The possible effects of pipe materials on drinking water quality have been analyzed in the distribution system of the water treatment plant of "La La Concepciónâ " in Tegucigalpa, Honduras. "La La Concepciónâ " is a surface water reservoir experiencing biogeochemical cycling of manganese. Black water problems have been reported in the distribution system since 1998. An evaluation of the potential influence that PVC and iron pipes could have on the concentration of iron and manganese in drinking water, the effects caused by the presence of manganese in PVC and iron pipe surfaces, and residual chlorine and Pb concentrations in the distribution system was performed. The sampled neighborhoods received an intermittent service. Water was suspended for 8 hours every day due to water quantity problems in the city. Water and pipe samples were obtained for PVC and galvanized iron pipes because these constitute the majority of the infrastructure used for distribution systems in Honduras. Thermodynamic and kinetic conditions for possible manganese oxidation by chlorine and dissolved oxygen in the distribution system were also evaluated. As expected, total Fe concentrations were greater for first flush conditions from the iron pipe. Water samples obtained from the PVC pipe showed higher total Mn concentrations and more black color than those obtained from the iron pipe for both first flush and continuous flow conditions. Residual chlorine decayed relatively fast along the sampled section of the distribution system. Pb concentrations were detected on water samples obtained from PVC for first flush and continuous flow and on iron pipe for first flush. Preliminary experiments showed that manganese-oxidizing and -reducing bacteria were present in the walls of both PVC and iron pipes. Higher numbers of colony-forming microorganisms were recovered from iron (30-fold more) compared to PVC pipe sections. However, the majority of isolates from the PVC biofilm (8 of 10, 80 %) were capable of Mn-oxidation while only 35 % (11 of 31) of isolates from the iron biofilm sample demonstrated Mn-oxidation. This research demonstrates the importance of the different interactions between water and the infrastructure used for its supply in producing safe drinking water. / Master of Science

Heat pipes are passive heat transfer devices in which a working fluid is sealed inside a metal enclosure. Properly designed wick structures on the inner surface of the heat pipe are critical as the wick aids in the return of the condensed liquid from the cold end back to the hot end where the vaporization-condensation cycle begins again. Additive manufacturing techniques allow for manufacturing complex parts that are typically not feasible with conventional manufacturing methods. Thus, additive manufacturing opens the possibility to develop high performance heat pipes with complex shapes. In this study, an additive manufacturing technique called Binder Jetting is used to fabricate a fully operational compact (78 mm x 48 mm x 8 mm) flat plate heat pipe. Rectangular grooves with converging cross section along the length act as the wicking structure. A converging cross section was designed to enhance the capillary force and to demonstrate the capability of additive manufacturing to manufacture complex shapes. This work describes the challenges associated with the development of heat pipes using additive manufacturing such as de-powdering and sintering. Multiple de-powdering holes and internal support pillars to improve the structural strength of the heat pipe were provided in order to overcome the manufacturing constraints. The heat pipe was experimentally characterized for thermal performance with acetone as the working fluid for two different power inputs. The heat pipe operated successfully with a 25% increase in effective thermal conductivity when compared to solid copper. / Master of Science / The number of transistors in electronic packages has been on an increasing trend in recent decades. Simultaneously there has been a push to package electronics into smaller regions. This increase in transistor density has resulted in thermal management changes of increased heat flux and localization of hotspots. Heat pipes are being used to overcome these challenges. Heat pipes are passive heat transfer devices in which a working fluid is sealed inside a metal enclosure. The fluid is vaporized at one end and condensed at the other end in order to efficiently move heat through the pipe by taking advantage of the latent heats of vaporization and condensation of the fluid. Properly designed wick structures on the inner surface of the heat pipe are used to move the condensed fluid from the cold end back to the hot end, and the wick is a critical component in a heat pipe. Additive manufacturing techniques offer the opportunity to manufacture complex parts that are typically not feasible with conventional manufacturing methods. Thus, additive manufacturing opens the possibility to develop high performance heat pipes with complex shapes as well as the ability to integrate heat exchangers with the heat source. In this study, an additive manufacturing technique called Binder Jetting is used to fabricate a fully operational compact (78 mm x 48 mm x 8 mm) flat plate heat pipe. Rectangular grooves with converging cross section along the length act as the wicking structure. This work describes the challenges associated with the development of heat pipes using additive manufacturing such as depowdering and sintering. The heat pipe was experimentally characterized for thermal performance with acetone as the working fluid for two different power inputs. The heat pipe was found to operate successfully with a 25% increase in effective thermal conductivity when compared with solid copper.

