رسائل ماجيستير
English
2015
Oil-Water Annular Flow and Heat Transfer in Horizontal Pipe
زهراء عامر عودة, عصام مجبل عبد
كلية الهندسة-جامعة بابل · العراق
There is a strong tendency for two immiscible fluids to arrange themselves so that the low-viscosity constituent is in the region of high shear. Therefore, it may be possible to introduce water in oil flow by introducing an amount of water as a lubrication fluid with oil flow in the pipeline.
In the present study, an experimental and theoretical investigation has been carried out to study the oil-water flow with and without heat transfer effect in a horizontal pipe. The purpose of this study is to examine the behavior of the simultaneous flow of oil and water in horizontal pipes to understand the flow characteristics and predict important parameters for oil pipeline flow.
The flow facility was built to enable visual observations by a high-speed camera, measurements of pressure, temperature, local volume fractions, and velocities in horizontal pipes. Also, the theoretical study was executed using the FLUENT program. Simulation results carried out with the model show more physical predictions with respect to the particle deposition process and concentration profile. The flow patterns were found to depend strongly on the superficial velocities of the two phases.
The flow rates of oil and water can be varied individually, producing different flow patterns according to variations in mixture velocity and input water cut. Two main classes of flows are observed: annular and small bubble in some experimental results. The pressure drop experiments showed that the pressure gradient in oil-water flow was more than that of oil-water flow with heat transfer effect. It increases until reaching 60.9 kPa/m for oil velocity equal to 1.77 m/s. Another observation is that the pressure gradients decrease with decreasing oil superficial velocity until reaching 2.54 kPa/m for oil velocity equal to 0.39 m/s.
This study presents a classification approach to determine the flow pattern by using visual observations to determine whether the flow is annular or bubble flow, which depends on the velocities and heat transfer effect to obtain annular flow in oil-water. Also, the mean heat transfer coefficient increases with increasing the mixture Reynolds number at the same power load. It increased until reaching the maximum value when the Reynolds number equals 65125 for water superficial velocity equal to 20 l/min and power 12000 watt. It is noted that the mean heat transfer coefficient increased with increasing power until reaching the maximum value at 80.234 kW/m²·K when power equals 12000 watt.
The theoretical results represent the pressure gradient distribution, velocities, mean heat transfer coefficient, pressure contours, and velocity vectors. Existing heat-transfer models for wall shear stress and void fractions were tested against the present data for mean heat-transfer coefficient. It was found that the methods with more restrictions give better predictions. Finally, the percentage difference between theoretical and experimental pressure drops is 6%. However, it is observed that there is a clear similarity in pressure drop along the pipe. A comparison of the pressure drop is accomplished with other previous works from the literature, and the present results are in good agreement with the correlation regarding the change in liquid (oil-water) superficial velocity.