A systematic study of coupled heat and mass transfer in unsaturated soils under complex boundary conditions was carried out and a mathematical model of heat and mass transfer in unsaturated soils was established by no...A systematic study of coupled heat and mass transfer in unsaturated soils under complex boundary conditions was carried out and a mathematical model of heat and mass transfer in unsaturated soils was established by non equilibrium thermodynamic theory. The gradient of volumetric moisture content, the gradient of temperature, the salt mass concentration and vapor pressure were the primary driving forces influencing the process of heat and mass transfer in unsaturated soils. Based on the thermodynamic analysis and the mass and energy conservation principles, a set of mass and energy equations were developed. The initial and boundary conditions of soil column for one dimension were also given out.展开更多
A new generation conical spray system for conventional diesel engines or premixed combustion diesel engines is introduced. By means of oriented impingement method, flexible spray penetration in design is realized. Hig...A new generation conical spray system for conventional diesel engines or premixed combustion diesel engines is introduced. By means of oriented impingement method, flexible spray penetration in design is realized. High-speed photograph was used to investigate the spatial distribution characteristics of the new spray for cases of different impingement angles and needle valve opening pressures. The results show that, by applying spray impingement orientation, fuel jets spread along the cone surface as shape of sectors, so the dispersion of jets is increased obviously. Changing on impingement angle leads to variation of penetration, which is critical in homogeneous mixture preparation. Due to the flexibility of spray penetration in design, the spray impingement on liner is avoided in a great extent. The results also indicate that higher needle valve opening pressure results in longer penetration and larger spray angle after impingement. Combustion characteristics of the impinged conical spray were studied in the 1135 type diesel engine. The new impinged conical spray system work smoothly in full load range with better fuel economy and lower emissions of NOx and soot than the original test engine.展开更多
In this paper, using fractal theory3 the geometric structure of real soil was described with its sectionview and section particle area fractal dimension d of porous media was counted. The volumetric solidcontent and t...In this paper, using fractal theory3 the geometric structure of real soil was described with its sectionview and section particle area fractal dimension d of porous media was counted. The volumetric solidcontent and the relation between volumetric solid content and porous media particle arrangementsas well as measure scale were obtainted. A heat conduction model was established and the effectivethermal conductivity of real soil based on the volumetric solid content was calculated.展开更多
Close-contact melting processes of phase change material (PCM) inside vertical cylindrical capsule are studied. PCM are heated by the capsule isothermally at the bottom and side. The theoretical formulas of the meltin...Close-contact melting processes of phase change material (PCM) inside vertical cylindrical capsule are studied. PCM are heated by the capsule isothermally at the bottom and side. The theoretical formulas of the melting rate and thickness of liquid layer during the heat transfer process are obtained by analysis, which are convenient for engineering predictions. Finally, the factors that affect melting are discussed, and conclusions are drawn.展开更多
The stability of the Karmen vortex street in gas-liquid two-phase flow wasstudied experimentally and theoretically. The values of the parameter h/l characterizing the vortexsirect structure (i. e. , the ratio of the v...The stability of the Karmen vortex street in gas-liquid two-phase flow wasstudied experimentally and theoretically. The values of the parameter h/l characterizing the vortexsirect structure (i. e. , the ratio of the vortex street width to the distance between two vortexes)for a stable vortex street in gas-liquid two-phase flow were obtained for the first lime. Theparameter h/l was proved to be a variable, not a constant as in single-phase flow, h/l is related tothe upstream fluid void fraction. In gas-liquid two-phase fluid flow to form a steady vortex streetis more difficult than in a single-phase fluid flow. Because in the unsteady vortex shedding thevortex shedding band frequency is broader than the one in the single phase fluid flow, so it iseasier to induce the cross-cylinder resonance than in the single phase fluid flow, and this caseshould give rise to the attention of engineers.展开更多
A general numerical method is presented for calculating steady three-dimensional and two-phase turbulent reactive flows with a nonstaggered body-fitted coordinate system in an annular gas turbine combustor with the du...A general numerical method is presented for calculating steady three-dimensional and two-phase turbulent reactive flows with a nonstaggered body-fitted coordinate system in an annular gas turbine combustor with the dump diffuser. The modified two-equation model and the EDC turbulent combustion model are used for the gas phase. The liquid phase equations are solved in a Lagrangian frame of reference by PSIC algorithm. The effect of different velocity profiles at the entry of the prediffuser on combustor flow characteristics is calculated.展开更多
