ALBERT

Description: Convective heat transfer characteristics of microencapsulated phase change material slurries (MPCSs) flowing in a circular tube under constant heat flux are studied and a feasible heat transfer model is presented. The heat transfer coefficient of MPCS and the wall temperature of the circular tube are simulated. The simulation results agree qualitatively with the experimental results. The effects of Stefan (Ste) number, mass concentration, phase change temperature range, and Reynolds (Re) number on heat transfer characteristics are discussed. The results indicate that the Ste-number and mass fraction are the most important parameters influencing heat transfer properties compared to the phase change temperature range and Re-number which less affect these characteristics. The heat transfer characteristics of microencapsulated phase change slurries are analyzed and the effects of Stefan number, mass concentration, and Reynolds number are discussed. The phase change process, Stefan number, and mass fraction influence these heat transfer characteristics significantly. The heat transfer coefficient increases with higher Reynolds numbers.

Description: Experiments were designed to ascertain the main factors for the Sauter mean drop size ( d 32 ) of the dispersed phase in a three-stage modified Scheibel extraction column with no mass transfer. A precise correlation applied to the liquid-liquid systems with low interfacial surface tension was proposed for calculating d 32 . The maximum relative error for all data was 16.0 % and the mean relative error �4.6 %. The Sauter mean drop sizes of the dispersed phase in a three-stage modified Scheibel extraction column with no mass transfer were investigated. A precise correlation with operation conditions and system physical properties applied to liquid-liquid systems with low interfacial surface tension was proposed for calculating the dispersed-phase mean drop size.

Description: Convective heat transfer characteristics of microencapsulated phase change material slurries (MPCSs) flowing in a circular tube under constant heat flux are studied and a feasible heat transfer model is presented. The heat transfer coefficient of MPCS and the wall temperature of the circular tube are simulated. The simulation results agree qualitatively with the experimental results. The effects of Stefan (Ste) number, mass concentration, phase change temperature range, and Reynolds (Re) number on heat transfer characteristics are discussed. The results indicate that the Ste-number and mass fraction are the most important parameters influencing heat transfer properties compared to the phase change temperature range and Re-number which less affect these characteristics. The heat transfer characteristics of microencapsulated phase change slurries are analyzed and the effects of Stefan number, mass concentration, and Reynolds number are discussed. The phase change process, Stefan number, and mass fraction influence these heat transfer characteristics significantly. The heat transfer coefficient increases with higher Reynolds numbers.

Description: The condensation characteristics model of the condensation part of a separate heat pipe in a cool storage air-conditioning system is presented. In this model, the shear stress between gas and liquid two-phase flow is considered. R134a is taken as working medium of the heat pipe. The liquid film thickness, shear stress, and heat transfer coefficient of the heat pipe are calculated. The effect of the shear stress on the film thickness and the variations of the heat transfer coefficient with heat pipe diameter and heat flux are analyzed. Influences of the heat pipe incline angle and heat flux on the heat transfer coefficient are also considered. The results indicate that the liquid film based on this model is thinner and the condensation heat transfer coefficient is larger than that based on the Nusselt model. The condensation heat transfer characteristics of the condensation part of a separate heat pipe in cool storage air-conditioning systems are studied by analyzing variations of the shear stress, liquid film thickness, and condensation heat transfer coefficient with the heat pipe length at various diameters, incline angles, and heat fluxes. The shear stress between gas and liquid two-phase flow is considered.

