The differential equations of continuum mechanics are the basis of an uncountable variety of phenomena and technological processes in fluid-dynamics and related fields.These equations contain derivatives of the first ...The differential equations of continuum mechanics are the basis of an uncountable variety of phenomena and technological processes in fluid-dynamics and related fields.These equations contain derivatives of the first order with respect to time.The derivation of the equations of continuum mechanics uses the limit transitions of the tendency of the volume increment and the time increment to zero.Derivatives are used to derive the wave equation.The differential wave equation is second order in time.Therefore,increments of volume and increments of time in continuum mechanics should be considered as small but finite quantities for problems of wave formation.This is important for calculating the generation of sound waves and water hammer waves.Therefore,the Euler continuity equation with finite time increments is of interest.The finiteness of the time increment makes it possible to take into account the quadratic and cubic invariants of the strain rate tensor.This is a new branch in hydrodynamics.Quadratic and cubic invariants will be used in differential wave equations of the second and third order in time.展开更多
Six surfaces were prepared with defferent surface division patterns for the experimental investigationof steam condensation heat transfer characteristics for dropwise and filmwise coexisting(DFC)condensationsurfaces u...Six surfaces were prepared with defferent surface division patterns for the experimental investigationof steam condensation heat transfer characteristics for dropwise and filmwise coexisting(DFC)condensationsurfaces under atmospheric pressure Dropwise condensation(DWC)was promoted with an ultrathin polytetrafluoroethylene(PTFE)film,which was prepared by the dynamic ion-beam mixed implantation(DIMI)method.The results showed that the condensation phenomena at the intersection between the dropwise andfilmwise condensation regios were quite different for different relative positions of the dropwise and filmwisecondensation regions.The experimental results revealed that the condensation heat transfer characteristics werehighly influenced by the surface division number and the relative area ratio of the dropwise and filmwise conden-sation regions.The impact of thesc findings on heat transfer enhancement mechanism for condensation heattransfer is discussed in detail.展开更多
We discuss a bifurcation phenomenon of Marangoni flow in a microchannel T-junction and its novel unidirectional pumping effect.The T-junction is formed by a main channel connected with a liquid reservoir and a side ch...We discuss a bifurcation phenomenon of Marangoni flow in a microchannel T-junction and its novel unidirectional pumping effect.The T-junction is formed by a main channel connected with a liquid reservoir and a side channel outlet to the atmosphere.A volatizing meniscus is formed in the side channel and Marangoni convections are generated due to the non-uniform evaporation on the meniscus.It is found for weak evaporations (Ma < 270) the Marangoni convections are symmetrical.However,for intense evaporations (Ma > 270),the initial inward symmetrical Marangoni convection becomes unstable and converted into one single vortex flow.Moreover,the single vortex induces a steady unidirectional flow in the main channel,acting like a pump.展开更多
In this paper the self-regeneration process of the mixed resins consisting of cationand anion ion exchangers in the electrolialyser of the packed bed is analyzed and anelectric regeneration method is put forward to su...In this paper the self-regeneration process of the mixed resins consisting of cationand anion ion exchangers in the electrolialyser of the packed bed is analyzed and anelectric regeneration method is put forward to supply the desalinated water by mixedbed The electric regeneration technology is a new one used for regeneration of theexhausted ion exchangers in the mixed bed instead of the traditional regeneratingprocess by using acid and abc liquor Electric energy is consumed to regenerat theion exchangers loaded by salts from water treatment without any chemicals- acid alkali. The advantage of the electric regeneration process edibited convenientoperation, no discharge any waste, and therefore no Polluted to the recehang waterbode and the environmental ground展开更多
Analytically solving a three-dimensional （3-D） bioheat transfer problem with phase change during a freezing process is extremely difficult but theoretically important. The moving heat source model and the Green func...Analytically solving a three-dimensional （3-D） bioheat transfer problem with phase change during a freezing process is extremely difficult but theoretically important. The moving heat source model and the Green function method are introduced to deal with the cryopreservation process of in vitro biomaterials. Exact solutions for the 3-D temperature transients of tissues under various boundary conditions, such as totally convective cooling, totally fixed temperature cooling and a hybrid between them on tissue surfaces, are obtained. Furthermore, the cryosurgical process in living tissues subject to freezing by a single or multiple cryoprobes is also analytically solved. A closed-form analytical solution to the bioheat phase change process is derived by considering contributions from blood perfusion heat transfer, metabolic heat generation, and heat sink of a cryoprobe. The present method is expected to have significant value for analytically solving complex bioheat transfer problems with phase change.展开更多
