A comparative optimal design of fluid-saturated prismatic cellular metal honeycombs （PCMHs） having different cell shapes is presented for thermal management applications. Based on the periodic topology of each PCMH,...A comparative optimal design of fluid-saturated prismatic cellular metal honeycombs （PCMHs） having different cell shapes is presented for thermal management applications. Based on the periodic topology of each PCMH, a unit cell （UC） for thermal transport analysis was selected to calculate its effective thermal conductivity. Without introducing any empirical coefficient, we modified and extended the analytical model of parallel-series thermal-electric network to a wider porosity range （0.7 ~ 0.98） by considering the effects of two-dimensional local heat conduction in solid ligaments inside each UC. Good agreement was achieved between analytical predictions and numerical simulations based on the method of finite volume. The concept of ligament heat conduction efficiency （LTCE） was proposed to physically explain the mechanisms underlying the effects of ligament configuration on effective thermal conductivity （ETC）. Based upon the proposed theory, a construct strategy was developed for designing the ETC by altering the equivalent interaction angle with the direction of heat flow： relatively small average interaction angle for thermal conduction and relatively large one for thermal insulation.展开更多
This paper studies the fracture behavior of a thermoelastic cylinder subjected to a sudden temperature change on its outer surface within the framework of non-classical heat conduction.The heat conduction equation is ...This paper studies the fracture behavior of a thermoelastic cylinder subjected to a sudden temperature change on its outer surface within the framework of non-classical heat conduction.The heat conduction equation is solved by separation of variable technique.Closed form solution for the temperature field and the associated thermal stress are established.The critical parameter governing the level of the transient thermal stress is identified.Exact expression for the transient stress intensity factor is obtained for a crack in the cylinder.The difference between the non-classical solutions and the classical solution are discussed.It is found that the traditional classical heat conduction considerably underestimates the transient thermal stress and thermal stress intensity factor.展开更多
This paper has solved the Chester modified heat conduction equation of the different relaxation time r value under different temperature conditions, different boundary conditions and the different initial conditions b...This paper has solved the Chester modified heat conduction equation of the different relaxation time r value under different temperature conditions, different boundary conditions and the different initial conditions by different means of methods. These solutions can help to obtain temperature field of laser thermal effects.展开更多
We study the size dependency of heat conduction in one-dimensional diatomic FPU-β lattices and establish that for low dimensional material,contribution from optical phonons is found more effective to the thermal cond...We study the size dependency of heat conduction in one-dimensional diatomic FPU-β lattices and establish that for low dimensional material,contribution from optical phonons is found more effective to the thermal conductivity and enhance heat transport in the thermodynamic limit N →∞.For the finite size,thermal conductivity of 1D diatomic lattice is found to be lower than 1D monoatomic chain of the same size made up of the constituent particle of the diatomic chain.For the present 1D diatomic chain,obtained value of power divergent exponent of thermal conductivity0.428±0.001 and diffusion exponent 1.2723 lead to the conclusions that increase in the system size,increases the thermal conductivity and existence of anomalous energy diffusion.Existing numerical data supports our findings.展开更多
