A study on heat transfer performance by thermal fluid coupling simulation for the fouling in a shell-tube heat exchanger used in engineering was presented. The coupling simulation was performed in a fluid and solid do...A study on heat transfer performance by thermal fluid coupling simulation for the fouling in a shell-tube heat exchanger used in engineering was presented. The coupling simulation was performed in a fluid and solid domains under three different fouling conditions: fouling inside the tube, fouling outside the tube, and fouling inside the shell. The flow field, temperature, and pressure distributions in the heat exchanger were solved numerically to analyze the heat transfer performance parameters, such as thermal resistance. It is found that the pressure drop of the heat exchanger and the thermal resistance of the tube wall increase by nearly 30% and 20%, respectively, when the relative fouling thickness reaches 10%. The fouling inside the tube has more impact on the heat transfer performance of the heat exchanger, and the fouling inside the shell has less impact.展开更多
Heat engines based on reciprocating machines remain in demand as energy converters in a variety of industries around the world.The aim of the study was to evaluate the gas-dynamic,consumable and heat exchange characte...Heat engines based on reciprocating machines remain in demand as energy converters in a variety of industries around the world.The aim of the study was to evaluate the gas-dynamic,consumable and heat exchange characteristics of non-stationary air flows in a supply system with transverse profiling of valve channels based on experimental studies.Valve channels with cross sections in the form of a circle,square and triangle were used to control the consumable and heat exchange characteristics of the flows in the supply system of the reciprocatingengine model.The article presents data on changes in local velocity,volumetric airflow and instantaneous heat transfer coefficient of non-stationary airflow in supply systems with different valve channel designs.A spectral analysis of the pulsations of the local heat transfer coefficient was also performed.The Nusselt number was calculated for the studied supply systems.The figured valve channels lead to an increase in the volumetric airflow through the supply systemupto32%comparedwiththe basic configuration.The useof a square valve channel leads to suppression of heat transfer(drop is about 15%)compared to the basic supply system,and the use of a triangular valve channel causes an intensification of heat transfer(growth is about 17.5%).The obtained data can be useful for refining mathematical models,adjusting machine learning algorithms,and improving design methods for supply systems of reciprocating machines to improve their technical,economic,and environmental characteristics.展开更多
The heat transfer analysis was performed for an AC electric arc furnace (EAF). Heat losses by conduction, convection and radiation from outer surface, roof, bottom and electrodes of EAF were determined in detail. Some...The heat transfer analysis was performed for an AC electric arc furnace (EAF). Heat losses by conduction, convection and radiation from outer surface, roof, bottom and electrodes of EAF were determined in detail. Some suggestions about decreasing heat losses were presented.展开更多
One quarter scale experiment device of a typical L-shape architecture structure including a burning room and an adjacent hallway is established to carry out the research.The smoke characteristics at the sampling point...One quarter scale experiment device of a typical L-shape architecture structure including a burning room and an adjacent hallway is established to carry out the research.The smoke characteristics at the sampling points below the ceiling of the burning compartment and the roof of the hallway are studied systematically to find out the effects of different ceilings on the local fire origin compartment and the smoke transportation to a remote area.A series of tests is reported and the smoke residence time,the concentration peak and the concentration build up rate are investigated as functions of the type of the ceiling.The smoke residence time,the most important factor concerning smoke toxicity,is described by a novel concept,wavelength,in this study.Furthermore,it is worth emphasizing that the PVC ceiling exhibits a phenomenon of frequent collapse during the fire developing period.The single heat action is conducted to judge the smoke and the heat effect on the fire risk.展开更多
In the present investigation we have discussed the flow of a Jeffrey-six constant incompressible fluid between two infinite coaxial cylinders in the presence of heat transfer analysis. The governing equations of Jeffr...In the present investigation we have discussed the flow of a Jeffrey-six constant incompressible fluid between two infinite coaxial cylinders in the presence of heat transfer analysis. The governing equations of Jeffrey-six constant fluid along with energy equation have been derived in cylindrical coordinates. The highly nonlinear equations are simplified with the help of non-dimensional parameters and then solved analytically with the help of homotopy analysis method （HAM） for two fundamental flows namely Couette and Generalized Couette flow. The effects of emerging parameters are discussed through graphs. The convergence of the HAM solution has been discussed by plotting h-curves.展开更多
We investigate the thermal characteristics of standard organic light-emitting diodes （OLEDs） using a simple and clear 1D thermal model based on the basic heat transfer theory. The thermal model can accurately estima...We investigate the thermal characteristics of standard organic light-emitting diodes （OLEDs） using a simple and clear 1D thermal model based on the basic heat transfer theory. The thermal model can accurately estimate the device temperature, which is linearly with electrical input power. The simulation results show that there is almost no temperature gradient within the OLED device working under steady state conditions. Furthermore, thermal analysis simulation results show that the surface properties （convective heat transfer coetficient and surface emissivity） of the substrate or cathode can significantly affect the temperature distribution of the OLED.展开更多
