Experimental study of the hydraulics of small circular holes in water pipes
- Authors: Coetzer, Abram Johannes
- Date: 2008-05-13T08:01:27Z
- Subjects: Water pipes , Hydrodynamics
- Type: Thesis
- Identifier: http://ujcontent.uj.ac.za8080/10210/365768 , uj:7062 , http://hdl.handle.net/10210/361
- Description: The aim of this investigation was to study the hydraulic behaviour of small circular openings in plastic water pipes. According to the theoretical orifice equation, the flow through an orifice is proportional to the square root of the pressure. However, a number of field studies have shown that this exponent can be considerably larger than 0.5, and typically varies between 0.5 and 2.79 with a median of 1.15 (Farley and Trow 2003). The implication is that water losses are substantially more sensitive to pressure than originally thought. Van Zyl and Clayton (2005) proposed four categories of factors that may be responsible for the observed behaviour: leak hydraulics, pipe material behaviour, soil hydraulics and water demand. The aim of this study was to investigate the hydraulics of small circular holes in water distribution systems to determine their behaviour under various conditions. Variables studied in this investigation include pipe material, leak size, surrounding media and pressure fluctuations. Boundary conditions need to be established to accurately simulate the conditions that a pipe in a water network experiences. The author designed and built the apparatus to provide these constant boundary conditions. The apparatus consists of six major components. These are the frame, casing, sample, pressure vessel, constant pressure regulators and measuring equipment. The frame provides structural stability to the apparatus during testing. The casing’s purpose is to house the material that surrounds the sample while being tested; it also creates the constant boundary conditions necessary for the experiments. 1mm and 2mm holes are drilled into the uPVC and HDPE pipes. This serves as the test samples. The pressure vessel is used to enable constant pressure with better pressure control. Constant pressure regulators help to provide the required conditions within the casing. The measuring equipment records that data from the experiments. The data is then processed into interpretable information. It was found that leaks discharging into air show good correlation with the theory, but differ significantly from the behaviour of leaks discharging into water or glass beads. Other findings of the study include that pressure fluctuations do not have a significant effect on the leak behaviour, the classification of the opening (as an orifice, tube or pipe) is important and that a discontinuity in the pressure leakage relationship occurs in holes classified as tubes. It is suspected that the discontinuity is caused by separation of the fluid stream from the tube wall, effectively changing it into an orifice. , Prof. J.E. Van Zyl Prof. C.R.I. Clayton
- Full Text:
Numerical analysis of the hydrodynamics of the flow in an axially rotating heat pipe
- Authors: Gutierrez, Gustavo , Jen, Tien-Chien
- Date: 2002
- Subjects: Hydrodynamics , Heat pipes , Drilling and boring
- Language: English
- Type: Conference proceedings
- Identifier: http://hdl.handle.net/10210/15688 , uj:15691 , Citation: Gutierrez, G. and Jen, T.-C. 2002. Numerical analysis of the hydrodynamics of the flow in an axially rotating heat pipe. Proceedings of IMECE2002 ASME International Mechanical Engineering Congress & Exposition, November 17-22, 2002, New Orleans, Louisiana, 5:1-13. , ISBN: 0-7918-3636-3
- Description: A numerical study is conducted on the vapor and liquid flow in a wick structure of an axially rotating heat pipe. For the vapor, the governing equations are the Navier-Stokes. For the liquid a space average of the Navier-Stokes equation is performed and a porous media model is introduced for the cross correlation that appears from the averaging process. A control volume approach on a staggered grid is used in the development of the computer program. Suction and blowing velocities are used as boundary conditions of the vapor and liquid, which are related to a local heat flux input in the evaporator section, and local heat flux output in the condenser section, respectively. The aim behind this study is the application of heat pipes in drilling applications. A triangular heat flux distribution is assumed in the evaporator due to the higher heat flux generated at the tip of the drill. A parametric study is conducted to analyze the effect of different parameters such as rotational speeds, saturation conditions, porosity, permeability and dimensions of the wick structure in the porous medium. These parameters significantly affect the pressure drop in the heat pipe and allow predicting failure conditions, which is critical in the design of heat pipes in drilling applications. The results of this study will be useful for the complete analysis of the heat pipe performance including the solution of the heat transfer on the solid wall as a conjugate problem.
- Full Text:
A mechanistic dynamic simulation for predicting the bottom of the line corrosion rate of mild steel in metal mine effluent and synthetic seawater flow
- Authors: Mothiba, Matsobane Phillip
- Date: 2020
- Subjects: Alloys - Corrosion , Reliability (Engineering) , Hydrodynamics
- Language: English
- Type: Masters (Thesis)
- Identifier: http://hdl.handle.net/10210/480440 , uj:43493
- Description: Abstract: This study was structured on the uncertainty of events that comes with internal pipe corrosion. Hitherto, the study of corrosion was structured on the combined effect of electrochemical activities (chemical dissolution) and flow properties (hydrodynamics) being the main parameter controlling the physical characteristics by forming semi-permeability or partial protective corrosion product barrier between the steel surface and the flowing MME/SSW solution. To disseminate the knowledge and raise the level of understanding, a multi specimen electrochemical test-rig prototype was developed to study the corrosion behaviour of mild steel in mine effluent (MME) and synthetic seawater (SSW). The electrochemical impedance spectroscopy (EIS) data showed the SSW corrosion-product charge transfer resistance (R2) decreased from 18597 Ohm to 3.367 Ohm with flow rate. The lower the charge transfer resistance indicates a high mild steel dissolution rate. Hence, a decrease in charge transfer (R3) with exposure time. The MME experiments were marked by a low charge transfer resistance (R3), hence the high corrosion rate (CR). The (a) factor indicated the permeability of the multi-layered corrosion film, thus, whether or not the multi-layer film behaved like a capacitor. The behaviour was supported by the constant phase element (Q3) which increased with CR... , M.Tech. (Engineering Metallurgy)
- Full Text: