An Air-Based Cavity-Receiver for Solar Trough Concentrators

A cylindrical cavity-receiver containing a tubular absorber that uses air as the heat transfer fluid is proposed for a novel solar trough concentrator design. A numerical heat transfer model is developed to determine the receiver's absorption efficiency and pumping power requirement. The 2D steady-state energy conservation equation coupling radiation, convection, and conduction heat transfer is formulated and solved numerically by finite volume techniques. The Monte Carlo ray-tracing and radiosity methods are applied to establish the solar radiation distribution and radiative exchange within the receiver. Simulations were conducted for a 50 m-long and 9.5 m-wide collector section with 120 degrees C air inlet temperature, and air mass flows in the range 0.1-1.2 kg/s. Outlet air temperatures ranged from 260 degrees C to 601 degrees C, and corresponding absorption efficiencies varied between 60% and 18%. Main heat losses integrated over the receiver length were due to reflection and spillage at the receiver's windowed aperture, amounting to 13% and 9% of the solar power input, respectively. The pressure drop along the 50 m module was in the range 0.23-11.84 mbars, resulting in isentropic pumping power requirements of 6.45 x 10 (4) -0.395% of the solar power input. [DOI: 10.1115/1.4001675]