Impingement heat transfer of staggered arrays of air jets confined in a channel

Impingement heat transfer of circular air jets confined in a channel was experimentally investigated. The impingement plate was exerted with a constant surface heat flux. Five jets, including one center jet and four neighboring jets, in staggered arrays were considered. The considered jet Reynolds number (Re) was in the range 5000-15,000; the jet height-to-jet diameter ratio (H/d) was in the range 1.0-4.0; the jet spacing-to-jet diameter ratio (S/d) was in the range 4.0-8.0; the jet plate width-to-jet diameter ratio (W/d) was in the range 6.25-18.75. Two jet plate length-to-jet diameter ratio (L/d), 31.7 and 83.3, were individually arranged. For the center jet with a specific Reynolds number, its stagnation Nusselt number was found to linearly increase with the jet Reynolds number of the four neighboring jets. For all the five jets with the same Reynolds number, the correlation result shows that the stagnation Nusselt number of the center jet is proportional to the 0.7 power of the Re and the -0.49 power of the W/d. A weak dependence of the stagnation Nusselt number on H/d, S/d and L/d was found. (c) 2007 Elsevier Ltd. All rights reserved

Production of a Fungistatic Substance by Pseudallescheria boydii Isolated from Soil Amended with Vegetable Tissues and Its Significance

Four fungal isolates that were able to use vegetable tissues for multiplication in soil were isolated and identified as Pseudallescheria boydii based on morphological characteristics and ITS sequence similarity. When grown in broth prepared from the same vegetable tissues used in soil amendment, all these isolates of P. boydii produced a substance capable of reducing the disease incidence of black leaf spot of spoon cabbage caused by Alternaria brassicicola and inhibiting the germination of A. brassicicola conidia. The substance, which was fungistatic, was very stable under high temperature and high or low pH value. It was soluble in polar solvents and insoluble in non-polar solvents. Molecular weight estimation and ion exchange ability tests suggest that the fungistatic compound has a molecular weight between 500 and 1,000 and has no charge on its molecule. Results from this study suggest the possession of a strong competitive saprophytic ability by P. boydii, which in turn may explain the widespread occurrence of this human pathogen in soil. Production of a fungistatic substance when P. boydii was grown in broth prepared from vegetable tissues suggests the importance of antibiotic production in its competitive saprophytic colonization of organic matters in soil