Experimental Analysis of Residual Gas of Vacuum Annulus in Parabolic Trough Solar Receivers

According to the operation statistics of SEGS power station, the average failure rate of early parabolic trough solar receivers is high to 4.1%, of which 29% is caused by vacuum failure. The vacuum characteristic of parabolic trough solar receiver is an important factor affecting the operation efficiency and service life of the power station. The reason and mechanism of vacuum failure need to be further studied. In this paper, a residual gas analysis experimental set-up is built. The gas composition and partial pressure in the annulus is tested and analyzed with Quadrupole Mass Spectrometer (QMS). The residual gas is analyzed after heating the receiver at 390 degrees C, 425 degrees C and 550 degrees C by electric heating for several hours. The results show that hydrogen is the main residual gas in the annulus, the nitrogen and argon are also not negligible. Meanwhile, the vacuum characteristic of the receiver is evaluated using heat transfer model of rarefied gas by Direct Simulation of Monte Carlo (DSMC). Vacuum lifetime is predicted using the vacuum lifetime model. The effects of outgassing, leaking, hydrogen permeation and getter adsorption on vacuum lifetime are analyzed. Residual gas analysis can directly and accurately evaluate the vacuum performance, and the results can be used to guide the selection of getters. It is also a very effective way to predict and evaluate the vacuum lifetime of the receiver.