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This paper reports our efforts to engineer a robust, user-friendly, and broadly tunable helium droplet nozzle, and to quantitatively measure its thermal and mass transport performance. In addition to describing the physical design in detail, we report helium throughput measurements for a 6.4 μm diameter nozzle over stagnation conditions ranging from 5 to 50 K and 10 to 100 bar. The measured flow rates were in excellent agreement with those predicted by a simple effusive flow model for nozzle temperatures above 20 K, but were systematically lower for both sub-critical and super-critical jets as the temperature was lowered. The helium flow through a 500 μm skimmer was also measured, and the skimmed fraction was found to vary by two orders of magnitude over the range of stagnation conditions investigated. These results indicate a substantial narrowing of the total jet angle spread from ~90° to 5° at temperatures below 10 K. Efforts to image the low temperature jet with Schlieren and shadowgraph techniques were unsuccessful. These details combined with previously reported theory and experiments on the droplet size distributions provide the necessary foundation to predict cluster production rates and to customize nozzle/pump designs for specific applications. 相似文献
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Measurement Techniques - 相似文献
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The photoabsorption cross section of C2H4 was measured in the spectral region 107-183 nm and those of C2H6 and C2H5D were accurately determined in the spectral region 107-162 nm using radiation from a synchrotron as source of VUV light. Typically, C2H4 present as a minor impurity in samples of C2H6 and C2H5D distorted the absorption cross section in curves of C2H6 and C2H5D in the onset region. We completely eliminated C2H4 from C2H6 and C2H5D using adsorption on activated Pd/charcoal at 195 K. By this means, we detected no C2H4 in samples of C2H6 and C2H5D according to their absorption spectra. The detection limit of C2H4 in C2H6 and C2H5D is less than 0.03 ppm with VUV absorption spectroscopy. 相似文献
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P. P. Olodovskii 《Journal of Engineering Physics and Thermophysics》2001,74(1):243-249
Based on a number of methods (adsorption, diffusion, IR spectroscopy) the author calculated the binding energy of cesium137 and strontium90 in disperse systems in the presence of hydroxonium ions and with their being removed and evaluated the transfer of radionuclides from soil to plants. 相似文献