet velocity (ms−1)
* Biplab Kumar Debnath [email protected] * Kishore Debnath [email protected] Ashish Babarao Khelkar [email protected] 1
Department of Mechanical Engineering, National Institute of Technology Meghalaya, Shillong, Meghalaya 793003, India
Introduction At present, solar energy is one of the most useful energy in daily life through various applications [1].Various techniques are established to harness the energy from the sun, namely non-concentrating and concentrating solar collectors, to name a few. Apart from experiments, various numerical tools, namely computational fluid dynamics (CFD), artificial neural networks (ANN), etc. are also used to analyse the solar collectors [2, 3]. When a large number of data sets are available for the specified input and output parameters, then ANN can predict unknown outputs accurately. However, with limited input data of a known physics, the prediction of unknown output can only be efficiently performed by CFD. The group of authors have compared various types of grooves in a parabolic trough solar collector, namely rectangular, semi-circular, triangular and trapezoidal ones created in the receiver tube. They reported that the thermo-hydraulic
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