In this paper, detailed optical of the solar parabolic dish concentrator is presented. The system has diameter D = 2,800 mm and focal length f = 1,400 mm. The efficient conversion of solar radiation in heat at these t...In this paper, detailed optical of the solar parabolic dish concentrator is presented. The system has diameter D = 2,800 mm and focal length f = 1,400 mm. The efficient conversion of solar radiation in heat at these temperature levels requires a use of concentrating solar collectors. In this paper, detailed optical design of the solar parabolic dish concentrator is presented. The parabolic dish of the solar system consists from 12 curvilinear trapezoidal reflective petals. This paper presents optical simulations of the parabolic solar concentrator unit using the ray-tracing software TracePro. The total flux on receiver and the distribution of irradiance for absorbed flux on center and periphery receiver are given. The total flux at the focal region is 4,031.3 W. The goal of this paper is to present optical design of a low-tech solar concentrator, that can be used as a potentially low-cost tool for laboratory-scale research on the medium-temperature thermal processes, cooling, industrial processes, solar cooking and polygeneration systems, etc.展开更多
The fact that the temperature of living tissue may respond oscillatorily to externalheating has been a classical difficulty in the field of bioheat transfer for a long time.Roemer et al. have carefully discussed this ...The fact that the temperature of living tissue may respond oscillatorily to externalheating has been a classical difficulty in the field of bioheat transfer for a long time.Roemer et al. have carefully discussed this in their serial articles, but experiments did notsupport their conclusions, Tharp et al. have artificially made a time-delay differential equs-tion to describe this phenomenon, but their model is short of a strict theoretical founda-展开更多
The classical power law non-Newtonian fluids energy boundary layer equation is proved improper to describe the self-similar heat transfer. A theoretical analysis for momentum and energy boundary layer transfer behavio...The classical power law non-Newtonian fluids energy boundary layer equation is proved improper to describe the self-similar heat transfer. A theoretical analysis for momentum and energy boundary layer transfer behavior is made and the full similarity heat boundary layer equation is developed, which may be characterized by a power law relationship between shear stress and velocity gradient with the Falkner-Skan equation as a special case. Both analytical and numerical solutions are presented for momentum and energy boundary layer equations by using the similarity transformation and shooting technique and the associated transfer characteristics are discussed.展开更多
Analytical and numerical solutions are established for momentum and energy laminar boundary layer induced by a shock wave. The results indicated that skin friction σ decreases with increasing in velocity ratio ξ(1...Analytical and numerical solutions are established for momentum and energy laminar boundary layer induced by a shock wave. The results indicated that skin friction σ decreases with increasing in velocity ratio ξ(1≤ξ【 6). For each specified ξ(1≤ξ【 6), temperature w(t) increases with increasing of Tw but decreases with Te , and for a range of t ∈[1,ξ], w(t) decreases with the increasing of t. Thermal diffusion increases with increasing of uw but decreases with increasing Ue.展开更多
In this article,a new evaporative condenser with an annular elliptic firmed tube heat exchanger that includes a round inner tube and elliptic outer finned tube was designed and analyzed.The refrigerant flows between t...In this article,a new evaporative condenser with an annular elliptic firmed tube heat exchanger that includes a round inner tube and elliptic outer finned tube was designed and analyzed.The refrigerant flows between the round inner tube and the elliptic outer tube,and it simultaneously exchanges heat with the cooling water in the inner tube,the spray water,and the cooling air flowing past the outer tube.Using field measurement for the traditional round finned tube evaporative condenser in the Futong Metro Station of Line 14 in Beijing,China,the theoretical heat transfer performance of the annular elliptic finned tube evaporative condenser was analyzed and simulated.Compared with a round finned tube heat exchanger,the heat exchange capacity of the annular elliptic finned tube increased by 2.34%to 9.28%;the total heat transfer coefficient increased by 47.42%,and the power consumption of the fan in the air-conditioning system with an annular elliptic finned tube heat exchanger decreased by 11.18%to 14.65%.Therefore,the energy-saving performance and the heat transfer performance of the new annular elliptic finned tube heat exchanger were enhanced compared to the round finned tube heat exchanger.展开更多