In this paper,by using the ECMWF objective analysed data as well as CAC and NOAA grid point data of 1981 and 1983,the sensible and latent heat fluxes at the air and sea boundary surface within the range of 45°E-7...In this paper,by using the ECMWF objective analysed data as well as CAC and NOAA grid point data of 1981 and 1983,the sensible and latent heat fluxes at the air and sea boundary surface within the range of 45°E-75°W, 35°N-35°S over the Pacific and the Indian Ocean are calculated. The purpose is to analyse the different revealing features during the mature stage and at the end of the 1982 -1983 El Nino event and to compare the difference of the features between thd El Nino and the normal. The result shows that the air and sea heat exchange west of the dateline over the central tropical Pacific during the EJ Nino period is more intense than that of the normal. However,the fluxes of the sensible and latent heat on the sea surface with strong warming of SSTneat by and on the south side of the equator east of 170°W are low and even negative,and the patterns of the sensible and latent heat fluxes over the Indian Ocean during the year of 1983 are similer to that of normal. Spatial patterns of the sensible heat ,the latent heat,SST,OLR and the wind speed exhibit large anomalies during the El Nino event. The corresponding relationships of the spatial distribution of the streng exchange of heat fluxes with regions of high SST and action convection or negative anomalies of OLR are relatively complicated. But the region of maximum air and sea heat exchange is in good coincidence with that of high value of the Vs. The strong heat exchange is weakened with the declining and the finishing of the El Nino event in the central tropical Pacific.展开更多
The response to single heat treatment and Step-down heat (SDH) treatment in vitro of V79 and L cells was studied. Colony-forming ability was assayed in medium after treatment in vitro. Time-response curves were establ...The response to single heat treatment and Step-down heat (SDH) treatment in vitro of V79 and L cells was studied. Colony-forming ability was assayed in medium after treatment in vitro. Time-response curves were established and subjected to Arrhenius analysis. The Arrhenius curves showed inflection points at 43℃ for V79 cells and at 42℃ for L cells. The activation energies were 145 kcal/mole and 400 kcal/mole above and below 43℃ (P<0.05), respectively, for V79 cells, while 160 kcal/mole and 300 kcal/mole above and below 42℃ (P<0.05), respectively, for L cells. Thermosensitivity of L cells are markedly higher than V79 cells. Both V79 and L cells were sensitized by SDH. The SDH effect was characterized by a reduction in shoulder (an addition effect to sublethal damage), an increase in slope (thermosensitization), and the delay and disappearance of thermotolerant 'tail' for V79 and L cells at 45℃ to 40℃ and 44℃ to 42℃ SDH treatment respectively. Particularly, 42℃ to 39℃ or 42℃ to 40℃ SDH for L cells resulted in thermosensitization effect up to a factor of 7.1 or 2.7, respectively. The effect was quantified by thermorsensitization ratio (TSR), defined as T0 single heated/T0SDH-heated. The relative ratio was much higher for V79 than for L cells. Heat killing with SDH characterized by Arrhenius analysis showed that Step-down heating reduced the activation energy for heat killing more than single heating. The decrease of activation energy for L cells was markedly greater than for V79. These data suggest that greater cellular sensitivity under step-down heating conditions may reflect a different mechanism for cell killing.展开更多
A boundary layer analysis is presented to investigate numerically the effects of radiation, thermophoresis and the dimensionless heat generation or absorption on hydromagnetic flow with heat and mass transfer over a f...A boundary layer analysis is presented to investigate numerically the effects of radiation, thermophoresis and the dimensionless heat generation or absorption on hydromagnetic flow with heat and mass transfer over a flat surface in a porous medium. The boundary layer equations are transformed to non-linear ordinary differential equations using scaling group of transformations and they are solved numerically by using the fourth order Runge-Kutta method with shooting technique for some values of physical parameters. Comparisons with previously published work are performed and the results are found to be in very good agreement. Many results are obtained and a representative set is displayed graphically to illustrate the influence of the various parameters on the dimensionless velocity, temperature and concentration profiles as well as the local skin-friction coefficient, wall heat transfer, particle deposition rate and wall thermophoretic deposition velocity. The results show that the magnetic field induces acceleration of the flow, rather than deceleration （as in classical magnetohydrodynamics （MHD） boundary layer flow） but to reduce temperature and increase concentration of particles in boundary layer. Also, there is a strong dependency of the concentration in the boundary layer on both the Schmidt number and mass transfer parameter.展开更多
Traditional feature-based turbine blade models can match the needs of geometric modeling but could hardly meet the requirement of data extraction in 1-D heat transfer analysis. In this paper, the requirements of data ...Traditional feature-based turbine blade models can match the needs of geometric modeling but could hardly meet the requirement of data extraction in 1-D heat transfer analysis. In this paper, the requirements of data extraction in 1-D heat transfer analysis are taken into consideration as well as geometric representation in parametric design process. An improved turbine blade parametric modeling method is proposed. Based on the modeling method proposed, a system structure of blade modeling process considering 1-D heat transfer analysis is devised. Eventually, a turbine blade parametric modeling system is constructed to test and verify the feasibility of the proposed modeling method and system structure. Experiments show that the blade parametric modeling method proposed can make geometric models better adapt to the specific requirements of 1-D heat transfer analysis and has certain reference value to the creation of high quality digital models.展开更多
Selection of air conditioning（AC） cold/heat sources generally concerns about certain aspects and cannot reveal the whole profile of the problems. Grey relation analysis （GRA） is a data processing method to categor...Selection of air conditioning（AC） cold/heat sources generally concerns about certain aspects and cannot reveal the whole profile of the problems. Grey relation analysis （GRA） is a data processing method to categorize the correlation extent of compared sequences and a certain reference sequence in a system with uncertain information. It is applied to evaluating and selecting AC cold/heat sources from four main aspects, which are technology, economy, reliability, and operation and management. Case study shows that the result for selecting AC cold/heat sources with the GRA method can be more reasonable and convincible. Thus it offers a new approach for designers in heating, ventilating and air conditioning field to compare and evaluate different AC cold/heat sou rces.展开更多