A mathematical model was developed for the rapid filling of an initially dry pipe. The pipe was assumed to be horizontal and to contain an orifice at the downstream end. The key elements of the model were the momentum equation governing the flow of the water, the thermodynamic equations for the compression and discharge of the entrapped air, and the equations for waterhammer resulting from the impact of the water with the orifice. A computer program of this model was then developed and tested. After initial testing, the model was used to examine the magnitudes of the pressures that could be produced from waterhammer and air compression for various lengths of pipe. The effects that different orifice diameters had on the flow were also analyzed. The results indicated that extremely high pressures can be generated from both waterhammer and air compression during the filling process. These pressures tend to increase as the orifice diameter is reduced. However, below a certain size the orifice constricts the air discharge enough to stop the water prior to its reaching the orifice. This results in an oscillatory behavior of the flow, and the relation between waterhammer and orifice diameter becomes much more difficult to predict. The results also demonstrated that these pressures are significantly reduced for longer pipe lengths, and for pipes with smaller diameters or otherwise offering greater frictional resistance to the flow. / M.S.

The corrosion of the drinking water distribution system is a serious problem in the United States. The annual cost to repair damages related to corrosion for public utilities in the United States are estimated at $22 billion. Polyurethane can be used as an in situ pipe liner which reduces the overall cost to rehabilitate water mains. Polyurethane is gaining popularity as a drinking water pipe liner. Not much is known about the effects of polyurethane to reline potable pipes. Polyurethane has only recently begun to be approved by the U.S. Environmental Protection Agency for use in drinking water piping, although it has been used in the United Kingdom since 1999. The American National Standards Institute/National Sanitation Foundation 61 Drinking Water System Components â Health Effects (ANSI/NSF 61) for pipe and pipe liners was used to investigate changes in water quality in contact with polyurethane lining material. In addition, the exposure time was extended to 30 days and odor analysis was performed. Polyurethane coupons were placed in headspace free borosilicate glass vessels with a surface area to volume ratio of 0.39. The water was pH 8 and comprised of salts: MgSO₄, NaHCO₃, CaSO₄, CaC1₂, Na₂SiO₃ and KNO₃ in a ratio typical of standard drinking water. Three types of disinfectant were used: no disinfectant, chlorine and monochloramine. The water was removed, sampled and replaced on days 1, 2, 4, 9, 11, 14, 15, 19, 21 and 30. The sample water was tested for pH, temperature, total organic carbon concentration (TOC), disinfectant residual, ammonia concentration as N-NH₃, hardness as combined Ca and Mg concentrations, alkalinity and temperature on days when the sample water was changed. Total solids (TS), odor, trihalomethanes (THMs), haloacetic acids (HAAs), and semivolatile organic carbons (SVOCs) were tested on days 1, 4, 9, and 14. The polyurethane lining had major impacts on pH, odor and haloacetic acids throughout the 30 day experiment. A 2-3 pH unit decrease to pH 6 was constant for all conditions tested. Odor panelists described the odor for both chlorinated and monochloraminated waters as "chlorinous" and either pleasant as "sweet chemical" or putrid as "locker room" . Haloacetic acids were formed and increased in concentration (by approximately 30 µg/L, which is half the US EPA regulated value of 60 µg/L). Trihalomethane formation was not seen. Total organic carbon leached from the polyurethane liners reached 0.65 mg/L above background on day 1 but by day 15 was only >0.1 mg/L above background. Chlorine and monochloramine were consumed by the polyurethane and increased exposure time leads to decreased disinfectant residual. It is important for water utilities to know how a lining material will affect the water quality. It has been shown that other polymeric lining materials have impacted the disinfection by-products as well as producing odor. Water treatment facilities are responsible for the water quality throughout the infrastructure and with Environmental Protection Agency regulations becoming stricter they cannot afford to not know the impact of polymeric lining materials in their system. / Master of Science