Fully developed turbulence measurements in pipe flow were made in theReynolds number range from 10 X 10~3 to 350 X 10~3 with hot-wire anemometer and a Pilot tube.Comparisons were made with the experimental results of ...Fully developed turbulence measurements in pipe flow were made in theReynolds number range from 10 X 10~3 to 350 X 10~3 with hot-wire anemometer and a Pilot tube.Comparisons were made with the experimental results of previous researchers. The mean velocityprofile and the turbulent intensity in the experiments indicate that for the mean velocity profile,in the fully developed turbulent pipe flow, von Karman's constant κ is a function of the Reynoldsnumber, i. e. κ increases slowly with the Reynolds number. For turbulent pipe flow, the outer limitdepends on whether the Kdrmdn number R^+ is greater or less than 850 in the centerline velocityprofile: a log law exists for 850 < R^+< 1750 in the experiment, and von Karman' s constant κ isshown to be 0. 408. Under the effects of the test trip at the inlet, fully developed turbulence wasobtained in pipe flow at lower Reynolds number when the entrance length (x/D) was larger than 40. Inthe experiment it was also found that turbulence quantities in pipe flow remain independent of theupstream conditions when the trip blockage ratio is higher than 20%, and the comparison with channelwater flow was also performed.展开更多
A more general model describing PCM close-contact melting outside a hot sphere is devel0ped withthe aid of introducing a parameter a and presenting a supplementary equation for the first time in thispaper. The governi...A more general model describing PCM close-contact melting outside a hot sphere is devel0ped withthe aid of introducing a parameter a and presenting a supplementary equation for the first time in thispaper. The governing integral-differential equations are solved by numerical method. The melt-filmthickness variation along the surface of sphere is obtained reasonably due to the consideration of theinterface shape more precisely. The calculation results of Peclet number, heat transferred and pressuredistribution are also compared with that in literature. The model presented in this paper can describethe whole close-contact region and the whole contact melting process. Closeeontact melting in spher-ical or cylindrical capsules to which the model can be extended is also discussed brielly.展开更多
The wall temperature distribution of the flame tube of the combustion chamber is strongly affected by the combustion,radiation and flow.The interaction of these influential factors forms a coupling system.In this pape...The wall temperature distribution of the flame tube of the combustion chamber is strongly affected by the combustion,radiation and flow.The interaction of these influential factors forms a coupling system.In this paper,a new method,which is different from the previous methods,has been developed for calculating the temperature distribution of the flame tube wall together with the flow field inside and outside the flame tube. In the calculation,the combustion,heat radiation,cooling air film and injection stream mixing inside the flame tube as well as the secondary air flowing outside the flame tube have been simulated.The calculation,in this paper,uses the SIMPLE algorithm,the k -εturbulence model and the auto-adjustable damping method.By using this method,the 3-D temperature distribution of the flame tube wall of the combustion chamber of an aeroengine has been simulated successfully.The calculation results are compared to the experimental data.The error of wall temperature is less than 10%.展开更多
An experimental investigation on the fluidization and drying characteristics of sliced food products in a centrifugal fluidized bed dryer was carried out. The rotating speed ranges from 300 rpm to 500 rpm.Sliced potat...An experimental investigation on the fluidization and drying characteristics of sliced food products in a centrifugal fluidized bed dryer was carried out. The rotating speed ranges from 300 rpm to 500 rpm.Sliced potato and radish were used as the testing materials. The results show that the sliced materials can be fluidised well in the centrifugal fluidized bed. The fiuidized curve has a maximum value and the critical fiuidised velocities Vary with the type of the test material, its shape and dimension as well as operating parameters. The sliced food materials can be dried very well and fast in the ceotrifugal fiuidised bed with a large productivity. The factors that influence the drying process were examined and discussed. The final shape and inner structure of the dried products were observed.The water recovery characteristics of the dried products were also investigated.展开更多
This paper presents a new method for in-line and in-situ particle sizing based on the Light Fluctuation Method, including the development of a novel optical probe capable of measuring particle size and concentration i...This paper presents a new method for in-line and in-situ particle sizing based on the Light Fluctuation Method, including the development of a novel optical probe capable of measuring particle size and concentration in the broad range of 10~1000 microns.展开更多
