The purpose of the present experimental work is to investigate the performance （1 ton） refrigeration system using nano-refrigerant. Nano-refrigerant is alumina （v-A1203） nanopartcal with size （20-30） nm is dispe...The purpose of the present experimental work is to investigate the performance （1 ton） refrigeration system using nano-refrigerant. Nano-refrigerant is alumina （v-A1203） nanopartcal with size （20-30） nm is dispersed into R-134a with volume fraction 0.01% and 0.02%. The experimental test rig consists of horizontal double tube counter flow heat exchanger fabricated of copper. The nano-refrigerant is evaporated inside the inner tube because of the heat gain from hot water passing in the annulus surrounding the inner tube. The experimental results indicate, when increasing the volume concentration of A1203 refrigerant by 0.01% and 0.02%, the heat transfer coefficient increases by 0.54% to 1.1%. The thermal conductivity increases by 11.5% and 14.2%, respectively, while the coefficient of performance increases by 3.33% to 12%, respectively. The heat transfer rate in the refrigeration side is enhancement about 6.7% to 21.4% compared with conventional refrigerant, and the power consumption by compressor is decreased by nearly 1.6% and 3.3%, respectively.展开更多
Highly ordered nanowire/tube arrays of Ni0.5Zn0.5Fe2O4were fabricated by the sol-gel method in the pores of anodic alumina membrane （AAM）. Whether nanowires or nanotubes were fabricated depends on immersion time. Th...Highly ordered nanowire/tube arrays of Ni0.5Zn0.5Fe2O4were fabricated by the sol-gel method in the pores of anodic alumina membrane （AAM）. Whether nanowires or nanotubes were fabricated depends on immersion time. The immersion time was 15- 40 s for nanotubes and over 60 s for nanowires. The topography and crystalline structure of the nanowire arrays were characterized by scanning electron microscopy （SEM）, transmission electron microscopy （TEM）, and X-ray diffraction （XRD）. It was found that the length and diameter of the Ni0.5Zn0.5Fe2O4 nanowires are related to the thickness of the AAM and the diameter of the pores. The results indicated that the Ni0.5Zn0.5Fe2O4 nanowires are uniform and parallel to each other.展开更多
Pure alumina ceramic tube and 95 alumina ceramic （the ceramic with 95.84% alumina） tube were prepared by using self-prepared alumina micrometer powder without agglomeration as raw material. The ceramic green was sha...Pure alumina ceramic tube and 95 alumina ceramic （the ceramic with 95.84% alumina） tube were prepared by using self-prepared alumina micrometer powder without agglomeration as raw material. The ceramic green was shaped by isostatic pressing and sintered at different temperature from 800 to 1 600 ℃ for 2 h. The 95 ceramic tube sintered at 1 550 ℃ for 2 h had mean particle size of 4 μm, bend strength of 437 MPa and volume density of 3.714 g/cm3. Shape memory effect during sintering was observed. XRD results showed that no phase transition occurred during shape memory process, which indicated that shape memory effect was not caused by phase transition. Several probable causes of the alumina ceramic shape memory effect were discussed in this paper.展开更多
文摘The purpose of the present experimental work is to investigate the performance （1 ton） refrigeration system using nano-refrigerant. Nano-refrigerant is alumina （v-A1203） nanopartcal with size （20-30） nm is dispersed into R-134a with volume fraction 0.01% and 0.02%. The experimental test rig consists of horizontal double tube counter flow heat exchanger fabricated of copper. The nano-refrigerant is evaporated inside the inner tube because of the heat gain from hot water passing in the annulus surrounding the inner tube. The experimental results indicate, when increasing the volume concentration of A1203 refrigerant by 0.01% and 0.02%, the heat transfer coefficient increases by 0.54% to 1.1%. The thermal conductivity increases by 11.5% and 14.2%, respectively, while the coefficient of performance increases by 3.33% to 12%, respectively. The heat transfer rate in the refrigeration side is enhancement about 6.7% to 21.4% compared with conventional refrigerant, and the power consumption by compressor is decreased by nearly 1.6% and 3.3%, respectively.
文摘Highly ordered nanowire/tube arrays of Ni0.5Zn0.5Fe2O4were fabricated by the sol-gel method in the pores of anodic alumina membrane （AAM）. Whether nanowires or nanotubes were fabricated depends on immersion time. The immersion time was 15- 40 s for nanotubes and over 60 s for nanowires. The topography and crystalline structure of the nanowire arrays were characterized by scanning electron microscopy （SEM）, transmission electron microscopy （TEM）, and X-ray diffraction （XRD）. It was found that the length and diameter of the Ni0.5Zn0.5Fe2O4 nanowires are related to the thickness of the AAM and the diameter of the pores. The results indicated that the Ni0.5Zn0.5Fe2O4 nanowires are uniform and parallel to each other.
基金Funded by the Natural Science Foundation of Guangxi University for Nationalities(Nos.200702YJ19 and 2008ZD011)National Natural Science Foundation of China(No.51172049)+2 种基金Special Prophase Project of 973 Program Research of China(No.2012CB722804)Guangxi Higher Education Institutes Talent Highland Innovation Team Scheme(No.GJR201147-12)Construction Project of Key Laboratory of Chemical and Biological Transformation Process of Guangxi Higher Education Institutes(No.GJKY20129)
文摘Pure alumina ceramic tube and 95 alumina ceramic （the ceramic with 95.84% alumina） tube were prepared by using self-prepared alumina micrometer powder without agglomeration as raw material. The ceramic green was shaped by isostatic pressing and sintered at different temperature from 800 to 1 600 ℃ for 2 h. The 95 ceramic tube sintered at 1 550 ℃ for 2 h had mean particle size of 4 μm, bend strength of 437 MPa and volume density of 3.714 g/cm3. Shape memory effect during sintering was observed. XRD results showed that no phase transition occurred during shape memory process, which indicated that shape memory effect was not caused by phase transition. Several probable causes of the alumina ceramic shape memory effect were discussed in this paper.
