Abdulmajid Addali

Gas Void Fraction Measurement in Two-Phase Gas/Liquid Slug Flow Using Acoustic Emission Technology

The gas-liquid two-phase slug flow regime phenomenon is commonly encountered in the chemical engineering industry, particularly in oil and gas production transportation pipelines. Slug flow regime normally occurs for a range of pipe inclinations, and gas and liquid flowrates. A pipeline operating in the slug flow regime creates high fluctuations in gas and liquid flowrates at the outlet. Therefore, the monitoring of slugs and the measurement of their characteristics, such as the gas void fraction, are necessary to minimize the disruption of downstream process facilities. In this paper, a correlation between gas void fraction, absolute acoustic emission energy and slug velocities in a two-phase air/water flow regime was developed using an acoustic emission technique. It is demonstrated that the gas void fraction can be determined by measurement of acoustic emission.

Monitoring oil film regimes with acoustic emission

The major purpose of a gear lubricant is to provide adequate oil film thickness to reduce and prevent gear tooth surface failures. Real-time monitoring for gear failures is important in order to predict and prevent unexpected failures which would have a negative impact on the efficiency, performance and safety of the gearbox. This paper presents experimental results on the influence of specific oil film thickness on acoustic emission activity for operational helical gears. Variation in film thickness during operations was achieved by spraying liquid nitrogen onto the rotating gear wheel. The experimental results demonstrated a clear relationship between the root mean square value of the acoustic emission signal and the specific film thickness. The findings demonstrate the potential of acoustic emission technology to quantify lubrication regimes on operational gears.

Acoustic Emission and Gas-Phase Measurements in Two-Phase Flow

The two-phase liquid/gas slug flow regime phenomenon can be encountered over a range of gas and liquid flowrates. Monitoring of slugs and measurement of their characteristics, such as the gas void fraction, are necessary to minimize the disruption of downstream process facilities. This article presents experimental results correlating acoustic emission measurements with gas void fraction in a two-phase water/air flow regime. It is concluded that the gas void fraction can be determined by the measurement of acoustic emission, which hitherto has not been investigated.

Observation of acoustic emission from gas bubble inception and burst

This technical note presents an experimental investigation aimed at exploring acoustic emission (AE) from gas bubble formation, motion, and destruction. AE in this particular investigation covers the frequency range between 100 and 1000 kHz. It is shown that AE energy and amplitude are directly correlated to bubble size at inception and burst.

Slug velocity measurement using acoustic emission technology

Two-phase flow is a common phenomenon that exists in the petroleum and chemical engineering industrial fields. An important feature employed to describe two-phase flow is the flow regime which varies depending on the individual velocities of the components within the two-phase flow. One of these regimes, the slug regime, can create significant pressure fluctuations that compromise the integrity of the transporting structure (pipes, separators, etc). This is in addition to other unwanted effects such as flooding at the receiving end, an increase in deposits of hydrates and corrosion. Under such circumstances, the detection of the slug and its associated characteristics are vitally important to the operator. This experimental study looks into the application of acoustic emission (AE) technology for detecting slug velocity in two phase (gas/liquid) flow. It is concluded that the slug velocity can be determined with AE sensors. The results were validated by using Ultrasound Transit Time technique and there was a good agreement between the two techniques at low gas void fraction.

A Review on Nanofluids: Fabrication, Stability, and Thermophysical Properties

Nanofluids have been receiving great attention in recent years due to their potential usage, not only as an enhanced thermophysical heat transfer fluid but also because of their great importance in applications such as drug delivery and oil recovery. Nevertheless, there are some challenges that need to be solved before nanofluids can become commercially acceptable. The main challenges of nanofluids are their stability and operational performance. Nanofluids stability is significantly important in order to maintain their thermophysical properties after fabrication for a long period of time. Therefore, enhancing nanofluids stability and understanding nanofluid behaviour are part of the chain needed to commercialise such type of advanced fluids. In this context, the aim of this article is to summarise the current progress on the study of nanofluids, such as the fabrication procedures, stability evaluation mechanism, stability enhancement procedures, nanofluids thermophysical properties, and current commercialisation challenges. Finally, the article identifies some possible opportunities for future research that can bridge the gap between in-lab research and commercialisation of nanofluids.