This work investigates the transient behaviour of a phase change material based cool thermal energy storage (CTES) system comprised of a cylindrical storage tank filled with encapsulated phase change materials (PCMs) ...This work investigates the transient behaviour of a phase change material based cool thermal energy storage (CTES) system comprised of a cylindrical storage tank filled with encapsulated phase change materials (PCMs) in spherical container integrated with an ethylene glycol chiller plant. A simulation program was developed to evaluate the temperature histories of the heat transfer fluid (HTF) and the phase change material at any axial location during the charging period. The results of the model were validated by comparison with experimental results of temperature profiles of HTF and PCM. The model was also used to investigate the effect of porosity, Stanton number, Stefan number and Peclet number on CTES system performance. The results showed that increase in porosity contributes to a higher rate of energy storage. However, for a given geometry and heat transfer coefficient, the mass of PCM charged in the unit decreases as the increase in porosity. The St number as well as the Ste number is also influential in the performance of the unit. The model is a convenient and more suitable method to determine the heat transfer characteristics of CTES system. The results reported are much useful for designing CTES system.展开更多
This paper presents an improved precise integration algorithm fortransient analysis of heat transfer and some other problems. Theoriginal precise integration method is improved by means of the inve-rse accuracy analys...This paper presents an improved precise integration algorithm fortransient analysis of heat transfer and some other problems. Theoriginal precise integration method is improved by means of the inve-rse accuracy analysis so that the parameter N, which has been takenas a constant and an independent pa- rameter without consideration ofthe problems in the original method, can be generated automaticallyby the algorithm itself.展开更多
The phase change characteristic of the power source of an underwater glider propelled by the ocean＇s thermal energy is the key factor in glider attitude control. A numerical model has been established based on the en...The phase change characteristic of the power source of an underwater glider propelled by the ocean＇s thermal energy is the key factor in glider attitude control. A numerical model has been established based on the enthalpy method to analyze the phase change heat transfer process under convective boundary conditions. Phase change is not an isothermal process, but one that occurs at a range of temperature. The total melting time of the material is very sensitive to the surrounding temperature. When the temperature of the surroundings decreases 8 degrees, the total melting time increases 1.8 times. But variations in surrounding temperature have little effect on the initial temperature of phase change, and the slope of the temperature time history curve remains the same. However, the temperature at which phase change is completed decreases significantly. Our research shows that the phase change process is also affected by container size, boundary conditions, and the power source＇s cross sectional area. Materials stored in 3 cylindrical containers with a diameter of 38ram needed the shortest phase change time. Our conclusions should be helpful in effective design of underwater glider power systems.展开更多
Due to the deterioration of serious energy dilemma,energy-conservation and emission–reduction have been the strategic target in the past decades,thus people have identified the vital importance of higher energy effic...Due to the deterioration of serious energy dilemma,energy-conservation and emission–reduction have been the strategic target in the past decades,thus people have identified the vital importance of higher energy efficiency and the influence of lower carbon development.Since work exchange network is a significant part of energy recovery system,its optima design will have dramatically significant effect on energy consumption reduction in chemical process system.With an extension of the developed transshipment model in isothermal process,a novel step-wise methodology for synthesis of direct work exchange network(WEN)in adiabatic process involving heat integration is first proposed in this paper,where a nonlinear programming(NLP)model is formulated by regarding the minimum utility consumption as objective function and optimizing the initial WEN in accordance with the presented matching rules to get the optimized WEN configuration at first.Furthermore,we focus on the work exchange network synthesis with heat integration to attain the minimal total annual cost(TAC)with the introduction of heat-exchange equipment that is achieved by the following strategies in sequence:introducing heat-exchange equipment directly,adjusting the work quantity of the adjacent utility compressors or expanders,and approximating upper/lower pressure limits consequently to obtain considerable cost savings of expanders or compressors and work utility.Finally,a case taken from the literature is studied to illustrate the feasibility and effectiveness of the proposed method.展开更多
We investigated the effects of monsoon onset vortex(MOV)on the mixed layer heat budget in the Bay of Bengal(BOB)in spring 2003 using the reanalysis datasets.The results suggest that the solar radiation flux penetratin...We investigated the effects of monsoon onset vortex(MOV)on the mixed layer heat budget in the Bay of Bengal(BOB)in spring 2003 using the reanalysis datasets.The results suggest that the solar radiation flux penetrating the mixed layer and the existence of barrier layer are both able to modulate the effects of MOV on the evolution of sea surface temperature(SST)in the BOB.Prior to the formation of BOB MOV,the local SST raised quickly due to mass of solar radiation reaching the sea surface under the clear-sky condition.Meanwhile,since the mixed layer was shallow before the onset of the Asian summer monsoon(ASM),some solar radiation flux could penetrate to directly heat the deeper water,which partly offset the warming effect of shortwave radiation.On the other hand,the in-situ SST started to cool due to the upwelling of cold water when the MOV generated over the BOB,along with the rapidly increased surface wind speed and its resultant deeper mixed layer.As the MOV developed and moved northward,the SST tended to decrease remarkably because of the strong upward surface latent heat flux over the BOB ascribed to the wind-evaporation mechanism.However,the MOV-related precipitation brought more fresh water into the upper ocean to produce a thicker barrier layer,whose thermal barrier effect damped the cooling effect of entrainment upwelling on the decrease tendency of the BOB SST.In other words,the thermal barrier effect could slow down the decreasing trend of the BOB SST even after the onset of ASM,which facilitated the further enhancement of the MOV.展开更多
