Chen Jiangping

Hydrogen Storage Properties of La1-xYxNi5-yAly Alloys

Abstract The feasibilities of La 1- x Y x Ni 5-y Al y alloys ( x =0.6, 0.7; y =0.1, 0.2) applied in metal hydride high-pressure compressor were investigated systematically in terms of the crystal structure, hydrogen absorption/desorption properties and pulverization resistance. XRD analyses show that all the investigated alloys present CaCu 5 type hexagonal structure and the unit cell volume decreases with the increase of Y, but increases with the increase of Al content. The pressure-composition isotherms and absorption kinetics were measured at 20, 30 and 40 °C by the volumetric method. Hydrogen absorption/desorption measurement reveals that Y and Al could effectively increase and decrease the equilibrium hydrogen pressure, respectively. They are ideal elements to adjust the equilibrium hydrogen pressure of LaNi 5 -based alloys without other remarkable negative influences. We think that the alloys could be matched as ‘alloy pairs’ and applied in a double-stage metal hydride compressor; the compressor could boost the feed hydrogen gas at room temperature from 2 MPa to 35∼40 MPa at 135∼155 °C.

Thermal-hydraulic performance of novel louvered fin using flat tube cross-flow heat exchanger

Experimental studies were conducted to investigate the air-side heat transfer and pressure drop characteristics of a novel louvered fins and flat tube heat exchangers. A series of tests were conducted for 9 heat exchangers with different fin space and fin length, at a constant tube-side water flow rate of 2.8 m3/h. The air side thermal performance data were analyzed using the effectiveness-NTU method. Results were presented as plot of Colburn j factor and friction factor f against the Reynolds number in the range of 500–6500. The characteristics of the heat transfer and pressure drop of different fin space and fin length were analyzed and compared. In addition, the curves of the heat transfer coefficients vs. pumping power per unit heat transfer area were plotted. Finally, the area optimization factor was used to evaluate the thermal hydraulic performance of the louvered fins with differential geometries. The results showed that the j and f factors increase with the decrease of the fin space and fin length, and the fin space has more obvious effect on the thermal hydraulic characteristics of the novel louvered fins.