Acoustic and Flow Aspects of Synthetic Jet Actuators with Chevron Orifices

The use of a chevron nozzle/orifice is one of the methods of heat transfer enhancement and noise reduction. In the case of synthetic jets, the number of papers on this topic is small. Therefore, a synthetic jet actuator with three different chevron orifices and one circular orifice is investigated. The aim of this study is to find the impact of orifice shape on centerline velocity (measured with a hot-wire anemometer) and determine if the chevron orifice reduces the generated noise. The sound pressure level was strongly dependent on the input actuator’s power, and only one chevron orifice ensured noise reduction for low power (p = 6; 8 W). At real power p = 12 W, the sound pressure level was lower for each chevron orifice actuator than in the case of the circular orifice actuator. It is shown that the application of a chevron nozzle does not have to provide noise reduction. It is important in the case of the design of new actuators that are to operate in places where noise levels should be limited (e.g., offices).

Experimental Determination of the Discharge Coeffcient Through Circular Orifice in PVC Pipes

Real water losses derived from water supply systems represent an important topic, nowadays. It is difficult to predict and to calculate the water lost volume, these values being crucial in any water balance. In addition, the leakage flow can be estimated only when the geometric and hydraulic characteristics of the pipes and the period of time associated to the leakage are known. Also, by using the equation of the water flow can be obtained inaccurate values, especially when incorrect values of discharge coefficient are used. The values of the discharge coefficient can vary between 0.6 and 0.85, depending on a multiple aspects, such as the pipe diameter, the orifice size and shape, the pipe material, the orifice position on the pipe wall, the pipe thickness and the hydraulic parameters of the water (flow and pressure). This paper is focused of an experimental study of a leak simulation in a PVC pipe. Thereby, a circular orifice is drilled on PVC pipe wall and the influence of the water flow and pressure on the discharge coefficient (Cd) is analysed. The experimental values obtained for de Cd are 0.59 - 0.86, values that are in accordance with the results from similar studies.

DEGRADATION OF CONGO RED DYE USINGHYDRODYNAMIC CAVITATION

Hydrodynamic cavitation (HC) has been applied in the present work for the degradation of Congo red dye. Initially, the Effect of dilution of the Dye on the efficiency of hydrodynamic cavitation has been studied using circular orifice as well as venturi as a cavitator. The process parameters such as initial dye concentration, solution pH, Hydraulic characteristics, comparative study of venturimeter and orificemeter, and flow rate were investigated in detail to evaluate their effects on the decolorization efficiency of Congo red Dye. In terms of removal rate and energy efficiency, an optimal inlet pressure value was found close to 0.4 MPa and cavitation number of 0.25. Maximum decolorization was obtained using orifice is 64%, and that of venturi is 73% in 90 min time at a temperature of 25±2°C.