TESTING AND ANALYSIS OF LOW PRESSURE, TRANSPARENT TUBE SOLAR RECEIVER FOR THE SUNSPOT CYCLE

Year 2017, Volume: 3 Issue: 3, 1294 - 1307, 01.07.2017

J. Hoffmann

https://doi.org/10.18186/journal-of-thermal-engineering.323395

Cited By: 2

Abstract

This paper proposes a low pressure tubular solar receiver for a solarized gas turbine. The receiver comprises of
concentric tubes with a transparent outer tube, and the annular space is filled with a porous medium. Air is heated
by concentrated solar radiation as it flows through the porous medium. To proof our concept, a single 1.5 m long
tube was tested on an existing eight mirror linear Fresnel collector, and test data is documented. A temperature
increase of about 40 °C was recorder for a concentration ratio of 7:1 and superficial velocity of 1 m/s. Volumetric
absorption was a disappointingly low 28 %, mainly due to the low packing factor and reflection of sunlight from
the tube’s outer surface. A computational fluid dynamics (CFD) model of the test set-up was used to extract the
extinction and absorption coefficients of the porous medium, by fitting a quadratic response surface through the
mean square errors between experimental and CFD data. Our analysis indicates that we can increase receiver
efficiency significantly through raising the packing factor and applying and anti-reflection coating to the tube
surface. 

Keywords

Low Pressure Solar Receiver, Transparent Tube, Linear Fresnel, Porous Medium

References

• [1] D.G. Kröger, The Stellenbosch University solar power thermodynamic cycle, http://sterg.sun.ac.za/wpcontent/uploads/2012/10/SUNSPOT_July_20121.pdf, 2012.
• [2] M. Lubkoll, T.W. von Backström, T.M. Harms ans D.G. Kröger, Initial analysis on the novel spiky central receiver air pre-heater (SCRAP) pressurized air receiver, Energy Procedia 69, 461 – 470, 2015.
• [3] K.J. Craig, P. Gauchè and H. Kretzschmar, CFD analysis of solar tower hybrid pressurized air receiver (HPAR) using a dual-banded radiation model, Solar Energy 110, 338 – 355, 2014.
• [4] L. Heller and P. Gauché, Dual-pressure air receiver cycle for direct storage charging, Energy Procedia 49, 1400 – 1409, 2014.
• [5] L. Heller and J.E. Hoffmann, A cost and performance evaluation of SUNDISC: a dual-pressure air receiver cycle, Energy Procedia 69, 1287 – 1295, 2015.
• [6] A.E. Bergles, 1997, Heat transfer enhancement – the encouragement and accommodation of high heat fluxes, Journal of Heat Transfer, 119, 8 – 19, 1997.