Numerical Analysis Of Heat Transfer Enhancement In The Parabolic Trough Solar Collector Using Twisted Tape With Perforated Plate And Nanofluids

Abstract

Solar energy is the most plentiful energy source on the planet, with around 1 kilowatt per square meter (kW/m2 ) of solar radiation reaching the earth's surface in clear conditions when the sun is near the zenith. This thesis's major goal is to investigate the numerical analysis of heat transfer enhancement in the PTSC employing twisted tape with perforated plates and nanofluid. The Tonatiuh ray tracing software is used to generate an optical model of the PTSC. A binary file containing the results of the ray-traced analysis is exported to MATLAB for further processing. Through surface and curve fitting to the data, the distribution of heat flux on the absorber tube's outer surface is determined. For the ANSYS Fluent Computational Fluid Dynamics (CFD) code, user-defined functions (UDFs) are made using the fitting relations. In ANSYS Fluent, the UDFs are employed for the boundary conditions and thermo-physical properties of nanofluid to solve fluid flow as well as heat transfer to the heat transfer fluid in the absorber tube. Because of their excellent thermal conductivity, water- 𝑍𝑟𝑂2 nanofluids at a concentration ratio of (𝑖.𝑒.𝜙 = 0%, 𝜙 = 0.2%, 𝜙 = 0.6%, 𝑎𝑛𝑑 𝜙 = 1%) are used in this work to enhance heat transfer. The flow inside the absorber tube was a fully developed and steady-state turbulent flow. Using CFD and k– 𝜀 RNG turbulence model with enhanced wall treatment, the hydrodynamic and heat transfer coefficients are determined using the finite volume method. The SIMPLE algorithm is used in the pressure velocity coupling approach, and a second-order upwind scheme is used for discretization. The thermal effects of using water-𝑍𝑟𝑂2 nanofluid with different concentrations with perforated plates and twisted tape inserts are investigated. Pitch ratios (l/D) = 12.78 and 23.32 of the perforated plate (PP) and the twisted tapes (TT) with twist ratios of (y/w) = 4, 5, and 6 are inserted into the centre of the stream. The Reynolds number covered is in the range of 4000 to 10000 for the turbulent flow of 𝑍𝑟𝑂2 nanofluid in the absorber tube. The investigation demonstrates that the combination of TT and PP for the Nusselt number, friction factor, and thermal performance factor is in the range of 132.39% to 321.37%, 232.13% to 551.58%, and 1.25 to 2.256, respectively over the plain tube. The highest thermal performance factor in the order of 2.256 over a plain tube was obtained for the integrated device consisting of the TT with (y/w) = 4 and PP with (l/D) = 12.78 at a concentration of 1% water- 𝑍𝑟𝑂2 nanofluid and at a Reynolds number of 7000.