The western Sichuan hydrothermal area is located at the northeastern margin of the eastern syntaxis of the Qinghai-Tibet Plateau, which is also the eastern end of the Mediterranean-Himalayan geothermal activity zone. ...The western Sichuan hydrothermal area is located at the northeastern margin of the eastern syntaxis of the Qinghai-Tibet Plateau, which is also the eastern end of the Mediterranean-Himalayan geothermal activity zone. There are 248 warm or hot springs in this area, and 11 have temperatures beyond the local boiling temperature. Most of these hot springs are distributed along the Jinshajiang, Dege-Xiangcheng, Ganzi-Litang, and Xianshuihe faults, forming a NW-SE hydrothermal belt. A geothermal analysis of this high-temperature hydrothermal area is an important basis for understanding the deep geodynamic process of the eastern syntaxis of the Qinghai-Tibet Plateau. In addition, this study offers an a priori view to utilize geothermal resources, which is important in both scientific research and application. We use gravity, magnetic, seismic, and helium isotope data to analyze the crust-mantle heat flow ratio and deep geothermal structure. The results show that the background terrestrial heat flow descends from southwest to northeast. The crustal heat ratio is not more than 60%. The high temperature hydrothermal active is related to crustal dynamics processes. Along the Batang-Litang-Kangding line, the Moho depth increases eastward, which is consistent with the changing Qc/Qm(crustal/mantle heat flow) ratio trend. The geoid in the hydrothermal zone is 4–6 km higher than the surroundings, forming a local "platform". The NW-SE striking local tensile stress zone and uplift structure in the upper and middle crust corresponds with the surface hydrothermal active zone. There is an average Curie Point Depth(CPD) of 19.5–22.5 km in Batang, Litang, and Kangding. The local shear-wave(S-wave) velocity is relatively low in the middle and lower crust. The S-wave shows a low velocity trap(Vs<3.2 km s.1) at 15–30 km, which is considered a high-temperature partial melting magma, the crustal source of the hydrothermal active zone. We conclude that the hydrothermal system in this area can be divided into Batang-type and Kangding-type, both of which rely on a crustal heating cycle of atmospheric precipitation and surface water along the fracture zone. The heat is derived from the middle and lower crust: groundwater penetrates the deep faults bringing geothermal energy back to the surface and forming high-temperature springs.展开更多
The heat transfer property of the powder bed greatly affects the performance of a thermochemical heat storage system. Therefore, an accurate evaluation of effective thermal conductivity （ETC） is a key for developing...The heat transfer property of the powder bed greatly affects the performance of a thermochemical heat storage system. Therefore, an accurate evaluation of effective thermal conductivity （ETC） is a key for developing thermochemical heat storage systems. This paper focuses on the ETCs of commonly used por- ous thermochemical materials, such as MgOJMg（OH）2 and CaOJCa（OH）2 powders, as well as the corre- sponding composites with embedded metal foams. Random sphere-like particles packing （RSPP） method is proposed to reconstruct the microstructures of the powder and micro-scale generation method and computed tomography are adopted for the metal foams. Energy transport equations through porous media are solved by the lattice Boltzmann method （LBM） to obtain ETC. Results obtained using RSPP-LBM method agree with experimental data better than other existing methods. For thermochemical heat stor- age, the variation of ETC during chemical reactions is numerically predicted. Metal foam-embedded ther- rnochemical materials are also studied to evaluate the enhancing effects of the metal foams. Results show that ETC of the powders is dominated by the gas phase, whereas that of the metal foam composites is dominated by the metal Phase.展开更多
A microfluidic chemical solution method is developed for the synthesizing Cu nanofluids. The method replaces batch-based macroreactors in the conventional chemical solution method by continuous-flow microfluidic micro...A microfluidic chemical solution method is developed for the synthesizing Cu nanofluids. The method replaces batch-based macroreactors in the conventional chemical solution method by continuous-flow microfluidic microreactors, thereby enabling the synthesis of nanofluids with various microstructures. The Cu nanofluids synthesized by this technology show a better stability, remaining stable even after more than 100 h standing. The measured thermal conductivity shows that the presence of nanoparticles can either upgrade or downgrade fluid conductivity, a phenomenon predicted by the recent thermal-wave theory of nanofluids.展开更多