Ten F1 combinations with their male and female parents were employed to evaluate their heat tolerance during the flowering and early grain filling stages. The rice plants were subjected to heat stress（39 °C–43 ...Ten F1 combinations with their male and female parents were employed to evaluate their heat tolerance during the flowering and early grain filling stages. The rice plants were subjected to heat stress（39 °C–43 °C） for 1–15 d during flowering. Based on the heat stress index, heat tolerance was only observed in the F1 combinations H2（K22A × R207）, H3（Bobai A × R207） and H4（Bobai A × Minghui 63）, whereas the others received above 0.5000 of heat stress index. Both parents of the tolerant combination（heat-tolerant × heat-tolerant） possessed heat tolerance, whereas the susceptible combinations were crossed by heat-tolerant（sterile lines） × heat-susceptible（restorer lines）, heat-susceptible × heat-tolerant, or heat-susceptible × heat-susceptible parents. This result indicated that heat tolerance in rice was controlled by recessive genes. Thus, both parents should possess high temperature tolerance to develop heat-tolerant F1 combinations. Furthermore, the heat stress index of F1 combinations was significantly correlated with the heat stress index of restorer lines but not with the heat stress index of maintainer lines. This result suggested that male parents play a more important role in heat-tolerant combinations than female parents. Therefore, the heat susceptibility of the hybrid rice in China is mainly due to the wide application of low-heat-tolerant restorer lines with high yield in three-line hybrid rice breeding.展开更多
A simple and highly accurate semi-analytical method, called the differential transformation method(DTM), was used for solving the nonlinear temperature distribution equation in solid and porous longitudinal fin with t...A simple and highly accurate semi-analytical method, called the differential transformation method(DTM), was used for solving the nonlinear temperature distribution equation in solid and porous longitudinal fin with temperature dependent internal heat generation. The problem was solved for two main cases. In the first case, heat generation was assumed variable by fin temperature for a solid fin and in second heat generation varied with temperature for a porous fin. Results are presented for the temperature distribution for a range of values of parameters appearing in the mathematical formulation(e.g. N, εG, and G). Results reveal that DTM is very effective and convenient. Also, it is found that this method can achieve more suitable results in comparison to numerical methods.展开更多
The laminar fully developed nanofluid flow and heat transfer in a horizonal channel are investigated. Highly accurate solutions for the temperature and nanopavticle concentration distributions are obtained. The effect...The laminar fully developed nanofluid flow and heat transfer in a horizonal channel are investigated. Highly accurate solutions for the temperature and nanopavticle concentration distributions are obtained. The effects of the Brownian motion parameter Nb, the thermophoresis parameter Nt, and the Lewis number Le on the temperature and nanoparticle concentration distributions are discussed. The current analysis shows that the nanoparticles can improve the heat transfer characteristics significantly for this flow problem.展开更多
Changes of the net ocean surface heat flux（Q_（net）） into the tropical Indian Ocean（TIO） may be an indicator of the climate changes in the Asia and Indian–Pacific Ocean regions with the steadily warming trend in...Changes of the net ocean surface heat flux（Q_（net）） into the tropical Indian Ocean（TIO） may be an indicator of the climate changes in the Asia and Indian–Pacific Ocean regions with the steadily warming trend in the TIO since the 1950 s. Using two observational ocean surface flux products,this letter evaluates the historical simulations of Q_（net） over the TIO during 1984–2005 in two versions of FGOALS, from CMIP5. The results show that both models present a basin-wide underestimation of net surface heat flux, possibly resulting from the positive latent heat flux biases extending over almost the entire TIO basin. Both models share an Indian Ocean dipole-like bias in the net surface heat flux, consistent with precipitation, SST, and subsurface ocean temperature biases, which can be traced to errors in the South Asian summer monsoon. Area-averaged annual time series analyses of the surface heat budget imply that the FGOALS-s2 bias lies more in radiative imbalance, illustrating the need to improve cloud simulation; while the FGOALS-g2 bias presents ocean surface turbulence flux as the key process, requiring improvement in the simulation of oceanic processes. Neither FGOALS-g2 nor FGOALS-s2 can capture the decreasing tendency of Q_（net） well. All observed and simulated datasets imply surface latent heat flux as the primary contributing component, indicating the simulation biases of models may derive mainly from the biases in simulating latent heat flux. A small latent heat flux increase in models can be considered to be slowed by relaxed wind, increased stability, and surface relative humidity.展开更多
基金National Natural Science Foundation of China (21878102)
文摘A study on heat transfer performance by thermal fluid coupling simulation for the fouling in a shell-tube heat exchanger used in engineering was presented. The coupling simulation was performed in a fluid and solid domains under three different fouling conditions: fouling inside the tube, fouling outside the tube, and fouling inside the shell. The flow field, temperature, and pressure distributions in the heat exchanger were solved numerically to analyze the heat transfer performance parameters, such as thermal resistance. It is found that the pressure drop of the heat exchanger and the thermal resistance of the tube wall increase by nearly 30% and 20%, respectively, when the relative fouling thickness reaches 10%. The fouling inside the tube has more impact on the heat transfer performance of the heat exchanger, and the fouling inside the shell has less impact.
