In this paper, we try to use the entransy theory to analyze the heat–work conversion systems with inner irreversible thermodynamic cycles. First, the inner irreversible thermodynamic cycles are analyzed. The influenc...In this paper, we try to use the entransy theory to analyze the heat–work conversion systems with inner irreversible thermodynamic cycles. First, the inner irreversible thermodynamic cycles are analyzed. The influences of different inner irreversible factors on entransy loss are discussed. We find that the concept of entransy loss can be used to analyze the inner irreversible thermodynamic cycles. Then, we analyze the common heat–work conversion systems with inner irreversible thermodynamic cycles. As an example, the heat–work conversion system in which the working fluid of the thermodynamic cycles is heated and cooled by streams is analyzed. Our analyses show that larger entransy loss leads to larger output work when the total heat flow from the high temperature heat source and the corresponding equivalent temperature are fixed.Some numerical cases are presented, and the results verify the theoretical analyses. On the other hand, it is also found that larger entransy loss does not always lead to larger output work when the preconditions are not satisfied.展开更多
The present work relates to a numerical investigation of double diffusive mixed convection around a horizontal annulus with a finned inner cylinder.The solutal and thermal buoyancy forces are sustained by maintaining ...The present work relates to a numerical investigation of double diffusive mixed convection around a horizontal annulus with a finned inner cylinder.The solutal and thermal buoyancy forces are sustained by maintaining the inner and outer cylinders at uniform temperatures and concentrations.Buoyancy effects are also considered,with the Boussinesq approximation.The forced convection effect is induced by the outer cylinder rotating with an angular velocity(ω)in an anti-clockwise direction.The studies are made for various combinations of dimensionless numbers;buoyancy ratio number(N),Lewis number(Le),Richardson number(Ri)and Grashof number(Gr).The isotherms,isoconcentrations and streamlines as well as both average and local Nusselt and Sherwood numbers were studied.A finite volume scheme is adopted to solve the transport equations for continuity,momentum,energy and mass transfer.The results indicate that the use of fins on the inner cylinder with outer cylinder rotation,significantly improves the heat and mass transfer in the annulus.展开更多
Based on the energy equation of gas-liquid flow in pipeline,the explicit temperature drop formula for gas-liquid steady state calculation was derived.This formula took into consideration the Joule-Thomson effect,impac...Based on the energy equation of gas-liquid flow in pipeline,the explicit temperature drop formula for gas-liquid steady state calculation was derived.This formula took into consideration the Joule-Thomson effect,impact of terrain undulation and heat transfer with the surroundings along the line.Elimination of temperature iteration loop and integration of the explicit temperature equation,instead of enthalpy energy equation,into the conjugated hydraulic and thermal computation have been found to improve the efficiency of algorithm.Then,the inner wall temperature of gas-liquid flow was calculated by using explicit temperature equation and inner wall convective heat transfer coefficient of mixed flow which can be obtained by liquid convective heat transfer coefficient and gas convective heat transfer coefficient on the basis of liquid holdup.The temperature results of gas-liquid flow and inner wall in the case example presented both agree well with those in professional multiphase computational software OLGA.展开更多
Thermal manikin plays important roles in simulating thethermal state of human bodies to facilitate the evaluationof thermal comfort properties of various clothing assem-blies.Based on the heat balance principle and an...Thermal manikin plays important roles in simulating thethermal state of human bodies to facilitate the evaluationof thermal comfort properties of various clothing assem-blies.Based on the heat balance principle and analysis ofrelated factors,the heat production rate of manikin isrecommended as an efficient evaluation index.Whereas,its inside heat production which occurs as a result of theexistence of temperature difference between its insidepart and outside surface,should not be ignored.Through a series of theoretical analysis and calculations,a compensative equation is deduced in this paper.展开更多
A numerical study of heat transfer problem by natural convection of a fluid inside a square cavity with two inner bodies is presented. This subject is of great interest in the engineering area, mainly in applications ...A numerical study of heat transfer problem by natural convection of a fluid inside a square cavity with two inner bodies is presented. This subject is of great interest in the engineering area, mainly in applications involving development of heat exchangers and cooling or heating systems of bodies by natural convection mechanism. Two cases have been studied. The inner bodies are square in case 1 and circular in case 2. In both cases, the bodies are solid and thermally conductive, the cavity lower and upper horizontal surfaces are isothermal with high temperature Th and low temperature Tc, respectively. Both vertical surfaces are adiabatic. A FORTRAN code using Finite Element Method (FEM) is developed to simulate the problem and solve the governing equations. The distributions of stream function, ψ, dimensionless temperature, θ, and vorticity, ω, are determined. Heat transfer is evaluated by analyzing the behavior of the average Nusselt number. The Grashof number and thermal diffusivity ratio are considered in range from 2 × 104 to 105 and from 0.1 to 100, respectively. The fluid is air with Prandtl number fixed in 0.733.展开更多
The effect of inner-surface roughness of conical targets on the generation of fast electrons in the laser-cone interaction is investigated using particle-in-cell simulation. It is found that the surface roughness can ...The effect of inner-surface roughness of conical targets on the generation of fast electrons in the laser-cone interaction is investigated using particle-in-cell simulation. It is found that the surface roughness can reduce the fast-electron number （in the energy range E 〉 1 MeV） and energy, as compared to that from a cone with smooth inner wall. A scaling law for the laser reflectivity based on the vacuum-heating model is derived. Both theory and simulation indicate that laser reflection increases with the height-to-width ratio of the periodic inner surface structure and approaches that of a smooth cone as this ratio becomes zero.展开更多
基金Project supported by the National Natural Science Foundation of China(Grant Nos.51376101 and 51356001)
文摘In this paper, we try to use the entransy theory to analyze the heat–work conversion systems with inner irreversible thermodynamic cycles. First, the inner irreversible thermodynamic cycles are analyzed. The influences of different inner irreversible factors on entransy loss are discussed. We find that the concept of entransy loss can be used to analyze the inner irreversible thermodynamic cycles. Then, we analyze the common heat–work conversion systems with inner irreversible thermodynamic cycles. As an example, the heat–work conversion system in which the working fluid of the thermodynamic cycles is heated and cooled by streams is analyzed. Our analyses show that larger entransy loss leads to larger output work when the total heat flow from the high temperature heat source and the corresponding equivalent temperature are fixed.Some numerical cases are presented, and the results verify the theoretical analyses. On the other hand, it is also found that larger entransy loss does not always lead to larger output work when the preconditions are not satisfied.
