以R141b制冷剂为基液,Al_2O_3为纳米颗粒,采用两步法制备了质量分数分别为0.2%、0.5%和0.8%的Al_2O_3-R141b纳米制冷剂,并进行了纳米制冷剂及R141b纯制冷剂在水力直径为1.33 mm的矩形微通道内流动沸腾传热实验。实验工况范围:饱和压力为...以R141b制冷剂为基液,Al_2O_3为纳米颗粒,采用两步法制备了质量分数分别为0.2%、0.5%和0.8%的Al_2O_3-R141b纳米制冷剂,并进行了纳米制冷剂及R141b纯制冷剂在水力直径为1.33 mm的矩形微通道内流动沸腾传热实验。实验工况范围:饱和压力为176 k Pa,入口过冷度为6~12℃,体积流量为20~50 L/h,热流密度为11.1~26.6 k W/m^2。实验结果与7个纯工质传热模型、2个纳米制冷剂传热模型进行比较评价。结果发现,在本实验研究范围内,纯工质传热模型不适用于纳米制冷剂传热系数的预测;Peng-Ding纳米制冷剂传热模型与KimMudawar纯工质传热模型组合对纳米制冷剂传热系数的预测值最接近实验值,平均绝对误差为17.22%,且能较好地反映纳米颗粒对流动沸腾传热影响的规律;结合实验数据对Peng-Ding模型的纳米影响因子(纳米制冷剂与纯制冷剂的传热系数之比)关联式进行修正,新关联式具有较好的预测效果,平均绝对误差为15.2%,且与Bertsch模型的组合能较好地预测微通道内纳米制冷剂传热系数,平均绝对误差降为16.4%。展开更多
The use of nanorefrigerants in Organic Rankine Cycle(ORC)units is believed to affect the cycle environment performance,but backed with very few relevant studies.For this purpose,a life cycle assessment(LCA)has been pe...The use of nanorefrigerants in Organic Rankine Cycle(ORC)units is believed to affect the cycle environment performance,but backed with very few relevant studies.For this purpose,a life cycle assessment(LCA)has been performed for the ORC system using nanorefrigerant,the material and energy input,characteristic indicators and comprehensive index of environmental impact,total energy consumption and energy payback time(BPBT)of the whole life cycle of ORC system using Al_(2)O_(3)/R141b nanorefrigerant were calculated.Total environmental comprehensive indexes reveal that ECER-135 index decrease by 1.5%after adding 0.2%Al_(2)O_(3)nanoparticles to R141b.Based on the contribution analysis and sensitivity analysis,it can be found out ORC system manufacturing is of the most critical stage,where,the ECER-135 index of ORC component production is the greatest,followed by the preparation process of R141b,transportation phase,and that of Al_(2)O_(3)nanoparticles preparation is small.The retirement phase which has good environmental benefits affects the result significantly by recycling important materials.Meanwhile,the main cause and relevant suggestion for improvement were traced respectively.Finally,the environmental impacts of various power generations were compared,and results show that the power route is of obvious advantage.Among the renewable energy,ORC system using Al_(2)O_(3)/R141b nanorefrigerant with minimal environmental impact is only 0.67%of coal-fired power generation.The environmental impact of current work is about 14.34%of other nations’PV results.展开更多
In this paper the reliability and performance of a vapour compression refrigeration system with ZnO nanoparticles in the working fluid was investigated experimentally. Nanorefrigerant was synthesized on the basis of t...In this paper the reliability and performance of a vapour compression refrigeration system with ZnO nanoparticles in the working fluid was investigated experimentally. Nanorefrigerant was synthesized on the basis of the concept of the nanofluids, which was prepared by mixing ZnO nanoparticles with R152a refrigerant. The conventional refrigerant R134a has a global warming potential （GWP） of 1300 whereas R152a has a significant reduced value of GWP of 140 only. An experimental test rig is designed and fabricated indigenously in the laboratory to carry out the investigations. ZnO nanopar- ticles with refrigerant mixture were used in HFC R152a refrigeration system. The system performance with