基金supported by the Russian Science Foundation(Grant No.23-29-00022).
文摘Heat engines based on reciprocating machines remain in demand as energy converters in a variety of industries around the world.The aim of the study was to evaluate the gas-dynamic,consumable and heat exchange characteristics of non-stationary air flows in a supply system with transverse profiling of valve channels based on experimental studies.Valve channels with cross sections in the form of a circle,square and triangle were used to control the consumable and heat exchange characteristics of the flows in the supply system of the reciprocatingengine model.The article presents data on changes in local velocity,volumetric airflow and instantaneous heat transfer coefficient of non-stationary airflow in supply systems with different valve channel designs.A spectral analysis of the pulsations of the local heat transfer coefficient was also performed.The Nusselt number was calculated for the studied supply systems.The figured valve channels lead to an increase in the volumetric airflow through the supply systemupto32%comparedwiththe basic configuration.The useof a square valve channel leads to suppression of heat transfer(drop is about 15%)compared to the basic supply system,and the use of a triangular valve channel causes an intensification of heat transfer(growth is about 17.5%).The obtained data can be useful for refining mathematical models,adjusting machine learning algorithms,and improving design methods for supply systems of reciprocating machines to improve their technical,economic,and environmental characteristics.
文摘The heat transfer analysis was performed for an AC electric arc furnace (EAF). Heat losses by conduction, convection and radiation from outer surface, roof, bottom and electrodes of EAF were determined in detail. Some suggestions about decreasing heat losses were presented.
文摘One quarter scale experiment device of a typical L-shape architecture structure including a burning room and an adjacent hallway is established to carry out the research.The smoke characteristics at the sampling points below the ceiling of the burning compartment and the roof of the hallway are studied systematically to find out the effects of different ceilings on the local fire origin compartment and the smoke transportation to a remote area.A series of tests is reported and the smoke residence time,the concentration peak and the concentration build up rate are investigated as functions of the type of the ceiling.The smoke residence time,the most important factor concerning smoke toxicity,is described by a novel concept,wavelength,in this study.Furthermore,it is worth emphasizing that the PVC ceiling exhibits a phenomenon of frequent collapse during the fire developing period.The single heat action is conducted to judge the smoke and the heat effect on the fire risk.
文摘In the present investigation we have discussed the flow of a Jeffrey-six constant incompressible fluid between two infinite coaxial cylinders in the presence of heat transfer analysis. The governing equations of Jeffrey-six constant fluid along with energy equation have been derived in cylindrical coordinates. The highly nonlinear equations are simplified with the help of non-dimensional parameters and then solved analytically with the help of homotopy analysis method （HAM） for two fundamental flows namely Couette and Generalized Couette flow. The effects of emerging parameters are discussed through graphs. The convergence of the HAM solution has been discussed by plotting h-curves.
基金Supported by the National Natural Science Foundation of China under Grant No 11304247the Shaanxi Provincial Research Plan for Young Scientific and Technological New Stars(No 2015KJXX-40)the Youth Foundation of Xi’an University of Post&Telecommunication under Grant Nos 1011215 and 1010473
文摘We investigate the thermal characteristics of standard organic light-emitting diodes （OLEDs） using a simple and clear 1D thermal model based on the basic heat transfer theory. The thermal model can accurately estimate the device temperature, which is linearly with electrical input power. The simulation results show that there is almost no temperature gradient within the OLED device working under steady state conditions. Furthermore, thermal analysis simulation results show that the surface properties （convective heat transfer coetficient and surface emissivity） of the substrate or cathode can significantly affect the temperature distribution of the OLED.