The behavior for a class of initial, boundary value problems of generalized diffusion equations was studied utilizing the similarity transformation and shooting technique. Numerical solutions are presented fork(s) = S...The behavior for a class of initial, boundary value problems of generalized diffusion equations was studied utilizing the similarity transformation and shooting technique. Numerical solutions are presented fork(s) = SM exponent M 1.0 to 5.0, and power law parameter N (N = 0.3 to 3.0). The results shown that for each fixed M, the temperature distribution e decreases with increasing in power law parameter N, and for each fixed N, the temperature distribution 6 increases with the decreasing of M.展开更多
This paper presented an experimental study on convective drying of waste water sludge collected from Beijing GaoBeiDian Sewage Treatment Plant, particularly on the correlation between the observed shrinkage dynamics o...This paper presented an experimental study on convective drying of waste water sludge collected from Beijing GaoBeiDian Sewage Treatment Plant, particularly on the correlation between the observed shrinkage dynamics of sludge cake and the drying curve. During the initial stage of drying the process resembles to that of a particulate bed, in which moisture diffuses and evaporates at the upper surface. Conventional drying theory assuming a diffusion-evaporating front interprets this period of drying. Consequently, owing to the very large shrinkage ratio of the dried cake, cracks emerges and propagates on and within the cake body, whence inducing evaporating channel that facilitates the water removal. This occurrence compensates the reduction of surface area for evaporation, whence extending the constant-rate period during the test. Afterwards, the cracks meet with each other and form isolated cake piles, while the subsequent drying occur mainly within these piles and the conventional theory fails. The展开更多
The recent investigations on the rewettmg and film boiling of liquid flowing along a hot/heated surface are briefly reviewed and discussed.Some advanced theoretical analyses are conducted and new conclusions achieved....The recent investigations on the rewettmg and film boiling of liquid flowing along a hot/heated surface are briefly reviewed and discussed.Some advanced theoretical analyses are conducted and new conclusions achieved.These investigations describe the fundamental characteristics of liquid flow boiling and further the complicated rewetting phenomena,and have resulted in considerable insight intothe mechanism.展开更多
The response of living tissue temperature to the external thermal perturbation can be regarded as a dynamic process. The authors introduced for the first time the thermal wave theory to study temperature oscillations ...The response of living tissue temperature to the external thermal perturbation can be regarded as a dynamic process. The authors introduced for the first time the thermal wave theory to study temperature oscillations in living tissue and described two approaches to obtaining an oscillation criterion. But the criterion obtained through the first method is in implicit form of thermal properties and inconvenient for quantitatively analyzing these properties’influence. The second method gives a clearer criterion but is over simplified. Liapnov’s stability analysis is adopted in the present note for the problem to obtain a criterion, which gives deeper insight into this phenomenon. Besides, a new dimensionless parameter W_τ with clear physical meaning is defined.展开更多
Experiments have been carried out for steady turbulent-flow film boiling of subcooledliquid R11 flowing upward in a vertical circular tube with velocities in a range of 1 .3-4.9m/s and liquid temperatures subcooling i...Experiments have been carried out for steady turbulent-flow film boiling of subcooledliquid R11 flowing upward in a vertical circular tube with velocities in a range of 1 .3-4.9m/s and liquid temperatures subcooling in a range of 16.2-32 .5℃. The exponent ofRe_D in a semi-empirical expression is determined as m = 0.65 from the experimental dataobtained, which coincides with the theoretical value m = 2/3 reported previously. Mean-while, the modified semi-empirical theory is verified and further discussed, and the onlyempirical constant c is determined as 5.4 ×10~5.展开更多
Interactions among dry patches at high heat flux are theoretically analyzed. The high heat flux boiling experiments on metal plate wall with different materials and thickness are correspondingly conducted. The duality...Interactions among dry patches at high heat flux are theoretically analyzed. The high heat flux boiling experiments on metal plate wall with different materials and thickness are correspondingly conducted. The duality of boiling system, i.e. hydrodynamic performance and self-organized performance is identified. A unified explanation of hydrodynamic models and dry patches models is given. The scatter and uncertainty in boiling data can be mainly attributed to the intrinsic duality, but not the sole surface effects. The present experimental results explain why the deviation point at high flux boiling is seen only on occasion and why the self-organization of dry patches is often ignored in available literature.展开更多
