A novel vertical graded source tunnel field-effect transistor(VGS-TFET)is proposed to improve device performance.By introducing a source with linearly graded component,the on-state current increases by more than two d...A novel vertical graded source tunnel field-effect transistor(VGS-TFET)is proposed to improve device performance.By introducing a source with linearly graded component,the on-state current increases by more than two decades higher than that of the conventional GaAs TFETs without sacrificing the subthreshold swing(SS)due to the improved band-to-band tunneling efficiency.Compared with the conventional TFETs,much larger drive current range can be achieved by the proposed VGS-TFET with SS below the thermionic limitation of 60 mV/dec.Furthermore,the minimum SS about 20 mV/dec indicates its promising potential for further ultralow power applications.展开更多
In this work exergetical performance analysis is carried out based on the second law of thermodynamics for organic flash cycle(OFC) using a two-phase expander instead of throttle expansion in order to recover efficien...In this work exergetical performance analysis is carried out based on the second law of thermodynamics for organic flash cycle(OFC) using a two-phase expander instead of throttle expansion in order to recover efficiently finite thermal reservoirs.The exergy destructions(anergies) at various components of the system are theoretically investigated as well as the exergy efficiency.Results show that the anergy of heat exchanger or two-phase expander decreases while the anergy of throttle valve increases with increasing flash temperature,and the exergy efficiency has an optimum value with respect to the flash temperature.Under the optimal conditions with respect to the flash temperature,exergy efficiency increases with the heating temperature and the component having the largest exergy destruction varies with the flash temperature or heating temperature.展开更多
Ecological adsorption technology is becoming a focus of attention by industry due to the utilization of low grade thermal energy sources for cooling production. It can be a promising part of sustainable development co...Ecological adsorption technology is becoming a focus of attention by industry due to the utilization of low grade thermal energy sources for cooling production. It can be a promising part of sustainable development concept of the global economy. Therefore, research aiming at improving their performance i.e. Coefficient of Performance(COP) by optimizing the construction of sorption beds with a built in heat exchanger system is crucial. The heat transfer characteristics between the bed of porous media(sorbent) and surface of the heat exchanger system determine the heating power of an adsorption chiller. The HP increase can be obtained by heat transfer intensification due to the increase in the thermal conductivity of the sorbent layer in the vicinity of the heat exchanger's surface. The novel modification of the sorbent layer structure is proposed in the paper in order to improve the heat transfer processes in the heat exchanger boundary layer. The analysis of desorption process conditions in the parametric model of a coated and fixed adsorption bed design is presented in the paper. The computational fluid dynamics(CFD) with conjugate heat transfer analysis is used to determine the crucial input parameters(temperature distribution in the sorbent bed) for further analytical calculations. The commercial code Ansys Fluent was used to perform numerical simulations. The developed computational model consisted of three subdomains representing heating water, heat exchanger material(copper) and sorbent(silica gel). The comparison of a novel coated design and a conventional fixed bed is discussed in the paper. The numerical analysis is based on experimental thermal conductivity measurements of the sorbent layer in different configurations, which were performed using Laser Flash Method.展开更多
基金Project supported by the National Natural Science Foundation of China(Grant No.90304190002).
文摘A novel vertical graded source tunnel field-effect transistor(VGS-TFET)is proposed to improve device performance.By introducing a source with linearly graded component,the on-state current increases by more than two decades higher than that of the conventional GaAs TFETs without sacrificing the subthreshold swing(SS)due to the improved band-to-band tunneling efficiency.Compared with the conventional TFETs,much larger drive current range can be achieved by the proposed VGS-TFET with SS below the thermionic limitation of 60 mV/dec.Furthermore,the minimum SS about 20 mV/dec indicates its promising potential for further ultralow power applications.
基金supported by Research Fund,Kumoh National Institute of Technology
文摘In this work exergetical performance analysis is carried out based on the second law of thermodynamics for organic flash cycle(OFC) using a two-phase expander instead of throttle expansion in order to recover efficiently finite thermal reservoirs.The exergy destructions(anergies) at various components of the system are theoretically investigated as well as the exergy efficiency.Results show that the anergy of heat exchanger or two-phase expander decreases while the anergy of throttle valve increases with increasing flash temperature,and the exergy efficiency has an optimum value with respect to the flash temperature.Under the optimal conditions with respect to the flash temperature,exergy efficiency increases with the heating temperature and the component having the largest exergy destruction varies with the flash temperature or heating temperature.
基金the project:"The development of innovative technology of adsorption chiller NETI?,using special,glued construction of the adsorption beds"(number:POIR.01.01.01-00-1659/15)partially supported by National Science Centre of Poland (Narodowe Centrum Nauki) grant number 2017/01/X/ST8/00019granted by the Faculty of Mathematics and Natural Sciences of Jan Dlugosz University in Czestochowa.
文摘Ecological adsorption technology is becoming a focus of attention by industry due to the utilization of low grade thermal energy sources for cooling production. It can be a promising part of sustainable development concept of the global economy. Therefore, research aiming at improving their performance i.e. Coefficient of Performance(COP) by optimizing the construction of sorption beds with a built in heat exchanger system is crucial. The heat transfer characteristics between the bed of porous media(sorbent) and surface of the heat exchanger system determine the heating power of an adsorption chiller. The HP increase can be obtained by heat transfer intensification due to the increase in the thermal conductivity of the sorbent layer in the vicinity of the heat exchanger's surface. The novel modification of the sorbent layer structure is proposed in the paper in order to improve the heat transfer processes in the heat exchanger boundary layer. The analysis of desorption process conditions in the parametric model of a coated and fixed adsorption bed design is presented in the paper. The computational fluid dynamics(CFD) with conjugate heat transfer analysis is used to determine the crucial input parameters(temperature distribution in the sorbent bed) for further analytical calculations. The commercial code Ansys Fluent was used to perform numerical simulations. The developed computational model consisted of three subdomains representing heating water, heat exchanger material(copper) and sorbent(silica gel). The comparison of a novel coated design and a conventional fixed bed is discussed in the paper. The numerical analysis is based on experimental thermal conductivity measurements of the sorbent layer in different configurations, which were performed using Laser Flash Method.