文摘The present work relates to a numerical investigation of double diffusive mixed convection around a horizontal annulus with a finned inner cylinder.The solutal and thermal buoyancy forces are sustained by maintaining the inner and outer cylinders at uniform temperatures and concentrations.Buoyancy effects are also considered,with the Boussinesq approximation.The forced convection effect is induced by the outer cylinder rotating with an angular velocity(ω)in an anti-clockwise direction.The studies are made for various combinations of dimensionless numbers;buoyancy ratio number(N),Lewis number(Le),Richardson number(Ri)and Grashof number(Gr).The isotherms,isoconcentrations and streamlines as well as both average and local Nusselt and Sherwood numbers were studied.A finite volume scheme is adopted to solve the transport equations for continuity,momentum,energy and mass transfer.The results indicate that the use of fins on the inner cylinder with outer cylinder rotation,significantly improves the heat and mass transfer in the annulus.
基金Project(2011ZX05000-026-004) supported by the National Science & Technology Specific Program of ChinaProject(2010D-5006-0604) supported by the China National Petroleum Corporation (CNPC) Innovation FoundationProject(51004167) supported by the National Natural Science Foundation of China
文摘Based on the energy equation of gas-liquid flow in pipeline,the explicit temperature drop formula for gas-liquid steady state calculation was derived.This formula took into consideration the Joule-Thomson effect,impact of terrain undulation and heat transfer with the surroundings along the line.Elimination of temperature iteration loop and integration of the explicit temperature equation,instead of enthalpy energy equation,into the conjugated hydraulic and thermal computation have been found to improve the efficiency of algorithm.Then,the inner wall temperature of gas-liquid flow was calculated by using explicit temperature equation and inner wall convective heat transfer coefficient of mixed flow which can be obtained by liquid convective heat transfer coefficient and gas convective heat transfer coefficient on the basis of liquid holdup.The temperature results of gas-liquid flow and inner wall in the case example presented both agree well with those in professional multiphase computational software OLGA.
文摘Thermal manikin plays important roles in simulating thethermal state of human bodies to facilitate the evaluationof thermal comfort properties of various clothing assem-blies.Based on the heat balance principle and analysis ofrelated factors,the heat production rate of manikin isrecommended as an efficient evaluation index.Whereas,its inside heat production which occurs as a result of theexistence of temperature difference between its insidepart and outside surface,should not be ignored.Through a series of theoretical analysis and calculations,a compensative equation is deduced in this paper.
文摘A numerical study of heat transfer problem by natural convection of a fluid inside a square cavity with two inner bodies is presented. This subject is of great interest in the engineering area, mainly in applications involving development of heat exchangers and cooling or heating systems of bodies by natural convection mechanism. Two cases have been studied. The inner bodies are square in case 1 and circular in case 2. In both cases, the bodies are solid and thermally conductive, the cavity lower and upper horizontal surfaces are isothermal with high temperature Th and low temperature Tc, respectively. Both vertical surfaces are adiabatic. A FORTRAN code using Finite Element Method (FEM) is developed to simulate the problem and solve the governing equations. The distributions of stream function, ψ, dimensionless temperature, θ, and vorticity, ω, are determined. Heat transfer is evaluated by analyzing the behavior of the average Nusselt number. The Grashof number and thermal diffusivity ratio are considered in range from 2 × 104 to 105 and from 0.1 to 100, respectively. The fluid is air with Prandtl number fixed in 0.733.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11175030,11175029,91230205,and 11375032)the National High-Tech ICF Committee of China,the National Basic Research Program of China(Grant Nos.2008CB717806 and 2011CB808104)the Science and Technology Foundation of China Academy of Engineering Physics(Grant No.2011A0102008)
文摘The effect of inner-surface roughness of conical targets on the generation of fast electrons in the laser-cone interaction is investigated using particle-in-cell simulation. It is found that the surface roughness can reduce the fast-electron number （in the energy range E 〉 1 MeV） and energy, as compared to that from a cone with smooth inner wall. A scaling law for the laser reflectivity based on the vacuum-heating model is derived. Both theory and simulation indicate that laser reflection increases with the height-to-width ratio of the periodic inner surface structure and approaches that of a smooth cone as this ratio becomes zero.
