The hydraulic and thermal transients in pipeline flow were studied. The method of characteristics for hydraulic transient analysis of batch transport of pipeline flow had been improved. The thermal transient equation,...The hydraulic and thermal transients in pipeline flow were studied. The method of characteristics for hydraulic transient analysis of batch transport of pipeline flow had been improved. The thermal transient equation, in which the term with v 3 was involved, had been inferred, while the corresponding method of characteristics was constructed. The double method of characteristics, which can be used to study the coherent hydraulic-thermal transients of batch transport of pipeline flow, was developed.展开更多
Thermal conductivity is an important material parameter of silicon when studying the performance and reliability of devices or for guiding circuit design when considering heat dissipation, especially when the self-hea...Thermal conductivity is an important material parameter of silicon when studying the performance and reliability of devices or for guiding circuit design when considering heat dissipation, especially when the self-heating effect becomes prominent in ultra-scaled MOSFETs.The cross-plane thermal conductivity of a thin silicon film is lacking due to the difficulty in sensing high thermal conductivity in the vertical direction.In this paper, a feasible method that utilizes an ultra-fast electrical pulse within 20 μs combined with the hot strip technique is adopted.To the best of our knowledge, this is the first work that shows how to extract the cross-plane thermal conductivity of sub-50 nm(30 nm, 17 nm, and 10 nm)silicon films on buried oxide.The ratio of the extracted cross-plane thermal conductivity of the silicon films over the bulk value is only about 6.9%, 4.3%, and 3.8% at 300 K, respectively.As the thickness of the films is smaller than the phonon mean free path, the classical heat transport theory fails to predict the heat dissipation in nanoscale transistors.Thus, in this study, a ballistic model, derived from the heat transport equation based on extended-irreversible-hydrodynamics(EIT), is used for further investigation, and the simulation results exhibit good consistence with the experimental data.The extracted effective thermal data could provide a good reference for precise device simulations and thermoelectric applications.展开更多
This paper uses finite element method to obtain the three-dimensional temperature field of laser-induced transient thermal grating （TTG） for two-layered structure of diamond film on ZnSe substrate. The numerical res...This paper uses finite element method to obtain the three-dimensional temperature field of laser-induced transient thermal grating （TTG） for two-layered structure of diamond film on ZnSe substrate. The numerical results indicate that unique two-times heating process is gradually experienced in the area between two adjacent grating stripes. However, there is a little change for the temperature field along the depth direction for the diamond film due to its great thermal conductivity. It further finds that the thickness of the diamond film has a significant influence on the temperature field in diamond/ZnSe system. The results are useful for the application of laser-induced TTG technique in film/substrate system.展开更多
We report a numerical simulation of continuous terahertz beam induced transient thermal effects on static water. The terahertz wave used in this paper has a Gaussian beam profile. Based on the transient heat conductio...We report a numerical simulation of continuous terahertz beam induced transient thermal effects on static water. The terahertz wave used in this paper has a Gaussian beam profile. Based on the transient heat conduction equation, the finite element method （FEM） is utilized to calculate the temperature distribution. The simulation results show the dynamic process of temperature change in water during terahertz irradiation. After about 300 s, the temperature reaches a steady state with a water layer thickness of 5 mm and a beam radius of 0.25 mm. The highest temperature increase is 7 K/mW approximately. This work motivates further study on the interaction between terahertz wave and bio-tissue, which has a high water content.展开更多
The accurate analyses for a plate fin heat sink with the ability to control the temperature of the avionics devices within a pre-set controllable temperature range are required both in the process of circuit design an...The accurate analyses for a plate fin heat sink with the ability to control the temperature of the avionics devices within a pre-set controllable temperature range are required both in the process of circuit design and for the real-time temperature monitoring purposes. In order to provide an insight into the behavior of the temperature of a plate fin heat sink subjected non-uniform heat density on the surfaces, it is necessary to obtain accurate analytical solutions yielding explicit formulas relating the dissipated power to the temperature rise at any point of avionics devices. This paper presents a method for thermal simulation of a plate fin heat sink using an analytical solution of the three-dimensional heat equation resulting from an appropriate plate fin heat sink transient thermal model. The entire solution methodology is illustrated in detail on the particular examples of the plate fin heat sink subjected non-uniform heat density on the surfaces. The transient temperature profiles are obtained for different positions at the surface of the plate fin heat sink. The analytical results are compared with measurements made on the surface of the cold plate and it is found that they are in good agreement with an error of less than 3 K.展开更多
