Ammar Alkhalidi

Rarefied flow and heat transfer characteristics over a vertical stretched surface

Similarity solution for the steady-state two-dimensional laminar natural convection heat transfer for a rarefied flow over a linearly vertical stretched surface is being proposed. Similarity conditions are obtained for the boundary layer equations for the vertical flat plate subjected to power law for the temperature variations. It is found that the similarity solution exists for linear temperature variation and linear stretching surface. The study shows that there are three different parameters affecting the flow and heat transfer characteristics for the rarefied flow over a vertical linearly stretched surface. These parameters represent the effects of the velocity slip (K1), temperature jump (K2), and the Prandtl number (Pr). The effects of these parameters are presented. It is found that the velocity slip parameter affects both the hydrodynamic and thermal behaviors of such flows. Correlations for the skin friction as well as Nusselt number are being proposed in terms of Grashof number (Grx), the slip velocity parameter (K1), and the temperature jump parameter (K2).

Factor Affecting Bubble Creation and Bubble Size

This paper presents the factors affecting air bubble size when air is injected through a perforated membrane into a water pool. Critical factors that govern the size of air bubbles are the air pressure and the flow rate as well as the hole size of the diffuser membrane. In order to have a better understanding of how bubble size can be affected and what the most effecting conditions are, the study was conducted in a computational fluid dynamic (CFD) investigation, which was validated by the experimental results.Copyright

Study of Air Bubble Formation Process in Aeration System

This paper addresses a study of air bubble creation through an investigation by using CFD (computational fluid dynamic), which were validated to experimental results. Contact angle was also investigated for the air, water interface at a rubber surface to find the contact angle for air exiting diffuser plate. The results show very good comparison with the experimental results.Copyright

Wave generation in subsurface aeration system: a new approach to enhance mixing in aeration tank in wastewater treatment

AbstractEnergy crises in the early 1970’s created awareness of the cost of wastewater treatment and the energy required for each stage. Aeration process was the focal point of energy saving research, due to its high power consumption, which led to change the use of coarse bubble aeration system to fine bubble aeration. Until now, all commercially existing aeration systems use continuous airflow. Meanwhile, the system investigated in this paper uses pulsation flow to reduce energy consumption in aeration tank by improving oxygen transfer efficiency (OTE). In this study, a new innovative air injection method is proposed to improve OTE in the aeration basin without extra power depletion. The suggested method is simply to inject air alternatingly from two adjacent diffusers into the aeration system. It was found that OTE was improved using this method. This improvement could be attributed to water agitation caused by transient condition operation. Timing the separation between two injections is a very importa...

An Experimental Study of Reducing Back Pressure of Fine Air Diffuser Used in Wastewater Plants

Aeration is the process at which air is added to water, an essential stage in wastewater treatment plants, since most of organic compounds are being treated through such an aeration process. This process also helps aerobic bacteria to survive from oxygenation to proliferate and digest organic materials. However, aeration consumes around 60% of the total cost of remediation. Therefore, any improvement in aeration efficiency (AE) will save a considerable amount of energy consumption. One way of reducing the power required is to decrease the back pressure of the air diffuser itself. In this study, a new material for manufacturing of fine air diffuser is presented. Polypropylene (PP) membrane, which is the new material chosen, shows lower back pressure values in comparison with Silver Series 2 (SS2) membrane at relatively low flow rates. The main reason behind choosing Polypropylene (PP) is that it has lower material resistance than SS2 with maintaining the capability of operation at the same pressure ranges in the aeration process. Despite the fact that SS2 has better oxygen transfer efficiency (OTE), PP membranes have significantly lower back pressure at relatively low flow rates which resulted in higher AE. In addition, contact angle measurements were done for PP and compared with previous measurements for the contact angle of SS2.Copyright

Design of a Deflector for Water Aeration in Wastewater Treatment

The aeration phase within wastewater treatment is the most power consuming step required in the treatment of waste water. After the energy crisis in 1970s increasing attention has been paid for this step to reduce the energy cost [1]. Higher standard oxygen transfer efficiency (SOTE) reduces the amount of air required to aerate wastewater which reduce the air blower power consumption. In this study SOTE was investigated for the case of adding a bubble deflector, i.e. an external geometry that directs the bubbles toward the less oxygenated water, which improves the efficiency and eliminates the effect of dead zones in a rectangular water tank.Copyright

Water Aeration in Wastewater Treatment

The primary objective of this paper is to examine ways to increase the efficiency of water aeration process. This objective was completed through the use of a propeller and fan blade designs. Both Standard oxygen transfer efficiency (SOTE) and power reclamation were analyzed. Results of SOTE analysis indicated a decrease in efficiency, when compared to the standard model air diffuser. While the propeller design was able to successfully breakup the forming bubble column, the system reduced the circulatory currents that create mixing within the experimental tank. Results indicate a small SOTE drop, throughout the system. Power reclamation was able to yield, at a peak depth of 25cm (10 in) below the top water surface, 0.8W, with input energy of approximately 45 W resulting in reclamation of 1.8% of the power put into the system. This data was retrieved at a volumetric flow rate of 9.4 × 10−4 m3/s (2 CFM) with a pressure of 55kPa (8psi).Copyright

Aerodynamic Analysis in Lean Blade Effects in Centrifugal Compressor

Turbomachinery industries are interested in using optimization procedures that enable to enhance compressor efficiency and wide operating ranges. Most of the design processes are focus on either in aerodynamics or structure. However, the compressor design is an integration between the aerodynamics and structure. This paper presents the recent developments of the aerodynamic integral design system. A design process including the meanline design, throughflow optimization and three-dimensional viscous analysis was used in the centrifugal compressor design. The aerodynamic design design needs to optimize at same time. Normally the most of performance of the favorite features are not friendly to the structure reliability of the compressor wheel. The optimization between aerodynamic performance and structure reliability is critical to provide the maximal potential of the compressor design. The main purpose of current paper is to discuss the importance of the aerodynamic optimization through lean effects. It can be seen from the discussion that the integration of aerodynamics is very important.Copyright

Improvement of wind turbine blade aerodaynamics

Recently there has been an increase in the demand for the utilization of clean renewable energy sources. This is a direct result of a rise in oil prices and an increased awareness of human induced climate change. Wind energy has been shown to be one of the most promising sources of renewable energy. With current technology, the low cost of wind energy is competitive with more conventional sources of energy such as coal. This paper explores the possibility of increasing the number of profitable sites by optimizing wind turbine blade design for low wind speed areas