The 20th CGS academic annual meeting, with 556 participants and 534 papers, was convened in Xi'an on 16-20 October 2004. Seminars, discussions and forums were organized covering 23 special topics.
The EGR (exhaust gas recirculation) technique can greatly reduce the NOx emission of diesel engines, especially when an EGR cooler is employed. Numerical simulations are applied to study the flow field and temperature...The EGR (exhaust gas recirculation) technique can greatly reduce the NOx emission of diesel engines, especially when an EGR cooler is employed. Numerical simulations are applied to study the flow field and temperature distributions inside the EGR cooler. Three different models of EGR cooler are investigated, among which model A is a traditional one, and models B and C are improved by adding a helical baffle in the cooling area. In models B and C the entry directions of cooling water are different, which mostly influences the flow resistance. The results show that the improved structures not only lengthen the flow path of the cooling water, but also enhance the heat exchange rate between the cool and hot media. In conclusion we suggest that the improved structures are more powerful than the traditional one.展开更多
Nano fluid is considered to be a class of high efficient heat transfer fluid created by dispersing some special solid nanoparticles (normally less than 100 nm) in traditional heat transfer fluid. The present experimen...Nano fluid is considered to be a class of high efficient heat transfer fluid created by dispersing some special solid nanoparticles (normally less than 100 nm) in traditional heat transfer fluid. The present experiment was conducted aiming at investigating the forced heat transfer characteristics of aqueous copper (Cu) nanofluid at varying concentration of Cu nano-particles in different flow regimes (300<Re≤16 000). The forced convective heat transfer enhancement is available both in the laminar and turbulent flow with increasing the concentration. Especially, the enhancement rate increases dramatically in laminar flow regime, for instance, the heat transfer coefficient of Cu/water nanofluid increases by two times at around Re=2 000 compared with that of base fluid water, and averagely increases by 62% at 1% volume fraction. However, the heat transfer coefficient of Cu/water decreases sharply in the transition flow regime. Furthermore, it has the trend that the heat transfer coefficient displays worse with increasing the concentration.展开更多
Mode Water’, as a product of air-sea interaction, influences the thermal structure and circulation pattern in upper layer ocean and consequently affects the variations of climate. In this paper the recent research re...Mode Water’, as a product of air-sea interaction, influences the thermal structure and circulation pattern in upper layer ocean and consequently affects the variations of climate. In this paper the recent research results about the subtropi-cal Mode Water in the North Pacific are overiewed. A detailed description of the three kinds of Mode Water in the subtropical North Pacific and some comparisons of their similarities and differences are introduced. Some science problems that need further exploration have been raised.展开更多
Using monthly reanalysis data of the National Center for Environmental Research/National Center for Atmospheric Research(NCEP/NCAR) and Objectively Analyzed Air-Sea Heat Flux(OAFlux) gathered during the winter,singula...Using monthly reanalysis data of the National Center for Environmental Research/National Center for Atmospheric Research(NCEP/NCAR) and Objectively Analyzed Air-Sea Heat Flux(OAFlux) gathered during the winter,singular vector decomposition(SVD) analysis was conducted to reveal the coupled mode between the Kuroshio marine heating anomaly and the geopotential height at 500 hPa(Z500) over the North Pacific.The first SVD mode showed that when the northern Kuroshio marine heating anomaly was positive,the Z500 in the central and western sections of the North Pacific was anomalously low.By composing the meteorological field anomalies in the positive(or negative) years,it has been revealed that while the Aleutian Low deepens(or shallows),the northwesterly wind overlying the Kuroshio strengthens(or weakens) and induces the near-surface air to be cool(or warm).Furthermore,this increases(or decreases) the upward heat flux anomaly and cools(or warms) the sea surface temperature(SST) accordingly.In the vicinity of Kuroshio and its downstream region,the vertical structure of the air temperature along the latitude is baroclinic;however,the geopotential height is equivalently barotropic,which presents a cool trough(or warm ridge) spatial structure.The divergent wind and vertical velocities are introduced to show the anomalous zonal circulation cell.These are characterized by the rising(or descending) air in the central North Pacific,which flows westward and eastward toward the upper troposphere,descends(or rises) in the Kuroshio and in the western section of North America,and then strengthens(or weakens) the mid-latitude zonal cell(MZC).展开更多