文摘In this paper,by using the ECMWF objective analysed data as well as CAC and NOAA grid point data of 1981 and 1983,the sensible and latent heat fluxes at the air and sea boundary surface within the range of 45°E-75°W, 35°N-35°S over the Pacific and the Indian Ocean are calculated. The purpose is to analyse the different revealing features during the mature stage and at the end of the 1982 -1983 El Nino event and to compare the difference of the features between thd El Nino and the normal. The result shows that the air and sea heat exchange west of the dateline over the central tropical Pacific during the EJ Nino period is more intense than that of the normal. However,the fluxes of the sensible and latent heat on the sea surface with strong warming of SSTneat by and on the south side of the equator east of 170°W are low and even negative,and the patterns of the sensible and latent heat fluxes over the Indian Ocean during the year of 1983 are similer to that of normal. Spatial patterns of the sensible heat ,the latent heat,SST,OLR and the wind speed exhibit large anomalies during the El Nino event. The corresponding relationships of the spatial distribution of the streng exchange of heat fluxes with regions of high SST and action convection or negative anomalies of OLR are relatively complicated. But the region of maximum air and sea heat exchange is in good coincidence with that of high value of the Vs. The strong heat exchange is weakened with the declining and the finishing of the El Nino event in the central tropical Pacific.
文摘The response to single heat treatment and Step-down heat (SDH) treatment in vitro of V79 and L cells was studied. Colony-forming ability was assayed in medium after treatment in vitro. Time-response curves were established and subjected to Arrhenius analysis. The Arrhenius curves showed inflection points at 43℃ for V79 cells and at 42℃ for L cells. The activation energies were 145 kcal/mole and 400 kcal/mole above and below 43℃ (P<0.05), respectively, for V79 cells, while 160 kcal/mole and 300 kcal/mole above and below 42℃ (P<0.05), respectively, for L cells. Thermosensitivity of L cells are markedly higher than V79 cells. Both V79 and L cells were sensitized by SDH. The SDH effect was characterized by a reduction in shoulder (an addition effect to sublethal damage), an increase in slope (thermosensitization), and the delay and disappearance of thermotolerant 'tail' for V79 and L cells at 45℃ to 40℃ and 44℃ to 42℃ SDH treatment respectively. Particularly, 42℃ to 39℃ or 42℃ to 40℃ SDH for L cells resulted in thermosensitization effect up to a factor of 7.1 or 2.7, respectively. The effect was quantified by thermorsensitization ratio (TSR), defined as T0 single heated/T0SDH-heated. The relative ratio was much higher for V79 than for L cells. Heat killing with SDH characterized by Arrhenius analysis showed that Step-down heating reduced the activation energy for heat killing more than single heating. The decrease of activation energy for L cells was markedly greater than for V79. These data suggest that greater cellular sensitivity under step-down heating conditions may reflect a different mechanism for cell killing.
文摘A boundary layer analysis is presented to investigate numerically the effects of radiation, thermophoresis and the dimensionless heat generation or absorption on hydromagnetic flow with heat and mass transfer over a flat surface in a porous medium. The boundary layer equations are transformed to non-linear ordinary differential equations using scaling group of transformations and they are solved numerically by using the fourth order Runge-Kutta method with shooting technique for some values of physical parameters. Comparisons with previously published work are performed and the results are found to be in very good agreement. Many results are obtained and a representative set is displayed graphically to illustrate the influence of the various parameters on the dimensionless velocity, temperature and concentration profiles as well as the local skin-friction coefficient, wall heat transfer, particle deposition rate and wall thermophoretic deposition velocity. The results show that the magnetic field induces acceleration of the flow, rather than deceleration （as in classical magnetohydrodynamics （MHD） boundary layer flow） but to reduce temperature and increase concentration of particles in boundary layer. Also, there is a strong dependency of the concentration in the boundary layer on both the Schmidt number and mass transfer parameter.
文摘Traditional feature-based turbine blade models can match the needs of geometric modeling but could hardly meet the requirement of data extraction in 1-D heat transfer analysis. In this paper, the requirements of data extraction in 1-D heat transfer analysis are taken into consideration as well as geometric representation in parametric design process. An improved turbine blade parametric modeling method is proposed. Based on the modeling method proposed, a system structure of blade modeling process considering 1-D heat transfer analysis is devised. Eventually, a turbine blade parametric modeling system is constructed to test and verify the feasibility of the proposed modeling method and system structure. Experiments show that the blade parametric modeling method proposed can make geometric models better adapt to the specific requirements of 1-D heat transfer analysis and has certain reference value to the creation of high quality digital models.
文摘Selection of air conditioning（AC） cold/heat sources generally concerns about certain aspects and cannot reveal the whole profile of the problems. Grey relation analysis （GRA） is a data processing method to categorize the correlation extent of compared sequences and a certain reference sequence in a system with uncertain information. It is applied to evaluating and selecting AC cold/heat sources from four main aspects, which are technology, economy, reliability, and operation and management. Case study shows that the result for selecting AC cold/heat sources with the GRA method can be more reasonable and convincible. Thus it offers a new approach for designers in heating, ventilating and air conditioning field to compare and evaluate different AC cold/heat sou rces.