The primary wind of a low-NO_x coaxial swirling burner was visualized byusing glycol as smog tracer. The information of the visual flow field was input into a computerthrough image-capturing card with CCD camera as th...The primary wind of a low-NO_x coaxial swirling burner was visualized byusing glycol as smog tracer. The information of the visual flow field was input into a computerthrough image-capturing card with CCD camera as the image-capturing element. The boundary of thevisual zone, i. e. , the interface of the primary wind and secondary wind was obtained by imageprocessing. The fractal dimension (FD) of the boundary was examined and found to vary from 1. 10 to1. 40 with S_1, S_2 and ζ_1 . It is concluded that when FD is small, the complex level of theinterface is low, and mixture between the primary and secondary wind is weak near the exit of theburner at the initial phase of combustion resulting in stratified flow; when FD is big, mixturebecomes strong near the exit of the burner. It is showed that the flow with FD ranging from 1.10 to1. 20 is stratified flow, which is benefical to reduce NO_x yield and the flow with FD from 1. 25 to1. 40 is mixed flow, producing much NO_x. The mechanism of the forming of stratified flow and mixedflow was theoretically analyzed. The corresponding S_1 , S_2 and ζ_1 of these flows were given.展开更多
Numerical solutions for fully developed laminar flow in internally finned tubes with trapezoidal and triangular fin profiles were given with Finite Element Method (FEM): The heat transfer characteristics were obtained...Numerical solutions for fully developed laminar flow in internally finned tubes with trapezoidal and triangular fin profiles were given with Finite Element Method (FEM): The heat transfer characteristics were obtained and compared under the boundary conditions of uniform heat flux, uniform wall temperature, and the third boundary condition with finite wall thermal conductivity considered. The numerical results show that boundary conditions have pronounced effects on the temperature field.Furthermore, a new mechanism on the heat transfer augmentation of internally finned tubes is proposed.展开更多
Natural convection heat transfer in a horizontal enclosure filled with anisotropic porous media,being isothermally heated at bettom and cooled at top while the vertical walls being adiabatic, is numerically studied by...Natural convection heat transfer in a horizontal enclosure filled with anisotropic porous media,being isothermally heated at bettom and cooled at top while the vertical walls being adiabatic, is numerically studied by applying the Brinkman model-a modified form of Darcy model giving consideration to the viscous effect. The results show that:(1)a larger permeability ratio (K*) causes a lower flow intensity in the enclosure and a smaller Nusselt number, all Nusselt numbers approach unity in the limit of K* → ∞;a larger thermal conductivity ratio (λ*) causes a stranger distortion of isotherms in the enclosure and a higher flow velocity near the walls, all the Nusselt numbers approach unity in the limit of λ*→0; the permeability and thermal conductivity ratios generally have opposing effects on the Nusselt number. (2) an increasing Darcy number decreases the flow intensity and heat transfer rates,which is more significant at a lower permeability ratio. In particular, with K*0.25, the Nusselt number for Da=10-3 would differ from that of Darcy flow up to an amount of 30%, an analysis neglecting the non-Darican effect will inevitably be of considerable error.展开更多
An imaginary plane method for calculation of radiative heat trensfer and its application in the freeboard of AFBC boiler is presented in this paper. The combustion reaction and particle concentration are taken into ac...An imaginary plane method for calculation of radiative heat trensfer and its application in the freeboard of AFBC boiler is presented in this paper. The combustion reaction and particle concentration are taken into account in this method. With is method, one-dimensional freeboard model for radiative heat transfer has been made. Results from this model have been compared with the experimental results of a 130 t/h AFBC boiler. The distribution of flue gas temperature and heat flux at the waterwell are obtained. It is shown that this model has the advantage of good accuracy and requiring less computation time. The applicability of the predicted results in the AFBC boiler design and operation was also discussed.展开更多
A simple theoretical equation of state is derived by applying the Tower-Well potential model about the molecular distribution based on the generalized van der Waals partition function. It needs only three molecular pa...A simple theoretical equation of state is derived by applying the Tower-Well potential model about the molecular distribution based on the generalized van der Waals partition function. It needs only three molecular parameters which have distinct physical meanings. The resulting equation of state predicts rather well the Vapor pressures, saturate liquid volumes, saturated vapor volumes and PVT thermodynamic properties of polar and structurally complex molecules over a wide temperature and pressure range.展开更多
In this paper, a local simulation method is employed to investigate the heat transfer and pressure dropcharacteristics of two configurations of pin finned tubes deployed in an in-line array. In this research,heat pipe...In this paper, a local simulation method is employed to investigate the heat transfer and pressure dropcharacteristics of two configurations of pin finned tubes deployed in an in-line array. In this research,heat pipes are adopted as heating elements. Therefore, the experimental equipment becomes simpleand has an advantage of sufficient reducibility. The air-side heat transfer and pressure drop correlations for each type of pin fin surface including the effect of the tube-row number are obtained in theReynolds number range commonly encountered in engineering. These correlations may be used in thedesign of pin finned tube heat exchangers.展开更多