This work briefly summarized the recent research efforts made on the phase heat transfer processes involving biological aggregates, with particular attention on the correlation of aggregate structure and state of wate...This work briefly summarized the recent research efforts made on the phase heat transfer processes involving biological aggregates, with particular attention on the correlation of aggregate structure and state of water with the process efficiency. The phase change processes include boiling, drying, freezing, sintering, pyrolysis, and supercritical extraction, while the former three were discussed in some detail.展开更多
文摘The differential equations of continuum mechanics are the basis of an uncountable variety of phenomena and technological processes in fluid-dynamics and related fields.These equations contain derivatives of the first order with respect to time.The derivation of the equations of continuum mechanics uses the limit transitions of the tendency of the volume increment and the time increment to zero.Derivatives are used to derive the wave equation.The differential wave equation is second order in time.Therefore,increments of volume and increments of time in continuum mechanics should be considered as small but finite quantities for problems of wave formation.This is important for calculating the generation of sound waves and water hammer waves.Therefore,the Euler continuity equation with finite time increments is of interest.The finiteness of the time increment makes it possible to take into account the quadratic and cubic invariants of the strain rate tensor.This is a new branch in hydrodynamics.Quadratic and cubic invariants will be used in differential wave equations of the second and third order in time.
文摘Six surfaces were prepared with defferent surface division patterns for the experimental investigationof steam condensation heat transfer characteristics for dropwise and filmwise coexisting(DFC)condensationsurfaces under atmospheric pressure Dropwise condensation(DWC)was promoted with an ultrathin polytetrafluoroethylene(PTFE)film,which was prepared by the dynamic ion-beam mixed implantation(DIMI)method.The results showed that the condensation phenomena at the intersection between the dropwise andfilmwise condensation regios were quite different for different relative positions of the dropwise and filmwisecondensation regions.The experimental results revealed that the condensation heat transfer characteristics werehighly influenced by the surface division number and the relative area ratio of the dropwise and filmwise conden-sation regions.The impact of thesc findings on heat transfer enhancement mechanism for condensation heattransfer is discussed in detail.
基金Supported by the National Natural Science Foundation of China Co-operated with Guangdong Provincial Department of Science and Technology under Grant No U0934006Common Development Fund of Beijing.
文摘We discuss a bifurcation phenomenon of Marangoni flow in a microchannel T-junction and its novel unidirectional pumping effect.The T-junction is formed by a main channel connected with a liquid reservoir and a side channel outlet to the atmosphere.A volatizing meniscus is formed in the side channel and Marangoni convections are generated due to the non-uniform evaporation on the meniscus.It is found for weak evaporations (Ma < 270) the Marangoni convections are symmetrical.However,for intense evaporations (Ma > 270),the initial inward symmetrical Marangoni convection becomes unstable and converted into one single vortex flow.Moreover,the single vortex induces a steady unidirectional flow in the main channel,acting like a pump.
文摘In this paper the self-regeneration process of the mixed resins consisting of cationand anion ion exchangers in the electrolialyser of the packed bed is analyzed and anelectric regeneration method is put forward to supply the desalinated water by mixedbed The electric regeneration technology is a new one used for regeneration of theexhausted ion exchangers in the mixed bed instead of the traditional regeneratingprocess by using acid and abc liquor Electric energy is consumed to regenerat theion exchangers loaded by salts from water treatment without any chemicals- acid alkali. The advantage of the electric regeneration process edibited convenientoperation, no discharge any waste, and therefore no Polluted to the recehang waterbode and the environmental ground
基金Project supported by the National Natural Science Foundation of China (No. 50776097)
文摘Analytically solving a three-dimensional （3-D） bioheat transfer problem with phase change during a freezing process is extremely difficult but theoretically important. The moving heat source model and the Green function method are introduced to deal with the cryopreservation process of in vitro biomaterials. Exact solutions for the 3-D temperature transients of tissues under various boundary conditions, such as totally convective cooling, totally fixed temperature cooling and a hybrid between them on tissue surfaces, are obtained. Furthermore, the cryosurgical process in living tissues subject to freezing by a single or multiple cryoprobes is also analytically solved. A closed-form analytical solution to the bioheat phase change process is derived by considering contributions from blood perfusion heat transfer, metabolic heat generation, and heat sink of a cryoprobe. The present method is expected to have significant value for analytically solving complex bioheat transfer problems with phase change.