No / This paper considers both the linear elastic and creep buckling of polymeric pipe linings used for the rehabilitation of gravity pipes, for which external groundwater pressure has been identified as the prime source of loading. Theoretically perfect and imperfect conditions are considered, with the imperfections taken to be in the form of a concentric or eccentric annulus between the rigid host pipe (cylindrical constraint) and polymeric lining. Under these conditions two recently obtained mathematical procedures for the prediction of linearly and non-linearly elastic buckling are compared with the results of complementary laboratory testing. Linear elastic conditions are shown to be well approximated by undertaking short-term (¿30 min) testing under increasing pressure to failure. Controlled imperfections are introduced into the laboratory tests and excellent correlation with the theoretical predictions is obtained. In particular, the dominant geometrical imperfections are shown to be major influences on the obtained buckling pressure. The mathematical models are then adapted to simulate the creep buckling process under long-term constant pressure. The results obtained are again compared with those provided by complementary physical testing, and appropriate conclusions are made.

Internal convective cooling is a method by which components, such as gas turbine blades, are protected from damage caused by elevated temperatures. Heat pipes are structures that transport and dissipate large quantities of pressurized thermal energy. The thermal energy is transported from a heat source to a thermal sink via evaporative cooling. A radially rotating high temperature heat pipe employs centrifugal force to return or drive the working saturated-vapor mixture from the condenser section to the evaporator section. A rotating heat rig is being developed at the University of Central Florida (UCF) in order to gain a better understanding of the interaction between thermal Conductivity, rotational speed, operating temperatures and thermal loads. As a part of its development, this study will focus on identifying key factors that maximize the first critical speeds on rotating heat pipe assemblies having non-uniform temperature distributions. It was found that in order to avoid reaching the first critical speed the use of double bearings should be implemented. Since the temperature of the heat pipe will be non-uniform, this will have a minimal effect on the critical speed of the rotating rig. The first phase of the construction of the rotating rig will be stable and will provide valuable test data without reaching any critical speeds.

Aging and leaking water infrastructure wastes water resources and creates public health risks. Upgrading of potable water systems represents a large financial burden for water utilities and private property owners. The conventional approaches of repair, rehabilitation and replacement are very effective, but will take decades to implement even if a financial commitment to do so was made immediately. A novel approach of in-situ remediation of leaks, achieved by harnessing the ability of water or pipe to repair leaks via clogging, could potentially reduce leak rates and extend the lifetime of existing infrastructure at relatively low cost and inconvenience. Physical clogging, precipitation and metallic corrosion were identified as major mechanisms of in-situ leak remediation in potable water pipelines. Autogenous repair (i.e., self-repair without added particles) of small leak-holes (150–"1000 μm) in copper and iron was validated in the laboratory at water pHs of 3.0–11.0, operating water pressures of 20–60 psi, upward and downward leak orientations, and for a range of water chemistries. In bench scale experiments, the time to repair of iron pipe leaks increased with leak size to the power of 0.89–1.89, and decreased with pipe wall thickness to the power of -1.9 to -1.0. The time to repair of copper pipe leaks increased with water pressure to the power of 1.7. Additionally, the waters with a higher DO and corrosivity as measured by RSI, significantly decreased the time to repair of carbon steel 400 μm leaks by 50–70%. The presence of chlorine dioxide significantly increased the fraction of repaired 200 μm copper pipe leaks by 3 times when compared to the control without any disinfectant. In the building scale study, the fraction of repaired iron pipe leaks decreased with the logarithmic leak size with a slope of -0.65 after one-year duration of experiments, while leak orientation and water pressure were not influential in time to or likelihood of repair for iron pipe leaks. Addition of calcium carbonate particles (~8.8 μ]m), silica particles (~29 μm) and wood ash particles (~160 μm) in Blacksburg, VA tap water at a water pressure of 10 psi increased the fraction of remediated iron pipe leaks of 280–1000 μm diameter sizes. Although the control condition with no added particles for 58 days resulted in remediation of 0/12 leaks, remediation rate increased to 1/12 with calcium carbonate particles, to 10/12 with silica particles and to 10/12 with wood ash particles. Leak size and particle size played an important role in controlling the remediation success rate. The strength of the in-situ leak repair was sometimes very strong and resilient. The sealing materials of leak-holes repaired at 20–60 psi could sometimes withstand a 100 psi water pressure without failure, demonstrating the potential of the approach to sustain aging and leaking infrastructure. In-situ leak repair can also occur naturally, and the success rate might be unintentionally altered by adjustment of chemistry or treatments that decrease or increase particulates. / Ph. D. / Old and leaking pipes waste water resources and can contaminate water. Upgrading of drinking water systems represents a large financial burden for water utilities and home owners. The traditional approaches to repair or replace the leaking water pipes are very effective, but will take decades to implement even if a financial commitment to do so was made immediately. A new approach of leak remediation, achieved by changing the drinking water chemistry, could potentially reduce leak rates and repair water leaks while in use without digging up the buried water pipes. Therefore, leak remediation could extend the lifetime of existing infrastructure at relatively low cost and inconvenience, and may be necessary if society cannot afford pipe replacement. Recent field observations indicate that metal corrosion, one type of reaction that eats up water pipes and causes water leaks, could clog the leaks via the corrosion products. And the repair in most cases could last for a long period of time. Our work was the first to reproduce the field observations in the laboratory, revealing that water pipe leaks could be successfully clogged or remediated by natural corrosion reaction products, if the water chemistry is favorable. Additionally, our work also showed that water leaks could be clogged or remediated by addition of water particles to drinking water, which was practiced by Roman engineers a long time ago. There are legitimate health concerns about particulates because they are indicative of microbial risks, but addition of particulates to water at low levels might heal pipes without such concerns. We also proved that in some cases the repaired materials clogging the leaks could withstand a very high household water pressure, showing that the sealing materials in water leaks repaired with natural corrosion products or added water particles could create long term repairs. With improved practical understanding this approach might be usefully applied, either intentionally to repair existing leaks, or make sure that changes to water chemistry do not unintentionally make problems worse.