Investigation of the influence of flow rate on bubble formation and collapse in ball valves at various opening percentages using an AE technique

Investigation of the Influence of Flow Rate on Bubble Formation and Collapse in Ball Valves at Various Opening Percentages Using an AE Technique Tiahiret Alhashan, Abdulmajid Addali and Joao Amaral Teixeira 1 School of Energy, Cranfield University, Cranfield, Beds. MK43 0AL. Email: t.a.alhashan@cranfield.ac.uk Abstract Ball valves are popularly used in many different industrial processes and hydraulic systems because of their light weight and simple structure. However, they are susceptible to cavitation phenomena and the growth and collapse of the bubbles formed leads to erosion and pitting of the metal surfaces. This paper presents the monitoring and detection of bubble formation at an early stage in a ball valve using acoustic emission (AE). It is shown that AE will detect incipient cavitation and that there is a clear correlation between AE signal levels and the flow rate through the ball valve at a constant opening percentage.

Heat transfer characteristics of an orthogonal jet impinging on roughened flat plate

The purpose of this research paper is to investigate the effect of surface roughness on heat transfer. This was achieved by investigating the heat transfer in two cases: a smooth, horizontal surface (the baseline case) and the same surface with a roughness element added to it. The roughness elements took the shape of hemispherical pin-fin. The roughness element was further investigated by varying its height and width (e by e) to study their impact on the average Nu. Results are presented in the form of average Nusselt number within and beyond the stagnation region. Each roughness element was arranged in a circle concentric with the geometric centre (i.e. centre of jet) with a radius of one and a half jet diameters (R/D = 1.5) to keep it within the stagnation region. The jet diameter kept constant for all simulations (D=13.5mm) where the plane was located at H/D = 6 below the jet, for all the tests with a jet Reynolds number of 20,000 and jet temperature is 20°. The spherical pin-fin was tested for six different heights (e) from 0.25 mm to 1.50 mm in incremental steps of 0.25 mm for jet angle (α) of 90°. This research investigated how the roughness geometry impacted on the average Nusselt number.

Jet Impingement Heat Transfer Enhancement on a rib-roughened Flat Plate

American Institute of Aeronautics and Astronautics Cooling by impingement jet is known to have a significant high heat transfer rate which make it widely used in industrial cooling systems. The heat transfer characteristics of an impinging jet on ribroughened flat plate has been investigated numerically numerous times. This paper was set out to investigate the effect of both rib height and rib pitch on the heat transfer coefficient. This study focuses on finding the optimum rib-to-rib distance and rib height which would be the best to maximize the heat transfer rate downstream the plate. The highest value of normalized averaged Nusselt number as demonstrated by this research was found at a rib distance of 2.5Dh from the stagnation point. It was also found that the maximum average Nusselt number was achieved when the rib height was close to the corresponding boundary layer thickness of a smooth case at the rib position. This investigation adapted rounded nozzle of 13.5 mm diameter (D) and Reynolds number Re =23,000.

Investigating the Capability of Acoustic Emission Technology to Determine Slug Velocity in Gas/Water Two Phase Flow in Horizontal Pipes

Two phase flow is a common phenomenon that exists in the petroleum and chemical engineering industrial fields. An important feature employed to describe two phase flow is the flow regime which varies depending on the individual velocities of the components within the two-phase flow. One of these regimes, the slug regime, can create significant pressure fluctuations that compromise the integrity of the transporting structure (pipes, separators, etc). This is in addition to other unwanted effects such as flooding at the receiving end, an increase in deposits of hydrates and corrosion. Under such circumstances the detection of the slug and its associated characteristics are vitally important to the operator. This experimental study looks into the application of Acoustic Emission (AE) technology for detecting slug velocity in two phase (gas/liquid) flow. It is verified that slug velocity can be determined by using acoustic emission sensors.