| Summary: | 碩士 === 國立中央大學 === 機械工程研究所 === 83 === The experimental study on the evacuated tubular collectors by
the ITRI is performed by considering the effect of vacuum
degrees and conduction fins. The experiments are divided into
tow parts: firstly, evacuated tubular collectors are inserted
by an electrical heater, the convective heat transfer propert-
ies are then determined under different heating conditions.
Secondly, the efficiencies of evacuated tubular collectors are
tested for different types of conduction fins and vacuum degr-
ees. All these experimental data will be compared with the num-
erical results of Maa. The experimental data show that the
convective heat transf- er coefficients of the residual gases
inside the vacuum layer will getting smaller with the decrease
of the pressure. The perf- ormances of the high evacuated
collectors are much better then those of the none evacuated
collectors. The results of numerical studies also show the same
physical tendency. The cross-shaped conduction fin provides a
better perform- ance on the tubular collectors, yet, the shapes
,material and manufacturing costs for the conduction fins are
still needed to be considered. All the results determined by
the experiments off- er the advices for the technical
improvments of the evacuated tubular collectors.
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