Sinking columns are one of the most hazardous geological structures in north Chine typed coal fields. To understand the sinking column formation, to judge if the columns are hazardous or not, the inner circle mechanis...Sinking columns are one of the most hazardous geological structures in north Chine typed coal fields. To understand the sinking column formation, to judge if the columns are hazardous or not, the inner circle mechanism of groundwater in forming sinking columns in the relatively isolated areas was proposed according to the investigation on formation or distribution of sinking columns in some north China typed coal fields, such as Fengfeng, Xiangtai, Huaibei, Yangquan and so on. The heat generated by magma energized groundwater circulation and developed limestone karst in the relatively isolated areas. The CaCO3 solution accelerated by geothermal abnormality, the effect of high content of CO2 on dissolution and saturation of CaCO3 were discussed. Compared the forming conditions of the sinking columns developed in other coal mining areas in north China coal field, the paper deduced that the above factors collude karst development and sinking column formation, the columns in current geothermal areas are permeable and those in high coal rank areas or in paleo abnormally geothermal areas. The paper suggested that the sinking columns in the current abnormally geothermal areas were permeable, but those in the areas with high coal rank were not on contract.展开更多
A model is proposed to predict boiling heat transfer coefficient in a three-phase circulating fluidized bed (CFB), which is a new type of evaporation boiling means for enhancing heat transfer and preventing fouling. T...A model is proposed to predict boiling heat transfer coefficient in a three-phase circulating fluidized bed (CFB), which is a new type of evaporation boiling means for enhancing heat transfer and preventing fouling. To verify the model, experiments are conducted in a stainless steel column with 39mm ID and 2.0m height, in which the heat transfer coefficient is measured for different superficial velocities, steam pressures, particle concentrations and materials of particle. As the steam pressure and particle concentrations increase, the heat transfer coefficient in the bed increases. The heat transfer coefficient increases with the liquid velocity but it exhibits a local minimum.The heat transfer coefficient is correlated with cluster renewed model and two-mechanism method. The prediction of the model is in good agreement with experimental data.展开更多
To improve energy conversion efficiency, optimization of the working fluids in organic Rankine cycles(ORCs) was explored in the range of low-temperature heat sources. The concept of unit-heat-exchange-area(UHEA) net p...To improve energy conversion efficiency, optimization of the working fluids in organic Rankine cycles(ORCs) was explored in the range of low-temperature heat sources. The concept of unit-heat-exchange-area(UHEA) net power, embodying the cost/performance ratio of an ORC system, was proposed as a new indicator to judge the suitability of ORC working fluids on a given condition. The heat exchange area was computed by an improved evaporator model without fixing the minimum temperature difference between working fluid and hot fluid, and the flow pattern transition during heat exchange was also taken into account. The maximum UHEA net powers obtained show that dry organic fluids are more suitable for ORCs than wet organic fluids to recover low-temperature heat. The organic fluid 1-butene is recommended if the inlet temperature of hot fluid is 353.15-363.15 K or443.15-453.15 K, heptane is more suitable at 373.15-423.15 K, and R245 ca is a good option at 483.15-503.15 K.展开更多
文摘The 20th CGS academic annual meeting, with 556 participants and 534 papers, was convened in Xi'an on 16-20 October 2004. Seminars, discussions and forums were organized covering 23 special topics.
文摘The EGR (exhaust gas recirculation) technique can greatly reduce the NOx emission of diesel engines, especially when an EGR cooler is employed. Numerical simulations are applied to study the flow field and temperature distributions inside the EGR cooler. Three different models of EGR cooler are investigated, among which model A is a traditional one, and models B and C are improved by adding a helical baffle in the cooling area. In models B and C the entry directions of cooling water are different, which mostly influences the flow resistance. The results show that the improved structures not only lengthen the flow path of the cooling water, but also enhance the heat exchange rate between the cool and hot media. In conclusion we suggest that the improved structures are more powerful than the traditional one.
基金supported by Basic Science Research Program through the National Research Foundation of Korea (NRF)funded by the Ministry of Education, Science and Technology (No.2012-0004544)
文摘Nano fluid is considered to be a class of high efficient heat transfer fluid created by dispersing some special solid nanoparticles (normally less than 100 nm) in traditional heat transfer fluid. The present experiment was conducted aiming at investigating the forced heat transfer characteristics of aqueous copper (Cu) nanofluid at varying concentration of Cu nano-particles in different flow regimes (300<Re≤16 000). The forced convective heat transfer enhancement is available both in the laminar and turbulent flow with increasing the concentration. Especially, the enhancement rate increases dramatically in laminar flow regime, for instance, the heat transfer coefficient of Cu/water nanofluid increases by two times at around Re=2 000 compared with that of base fluid water, and averagely increases by 62% at 1% volume fraction. However, the heat transfer coefficient of Cu/water decreases sharply in the transition flow regime. Furthermore, it has the trend that the heat transfer coefficient displays worse with increasing the concentration.
基金supported by the NSFC(No.49976004 and 40028605)National Key Program for Developing Basic Science(No.G1999043807).