Power Electronic (PE) will play an essential role in future drive concepts. Nowadays, mainly water/glycol-based cooling media are used to cool PE. Due to their high electrical conductivity (EC), water/glycol-based coo...Power Electronic (PE) will play an essential role in future drive concepts. Nowadays, mainly water/glycol-based cooling media are used to cool PE. Due to their high electrical conductivity (EC), water/glycol-based coolants cannot be used for direct cooling of the electrical components. Direct cooling concepts with dedicated transmission fluids show potential usage of fluid in direct contact with electrified parts. This results in special requirements for the fluids and materials. The aimed action as a coolant requires a defined measurement and characterization of fluid properties and heat transfer in order to assess the cooling ability of a fluid. The purpose of the work was to develop a new measurement setup based on the thermal transient method with which the thermal requirements of cooling fluids for a direct cooling concept can be assessed. With this method, relevant transmission fluids have been tested and the thermal performance compared to indirect cooling effect of water/glycol is discussed. The result of the work is that the measurement method is very well suited for the application-related evaluation of the fluids. Direct oil cooling with transmission fluids could increase heat transfer coefficient by a factor of 3 to 8, compared to the indirect cooing with water/glycol as cooling media.展开更多
PVC/CdS nanocomposites have been prepared by solution casting method taking 2, 4, 6 and 8 wt% of CdS nanoparticles. PVC/CdS nanocomposites were characterized through TEM measurement. The measurement of effective therm...PVC/CdS nanocomposites have been prepared by solution casting method taking 2, 4, 6 and 8 wt% of CdS nanoparticles. PVC/CdS nanocomposites were characterized through TEM measurement. The measurement of effective thermal conductivity of PVC/CdS nanocomposites has also been done using transient plane source (TPS) method. The effects of concentration of CdS nanoparticles and temperature on the effective thermal conductivity of polymer PVC/CdS nanocomposites have been studied. The variation of effective thermal conductivity with the concentration of filler particles and temperature has also been discussed in terms of dispersion of filler particles into polymer matrix and phonon scattering mechanism, respectively.展开更多
We have reported a method for measuring the thermal conductivity of liguids un-der high pressure previously [1,2].Such data are necessary for improving thetechnologies such like processing as acidity,pressure cracking...We have reported a method for measuring the thermal conductivity of liguids un-der high pressure previously [1,2].Such data are necessary for improving thetechnologies such like processing as acidity,pressure cracking,thermal exploitation ofpetroleum,etc. An apparatus has thus been constructed,as shown schematically in Fig.1,tomeasure the thermal conductivity of liquids under pressure up to 25 MPa and temperatureranging from 150 to 250℃.The thermal conductivity cell is cylindrical in from,35mmin length and 25mm in inner diameter.The sample is poured into the cell through展开更多
针对油浸式电力变压器瞬态温升计算效率过低的问题,该文提出本征正交分解-αATS(proper orthogonal decomposition-adaptive time stepping based onαfactor,POD-αATS)降阶自适应变步长瞬态计算方法。首先,推导变压器绕组瞬态温升计...针对油浸式电力变压器瞬态温升计算效率过低的问题,该文提出本征正交分解-αATS(proper orthogonal decomposition-adaptive time stepping based onαfactor,POD-αATS)降阶自适应变步长瞬态计算方法。首先,推导变压器绕组瞬态温升计算的有限元离散方程;其次,采用POD降阶算法改善传统瞬态计算中存在的条件数过大及方程阶数过高的问题;同时对于瞬态计算中的时间步长选择问题,提出适用于非线性问题的αATS变步长策略;然后,为验证方法的有效性,基于110 kV油浸式电力变压器绕组的基本结构建立二维八分区数值计算模型,同时将计算结果与基于110 kV绕组的温升实验结果进行对比。数值计算及实验结果表明,所提算法与全阶定步长算法在流场和温度场中的精度几乎相同,且流场计算效率提升约45倍,温度场计算效率提升约38倍,计算速度得到显著提高。这一点在温升实验中同样得到验证,说明该文所提算法的准确性、高效性及一定的工程实用性。展开更多
This article deals with the characterization of local materials used in insulation building heat. These materials are bricks of earth compressed and stabilized with rice husks. Thermal conductivity, the specific heat ...This article deals with the characterization of local materials used in insulation building heat. These materials are bricks of earth compressed and stabilized with rice husks. Thermal conductivity, the specific heat and the thermal diffusivity of materials based on clay incorporating rate of 0, 2%, 4%, 6%, 8% and 10% are determined. The results showed that the clay blocks + rice balls had better thermal insulators than simple clay blocks. However, these composite materials used for the envelope of the building must have sufficient mechanical resistance when used in construction. The measurement of mechanical properties such as compressive strength showed an improvement of 6% and beyond, a drop in resistance when increasing rice husks in clay is observed. These results allow to specify the optimal conditions of use of these materials for the building envelope.展开更多
文摘The hydraulic and thermal transients in pipeline flow were studied. The method of characteristics for hydraulic transient analysis of batch transport of pipeline flow had been improved. The thermal transient equation, in which the term with v 3 was involved, had been inferred, while the corresponding method of characteristics was constructed. The double method of characteristics, which can be used to study the coherent hydraulic-thermal transients of batch transport of pipeline flow, was developed.
