Printed circuit heat exchangers(PCHEs)are considered as the most promising heat exchangers for use of the supercritical carbon dioxide(S-CO_(2))Brayton cycle.As crucial components operating at high pressure and therma...Printed circuit heat exchangers(PCHEs)are considered as the most promising heat exchangers for use of the supercritical carbon dioxide(S-CO_(2))Brayton cycle.As crucial components operating at high pressure and thermal load at the same time,PCHE structural integrity evaluations are essential.In this study,to assess the structural strength of PCHEs serving as recuperators and precoolers in the S-CO_(2) Brayton cycle as a waste heat recovery system for marine engines,the finite element method(FEM)is used and compared with a currently used method from ASME codes.The effects of temperature and pressure on the hot and cold sides are studied in terms of the temperature and pressure differences between the two sides and the main factors affecting its strength discussed.Then,detailed stress intensities of a PCHE under design conditions are investigated,and the results indicate that the highest stress appears at the middle of the semicircular arc of the channel,except for a concentration near the channel tip regions.Stresses of the PCHE are mainly caused by both pressure and temperature differences,with the minimum effect from temperature.The synthesis of the temperature and pressure fields exhibits a complicated action on the total stress under the design conditions.FEM was a more comprehensive means for structural assessment than the method from ASME codes.Further structural optimization of PCHE is conducted to ensure a maximum life span.This research work can provide theoretical guidance for structural integrity assessment of PCHE for the S-CO_(2) Brayton cycle.展开更多
The equivalent circuit with complex physical constants for a piezoelectric ceramic in thickness mode is established. In the equivalent circuit, electric components （equivalent circuit parameters） are connected to re...The equivalent circuit with complex physical constants for a piezoelectric ceramic in thickness mode is established. In the equivalent circuit, electric components （equivalent circuit parameters） are connected to real and imaginary parts of complex physical coefficients of piezoelectric materials. Based on definitions of dissipation factors, three of them （dielectric, elastic and piezoelectric dissipation factors） are represented by equivalent circuit parameters. Since the equivalent circuit parameters are detectable, the dissipation factors can be easily obtained. In the experiments, the temperature and the stress responses of the three dissipation factors are measured.展开更多
A new low leakage 3×VDD-tolerant electrostatic discharge(ESD)detection circuit using only low-voltage device without deep N-well is proposed in a standard 90-nm 1.2-V CMOS process.Stacked-transistors technique is...A new low leakage 3×VDD-tolerant electrostatic discharge(ESD)detection circuit using only low-voltage device without deep N-well is proposed in a standard 90-nm 1.2-V CMOS process.Stacked-transistors technique is adopted to sustain high-voltage stress and reduce leakage current.No NMOSFET operates in high voltage range and it is unnecessary to use any deep N-well.The proposed detection circuit can generate a 38 mA current to turn on the substrate triggered silicon-controlled rectifier(STSCR)under the ESD stress.Under normal operating conditions,all the devices are free from over-stress voltage threat.The leakage current is 88 nA under 3×VDD bias at 25°C.The simulation result shows the circuit can be successfully used for 3×VDD-tolerant I/O buffer.展开更多
基金financially supported by the High-Tech Ship Research Project of Ministry of Industry and Information Technology(No.MIIT[2017]614)the Fundamental Research Funds for the Central Universities(WUT:2021IUA105)。
文摘Printed circuit heat exchangers(PCHEs)are considered as the most promising heat exchangers for use of the supercritical carbon dioxide(S-CO_(2))Brayton cycle.As crucial components operating at high pressure and thermal load at the same time,PCHE structural integrity evaluations are essential.In this study,to assess the structural strength of PCHEs serving as recuperators and precoolers in the S-CO_(2) Brayton cycle as a waste heat recovery system for marine engines,the finite element method(FEM)is used and compared with a currently used method from ASME codes.The effects of temperature and pressure on the hot and cold sides are studied in terms of the temperature and pressure differences between the two sides and the main factors affecting its strength discussed.Then,detailed stress intensities of a PCHE under design conditions are investigated,and the results indicate that the highest stress appears at the middle of the semicircular arc of the channel,except for a concentration near the channel tip regions.Stresses of the PCHE are mainly caused by both pressure and temperature differences,with the minimum effect from temperature.The synthesis of the temperature and pressure fields exhibits a complicated action on the total stress under the design conditions.FEM was a more comprehensive means for structural assessment than the method from ASME codes.Further structural optimization of PCHE is conducted to ensure a maximum life span.This research work can provide theoretical guidance for structural integrity assessment of PCHE for the S-CO_(2) Brayton cycle.
基金Project supported by the National Natural Science Foundation of China （Grant No 50278098）.
文摘The equivalent circuit with complex physical constants for a piezoelectric ceramic in thickness mode is established. In the equivalent circuit, electric components （equivalent circuit parameters） are connected to real and imaginary parts of complex physical coefficients of piezoelectric materials. Based on definitions of dissipation factors, three of them （dielectric, elastic and piezoelectric dissipation factors） are represented by equivalent circuit parameters. Since the equivalent circuit parameters are detectable, the dissipation factors can be easily obtained. In the experiments, the temperature and the stress responses of the three dissipation factors are measured.
基金supported by the National Natural Science Foundation of China (Grant Nos. 61076097,60936005)in part by Cultivation Fund of the Key Scientific and Technical Innovation Project,Ministry of Education of China Program (Grant No. 20110203110012)
文摘A new low leakage 3×VDD-tolerant electrostatic discharge(ESD)detection circuit using only low-voltage device without deep N-well is proposed in a standard 90-nm 1.2-V CMOS process.Stacked-transistors technique is adopted to sustain high-voltage stress and reduce leakage current.No NMOSFET operates in high voltage range and it is unnecessary to use any deep N-well.The proposed detection circuit can generate a 38 mA current to turn on the substrate triggered silicon-controlled rectifier(STSCR)under the ESD stress.Under normal operating conditions,all the devices are free from over-stress voltage threat.The leakage current is 88 nA under 3×VDD bias at 25°C.The simulation result shows the circuit can be successfully used for 3×VDD-tolerant I/O buffer.