Metal pipes are sometimes swaged by a metal cone to enlarge them, which increases the strain in the material. The amount of strain is important because it affects the burst and collapse strength. Burst strength is the amount of internal pressure that a pipe can withstand before failure, while collapse strength is the amount of external pressure that a pipe can withstand before failure. If the burst or collapse strengths are exceeded, the pipe may fracture, causing critical failure. Such an event could cost the owners and their customers millions of dollars in clean up, repair, and lost time, in addition to the potential environmental damage. Therefore, a reliable way of estimating the burst and collapse strength of strained pipe is desired and valuable. The sponsor currently rates strained pipes using the properties of raw steel, because those properties are easily measured (for example, yield strength). In the past, the engineers assumed that the metal would be work-hardened when swaged, so that yield strength would increase. However, swaging introduces anisotropic strain, which may decrease the yield strength. This study measured the yield strength of strained material in the transverse and axial direction and compared them to raw material, to determine the amount of anisotropy. This information will be used to more accurately determine burst and collapse ratings for strained pipes. More accurate ratings mean safer products, which will minimize risk for the sponsor’s customers. Since the strained metal has a higher yield strength than the raw material, using the raw yield strength to calculate burst and collapse ratings is a conservative method. The metal has even higher yield strength after strain aging, which indicates that the stresses are relieved. Even with the 12% anisotropy in the strained and 9% anisotropy in the strain aged specimens, the raw yield strengths are lower and therefore more conservative. I recommend that the sponsor continue using the raw yield strength to calculate these ratings. I set out to characterize the anisotropic nature of swaged metal. As expected, the tensile tests showed a difference between the axial and transverse tensile strength. The correlation was 12% difference in yield strength in the axial and transverse directions for strained material and 9% in strained and aged material. This means that the strength of the metal in the hoop (transverse) direction is approximately 10% stronger than in the axial direction, because the metal was work hardened during the swaging process. Therefore, the metal is more likely to fail in axial tension than in burst or collapse. I presented the findings from the microstructure examination, standard tensile tests, and SEM data. All of this data supported the findings of the mini-tensile tests. This information will help engineers set burst and collapse ratings and allow material scientists to predict the anisotropic characteristics of swaged steel tubes.