文摘This work investigates the transient behaviour of a phase change material based cool thermal energy storage (CTES) system comprised of a cylindrical storage tank filled with encapsulated phase change materials (PCMs) in spherical container integrated with an ethylene glycol chiller plant. A simulation program was developed to evaluate the temperature histories of the heat transfer fluid (HTF) and the phase change material at any axial location during the charging period. The results of the model were validated by comparison with experimental results of temperature profiles of HTF and PCM. The model was also used to investigate the effect of porosity, Stanton number, Stefan number and Peclet number on CTES system performance. The results showed that increase in porosity contributes to a higher rate of energy storage. However, for a given geometry and heat transfer coefficient, the mass of PCM charged in the unit decreases as the increase in porosity. The St number as well as the Ste number is also influential in the performance of the unit. The model is a convenient and more suitable method to determine the heat transfer characteristics of CTES system. The results reported are much useful for designing CTES system.
基金the National Natural Science Foundation of China (No.19872016,19872017)the National Key Basic Research Special Foundation (G1999032805)the Foundation for University Key Teachers by the Ministry of Education of China
文摘This paper presents an improved precise integration algorithm fortransient analysis of heat transfer and some other problems. Theoriginal precise integration method is improved by means of the inve-rse accuracy analysis so that the parameter N, which has been takenas a constant and an independent pa- rameter without consideration ofthe problems in the original method, can be generated automaticallyby the algorithm itself.
基金Supported by the Sustainable Energy Propulsion System Program of 211’s Engineering Foundation, Shanghai Jiaotong University.
文摘The phase change characteristic of the power source of an underwater glider propelled by the ocean＇s thermal energy is the key factor in glider attitude control. A numerical model has been established based on the enthalpy method to analyze the phase change heat transfer process under convective boundary conditions. Phase change is not an isothermal process, but one that occurs at a range of temperature. The total melting time of the material is very sensitive to the surrounding temperature. When the temperature of the surroundings decreases 8 degrees, the total melting time increases 1.8 times. But variations in surrounding temperature have little effect on the initial temperature of phase change, and the slope of the temperature time history curve remains the same. However, the temperature at which phase change is completed decreases significantly. Our research shows that the phase change process is also affected by container size, boundary conditions, and the power source＇s cross sectional area. Materials stored in 3 cylindrical containers with a diameter of 38ram needed the shortest phase change time. Our conclusions should be helpful in effective design of underwater glider power systems.
基金Supported by the National Natural Science Foundation of China(21576036,21406026)
文摘Due to the deterioration of serious energy dilemma,energy-conservation and emission–reduction have been the strategic target in the past decades,thus people have identified the vital importance of higher energy efficiency and the influence of lower carbon development.Since work exchange network is a significant part of energy recovery system,its optima design will have dramatically significant effect on energy consumption reduction in chemical process system.With an extension of the developed transshipment model in isothermal process,a novel step-wise methodology for synthesis of direct work exchange network(WEN)in adiabatic process involving heat integration is first proposed in this paper,where a nonlinear programming(NLP)model is formulated by regarding the minimum utility consumption as objective function and optimizing the initial WEN in accordance with the presented matching rules to get the optimized WEN configuration at first.Furthermore,we focus on the work exchange network synthesis with heat integration to attain the minimal total annual cost(TAC)with the introduction of heat-exchange equipment that is achieved by the following strategies in sequence:introducing heat-exchange equipment directly,adjusting the work quantity of the adjacent utility compressors or expanders,and approximating upper/lower pressure limits consequently to obtain considerable cost savings of expanders or compressors and work utility.Finally,a case taken from the literature is studied to illustrate the feasibility and effectiveness of the proposed method.
基金Supported by the Strategic Priority Research Program of Chinese Academy of Sciences(No.XDA20060502)the Key Special Project for Introduced Talents Team of Southern Marine Science and Engineering Guangdong Laboratory(Guangzhou)(No.GML2019ZD0306)+4 种基金the National Natural Science Foundation of China(Nos.41776023,41731173,41521005,41676013,41775052,41506003)the Rising Star Foundation of the South China Sea Institute of Oceanology(No.NHXX2018WL0201)the Innovation Academy of South China Sea Ecology and Environmental Engineering,Chinese Academy of Sciences(No.ISEE2018PY06)the Independent Research Project Program of State Key Laboratory of Tropical Oceanography(No.LTOZZ1802)the Basic Scientifi c Research and Operation Foundation of the CAMS(Nos.2018Z006,2017R001)。
文摘We investigated the effects of monsoon onset vortex(MOV)on the mixed layer heat budget in the Bay of Bengal(BOB)in spring 2003 using the reanalysis datasets.The results suggest that the solar radiation flux penetrating the mixed layer and the existence of barrier layer are both able to modulate the effects of MOV on the evolution of sea surface temperature(SST)in the BOB.Prior to the formation of BOB MOV,the local SST raised quickly due to mass of solar radiation reaching the sea surface under the clear-sky condition.Meanwhile,since the mixed layer was shallow before the onset of the Asian summer monsoon(ASM),some solar radiation flux could penetrate to directly heat the deeper water,which partly offset the warming effect of shortwave radiation.On the other hand,the in-situ SST started to cool due to the upwelling of cold water when the MOV generated over the BOB,along with the rapidly increased surface wind speed and its resultant deeper mixed layer.As the MOV developed and moved northward,the SST tended to decrease remarkably because of the strong upward surface latent heat flux over the BOB ascribed to the wind-evaporation mechanism.However,the MOV-related precipitation brought more fresh water into the upper ocean to produce a thicker barrier layer,whose thermal barrier effect damped the cooling effect of entrainment upwelling on the decrease tendency of the BOB SST.In other words,the thermal barrier effect could slow down the decreasing trend of the BOB SST even after the onset of ASM,which facilitated the further enhancement of the MOV.
