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
As a peptide hormone, CLV3 restricts the stem cell number in shoot apical meristem (SAM) by interacting with CLV1/CLV2/CRN/RPK2 receptor complexes. To elucidate how the function of the CLV3 peptide in SAM maintenanc...As a peptide hormone, CLV3 restricts the stem cell number in shoot apical meristem (SAM) by interacting with CLV1/CLV2/CRN/RPK2 receptor complexes. To elucidate how the function of the CLV3 peptide in SAM maintenance is established at the amino acid (AA) level, alanine substitutions were performed by introducing point mutations to individual residues in the peptide-coding region of CLV3 and its flanking sequences. Constructs carrying such substitutions, expressed under the control of CLV3 regulatory elements, were transformed to the clv3-2 null mutant to evaluate their efficiencies in complementing its defects in SAMs in vivo. These studies showed that aspartate-8, histidine-11, glycine-6, proline-4, arginine-1, and proline-9, arranged in an order of importance, were critical, while threonine-2, valine-3, serine-5, and the previously assigned hydroxylation and arabinosylation residue proline-7 were trivial for the endogenous CLV3 function in SAM maintenance. In contrast, substitutions of flanking residues did not impose much damage on CLV3. Complementation of different alanine-substituted constructs was confirmed by measurements of the sizes of SAMs and the WUS expression levels in transgenic plants. These studies established a complete contribution map of individual residues in the peptide-coding region of CLV3 for its function in SAM, which may help to understand peptide hormones in general.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This work was supported by the Ministry of China (2007CB948200), Chinese of Science and Technology Academy of Sciences (1105000003 and 200904910192008), and the National Natural Science Foundation of China (30821007 and 31000623). ACKNOWLEDGMENTS We thank Dr Trevor L. Wang at the John Innes Centre, UK, for critical reading of the manuscript Prof. Kexue Xu at the Institute of Botany, Chinese Academy of Sciences, for suggestions regarding the statistica~ data analysis and Dr Wei Gao at Beijing Forestry University for discussions of the results. No conflict of interest declared.
文摘As a peptide hormone, CLV3 restricts the stem cell number in shoot apical meristem (SAM) by interacting with CLV1/CLV2/CRN/RPK2 receptor complexes. To elucidate how the function of the CLV3 peptide in SAM maintenance is established at the amino acid (AA) level, alanine substitutions were performed by introducing point mutations to individual residues in the peptide-coding region of CLV3 and its flanking sequences. Constructs carrying such substitutions, expressed under the control of CLV3 regulatory elements, were transformed to the clv3-2 null mutant to evaluate their efficiencies in complementing its defects in SAMs in vivo. These studies showed that aspartate-8, histidine-11, glycine-6, proline-4, arginine-1, and proline-9, arranged in an order of importance, were critical, while threonine-2, valine-3, serine-5, and the previously assigned hydroxylation and arabinosylation residue proline-7 were trivial for the endogenous CLV3 function in SAM maintenance. In contrast, substitutions of flanking residues did not impose much damage on CLV3. Complementation of different alanine-substituted constructs was confirmed by measurements of the sizes of SAMs and the WUS expression levels in transgenic plants. These studies established a complete contribution map of individual residues in the peptide-coding region of CLV3 for its function in SAM, which may help to understand peptide hormones in general.