nanoparticles was then investigated. The concentration of nano ZnO ranges in the order of 0.1% v, 0.3% v and 0.5%v with particle size of 50nm and 150g of R152a was charged and tests were conducted. The compressor suction pressure, discharge pressure and evaporator temperature were measured. The results indicated that ZnO nanore- frigerant works normally and safely in the system. The ZnO nanoparticle concentration is an important factor considered for heat transfer enhancement in the refrigera- tion system. The performance of the system was significantly improved with 21% less energy consumption when 0.5%v ZnO-R152a refrigerant. Both the suction pressure and discharge pressure were lowered by 10.5% when nanorefrigerant was used. The evaporator tempera- ture was reduced by 6% with the use of nanorefrigerant. Hence ZnO nanoparticles could be used in refrigeration system to considerably reduce energy consumption. The usage of R 152a with zero ozone depleting potential （ODP） and very less GWP and thus provides a green and clean environment. The complete experimental results and their analysis are reported in the main paper.展开更多
为探究热流密度、质量通量和入口过冷度对微细通道流动沸腾压降波动特性的影响,以质量分数为0.8%的纳米制冷剂Al_2O_3-R141b及纯制冷剂R141b为工质在水力直径为1.33 mm的矩形微细通道内进行了流动沸腾实验。结果表明:热流密度从18.2 k W...为探究热流密度、质量通量和入口过冷度对微细通道流动沸腾压降波动特性的影响,以质量分数为0.8%的纳米制冷剂Al_2O_3-R141b及纯制冷剂R141b为工质在水力直径为1.33 mm的矩形微细通道内进行了流动沸腾实验。结果表明:热流密度从18.2 k W/m2增加到25.4 k W/m^2时,工质进出口压降波动更为剧烈;较大质量通量和较高入口过冷度一定程度上可以使压降波动更平缓;与纯制冷剂相比,质量分数为0.8%的纳米制冷剂Al_2O_3-R141b的压降波动较为平缓,其压降标准差最大降低了18%。展开更多
We demonstrate an original method based on controlled oxidation for creating high-quality tunnel junctions between superconducting A1 reservoirs and InAs semiconductor nanowires （NWs）. We show clean tunnel character...We demonstrate an original method based on controlled oxidation for creating high-quality tunnel junctions between superconducting A1 reservoirs and InAs semiconductor nanowires （NWs）. We show clean tunnel characteristics with a current suppression by 〉4 orders of magnitude for a junction bias well below the A1 gap of △0≈ 200 μeV. The experimental data agree well with the Bardeen- Cooper-Schrieffer theoretical expectations for a superconducting tunnel junction. The studied devices employ small-scale tunnel contacts functioning as thermometers as well as larger electrodes that provide proof-of-principle active cooling of the electron distribution in the NWs. A peak refrigeration of approximately δT = 10 mK is achieved at a bath temperature of Tbath≈ 250-350 mK for our prototype devices. This method introduces important perspectives for the investigation of the thermoelectric effects in semiconductor nanostructures and for nanoscale refrigeration.展开更多
文摘以R141b制冷剂为基液,Al_2O_3为纳米颗粒,采用两步法制备了质量分数分别为0.2%、0.5%和0.8%的Al_2O_3-R141b纳米制冷剂,并进行了纳米制冷剂及R141b纯制冷剂在水力直径为1.33 mm的矩形微通道内流动沸腾传热实验。实验工况范围:饱和压力为176 k Pa,入口过冷度为6~12℃,体积流量为20~50 L/h,热流密度为11.1~26.6 k W/m^2。实验结果与7个纯工质传热模型、2个纳米制冷剂传热模型进行比较评价。结果发现,在本实验研究范围内,纯工质传热模型不适用于纳米制冷剂传热系数的预测;Peng-Ding纳米制冷剂传热模型与KimMudawar纯工质传热模型组合对纳米制冷剂传热系数的预测值最接近实验值,平均绝对误差为17.22%,且能较好地反映纳米颗粒对流动沸腾传热影响的规律;结合实验数据对Peng-Ding模型的纳米影响因子(纳米制冷剂与纯制冷剂的传热系数之比)关联式进行修正,新关联式具有较好的预测效果,平均绝对误差为15.2%,且与Bertsch模型的组合能较好地预测微通道内纳米制冷剂传热系数,平均绝对误差降为16.4%。
基金Fund Project in 2020,China(No.KKZ3202052058)and the support of Scientific Research Fund from Yunnan Education Department in China(No.2022J0064).