文摘In this paper, detailed optical of the solar parabolic dish concentrator is presented. The system has diameter D = 2,800 mm and focal length f = 1,400 mm. The efficient conversion of solar radiation in heat at these temperature levels requires a use of concentrating solar collectors. In this paper, detailed optical design of the solar parabolic dish concentrator is presented. The parabolic dish of the solar system consists from 12 curvilinear trapezoidal reflective petals. This paper presents optical simulations of the parabolic solar concentrator unit using the ray-tracing software TracePro. The total flux on receiver and the distribution of irradiance for absorbed flux on center and periphery receiver are given. The total flux at the focal region is 4,031.3 W. The goal of this paper is to present optical design of a low-tech solar concentrator, that can be used as a potentially low-cost tool for laboratory-scale research on the medium-temperature thermal processes, cooling, industrial processes, solar cooking and polygeneration systems, etc.
基金Project supported by the National Natural Science Foundation of China.
文摘The fact that the temperature of living tissue may respond oscillatorily to externalheating has been a classical difficulty in the field of bioheat transfer for a long time.Roemer et al. have carefully discussed this in their serial articles, but experiments did notsupport their conclusions, Tharp et al. have artificially made a time-delay differential equs-tion to describe this phenomenon, but their model is short of a strict theoretical founda-
文摘The classical power law non-Newtonian fluids energy boundary layer equation is proved improper to describe the self-similar heat transfer. A theoretical analysis for momentum and energy boundary layer transfer behavior is made and the full similarity heat boundary layer equation is developed, which may be characterized by a power law relationship between shear stress and velocity gradient with the Falkner-Skan equation as a special case. Both analytical and numerical solutions are presented for momentum and energy boundary layer equations by using the similarity transformation and shooting technique and the associated transfer characteristics are discussed.
基金The authors express their thanks for the support by "Cross-Century Talents Projects of Educational Ministry of China" the "973" key foundation under the contract No.G1998061510
文摘Analytical and numerical solutions are established for momentum and energy laminar boundary layer induced by a shock wave. The results indicated that skin friction σ decreases with increasing in velocity ratio ξ(1≤ξ【 6). For each specified ξ(1≤ξ【 6), temperature w(t) increases with increasing of Tw but decreases with Te , and for a range of t ∈[1,ξ], w(t) decreases with the increasing of t. Thermal diffusion increases with increasing of uw but decreases with increasing Ue.
基金The work was supported by the Natural Science Foundation of Shaanxi Province(No.2018JM5084)“the 13th Five-Year”National Science and Technology Major Project of China(No.2017YFC0702202)+1 种基金the Shaanxi Key Science and Technology Innovative Tea m Project(No.2016KCT-22)the Fundamental Research Funds for the Central Universities(CHD300102289203).
文摘In this article,a new evaporative condenser with an annular elliptic firmed tube heat exchanger that includes a round inner tube and elliptic outer finned tube was designed and analyzed.The refrigerant flows between the round inner tube and the elliptic outer tube,and it simultaneously exchanges heat with the cooling water in the inner tube,the spray water,and the cooling air flowing past the outer tube.Using field measurement for the traditional round finned tube evaporative condenser in the Futong Metro Station of Line 14 in Beijing,China,the theoretical heat transfer performance of the annular elliptic finned tube evaporative condenser was analyzed and simulated.Compared with a round finned tube heat exchanger,the heat exchange capacity of the annular elliptic finned tube increased by 2.34%to 9.28%;the total heat transfer coefficient increased by 47.42%,and the power consumption of the fan in the air-conditioning system with an annular elliptic finned tube heat exchanger decreased by 11.18%to 14.65%.Therefore,the energy-saving performance and the heat transfer performance of the new annular elliptic finned tube heat exchanger were enhanced compared to the round finned tube heat exchanger.