An equation of atomization quantity from energy dissipation by hydraulic jumpwas derived from dimensional analysis. Applying the Gauss diffusion equation, the spray diffusionin valley was studied under the conditions ...An equation of atomization quantity from energy dissipation by hydraulic jumpwas derived from dimensional analysis. Applying the Gauss diffusion equation, the spray diffusionin valley was studied under the conditions of continuous line source and random wind direction.Considering the spray-rain switching process, coagulation, condensation and evaporation of droplets,the authors calculated the air temperature, air relative humidity, spray density and the rainfallintensity in the lower reaches. The 3-D numerical results agree well with portotype monitoring data.展开更多
A new instrument was developed for measuring the local moisture content in moist porous media based on the needle-type capacitance sensor and single-chip microprocessor technique. The working principle, the structure ...A new instrument was developed for measuring the local moisture content in moist porous media based on the needle-type capacitance sensor and single-chip microprocessor technique. The working principle, the structure and characteristics of the hardware and software of the instrument were presented. The dynamic response characteristics and reliability of the instrument were experimentally determined. As an example, the instrument was employed to measure the heat and mass transport properties of a moist porous material. The experimental results show that the instrument can be used for measuring the local moisture content in moist porous media and would be an effective tool for determining the heat and mass transport properties in moist porous media.展开更多
文摘A systematic study of coupled heat and mass transfer in unsaturated soils under complex boundary conditions was carried out and a mathematical model of heat and mass transfer in unsaturated soils was established by non equilibrium thermodynamic theory. The gradient of volumetric moisture content, the gradient of temperature, the salt mass concentration and vapor pressure were the primary driving forces influencing the process of heat and mass transfer in unsaturated soils. Based on the thermodynamic analysis and the mass and energy conservation principles, a set of mass and energy equations were developed. The initial and boundary conditions of soil column for one dimension were also given out.
文摘A new generation conical spray system for conventional diesel engines or premixed combustion diesel engines is introduced. By means of oriented impingement method, flexible spray penetration in design is realized. High-speed photograph was used to investigate the spatial distribution characteristics of the new spray for cases of different impingement angles and needle valve opening pressures. The results show that, by applying spray impingement orientation, fuel jets spread along the cone surface as shape of sectors, so the dispersion of jets is increased obviously. Changing on impingement angle leads to variation of penetration, which is critical in homogeneous mixture preparation. Due to the flexibility of spray penetration in design, the spray impingement on liner is avoided in a great extent. The results also indicate that higher needle valve opening pressure results in longer penetration and larger spray angle after impingement. Combustion characteristics of the impinged conical spray were studied in the 1135 type diesel engine. The new impinged conical spray system work smoothly in full load range with better fuel economy and lower emissions of NOx and soot than the original test engine.
文摘In this paper, using fractal theory3 the geometric structure of real soil was described with its sectionview and section particle area fractal dimension d of porous media was counted. The volumetric solidcontent and the relation between volumetric solid content and porous media particle arrangementsas well as measure scale were obtainted. A heat conduction model was established and the effectivethermal conductivity of real soil based on the volumetric solid content was calculated.
文摘Close-contact melting processes of phase change material (PCM) inside vertical cylindrical capsule are studied. PCM are heated by the capsule isothermally at the bottom and side. The theoretical formulas of the melting rate and thickness of liquid layer during the heat transfer process are obtained by analysis, which are convenient for engineering predictions. Finally, the factors that affect melting are discussed, and conclusions are drawn.
基金This work was supported by the S and T Development Fund of Shanghai Municipal Commission of Education (Grant No: 01I03)the Natural Science Key Project of Basic Research of China (Grant No: G1999022308)the Fund of the Key Rising Discipline of Shanghai
文摘The stability of the Karmen vortex street in gas-liquid two-phase flow wasstudied experimentally and theoretically. The values of the parameter h/l characterizing the vortexsirect structure (i. e. , the ratio of the vortex street width to the distance between two vortexes)for a stable vortex street in gas-liquid two-phase flow were obtained for the first lime. Theparameter h/l was proved to be a variable, not a constant as in single-phase flow, h/l is related tothe upstream fluid void fraction. In gas-liquid two-phase fluid flow to form a steady vortex streetis more difficult than in a single-phase fluid flow. Because in the unsteady vortex shedding thevortex shedding band frequency is broader than the one in the single phase fluid flow, so it iseasier to induce the cross-cylinder resonance than in the single phase fluid flow, and this caseshould give rise to the attention of engineers.
