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ISSN Online: 2377-424X

ISBN Print: 978-1-56700-474-8

ISBN Online: 978-1-56700-473-1

International Heat Transfer Conference 16
August, 10-15, 2018, Beijing, China

HEAT LOSS ANALYSIS FOR AN OPEN-CAVITY TUBULAR SOLAR RECEIVER

Get access (open in a dialog) DOI: 10.1615/IHTC16.nee.024010
pages 7695-7702

Sinopsis

A small-scale open solar-thermal Brayton cycle using a parabolic dish as the concentrated solar power system is a solution to the problem Southern Africa faces, which is that communities stay too far from the national grid and therefore do not have access to electricity and hot water. This small-scale system will be mobile and offer the ability to produce off-grid electricity and hot water by using concentrated solar power. An open-cavity tubular solar receiver, and the heat losses that occur due to conduction, convection and radiation is investigated. The solar receiver receives concentrated solar energy from a 4.8 m parabolic dish, which then heats compressed air to turn the turbine of a turbocharger, which would power a compressor and an electric generator. The insulated receiver was tested in a solar dish set-up by sending hot compressed air through it. By measuring surface temperatures at specific intervals from inlet to outlet, as well as the inlet and outlet air temperatures, as well as the temperatures on the exterior of the insulation, a thorough heat loss analysis can be done. Testing done without solar exposure in stow position (or an angle of 0°), taking weather conditions into account proved that most of the heat lost at this angle is due to radiation, and on very windy days the convection losses are greater than normal. The receiver analyzed in this paper had a total heat loss rate of 6.3 kW at an average surface temperature of about 950K, with the conduction, radiation and convection heat losses accounting for 17%, 45% and 38% respectively. Assuming the receiver receives about 13 kW of solar energy from the collector, the receiver efficiency is calculated to be approximately 50%.