基金funded by the National Natural Science Foundation of China (Grant Nos. 31201150 and 31101116)the Research Grant of China National Rice Research Institute (Grant No. 2012RG004-3)+1 种基金the Special Fund for Agro-Scientific Research in the Public Interest (Grant No. 201203029)the National System of Rice Industry (Grant No. CARS-01-27)
文摘Ten F1 combinations with their male and female parents were employed to evaluate their heat tolerance during the flowering and early grain filling stages. The rice plants were subjected to heat stress（39 °C–43 °C） for 1–15 d during flowering. Based on the heat stress index, heat tolerance was only observed in the F1 combinations H2（K22A × R207）, H3（Bobai A × R207） and H4（Bobai A × Minghui 63）, whereas the others received above 0.5000 of heat stress index. Both parents of the tolerant combination（heat-tolerant × heat-tolerant） possessed heat tolerance, whereas the susceptible combinations were crossed by heat-tolerant（sterile lines） × heat-susceptible（restorer lines）, heat-susceptible × heat-tolerant, or heat-susceptible × heat-susceptible parents. This result indicated that heat tolerance in rice was controlled by recessive genes. Thus, both parents should possess high temperature tolerance to develop heat-tolerant F1 combinations. Furthermore, the heat stress index of F1 combinations was significantly correlated with the heat stress index of restorer lines but not with the heat stress index of maintainer lines. This result suggested that male parents play a more important role in heat-tolerant combinations than female parents. Therefore, the heat susceptibility of the hybrid rice in China is mainly due to the wide application of low-heat-tolerant restorer lines with high yield in three-line hybrid rice breeding.
文摘A simple and highly accurate semi-analytical method, called the differential transformation method(DTM), was used for solving the nonlinear temperature distribution equation in solid and porous longitudinal fin with temperature dependent internal heat generation. The problem was solved for two main cases. In the first case, heat generation was assumed variable by fin temperature for a solid fin and in second heat generation varied with temperature for a porous fin. Results are presented for the temperature distribution for a range of values of parameters appearing in the mathematical formulation(e.g. N, εG, and G). Results reveal that DTM is very effective and convenient. Also, it is found that this method can achieve more suitable results in comparison to numerical methods.
基金Project supported by the National Natural Science Foundation of China （No. 10972136） and the Doctoral Fund for New Teachers of Higher Eduation of China （No. 20090073120014）
文摘The laminar fully developed nanofluid flow and heat transfer in a horizonal channel are investigated. Highly accurate solutions for the temperature and nanopavticle concentration distributions are obtained. The effects of the Brownian motion parameter Nb, the thermophoresis parameter Nt, and the Lewis number Le on the temperature and nanoparticle concentration distributions are discussed. The current analysis shows that the nanoparticles can improve the heat transfer characteristics significantly for this flow problem.
基金supported by the National Basic Research Program of China[grant number 2012CB417403]State Key Laboratory of Tropical Oceanography,South China Institute of Oceanology,Chinese Academy of Sciences[project number LTO1502]
文摘Changes of the net ocean surface heat flux（Q_（net）） into the tropical Indian Ocean（TIO） may be an indicator of the climate changes in the Asia and Indian–Pacific Ocean regions with the steadily warming trend in the TIO since the 1950 s. Using two observational ocean surface flux products,this letter evaluates the historical simulations of Q_（net） over the TIO during 1984–2005 in two versions of FGOALS, from CMIP5. The results show that both models present a basin-wide underestimation of net surface heat flux, possibly resulting from the positive latent heat flux biases extending over almost the entire TIO basin. Both models share an Indian Ocean dipole-like bias in the net surface heat flux, consistent with precipitation, SST, and subsurface ocean temperature biases, which can be traced to errors in the South Asian summer monsoon. Area-averaged annual time series analyses of the surface heat budget imply that the FGOALS-s2 bias lies more in radiative imbalance, illustrating the need to improve cloud simulation; while the FGOALS-g2 bias presents ocean surface turbulence flux as the key process, requiring improvement in the simulation of oceanic processes. Neither FGOALS-g2 nor FGOALS-s2 can capture the decreasing tendency of Q_（net） well. All observed and simulated datasets imply surface latent heat flux as the primary contributing component, indicating the simulation biases of models may derive mainly from the biases in simulating latent heat flux. A small latent heat flux increase in models can be considered to be slowed by relaxed wind, increased stability, and surface relative humidity.
