Abstract
ABSTRACTThe paper is related to the use of magnetic nanofluids (ferrofluids) in a direct absorption solar parabolic trough collector, which enhances thermal efficiency compared to conventional solar collectors. By applying the right magnetic intensity and magnetic field direction, the thermal conductivity of the fluid increased higher than typical nanofluids. Moreover, the ferrofluids exhibit excellent optical properties. The external magnetic source is installed to alter the thermo-physical properties of the fluid, and the absorber tube does not have selective surface allowing ferrofluids to absorb the incoming solar irradiance directly. In this paper, an experimental investigation of the performance of small scale direct absorption solar collector using ferrofluids as an absorber was conducted. Nanoparticle concentrations of 0.05 vol% at the operational temperatures between 19°C and 40°C were used in the current study. The results show that using ferrofluids as a heat transfer fluid increases the efficiency of solar collectors. In the presence of the external magnetic field, the solar collector efficiency increases to the maximum, 25% higher than the conventional parabolic trough. At higher temperatures, the ferrofluids show much better efficiency than conventional heat transfer fluid. The study indicated that nanofluids, even of low-content, have good absorption of solar radiation, and can improve the outlet temperatures and system efficiencies. The study shows the potential of using ferrofluids in the direct absorption solar collector.
Highlights
The demand for modern energy services is increasing rapidly
An experimental comparison of thermal efficiency between two heat transfer fluids Fe3O4-water ferrofluids with 0.05% and distilled water, working in the same parabolic trough, has been performed. This parabolic trough benefits from the magnetic and optical property of ferrofluids which enhance the thermal efficiency of the collector
The results show that using ferrofluids as a heat transfer fluid increases the efficiency of solar collectors
Summary
The demand for modern energy services is increasing rapidly. Solar energy has the potential to meet a significant portion of the world’s energy demand. Parabolic trough is effective in power generation and useful for industrial process heat application. The successful operation of the first solar electricity generation system (SEGS) in California’s Mojave Desert was the reason for the technical and commercial success of parabolic trough systems. One of the methods to reduce cost is increasing the heat transfer performance of parabolic trough systems. Increasing the heat transfer performance will decrease the absorber surface temperature and subsequently reduce the receiver thermal loss at the high operation temperatures [7,8]. This could be achieved by enhancing the convective heat transfer in the absorber tube
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