文摘A general numerical method is presented for calculating steady three-dimensional and two-phase turbulent reactive flows with a nonstaggered body-fitted coordinate system in an annular gas turbine combustor with the dump diffuser. The modified two-equation model and the EDC turbulent combustion model are used for the gas phase. The liquid phase equations are solved in a Lagrangian frame of reference by PSIC algorithm. The effect of different velocity profiles at the entry of the prediffuser on combustor flow characteristics is calculated.
文摘Fully developed turbulence measurements in pipe flow were made in theReynolds number range from 10 X 10~3 to 350 X 10~3 with hot-wire anemometer and a Pilot tube.Comparisons were made with the experimental results of previous researchers. The mean velocityprofile and the turbulent intensity in the experiments indicate that for the mean velocity profile,in the fully developed turbulent pipe flow, von Karman's constant κ is a function of the Reynoldsnumber, i. e. κ increases slowly with the Reynolds number. For turbulent pipe flow, the outer limitdepends on whether the Kdrmdn number R^+ is greater or less than 850 in the centerline velocityprofile: a log law exists for 850 < R^+< 1750 in the experiment, and von Karman' s constant κ isshown to be 0. 408. Under the effects of the test trip at the inlet, fully developed turbulence wasobtained in pipe flow at lower Reynolds number when the entrance length (x/D) was larger than 40. Inthe experiment it was also found that turbulence quantities in pipe flow remain independent of theupstream conditions when the trip blockage ratio is higher than 20%, and the comparison with channelwater flow was also performed.
文摘A more general model describing PCM close-contact melting outside a hot sphere is devel0ped withthe aid of introducing a parameter a and presenting a supplementary equation for the first time in thispaper. The governing integral-differential equations are solved by numerical method. The melt-filmthickness variation along the surface of sphere is obtained reasonably due to the consideration of theinterface shape more precisely. The calculation results of Peclet number, heat transferred and pressuredistribution are also compared with that in literature. The model presented in this paper can describethe whole close-contact region and the whole contact melting process. Closeeontact melting in spher-ical or cylindrical capsules to which the model can be extended is also discussed brielly.
文摘The wall temperature distribution of the flame tube of the combustion chamber is strongly affected by the combustion,radiation and flow.The interaction of these influential factors forms a coupling system.In this paper,a new method,which is different from the previous methods,has been developed for calculating the temperature distribution of the flame tube wall together with the flow field inside and outside the flame tube. In the calculation,the combustion,heat radiation,cooling air film and injection stream mixing inside the flame tube as well as the secondary air flowing outside the flame tube have been simulated.The calculation,in this paper,uses the SIMPLE algorithm,the k -εturbulence model and the auto-adjustable damping method.By using this method,the 3-D temperature distribution of the flame tube wall of the combustion chamber of an aeroengine has been simulated successfully.The calculation results are compared to the experimental data.The error of wall temperature is less than 10%.
文摘An experimental investigation on the fluidization and drying characteristics of sliced food products in a centrifugal fluidized bed dryer was carried out. The rotating speed ranges from 300 rpm to 500 rpm.Sliced potato and radish were used as the testing materials. The results show that the sliced materials can be fluidised well in the centrifugal fluidized bed. The fiuidized curve has a maximum value and the critical fiuidised velocities Vary with the type of the test material, its shape and dimension as well as operating parameters. The sliced food materials can be dried very well and fast in the ceotrifugal fiuidised bed with a large productivity. The factors that influence the drying process were examined and discussed. The final shape and inner structure of the dried products were observed.The water recovery characteristics of the dried products were also investigated.
文摘This paper presents a new method for in-line and in-situ particle sizing based on the Light Fluctuation Method, including the development of a novel optical probe capable of measuring particle size and concentration in the broad range of 10~1000 microns.
