No abstract

The present paper describes an experimental investigation of the various parameters affecting the operation of industrial pneumatic controllers based on the jet nozzle principle. A test rig was built to monitor supply pressure, air temperature, airflow characteristics, and the static pressure distribution over the flat plate on which the jet impinges. The results demonstrate the existence of a low pressure, separated flow zone, subject to fouling, which subsequently was eliminated by appropriate changes of the injection nozzle geometry. The previous experimental findings were also confirmed by numerical simulation of the flow. Experimental results also show that the internal diameter of the regulator, situated inside the measuring branch, has an important influence on the sensitivity of the apparatus, as well as influencing its range.

Drying of wheat (Algerian cultivar: Hadba03) in thin layers was studied and mass flux phenomenon was used to characterize the thin-layer drying process. Thin-layer drying of wheat was determined for drying air temperature range of 40-60 C, relative humidity of drying air from 10 to 30%, air velocity of 0.7 m/s, and initial grain moisture from 26 to 31% (dry basis). Equilibrium moisture content of wheat was determined using desorption isotherms obtained from the thin-layer drying data. An equilibrium model for a stationary deep bed with drying air moving vertically upward was developed using mass and energy balance between grain and drying air in the bed and drying air characteristics obtained from thin-layer drying experiments. The developed model was validated by drying wheat in a laboratory dryer using different drying air temperatures and initial moisture contents.

In this study, experimental investigation of thermal and aerodynamic performances of a rectangular mini-channel heat sink subjected to an impinging air jet was carried out with the aim to improve the cooling performance of personal computer CPUs. The influence of the impinging distance on the velocity profile, the pressure drop, the case temperature, the thermal resistance, and the heat transfer coefficient are studied. Moreover, the effect of the positioning of the microprocessor (heat source) on the thermal performance was investigated. The results show a ratio "height jet/diameter" Y/D=0.606 offer a better cooling, and a longitudinal displacement of the heat source (central processor unit) 10 mm from the original position (center) improve the cooling performance. The enhancement rate was in a range of 10% compared to the initial position (central position before shifting the source).

No abstract