Lithium heat pipes have broad applications in heat pipe cooling reactors and hypersonic vehicles owing to their ultra-high working temperature.In particular,when the length of the lithium heat pipe is ultra-long,the f...Lithium heat pipes have broad applications in heat pipe cooling reactors and hypersonic vehicles owing to their ultra-high working temperature.In particular,when the length of the lithium heat pipe is ultra-long,the flow and heat transfer characteristics are more complex.In this study,an improved lumped parameter model that considers the Marangoni effect,bending effect,and different vapor flow patterns and Mach numbers was developed.Thereafter,the proposed model was verified using the University of New Mexico’s Heat Pipe and HTPIPE models.Finally,the verified model was applied to simulate the steady-state operation of an ultra-long lithium heat pipe in a Heat PipeSegmented Thermoelectric Module Converters space reactor.Based on the results:(1)Vapor thermal resistance was dominant at low heating power and decreased with increasing heating power.The vapor flow inside the heat pipe developed from the laminar to the turbulent phase,whereas the liquid phase in the heat pipe was always laminar.(2)The vapor pressure drop caused by bending was approximately 22–23%of the total,and the bending effect on the liquid pressure drop could be ignored.(3)The Marangoni effect reduced the capillary limit by hindering the liquid reflux,especially at low vapor temperatures.Without considering the Marangoni effect,the capillary limit of the lithium heat pipe was overestimated by 9%when the vapor temperature was 1400 K.(4)The total thermal resistance of the heat pipe significantly increased with increasing adiabatic length when the vapor temperature was low.Further,the wick dryness increased with increasing adiabatic length at any vapor temperature.Such findings improve on current knowledge for the optimal design and safety analysis of a heat pipe reactor,which adopts ultra-long lithium heat pipes.展开更多
This paper introduces a new approach for the determination of the source region of beat wave(BW)modulation.This type of modulation is achieved by transmitting high-frequency(HF)continuous waves with a frequency differ...This paper introduces a new approach for the determination of the source region of beat wave(BW)modulation.This type of modulation is achieved by transmitting high-frequency(HF)continuous waves with a frequency difference f,where f is the frequency of modulated ELF/VLF(extremely low frequency/very low frequency)waves from two sub-arrays of a high power HF transmitter.Despite the advantages of BW modulation in terms of generating more stable ELF/VLF signal and high modulation efficiency,there exists a controversy on the physical mechanism of BW and its source region.In this paper,the two controversial theories,i.e.,BW based on D-E region thermal nonlinearity and BW based on F region ponderomotive nonlinearity are examined for cases where each of these two theories exists exclusively or both of them exist simultaneously.According to the analysis and simulation results presented in this paper,it is found that the generated VLF signal amplitude exhibits significant variation as a function of HF frequency in different source regions.Therefore,this characteristic can be utilized as a potential new approach to determine the physical mechanism and source location of BW.展开更多
The Indian Test Blanket Module（TBM） program in ITER is one of the major steps in its fusion reactor program towards DEMO and the future fusion power reactor vision. Research and development（RD） is focused on two t...The Indian Test Blanket Module（TBM） program in ITER is one of the major steps in its fusion reactor program towards DEMO and the future fusion power reactor vision. Research and development（RD） is focused on two types of breeding blanket concepts： lead–lithium ceramic breeder（LLCB） and helium-cooled ceramic breeder（HCCB） blanket systems for the DEMO reactor. As part of the ITER-TBM program, the LLCB concept will be tested in one-half of ITER port no. 2, whose materials and technologies will be tested during ITER operation. The HCCB concept is a variant of the solid breeder blanket, which is presently part of our domestic RD program for DEMO relevant technology development. In the HCCB concept Li_2TiO_3 and beryllium are used as the tritium breeder and neutron multiplier, respectively, in the form of a packed bed having edge-on configuration with reduced activation ferritic martensitic steel as the structural material. In this paper two design schemes, mainly two different orientations of pebble beds, are discussed. In the current concept（case-1）, the ceramic breeder beds are kept horizontal in the toroidal–radial direction. Due to gravity, the pebbles may settle down at the bottom and create a finite gap between the pebbles and the top cooling plate, which will affect the heat transfer between them. In the alternate design concept（case-2）, the pebble bed is vertically（poloidal–radial） orientated where the side plates act as cooling plates instead of top and bottom plates. These two design variants are analyzed analytically and 2 D thermal-hydraulic simulation studies are carried out with ANSYS, using the heat loads obtained from neutronic calculations.Based on the analysis the performance is compared and details of the thermal and radiative heat transfer studies are also discussed in this paper.展开更多
We experimentally observe that Si micro-ring modulator（MRM） modulation characteristics are strongly influenced by the modulation data rate and the data pattern and determine this influence is due to the temperature ...We experimentally observe that Si micro-ring modulator（MRM） modulation characteristics are strongly influenced by the modulation data rate and the data pattern and determine this influence is due to the temperature increase caused by dynamic power dissipation within the Si MRM device. We also quantitatively determine the amount of Si MRM resonance wavelength shift due to different modulation data rates, data patterns, and modulation voltages. Our results should be of great help for achieving reliable and optimal modulation characteristics for Si MRMs.展开更多
基金the CASHIPS Director’s Fund(No.YZJJ2021QN36)the Key Research Program of the Chinese Academy of Sciences(No.ZDRW-KT-2019-1-0202).