This paper demonstrates that we should use two different hierarchic composition methods for the two different types of levels in the AHP. The first method is using the weighted geometric mean to synthesize the judgmen...This paper demonstrates that we should use two different hierarchic composition methods for the two different types of levels in the AHP. The first method is using the weighted geometric mean to synthesize the judgments of alternative-type-level elements, which is the only hierarchic composition method for the alternative-type level in an AHP hierarchy, and the rank is preserved automatically. The second one is using the weighted arithmetic mean to synthesize the priorities of the criteria-type-level elements, which is the only hierarchic composition method for all the criteria-type levels, and rank reversals are allowed.展开更多
基金supported by the National Natural Science Foundation of China(51506160,11472208,11472209)China Post-Doctoral Science Foundation Project(2015M580845)+1 种基金the Fundamental Research Funds for Xi’an Jiaotong University(xjj2015102)the Beijing Key Lab of Heating,Gas Supply,Ventilating and Air Conditioning Engineering(NR2016K01)
文摘A comparative optimal design of fluid-saturated prismatic cellular metal honeycombs （PCMHs） having different cell shapes is presented for thermal management applications. Based on the periodic topology of each PCMH, a unit cell （UC） for thermal transport analysis was selected to calculate its effective thermal conductivity. Without introducing any empirical coefficient, we modified and extended the analytical model of parallel-series thermal-electric network to a wider porosity range （0.7 ~ 0.98） by considering the effects of two-dimensional local heat conduction in solid ligaments inside each UC. Good agreement was achieved between analytical predictions and numerical simulations based on the method of finite volume. The concept of ligament heat conduction efficiency （LTCE） was proposed to physically explain the mechanisms underlying the effects of ligament configuration on effective thermal conductivity （ETC）. Based upon the proposed theory, a construct strategy was developed for designing the ETC by altering the equivalent interaction angle with the direction of heat flow： relatively small average interaction angle for thermal conduction and relatively large one for thermal insulation.
基金supported by the National Natural Science Foundation of China (11172081)Shenzhen Research Innovation Fund,China (JCYJ20120613150312764)
文摘This paper studies the fracture behavior of a thermoelastic cylinder subjected to a sudden temperature change on its outer surface within the framework of non-classical heat conduction.The heat conduction equation is solved by separation of variable technique.Closed form solution for the temperature field and the associated thermal stress are established.The critical parameter governing the level of the transient thermal stress is identified.Exact expression for the transient stress intensity factor is obtained for a crack in the cylinder.The difference between the non-classical solutions and the classical solution are discussed.It is found that the traditional classical heat conduction considerably underestimates the transient thermal stress and thermal stress intensity factor.
基金This work was supported by the National Natural Science Foundation of China(No.60068001)and the Natural Science Foundation of Yunnan Province(No.2000A0021M)and ESF of Yunnan(No.0111054).
文摘This paper has solved the Chester modified heat conduction equation of the different relaxation time r value under different temperature conditions, different boundary conditions and the different initial conditions by different means of methods. These solutions can help to obtain temperature field of laser thermal effects.
基金Computer facility developed under DST-FIST Level–I programme,Department of Science and Technology,Government of India,New Delhi and financial assistance under DRS-SAP-I from University Grants Commission,New Delhi
文摘We study the size dependency of heat conduction in one-dimensional diatomic FPU-β lattices and establish that for low dimensional material,contribution from optical phonons is found more effective to the thermal conductivity and enhance heat transport in the thermodynamic limit N →∞.For the finite size,thermal conductivity of 1D diatomic lattice is found to be lower than 1D monoatomic chain of the same size made up of the constituent particle of the diatomic chain.For the present 1D diatomic chain,obtained value of power divergent exponent of thermal conductivity0.428±0.001 and diffusion exponent 1.2723 lead to the conclusions that increase in the system size,increases the thermal conductivity and existence of anomalous energy diffusion.Existing numerical data supports our findings.