文摘The primary wind of a low-NO_x coaxial swirling burner was visualized byusing glycol as smog tracer. The information of the visual flow field was input into a computerthrough image-capturing card with CCD camera as the image-capturing element. The boundary of thevisual zone, i. e. , the interface of the primary wind and secondary wind was obtained by imageprocessing. The fractal dimension (FD) of the boundary was examined and found to vary from 1. 10 to1. 40 with S_1, S_2 and ζ_1 . It is concluded that when FD is small, the complex level of theinterface is low, and mixture between the primary and secondary wind is weak near the exit of theburner at the initial phase of combustion resulting in stratified flow; when FD is big, mixturebecomes strong near the exit of the burner. It is showed that the flow with FD ranging from 1.10 to1. 20 is stratified flow, which is benefical to reduce NO_x yield and the flow with FD from 1. 25 to1. 40 is mixed flow, producing much NO_x. The mechanism of the forming of stratified flow and mixedflow was theoretically analyzed. The corresponding S_1 , S_2 and ζ_1 of these flows were given.
文摘Numerical solutions for fully developed laminar flow in internally finned tubes with trapezoidal and triangular fin profiles were given with Finite Element Method (FEM): The heat transfer characteristics were obtained and compared under the boundary conditions of uniform heat flux, uniform wall temperature, and the third boundary condition with finite wall thermal conductivity considered. The numerical results show that boundary conditions have pronounced effects on the temperature field.Furthermore, a new mechanism on the heat transfer augmentation of internally finned tubes is proposed.
文摘Natural convection heat transfer in a horizontal enclosure filled with anisotropic porous media,being isothermally heated at bettom and cooled at top while the vertical walls being adiabatic, is numerically studied by applying the Brinkman model-a modified form of Darcy model giving consideration to the viscous effect. The results show that:(1)a larger permeability ratio (K*) causes a lower flow intensity in the enclosure and a smaller Nusselt number, all Nusselt numbers approach unity in the limit of K* → ∞;a larger thermal conductivity ratio (λ*) causes a stranger distortion of isotherms in the enclosure and a higher flow velocity near the walls, all the Nusselt numbers approach unity in the limit of λ*→0; the permeability and thermal conductivity ratios generally have opposing effects on the Nusselt number. (2) an increasing Darcy number decreases the flow intensity and heat transfer rates,which is more significant at a lower permeability ratio. In particular, with K*0.25, the Nusselt number for Da=10-3 would differ from that of Darcy flow up to an amount of 30%, an analysis neglecting the non-Darican effect will inevitably be of considerable error.
文摘An imaginary plane method for calculation of radiative heat trensfer and its application in the freeboard of AFBC boiler is presented in this paper. The combustion reaction and particle concentration are taken into account in this method. With is method, one-dimensional freeboard model for radiative heat transfer has been made. Results from this model have been compared with the experimental results of a 130 t/h AFBC boiler. The distribution of flue gas temperature and heat flux at the waterwell are obtained. It is shown that this model has the advantage of good accuracy and requiring less computation time. The applicability of the predicted results in the AFBC boiler design and operation was also discussed.
文摘A simple theoretical equation of state is derived by applying the Tower-Well potential model about the molecular distribution based on the generalized van der Waals partition function. It needs only three molecular parameters which have distinct physical meanings. The resulting equation of state predicts rather well the Vapor pressures, saturate liquid volumes, saturated vapor volumes and PVT thermodynamic properties of polar and structurally complex molecules over a wide temperature and pressure range.
文摘In this paper, a local simulation method is employed to investigate the heat transfer and pressure dropcharacteristics of two configurations of pin finned tubes deployed in an in-line array. In this research,heat pipes are adopted as heating elements. Therefore, the experimental equipment becomes simpleand has an advantage of sufficient reducibility. The air-side heat transfer and pressure drop correlations for each type of pin fin surface including the effect of the tube-row number are obtained in theReynolds number range commonly encountered in engineering. These correlations may be used in thedesign of pin finned tube heat exchangers.
文摘An equation of atomization quantity from energy dissipation by hydraulic jumpwas derived from dimensional analysis. Applying the Gauss diffusion equation, the spray diffusionin valley was studied under the conditions of continuous line source and random wind direction.Considering the spray-rain switching process, coagulation, condensation and evaporation of droplets,the authors calculated the air temperature, air relative humidity, spray density and the rainfallintensity in the lower reaches. The 3-D numerical results agree well with portotype monitoring data.
文摘A new instrument was developed for measuring the local moisture content in moist porous media based on the needle-type capacitance sensor and single-chip microprocessor technique. The working principle, the structure and characteristics of the hardware and software of the instrument were presented. The dynamic response characteristics and reliability of the instrument were experimentally determined. As an example, the instrument was employed to measure the heat and mass transport properties of a moist porous material. The experimental results show that the instrument can be used for measuring the local moisture content in moist porous media and would be an effective tool for determining the heat and mass transport properties in moist porous media.