文摘Lithium heat pipes have broad applications in heat pipe cooling reactors and hypersonic vehicles owing to their ultra-high working temperature.In particular,when the length of the lithium heat pipe is ultra-long,the flow and heat transfer characteristics are more complex.In this study,an improved lumped parameter model that considers the Marangoni effect,bending effect,and different vapor flow patterns and Mach numbers was developed.Thereafter,the proposed model was verified using the University of New Mexico’s Heat Pipe and HTPIPE models.Finally,the verified model was applied to simulate the steady-state operation of an ultra-long lithium heat pipe in a Heat PipeSegmented Thermoelectric Module Converters space reactor.Based on the results:(1)Vapor thermal resistance was dominant at low heating power and decreased with increasing heating power.The vapor flow inside the heat pipe developed from the laminar to the turbulent phase,whereas the liquid phase in the heat pipe was always laminar.(2)The vapor pressure drop caused by bending was approximately 22–23%of the total,and the bending effect on the liquid pressure drop could be ignored.(3)The Marangoni effect reduced the capillary limit by hindering the liquid reflux,especially at low vapor temperatures.Without considering the Marangoni effect,the capillary limit of the lithium heat pipe was overestimated by 9%when the vapor temperature was 1400 K.(4)The total thermal resistance of the heat pipe significantly increased with increasing adiabatic length when the vapor temperature was low.Further,the wick dryness increased with increasing adiabatic length at any vapor temperature.Such findings improve on current knowledge for the optimal design and safety analysis of a heat pipe reactor,which adopts ultra-long lithium heat pipes.
基金supported by the National Natural Science Foundation of China(Grant No.41804149)China Scholarship Council。
文摘This paper introduces a new approach for the determination of the source region of beat wave(BW)modulation.This type of modulation is achieved by transmitting high-frequency(HF)continuous waves with a frequency difference f,where f is the frequency of modulated ELF/VLF(extremely low frequency/very low frequency)waves from two sub-arrays of a high power HF transmitter.Despite the advantages of BW modulation in terms of generating more stable ELF/VLF signal and high modulation efficiency,there exists a controversy on the physical mechanism of BW and its source region.In this paper,the two controversial theories,i.e.,BW based on D-E region thermal nonlinearity and BW based on F region ponderomotive nonlinearity are examined for cases where each of these two theories exists exclusively or both of them exist simultaneously.According to the analysis and simulation results presented in this paper,it is found that the generated VLF signal amplitude exhibits significant variation as a function of HF frequency in different source regions.Therefore,this characteristic can be utilized as a potential new approach to determine the physical mechanism and source location of BW.
文摘The Indian Test Blanket Module（TBM） program in ITER is one of the major steps in its fusion reactor program towards DEMO and the future fusion power reactor vision. Research and development（RD） is focused on two types of breeding blanket concepts： lead–lithium ceramic breeder（LLCB） and helium-cooled ceramic breeder（HCCB） blanket systems for the DEMO reactor. As part of the ITER-TBM program, the LLCB concept will be tested in one-half of ITER port no. 2, whose materials and technologies will be tested during ITER operation. The HCCB concept is a variant of the solid breeder blanket, which is presently part of our domestic RD program for DEMO relevant technology development. In the HCCB concept Li_2TiO_3 and beryllium are used as the tritium breeder and neutron multiplier, respectively, in the form of a packed bed having edge-on configuration with reduced activation ferritic martensitic steel as the structural material. In this paper two design schemes, mainly two different orientations of pebble beds, are discussed. In the current concept（case-1）, the ceramic breeder beds are kept horizontal in the toroidal–radial direction. Due to gravity, the pebbles may settle down at the bottom and create a finite gap between the pebbles and the top cooling plate, which will affect the heat transfer between them. In the alternate design concept（case-2）, the pebble bed is vertically（poloidal–radial） orientated where the side plates act as cooling plates instead of top and bottom plates. These two design variants are analyzed analytically and 2 D thermal-hydraulic simulation studies are carried out with ANSYS, using the heat loads obtained from neutronic calculations.Based on the analysis the performance is compared and details of the thermal and radiative heat transfer studies are also discussed in this paper.
基金supported by the National Research Foundation of Korea grant funded by the Korean Ministry of Science,ICT and Future Planning(No.2015R1A2A2A01007772)the Materials andParts Technology R&D Program funded by the Korean Ministry of Trade,Industry&Energy(Project No.10065666)
文摘We experimentally observe that Si micro-ring modulator（MRM） modulation characteristics are strongly influenced by the modulation data rate and the data pattern and determine this influence is due to the temperature increase caused by dynamic power dissipation within the Si MRM device. We also quantitatively determine the amount of Si MRM resonance wavelength shift due to different modulation data rates, data patterns, and modulation voltages. Our results should be of great help for achieving reliable and optimal modulation characteristics for Si MRMs.
