Row number effect on heat transfer in inline banks with finned tubes

The row number effect on heat transfer for gases in cross flow over inline finned tube banks has been studied. A two stream model was used to describe the air cross flow in the tube bank. One stream was the bypass stream which exists between the tips of fins of adjacent tubes, and it was assumed to give no heat transfer to or from the tubesurface. The other was the primary stream which flows across the heat transfer surface and exchanges heat with the surface. An interchange stream existing between the bypass and primary streams. The heat transfer coefficient of the primary stream is treated as the actual heat transfer coefficient. By using the two stream assumption, a mathematical model was developed to predict the air side temperature, row by row, and to reflect the row number effect on the apparent heat transfer coefficient.Chemical Engineerin

Synthesizing and characterization of hole doped nickel based layer superconductor (La1−x_{1-x}Srx_{x})ONiAs

We report the synthesizing and characterization of the hole doped Ni-based superconductor ($La_{1-x}Sr_{x})ONiAs$. By substituting La with Sr, the superconducting transition temperature $T_c$ is increased from 2.75 K of the parent phase $LaONiAs$ to 3.7 K at the doping levels x= 0.1 - 0.2. The curve $T_c$ versus hole concentration shows a symmetric behavior as the electron doped samples $La(O_{1-x}F_{x})NiAs$. The normal state resistivity in Ni-based samples shows a good metallic behavior and reveals the absence of an anomaly which appears in the Fe-based system at about 150 K, suggesting that this anomaly is not a common feature for all systems. Hall effect measurements indicate that the electron conduction in the parent phase $LaONiAs$ is dominated by electron-like charge carriers, while with more Sr doping, a hole-like band will emerge and finally prevail over the conduction, and accordingly the superconducting transition temperature $T_c$ increases.Comment: 4 pages, 5 figure