基金Cross-Century Talents Proects of Ministry of Education of China the "973" Key Foundation under the contractNo.G l99806l5l0.
文摘The behavior for a class of initial, boundary value problems of generalized diffusion equations was studied utilizing the similarity transformation and shooting technique. Numerical solutions are presented fork(s) = SM exponent M 1.0 to 5.0, and power law parameter N (N = 0.3 to 3.0). The results shown that for each fixed M, the temperature distribution e decreases with increasing in power law parameter N, and for each fixed N, the temperature distribution 6 increases with the decreasing of M.
基金The research was supported by the National Natural Science Foundation of China (No. 50136020).
文摘This paper presented an experimental study on convective drying of waste water sludge collected from Beijing GaoBeiDian Sewage Treatment Plant, particularly on the correlation between the observed shrinkage dynamics of sludge cake and the drying curve. During the initial stage of drying the process resembles to that of a particulate bed, in which moisture diffuses and evaporates at the upper surface. Conventional drying theory assuming a diffusion-evaporating front interprets this period of drying. Consequently, owing to the very large shrinkage ratio of the dried cake, cracks emerges and propagates on and within the cake body, whence inducing evaporating channel that facilitates the water removal. This occurrence compensates the reduction of surface area for evaporation, whence extending the constant-rate period during the test. Afterwards, the cracks meet with each other and form isolated cake piles, while the subsequent drying occur mainly within these piles and the conventional theory fails. The
基金Project supported by the National Natural Science Foundation of Chinaalso by NSFNASA of U.S.
文摘The recent investigations on the rewettmg and film boiling of liquid flowing along a hot/heated surface are briefly reviewed and discussed.Some advanced theoretical analyses are conducted and new conclusions achieved.These investigations describe the fundamental characteristics of liquid flow boiling and further the complicated rewetting phenomena,and have resulted in considerable insight intothe mechanism.
基金Project supported by the National Natural Science Foundation of China.
文摘The response of living tissue temperature to the external thermal perturbation can be regarded as a dynamic process. The authors introduced for the first time the thermal wave theory to study temperature oscillations in living tissue and described two approaches to obtaining an oscillation criterion. But the criterion obtained through the first method is in implicit form of thermal properties and inconvenient for quantitatively analyzing these properties’influence. The second method gives a clearer criterion but is over simplified. Liapnov’s stability analysis is adopted in the present note for the problem to obtain a criterion, which gives deeper insight into this phenomenon. Besides, a new dimensionless parameter W_τ with clear physical meaning is defined.
文摘Experiments have been carried out for steady turbulent-flow film boiling of subcooledliquid R11 flowing upward in a vertical circular tube with velocities in a range of 1 .3-4.9m/s and liquid temperatures subcooling in a range of 16.2-32 .5℃. The exponent ofRe_D in a semi-empirical expression is determined as m = 0.65 from the experimental dataobtained, which coincides with the theoretical value m = 2/3 reported previously. Mean-while, the modified semi-empirical theory is verified and further discussed, and the onlyempirical constant c is determined as 5.4 ×10~5.
文摘Interactions among dry patches at high heat flux are theoretically analyzed. The high heat flux boiling experiments on metal plate wall with different materials and thickness are correspondingly conducted. The duality of boiling system, i.e. hydrodynamic performance and self-organized performance is identified. A unified explanation of hydrodynamic models and dry patches models is given. The scatter and uncertainty in boiling data can be mainly attributed to the intrinsic duality, but not the sole surface effects. The present experimental results explain why the deviation point at high flux boiling is seen only on occasion and why the self-organization of dry patches is often ignored in available literature.
文摘This work briefly summarized the recent research efforts made on the phase heat transfer processes involving biological aggregates, with particular attention on the correlation of aggregate structure and state of water with the process efficiency. The phase change processes include boiling, drying, freezing, sintering, pyrolysis, and supercritical extraction, while the former three were discussed in some detail.