文摘Mode Water’, as a product of air-sea interaction, influences the thermal structure and circulation pattern in upper layer ocean and consequently affects the variations of climate. In this paper the recent research results about the subtropi-cal Mode Water in the North Pacific are overiewed. A detailed description of the three kinds of Mode Water in the subtropical North Pacific and some comparisons of their similarities and differences are introduced. Some science problems that need further exploration have been raised.
基金National Key Basic Research and Development Program of China (2007CB411800)
文摘Using monthly reanalysis data of the National Center for Environmental Research/National Center for Atmospheric Research(NCEP/NCAR) and Objectively Analyzed Air-Sea Heat Flux(OAFlux) gathered during the winter,singular vector decomposition(SVD) analysis was conducted to reveal the coupled mode between the Kuroshio marine heating anomaly and the geopotential height at 500 hPa(Z500) over the North Pacific.The first SVD mode showed that when the northern Kuroshio marine heating anomaly was positive,the Z500 in the central and western sections of the North Pacific was anomalously low.By composing the meteorological field anomalies in the positive(or negative) years,it has been revealed that while the Aleutian Low deepens(or shallows),the northwesterly wind overlying the Kuroshio strengthens(or weakens) and induces the near-surface air to be cool(or warm).Furthermore,this increases(or decreases) the upward heat flux anomaly and cools(or warms) the sea surface temperature(SST) accordingly.In the vicinity of Kuroshio and its downstream region,the vertical structure of the air temperature along the latitude is baroclinic;however,the geopotential height is equivalently barotropic,which presents a cool trough(or warm ridge) spatial structure.The divergent wind and vertical velocities are introduced to show the anomalous zonal circulation cell.These are characterized by the rising(or descending) air in the central North Pacific,which flows westward and eastward toward the upper troposphere,descends(or rises) in the Kuroshio and in the western section of North America,and then strengthens(or weakens) the mid-latitude zonal cell(MZC).
文摘Sinking columns are one of the most hazardous geological structures in north Chine typed coal fields. To understand the sinking column formation, to judge if the columns are hazardous or not, the inner circle mechanism of groundwater in forming sinking columns in the relatively isolated areas was proposed according to the investigation on formation or distribution of sinking columns in some north China typed coal fields, such as Fengfeng, Xiangtai, Huaibei, Yangquan and so on. The heat generated by magma energized groundwater circulation and developed limestone karst in the relatively isolated areas. The CaCO3 solution accelerated by geothermal abnormality, the effect of high content of CO2 on dissolution and saturation of CaCO3 were discussed. Compared the forming conditions of the sinking columns developed in other coal mining areas in north China coal field, the paper deduced that the above factors collude karst development and sinking column formation, the columns in current geothermal areas are permeable and those in high coal rank areas or in paleo abnormally geothermal areas. The paper suggested that the sinking columns in the current abnormally geothermal areas were permeable, but those in the areas with high coal rank were not on contract.
文摘A model is proposed to predict boiling heat transfer coefficient in a three-phase circulating fluidized bed (CFB), which is a new type of evaporation boiling means for enhancing heat transfer and preventing fouling. To verify the model, experiments are conducted in a stainless steel column with 39mm ID and 2.0m height, in which the heat transfer coefficient is measured for different superficial velocities, steam pressures, particle concentrations and materials of particle. As the steam pressure and particle concentrations increase, the heat transfer coefficient in the bed increases. The heat transfer coefficient increases with the liquid velocity but it exhibits a local minimum.The heat transfer coefficient is correlated with cluster renewed model and two-mechanism method. The prediction of the model is in good agreement with experimental data.
基金Projects(U0937604,50876116)supported by the National Natural Science Foundation of ChinaProjects(2010QZZD0107,2014zzts192)supported by the Fundamental Research Funds for the Central Universities of China
文摘To improve energy conversion efficiency, optimization of the working fluids in organic Rankine cycles(ORCs) was explored in the range of low-temperature heat sources. The concept of unit-heat-exchange-area(UHEA) net power, embodying the cost/performance ratio of an ORC system, was proposed as a new indicator to judge the suitability of ORC working fluids on a given condition. The heat exchange area was computed by an improved evaporator model without fixing the minimum temperature difference between working fluid and hot fluid, and the flow pattern transition during heat exchange was also taken into account. The maximum UHEA net powers obtained show that dry organic fluids are more suitable for ORCs than wet organic fluids to recover low-temperature heat. The organic fluid 1-butene is recommended if the inlet temperature of hot fluid is 353.15-363.15 K or443.15-453.15 K, heptane is more suitable at 373.15-423.15 K, and R245 ca is a good option at 483.15-503.15 K.