文摘The use of nanorefrigerants in Organic Rankine Cycle(ORC)units is believed to affect the cycle environment performance,but backed with very few relevant studies.For this purpose,a life cycle assessment(LCA)has been performed for the ORC system using nanorefrigerant,the material and energy input,characteristic indicators and comprehensive index of environmental impact,total energy consumption and energy payback time(BPBT)of the whole life cycle of ORC system using Al_(2)O_(3)/R141b nanorefrigerant were calculated.Total environmental comprehensive indexes reveal that ECER-135 index decrease by 1.5%after adding 0.2%Al_(2)O_(3)nanoparticles to R141b.Based on the contribution analysis and sensitivity analysis,it can be found out ORC system manufacturing is of the most critical stage,where,the ECER-135 index of ORC component production is the greatest,followed by the preparation process of R141b,transportation phase,and that of Al_(2)O_(3)nanoparticles preparation is small.The retirement phase which has good environmental benefits affects the result significantly by recycling important materials.Meanwhile,the main cause and relevant suggestion for improvement were traced respectively.Finally,the environmental impacts of various power generations were compared,and results show that the power route is of obvious advantage.Among the renewable energy,ORC system using Al_(2)O_(3)/R141b nanorefrigerant with minimal environmental impact is only 0.67%of coal-fired power generation.The environmental impact of current work is about 14.34%of other nations’PV results.
文摘In this paper the reliability and performance of a vapour compression refrigeration system with ZnO nanoparticles in the working fluid was investigated experimentally. Nanorefrigerant was synthesized on the basis of the concept of the nanofluids, which was prepared by mixing ZnO nanoparticles with R152a refrigerant. The conventional refrigerant R134a has a global warming potential （GWP） of 1300 whereas R152a has a significant reduced value of GWP of 140 only. An experimental test rig is designed and fabricated indigenously in the laboratory to carry out the investigations. ZnO nanopar- ticles with refrigerant mixture were used in HFC R152a refrigeration system. The system performance with nanoparticles was then investigated. The concentration of nano ZnO ranges in the order of 0.1% v, 0.3% v and 0.5%v with particle size of 50nm and 150g of R152a was charged and tests were conducted. The compressor suction pressure, discharge pressure and evaporator temperature were measured. The results indicated that ZnO nanore- frigerant works normally and safely in the system. The ZnO nanoparticle concentration is an important factor considered for heat transfer enhancement in the refrigera- tion system. The performance of the system was significantly improved with 21% less energy consumption when 0.5%v ZnO-R152a refrigerant. Both the suction pressure and discharge pressure were lowered by 10.5% when nanorefrigerant was used. The evaporator tempera- ture was reduced by 6% with the use of nanorefrigerant. Hence ZnO nanoparticles could be used in refrigeration system to considerably reduce energy consumption. The usage of R 152a with zero ozone depleting potential （ODP） and very less GWP and thus provides a green and clean environment. The complete experimental results and their analysis are reported in the main paper.
文摘为探究热流密度、质量通量和入口过冷度对微细通道流动沸腾压降波动特性的影响,以质量分数为0.8%的纳米制冷剂Al_2O_3-R141b及纯制冷剂R141b为工质在水力直径为1.33 mm的矩形微细通道内进行了流动沸腾实验。结果表明:热流密度从18.2 k W/m2增加到25.4 k W/m^2时,工质进出口压降波动更为剧烈;较大质量通量和较高入口过冷度一定程度上可以使压降波动更平缓;与纯制冷剂相比,质量分数为0.8%的纳米制冷剂Al_2O_3-R141b的压降波动较为平缓,其压降标准差最大降低了18%。
文摘We demonstrate an original method based on controlled oxidation for creating high-quality tunnel junctions between superconducting A1 reservoirs and InAs semiconductor nanowires （NWs）. We show clean tunnel characteristics with a current suppression by 〉4 orders of magnitude for a junction bias well below the A1 gap of △0≈ 200 μeV. The experimental data agree well with the Bardeen- Cooper-Schrieffer theoretical expectations for a superconducting tunnel junction. The studied devices employ small-scale tunnel contacts functioning as thermometers as well as larger electrodes that provide proof-of-principle active cooling of the electron distribution in the NWs. A peak refrigeration of approximately δT = 10 mK is achieved at a bath temperature of Tbath≈ 250-350 mK for our prototype devices. This method introduces important perspectives for the investigation of the thermoelectric effects in semiconductor nanostructures and for nanoscale refrigeration.