基金supported by the National Natural Science Foundation of China (Grant Nos. 41574074, 41174085, 41430319)the Innovation Team Project of Chinese Academy of Sciences (Grant No. KZZD-EW-TZ-19)the Strategic Pilot Technology of Chinese Academy of Sciences (Grant No. XDA1103010102)
文摘The western Sichuan hydrothermal area is located at the northeastern margin of the eastern syntaxis of the Qinghai-Tibet Plateau, which is also the eastern end of the Mediterranean-Himalayan geothermal activity zone. There are 248 warm or hot springs in this area, and 11 have temperatures beyond the local boiling temperature. Most of these hot springs are distributed along the Jinshajiang, Dege-Xiangcheng, Ganzi-Litang, and Xianshuihe faults, forming a NW-SE hydrothermal belt. A geothermal analysis of this high-temperature hydrothermal area is an important basis for understanding the deep geodynamic process of the eastern syntaxis of the Qinghai-Tibet Plateau. In addition, this study offers an a priori view to utilize geothermal resources, which is important in both scientific research and application. We use gravity, magnetic, seismic, and helium isotope data to analyze the crust-mantle heat flow ratio and deep geothermal structure. The results show that the background terrestrial heat flow descends from southwest to northeast. The crustal heat ratio is not more than 60%. The high temperature hydrothermal active is related to crustal dynamics processes. Along the Batang-Litang-Kangding line, the Moho depth increases eastward, which is consistent with the changing Qc/Qm(crustal/mantle heat flow) ratio trend. The geoid in the hydrothermal zone is 4–6 km higher than the surroundings, forming a local "platform". The NW-SE striking local tensile stress zone and uplift structure in the upper and middle crust corresponds with the surface hydrothermal active zone. There is an average Curie Point Depth(CPD) of 19.5–22.5 km in Batang, Litang, and Kangding. The local shear-wave(S-wave) velocity is relatively low in the middle and lower crust. The S-wave shows a low velocity trap(Vs<3.2 km s.1) at 15–30 km, which is considered a high-temperature partial melting magma, the crustal source of the hydrothermal active zone. We conclude that the hydrothermal system in this area can be divided into Batang-type and Kangding-type, both of which rely on a crustal heating cycle of atmospheric precipitation and surface water along the fracture zone. The heat is derived from the middle and lower crust: groundwater penetrates the deep faults bringing geothermal energy back to the surface and forming high-temperature springs.
基金supported by the National Key Basic Research Program of China (2013CB228303)
文摘The heat transfer property of the powder bed greatly affects the performance of a thermochemical heat storage system. Therefore, an accurate evaluation of effective thermal conductivity （ETC） is a key for developing thermochemical heat storage systems. This paper focuses on the ETCs of commonly used por- ous thermochemical materials, such as MgOJMg（OH）2 and CaOJCa（OH）2 powders, as well as the corre- sponding composites with embedded metal foams. Random sphere-like particles packing （RSPP） method is proposed to reconstruct the microstructures of the powder and micro-scale generation method and computed tomography are adopted for the metal foams. Energy transport equations through porous media are solved by the lattice Boltzmann method （LBM） to obtain ETC. Results obtained using RSPP-LBM method agree with experimental data better than other existing methods. For thermochemical heat stor- age, the variation of ETC during chemical reactions is numerically predicted. Metal foam-embedded ther- rnochemical materials are also studied to evaluate the enhancing effects of the metal foams. Results show that ETC of the powders is dominated by the gas phase, whereas that of the metal foam composites is dominated by the metal Phase.
基金support from the Research Grants Council of Hong Kong (GRF718009 and GRF717508) is gratefully acknowledged
文摘A microfluidic chemical solution method is developed for the synthesizing Cu nanofluids. The method replaces batch-based macroreactors in the conventional chemical solution method by continuous-flow microfluidic microreactors, thereby enabling the synthesis of nanofluids with various microstructures. The Cu nanofluids synthesized by this technology show a better stability, remaining stable even after more than 100 h standing. The measured thermal conductivity shows that the presence of nanoparticles can either upgrade or downgrade fluid conductivity, a phenomenon predicted by the recent thermal-wave theory of nanofluids.
文摘This paper demonstrates that we should use two different hierarchic composition methods for the two different types of levels in the AHP. The first method is using the weighted geometric mean to synthesize the judgments of alternative-type-level elements, which is the only hierarchic composition method for the alternative-type level in an AHP hierarchy, and the rank is preserved automatically. The second one is using the weighted arithmetic mean to synthesize the priorities of the criteria-type-level elements, which is the only hierarchic composition method for all the criteria-type levels, and rank reversals are allowed.
