Experimental Study of Pressure Loss in a 5 × 5–Rod Bundle With the Mixing Vane Spacer Grid

Axial and lateral pressure loss in a 5 × 5 rod–bundle with a split-type mixing vane spacer grid was experimentally measured using differential pressure transmitters at different sub-channel Reynolds numbers (Re) and orienting angles. The geometrical parameters of the 5 × 5–rod bundle are as follows: they have the same diameter (D = 9.5 mm) and pitch (p = 12.6 mm) as those of real fuel rods of a typical pressurized water reactor (PWR), with a sub-channel hydraulic diameter (D$_{h}$) of 11.78 mm. The characteristics and resistance models of pressure loss are discussed. The main axial pressure loss is caused by the spacer grid, and the spacer grid generates additional wall friction pressure loss downstream of the spacer grid. The lateral pressure loss shows strong correlations with orienting angles and distance from the spacer grid. The lateral pressure loss shows a sudden burst in the mixing vanes region and a slight augmentation at z = 3D$_{h}$. After 3D$_{h}$, the lateral pressure loss decays in an exponential way with distance from the spacer grid, and it becomes constant quickly at z = 20D$_{h}$

Same titanium glycolate precursor but different products: Successful synthesis of twinned anatase TiO2 nanocrystals with excellent solar photocatalytic hydrogen evolution capability

Exploiting a synthesis protocol to tailor TiO 2 with a unique morphology and crystal phase has received considerable interest in the energy and environmental fields. We here describe the use of a titanium glycolate precursor in a hydrothermal hydrolysis reaction to engineer TiO 2 nanocrystals with different crystal phases and structures. Anatase TiO 2 nanocrystals with twinned structures were obtained by using a lower amount of NaOH in the hydrolysis system, while brookite TiO 2 nanocrystals were formed when higher amounts of NaOH were employed. The as-synthesized different TiO 2 nanocrystals have a suitable bandgap to harvest photons and a more negative bottom level of the conduction band than the redox potential of H + /H 2 indicating their potential as hydrogen-evolution semiconductor photocatalysts. However, the TiO 2 nanotwins show promoted charge separation efficiency, and thus result in superior photocatalytic H 2 generation activity compared to the anatase and brookite TiO 2 nanocrystals. Our findings provide an effective and versatile solution for the fabrication of TiO 2 -based nanostructures with different phases and morphologies through chemical conversion of powder precursor nanoparticles, which could pave the way to the design of other functional nano-oxides with unique structures

Unified nonequilibrium dynamical theory for exchange bias and training effects

We investigate the exchange bias and training effects in the FM/AF heterostructures using a unified Monte Carlo dynamical approach. This real dynamical method has been proved reliable and effective in simulating dynamical magnetization of nanoscale magnetic systems. The magnetization of the uncompensated AF layer is still open after the first field cycling is finished. Our simulated results show obvious shift of hysteresis loops (exchange bias) and cycling dependence of exchange bias (training effect) when the temperature is below 45 K. The exchange bias fields decrease with decreasing the cooling rate or increasing the temperature and the number of the field cycling. With the simulations, we show the exchange bias can be manipulated by controlling the cooling rate, the distributive width of the anisotropy energy, or the magnetic coupling constants. Essentially, these two effects can be explained on the basis of the microscopical coexistence of both reversible and irreversible moment reversals of the AF domains. Our simulated results are useful to really understand the magnetization dynamics of such magnetic heterostructures. This unified nonequilibrium dynamical method should be applicable to other exchange bias systems.Comment: Chin. Phys. B, in pres