Heat transfer augmentation of flat plate solar collector through finite element-based parametric study
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Heat transfer augmentation of flat plate solar collector through finite element‑based parametric study Poonam Rani1 · P. P. Tripathy1 Received: 31 May 2020 / Accepted: 23 August 2020 © Akadémiai Kiadó, Budapest, Hungary 2020
Abstract The introduction of fins and baffles on the absorber plate is an effective way to ameliorate the thermal performance of flat plate solar collector (FPSC), but obstructs the air passage leading to considerable pumping power penalty. In the current work, attempt is made to improve the overall performance of collector with the incorporation of hollow semicircular loop fins and rectangular baffles over the absorber plate for air mass flow rate ranging from 0.006 to 0.02 kg s−1. A parametric study was carried out with finite element approach considering different radius (2–4 cm), pitch (6–20 cm) and number of semicircular loops per row in transverse direction (3–8 loops). Compared to intermittent loops, placement of continuous staggered semicircular loops was more effective for attaining uniform profile and higher magnitude of air temperature at collector outlet. With regard to FPSC, finned collector provided 2.64–2.95 times greater Nusselt number and 41–75% higher thermal efficiency, as well as exhibited 8.38–10.4 K higher collector outlet average air temperature. The pressure drop noted for FPSC was 0.14 Pa and increased to the range of 0.5–0.7 Pa with the addition of loops and baffles at an air mass flow rate of 0.01 kg s−1. Collector having baffles and continuous semicircular loops of radius 3 cm, made up of 2-mm-thick wire, presented maximum thermohydraulic performance factor of 1.73 in conjunction with showing maximum magnitude and uniform profile of collector outlet temperature. The modified collector with semicircular loops along with baffles will find its application in efficient drying of agricultural commodities. Keywords Heat transfer · Flat plate solar collector · Finite element modeling · Thermal performance · Baffles List of symbols Ac Cross-sectional area of the solar collector (m2) As Collector surface area (m2) cp Specific heat capacity of air (J kg−1 K−1) DH Hydraulic diameter (m) eb (T) Blackbody emissive power (W m−2) f Friction factor FPSC Flat plate solar collector h Convective heat transfer coefficient of air (W m−2 K−1) H Height of the rectangular duct (m) I Total incident solar radiation intensity (W m−2) kair Thermal conductivity of air (W m−1 K−1) kabs Thermal conductivity of absorber plate (W m−1 K−1) * P. P. Tripathy [email protected] 1
Agricultural and Food Engineering Department, Indian Institute of Technology Kharagpur, Kharagpur, West Bengal 721302, India
l Length of solar collector (m) MAE Mean absolute error MRE Mean relative error N Total number of observations Nu Nusselt number p Pressure ∆p Pressure drop patm Atmospheric pressure (Pa) P Perimeter of the cross section of collector (m) q Inward heat flux (W m−2) Qu Useful heat gain by the air (W m−2) Re Reynolds number S Solar energy absorbed by the absorber p
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