基金Project supported by the Zhejiang Provincial Natural Science Foundation of China(Grant No.LZ19F040001)the National Natural Science Foundation of China(Grant No.61473287)the NSFC–Zhejiang Joint Fund for the Integration of Industrialization Informatization,China(Grant No.U1609213)
文摘Thermal conductivity is an important material parameter of silicon when studying the performance and reliability of devices or for guiding circuit design when considering heat dissipation, especially when the self-heating effect becomes prominent in ultra-scaled MOSFETs.The cross-plane thermal conductivity of a thin silicon film is lacking due to the difficulty in sensing high thermal conductivity in the vertical direction.In this paper, a feasible method that utilizes an ultra-fast electrical pulse within 20 μs combined with the hot strip technique is adopted.To the best of our knowledge, this is the first work that shows how to extract the cross-plane thermal conductivity of sub-50 nm(30 nm, 17 nm, and 10 nm)silicon films on buried oxide.The ratio of the extracted cross-plane thermal conductivity of the silicon films over the bulk value is only about 6.9%, 4.3%, and 3.8% at 300 K, respectively.As the thickness of the films is smaller than the phonon mean free path, the classical heat transport theory fails to predict the heat dissipation in nanoscale transistors.Thus, in this study, a ballistic model, derived from the heat transport equation based on extended-irreversible-hydrodynamics(EIT), is used for further investigation, and the simulation results exhibit good consistence with the experimental data.The extracted effective thermal data could provide a good reference for precise device simulations and thermoelectric applications.
基金Project supported by the National Natural Science Foundation of China (Grant Nos 10374041 and 10574071)
文摘This paper uses finite element method to obtain the three-dimensional temperature field of laser-induced transient thermal grating （TTG） for two-layered structure of diamond film on ZnSe substrate. The numerical results indicate that unique two-times heating process is gradually experienced in the area between two adjacent grating stripes. However, there is a little change for the temperature field along the depth direction for the diamond film due to its great thermal conductivity. It further finds that the thickness of the diamond film has a significant influence on the temperature field in diamond/ZnSe system. The results are useful for the application of laser-induced TTG technique in film/substrate system.
基金supported by the National Basic Research Program of China (Grant Nos. 2007CB310403 and 2007CB310407)the National Natural Science Foundation of China (Grant No. 60801017)
文摘We report a numerical simulation of continuous terahertz beam induced transient thermal effects on static water. The terahertz wave used in this paper has a Gaussian beam profile. Based on the transient heat conduction equation, the finite element method （FEM） is utilized to calculate the temperature distribution. The simulation results show the dynamic process of temperature change in water during terahertz irradiation. After about 300 s, the temperature reaches a steady state with a water layer thickness of 5 mm and a beam radius of 0.25 mm. The highest temperature increase is 7 K/mW approximately. This work motivates further study on the interaction between terahertz wave and bio-tissue, which has a high water content.