Description: [1]  Natural carbon sources and sinks over China's terrestrial land ecosystems have an uncertain magnitude, but possibly an important role in the global carbon budget. In this paper we present an estimate of net ecosystem exchange of CO 2 (NEE) over China for the years 2001-2010 using the CarbonTracker Data Assimilation System for CO 2 (CTDAS). Additional Chinese and Asian CO 2 observations are used in CTDAS to improve our estimate. We found that the combined terrestrial ecosystems in China absorbed about –0.33 Pg Cy r -1 during 2001-2010, compensating approximately 20% of the total CO 2 emissions from fossil fuel burning and cement manufacturing from China (+1.70 Pg C yr -1 ). The uncertainty on Chinese terrestrial carbon exchange estimates as derived from a set of sensitivity experiments suggests a range of –0.29 to –0.64 Pg C yr -1 . This total Chinese terrestrial CO 2 sink is attributed to the three major biomes (forests, crop lands and grass/shrub lands) with estimated CO 2 fluxes of –0.12 Pg C yr -1 (range from –0.09 to –0.19 Pg C yr -1 ), –0.12 Pg C yr -1 (range from –0.09 to –0.26 Pg C yr -1 ) and –0.09 Pg C yr -1 (range from –0.09 to –0.17 Pg C yr -1 ), respectively. The peak-to-peak amplitude of inter-annual variability (IAV) of the Chinese terrestrial ecosystem carbon flux is 0.21 Pg C yr -1 (~64% of mean annual average), with the smallest CO 2 sink (–0.19 Pg C yr -1 ) in 2003 and the largest CO 2 sink (–0.40 Pg C yr -1 ) in 2007 corresponding with favorable temperature in spring/winter. We stress that our estimate of terrestrial ecosystem CO 2 uptake based on inverse modeling strongly depends on a limited number of atmospheric CO 2 observations used. More observations in China specifically, and in Asia in general are needed to improve the accuracy of terrestrial carbon budgeting for this region.

Description: The reactivity of 1-propanol, 1,3-propanediol, 1,2-propanediol and glycerol in electrocatalytic oxidation on Au, Pt and Pt-modified Au electrodes in alkaline solution has been investigated. Pt-modified Au electrodes have been prepared by depositing platinum on Au polycrystalline electrodes by the linear sweep voltammetric method. The oxidation of C 3 alcohols on an individual electrode shows only a little difference in peak potential but a significant difference in peak current, and peak current is determined by the number and position of hydroxyl groups in the molecular chain. The oxidation of an individual C 3 alcohol on Au and Pt electrodes shows the advantages of the Au electrode in peak current and of the Pt electrode in oxidation potential. Pt modification significantly improves the catalytic activity of Au electrodes. The catalytic activity shown by Pt-modified Au electrodes reflects the advantages of both Pt and Au electrodes. The electrocatalytic oxidation of C 3 alcohols on Au, Pt and Pt-modified Au electrodes in alkaline solution shows that the reactivity of these alcohols depends on the number and position of hydroxyl groups in the molecular chain. The catalytic activity exhibited by Pt-modified Au electrodes reflects the advantages of Au and Pt electrodes in oxidation potential and/or peak current.

Description: A novel and convenient route for the synthesis of phenylethenyl methyl carbonate by the methoxycarbonylation of phenylacetaldehyde with dimethyl carbonate was developed in the presence of solid base catalysts. The results showed that solid bases with moderate strength such as MgO favored the formation of phenylethenyl methyl carbonate, and the yield of phenylethenyl methyl carbonate could be linearly correlated with the amount of moderate basic sites. The function of basic catalysts was mainly ascribed to the activation of phenylacetaldehyde via the abstraction of α-H by the base sites. Phenylethenyl methyl carbonate was synthesized by the methoxycarbonylation of phenylacetaldehyde with dimethyl carbonate in the presence of solid base catalysts. Solid bases with moderate strength favored the formation of phenylethenyl methyl carbonate and the yield could be linearly correlated with the amount of moderate basic sites.

