Using the monthly geopotential heights and winds for 700 and 200 hPa for India during July and August, and the weekly M-100 Soviet rocketsonde temperature and wind data for Thumba (8.5 ° N, 76.9 ° E) during ...Using the monthly geopotential heights and winds for 700 and 200 hPa for India during July and August, and the weekly M-100 Soviet rocketsonde temperature and wind data for Thumba (8.5 ° N, 76.9 ° E) during the last week of June and the first week of September for the two contrasting summer monsoon years 1975 (a very strong monsoon year) and 1979 (a very weak monsoon year), a study has been made to examine the mean circulation features of the troposphere over India, and the structures of the temperatures and the winds of the middle atmosphere over Thumba. The study suggested that the axis of the monsoon trough (AMT) at 700 hPa shifted southward in 1975 and northward towards the foothills of the Himalayas in 1979, from its normal position. Superimposed on the low-pressure area (AMT) at 700 hPa, a well-defined divergence was noticed at 200 hPa over the northern India in 1975.The mean temperatures at 25,50 and 60 km (middle atmosphere) over Thumba were cooler in 1975 than in 1979. While a cooling trend in 1975 and warming trend in 1979 were observed at 25 and 50 km, a reversed picture was noticed at 60 km. There was a weak easterly / westerly (weak westerly phase) zonal wind in 1975 and a strong easterly zonal wind in 1979. A phase reversal of the zonal wind was observed at 50 km. A tentative physical mechanism was offered, in terms of upward propagation of the two equatorially trapped planetary waves i.e. the Kelvin and the mixed Rossby-gravity waves, to explain the occurrence of the two spells of strong warmings in the mesosphere in 1975.展开更多
Middle and low temperature thermal energy widely exists in the natural world and many industrial fields.Unlike fossil fuel power generation systems,the significant feature of middle and low temperature power generatio...Middle and low temperature thermal energy widely exists in the natural world and many industrial fields.Unlike fossil fuel power generation systems,the significant feature of middle and low temperature power generation systems is the temperature constraint of the heat source.Exploring the potential of the cycle within a limited temperature range is key to improve energy utilization efficiency.This study proposes the conception of supercritical organic fluid Brayton cycles (SOFBC) and evaluates the feasibility and application potential.R116,R23,R170 and N_(2)O are selected as the working fluids for cycle analysis based on their thermal properties.Then,thermodynamic models of the supercritical gas Brayton cycle based on simple regeneration and organic Rankine cycles (ORCs) have been established.According to the calculation results,the performances of regenerative Brayton cycles (RBCs) using four working fluids are better than that of CO_(2).The maximum thermal efficiencies of R116,R23,and R170 are 41.9%,20.2%,and 15.3%higher than that of CO_(2)at the highest temperature of 150℃.Even at 300℃,the corresponding values of three organic fluids are 25.6%,13.7%,and 13.7%higher than that of CO_(2).By analyzing the variations in isobaric specific heat capacity (c_(p)) of different working fluids,it is found that the c_(p) difference between the high and low pressure sides in the regenerator of CO_(2) is significantly higher than that of organic working fluids.Additionally,the performance of RBCs using R116 is better than the sub-ORC using R123 and the trans-RORC using R236fa at the same temperature range.The results can demonstrate that the SOFBC is superior in middle and low temperature power generation compared with the sCO_(2) Brayton cycle and ORCs.This study provides preliminary and rough evidence of the feasibility and potential for SOFBCs.展开更多
文摘Using the monthly geopotential heights and winds for 700 and 200 hPa for India during July and August, and the weekly M-100 Soviet rocketsonde temperature and wind data for Thumba (8.5 ° N, 76.9 ° E) during the last week of June and the first week of September for the two contrasting summer monsoon years 1975 (a very strong monsoon year) and 1979 (a very weak monsoon year), a study has been made to examine the mean circulation features of the troposphere over India, and the structures of the temperatures and the winds of the middle atmosphere over Thumba. The study suggested that the axis of the monsoon trough (AMT) at 700 hPa shifted southward in 1975 and northward towards the foothills of the Himalayas in 1979, from its normal position. Superimposed on the low-pressure area (AMT) at 700 hPa, a well-defined divergence was noticed at 200 hPa over the northern India in 1975.The mean temperatures at 25,50 and 60 km (middle atmosphere) over Thumba were cooler in 1975 than in 1979. While a cooling trend in 1975 and warming trend in 1979 were observed at 25 and 50 km, a reversed picture was noticed at 60 km. There was a weak easterly / westerly (weak westerly phase) zonal wind in 1975 and a strong easterly zonal wind in 1979. A phase reversal of the zonal wind was observed at 50 km. A tentative physical mechanism was offered, in terms of upward propagation of the two equatorially trapped planetary waves i.e. the Kelvin and the mixed Rossby-gravity waves, to explain the occurrence of the two spells of strong warmings in the mesosphere in 1975.
基金supported by Beijing Natural Science Foundation of China (Grant No.3222025)。
文摘Middle and low temperature thermal energy widely exists in the natural world and many industrial fields.Unlike fossil fuel power generation systems,the significant feature of middle and low temperature power generation systems is the temperature constraint of the heat source.Exploring the potential of the cycle within a limited temperature range is key to improve energy utilization efficiency.This study proposes the conception of supercritical organic fluid Brayton cycles (SOFBC) and evaluates the feasibility and application potential.R116,R23,R170 and N_(2)O are selected as the working fluids for cycle analysis based on their thermal properties.Then,thermodynamic models of the supercritical gas Brayton cycle based on simple regeneration and organic Rankine cycles (ORCs) have been established.According to the calculation results,the performances of regenerative Brayton cycles (RBCs) using four working fluids are better than that of CO_(2).The maximum thermal efficiencies of R116,R23,and R170 are 41.9%,20.2%,and 15.3%higher than that of CO_(2)at the highest temperature of 150℃.Even at 300℃,the corresponding values of three organic fluids are 25.6%,13.7%,and 13.7%higher than that of CO_(2).By analyzing the variations in isobaric specific heat capacity (c_(p)) of different working fluids,it is found that the c_(p) difference between the high and low pressure sides in the regenerator of CO_(2) is significantly higher than that of organic working fluids.Additionally,the performance of RBCs using R116 is better than the sub-ORC using R123 and the trans-RORC using R236fa at the same temperature range.The results can demonstrate that the SOFBC is superior in middle and low temperature power generation compared with the sCO_(2) Brayton cycle and ORCs.This study provides preliminary and rough evidence of the feasibility and potential for SOFBCs.