基金Aeronautical Science Foundation of China （2008ZC52024）
文摘The accurate analyses for a plate fin heat sink with the ability to control the temperature of the avionics devices within a pre-set controllable temperature range are required both in the process of circuit design and for the real-time temperature monitoring purposes. In order to provide an insight into the behavior of the temperature of a plate fin heat sink subjected non-uniform heat density on the surfaces, it is necessary to obtain accurate analytical solutions yielding explicit formulas relating the dissipated power to the temperature rise at any point of avionics devices. This paper presents a method for thermal simulation of a plate fin heat sink using an analytical solution of the three-dimensional heat equation resulting from an appropriate plate fin heat sink transient thermal model. The entire solution methodology is illustrated in detail on the particular examples of the plate fin heat sink subjected non-uniform heat density on the surfaces. The transient temperature profiles are obtained for different positions at the surface of the plate fin heat sink. The analytical results are compared with measurements made on the surface of the cold plate and it is found that they are in good agreement with an error of less than 3 K.
文摘Power Electronic (PE) will play an essential role in future drive concepts. Nowadays, mainly water/glycol-based cooling media are used to cool PE. Due to their high electrical conductivity (EC), water/glycol-based coolants cannot be used for direct cooling of the electrical components. Direct cooling concepts with dedicated transmission fluids show potential usage of fluid in direct contact with electrified parts. This results in special requirements for the fluids and materials. The aimed action as a coolant requires a defined measurement and characterization of fluid properties and heat transfer in order to assess the cooling ability of a fluid. The purpose of the work was to develop a new measurement setup based on the thermal transient method with which the thermal requirements of cooling fluids for a direct cooling concept can be assessed. With this method, relevant transmission fluids have been tested and the thermal performance compared to indirect cooling effect of water/glycol is discussed. The result of the work is that the measurement method is very well suited for the application-related evaluation of the fluids. Direct oil cooling with transmission fluids could increase heat transfer coefficient by a factor of 3 to 8, compared to the indirect cooing with water/glycol as cooling media.
文摘PVC/CdS nanocomposites have been prepared by solution casting method taking 2, 4, 6 and 8 wt% of CdS nanoparticles. PVC/CdS nanocomposites were characterized through TEM measurement. The measurement of effective thermal conductivity of PVC/CdS nanocomposites has also been done using transient plane source (TPS) method. The effects of concentration of CdS nanoparticles and temperature on the effective thermal conductivity of polymer PVC/CdS nanocomposites have been studied. The variation of effective thermal conductivity with the concentration of filler particles and temperature has also been discussed in terms of dispersion of filler particles into polymer matrix and phonon scattering mechanism, respectively.
文摘We have reported a method for measuring the thermal conductivity of liguids un-der high pressure previously [1,2].Such data are necessary for improving thetechnologies such like processing as acidity,pressure cracking,thermal exploitation ofpetroleum,etc. An apparatus has thus been constructed,as shown schematically in Fig.1,tomeasure the thermal conductivity of liquids under pressure up to 25 MPa and temperatureranging from 150 to 250℃.The thermal conductivity cell is cylindrical in from,35mmin length and 25mm in inner diameter.The sample is poured into the cell through
文摘针对油浸式电力变压器瞬态温升计算效率过低的问题,该文提出本征正交分解-αATS(proper orthogonal decomposition-adaptive time stepping based onαfactor,POD-αATS)降阶自适应变步长瞬态计算方法。首先,推导变压器绕组瞬态温升计算的有限元离散方程;其次,采用POD降阶算法改善传统瞬态计算中存在的条件数过大及方程阶数过高的问题;同时对于瞬态计算中的时间步长选择问题,提出适用于非线性问题的αATS变步长策略;然后,为验证方法的有效性,基于110 kV油浸式电力变压器绕组的基本结构建立二维八分区数值计算模型,同时将计算结果与基于110 kV绕组的温升实验结果进行对比。数值计算及实验结果表明,所提算法与全阶定步长算法在流场和温度场中的精度几乎相同,且流场计算效率提升约45倍,温度场计算效率提升约38倍,计算速度得到显著提高。这一点在温升实验中同样得到验证,说明该文所提算法的准确性、高效性及一定的工程实用性。
文摘This article deals with the characterization of local materials used in insulation building heat. These materials are bricks of earth compressed and stabilized with rice husks. Thermal conductivity, the specific heat and the thermal diffusivity of materials based on clay incorporating rate of 0, 2%, 4%, 6%, 8% and 10% are determined. The results showed that the clay blocks + rice balls had better thermal insulators than simple clay blocks. However, these composite materials used for the envelope of the building must have sufficient mechanical resistance when used in construction. The measurement of mechanical properties such as compressive strength showed an improvement of 6% and beyond, a drop in resistance when increasing rice husks in clay is observed. These results allow to specify the optimal conditions of use of these materials for the building envelope.