Description: [1]  We report two lower thermospheric enhanced sodium layer (TeSL) cases observed at a low latitude station, Lijiang, China (26.7°N, 100.0°E), on March 10 and April 10, 2012, respectively. The TeSLs in the two cases were located at altitudes near 122 and 112 km, respectively. In addition, strong sporadic sodium layers (SSLs) near 100 km accompanied the TeSL observed on March 10, 2012. Both the TeSLs and SSLs exhibited tidal-induced downward motion. The adjacent ground-based and space-borne ionospheric radio observations showed strong Es layers before the appearance of the TeSLs, suggesting an " Es – TeSLs (SSLs)" chain formed through the tidal wind shear mechanism. Assuming that the vertical tidal wavelengths remain unchanged, it is found that in different regions caused by the tidal wind shear, different TeSLs evolution processes are expected: (1) in a tidal-convergence region, a TeSL/SSL with a downward propagation phase is enhanced due to a rapid decrease in the Na + lifetime at the lower altitude; (2) in an ion convergence-divergence interface region, a TeSL/SSL will still follow the tidal downward phase progression, but sodium density does not exhibit evident enhancement; and (3) when a TeSL/SSL enters into a tidal wind-divergence zone, the layer density tends to decrease.

Description: [1]  We present in this study the results obtained when applying a physical algorithm based on a variational methodology, to data from the Advanced Technology Microwave Sounder (ATMS) onboard the Suomi National Polar-orbiting Partnership (SNPP), for a consistent retrieval of geophysical data in all-weather conditions. The algorithm, which runs operationally at the U.S. National Oceanic and Atmospheric Administration (NOAA), is applied routinely to a number of sounders from the Polar-orbiting Operational Environmental Satellites (POES), the Defense Meteorological Satellite Program (DMSP) and the European Meteorological Operational (MetOp) satellites constellations. The One-dimension variational (1DVAR) methodology, which relies on a forward operator, the Community Radiative Transfer Model (CRTM), allows for solving the inversion of the radiometric measurements into geophysical parameters which have a direct impact on the brightness temperatures. The parameters that are produced by this Microwave Integrated Retrieval System (MiRS) algorithm, include the atmospheric temperature T(p), moisture Q(p) and vertically-integrated total precipitable water (TPW), the surface skin temperature (Tskin) and emissivity (emiss) as well as the hydrometeor products of non-precipitating cloud liquid water (CLW), rain and ice water paths (RWP, IWP). In this algorithm, a simple post-processing is applied to the 1DVAR-generated emissivity to derive cryospheric products (snow water equivalent SWE and sea ice concentration SIC) when the data are measured over these surfaces. The post-processing is also applied to the hydrometeors products to generate a surface rainfall rate (RR). This comprehensive set of sounding, surface, hydrometeor and cryospheric products generated from SNPP/ATMS is therefore radiometrically consistent, meaning that when input to the forward operator, it will allow the simulation of the actual brightness temperatures measurements within noise levels. The geophysical consistency between the products, also critical, is satisfied due to the physical approach adopted and the geophysical constraints introduced through the correlation matrix used in the variational system. The results shown in this paper confirm that the performances of all products are within the expected accuracy and precision figures, and comparable to performances usually obtained with single-parameter dedicated algorithms, with the added value that the inverted products are both radiometrically and geophysically consistent.

Description: The morphology of low-latitude ionosphere is greatly affected by the zonal electric field, especially at disturbance time. In this study, historical data from two low-latitude ionosondes located at Haikou and Chongqing, China, are used to study the disturbance vertical drift properties of ionospheric F layer during the initial and main phases of 50 intense storms. The disturbance drift from an empirical model is used as an indicator to denote the E × B disturbance magnitude. It is found that the drifts both at the base and at the peak height are increased in magnitude when the disturbance becomes stronger. For the same disturbance, ionospheric vertical drifts at the base height are comparable with those at the peak height over Haikou, but they are larger than the latter over Chongqing, both drifts being smaller than those at the magnetic equator. The drifts are larger in daytime than in nighttime, but no rule is found on their seasonal dependence. This indicates that low-latitude storm time ionospheric vertical drift of the ionospheric layer exhibits both consistent and individual properties at different locations.