Shang Xiandong. / "September 2002." / Thesis (Ph.D.)--Chinese University of Hong Kong, 2002. / Includes bibliographical references (p. 141-146). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Mode of access: World Wide Web. / Abstracts in English and Chinese.

Scalar (heat or mass) transfer plays an important role in many industrial and engineering applications. Difficulties in experimental measurements means that there is limited detailed information available, especially in the near-wall region. Prediction in simple flows is well documented and the basis for development of many Computational Fluid Dynamics (CFD) models. This is, however, not the case for scalar transfer, especially when the Prandtl (Pr) or Schmidt number (Sc) is much greater than unity. In complex flows that involve separation and reattachment, the scalar transfer coefficient is significantly different to that of fully developed turbulent flow. The purpose of this Thesis is to investigate high Prandtl number (Pr ≥ 10) scalar transfer in fully developed (pipe) and disturbed (sudden pipe expansion) turbulent flow using CFD. Direct Numerical Simulation (DNS) is the most straight-forward approach to the solution of turbulent flows with scalar transfer. However, this technique is computationally intensive because all turbulent scales need to be resolved by the simulation. Large eddy simulation (LES) is a compromise compared to DNS. Instead of resolving all spatial scales, LES resolves only the large-scales with the small-scales being accounted for by a subgrid-scale model. Chapter 2 details the mathematical, numerical and computational details of LES with scalar transfer. From this, an optimized and highly scalable parallel LES solver was developed based on state-of-the-art LES subgrid-scale models and numerical techniques. Chapter 3 provides a verification of the LES solver for fully developed turbulent pipe flow. Reynolds numbers between Re = 180 and 1050 were simulated with a single Prandtl number of Pr = 0.71. Detailed turbulent statistics are provided for Re = 180, 395 and 590 with varying grid resolution for each Reynolds number. The results from these simulations were compared to established experimental and numerical databases of fully developed turbulent pipe and channel flows. The LES solver was shown to be in good agreement with the prior work with most discrepancies being accounted for by only reporting the resolved (large-scale) component directly reported from the LES results. For a Prandtl number close to unity, the mechanisms of turbulent transport and scalar transfer are similar. The near-wall region was shown to be dominated by large-scale sweeping structures that bring high momentum and scalar concentrations to the near-wall region. These are convected parallel to the wall as diffusion mechanisms act to transfer this to the wall where dissipation takes effect. An ejection structure then acts to transport the resultant low momentum, scalar depleted fluid back to the bulk to be replenished and continue the cycle. As the Prandtl number increases, molecular diffusivity decreases relative to viscosity, and the mechanisms of scalar transfer differ to those at Pr = 0.71. This is investigated in Chapter 4 using simulations at Re = 180, 395 and 590, with detailed statistics at Re = 395 for Pr = 0.71, 5, 10, 100 and 200. Where possible the results are compared to other numerical work and the LES solver was shown to accurately resolve the higher Prandtl number flows. There are marked variations in the scalar transfer with increasing Prandtl number as the turbulent scalar transfer becomes concentrated closer to the wall and dominated by large-scale turbulent structures. Sweeping structures are still responsible for bringing the high scalar concentrations towards the wall, however, high Prandtl number scalars are unable to completely diffuse to the wall in the time that the structure is convected parallel to the wall adjacent to the diffusive sublayer. Therefore, most of the high Prandtl number scalar is returned to the bulk via the ejection structure rather than being dissipated at the wall. Chapter 5 uses the sudden pipe expansion (SPE) to investigate disturbed turbulent flow for an inlet Reynolds numbers of Reb = 15600 and a diameter ratio of E = 1.6. These simulation parameters were chosen to match the experimental LDA measurements of Stieglmeier et al. (1989). The LES results for a range of grid resolutions were shown to be in very good agreement with the experimental work. From the LES results it was determined that the fluctuations in the wall shear stress are important in the near-wall turbulent transport. These are the result of eddies originating from the free shear layer down-washing and impinging upon the wall. This is a more effective sweeping mechanism than that observed for the fully developed turbulent pipe flow. Despite the down-wash structures impinging upon the wall, a viscous sublayer still exists in the reattachment region, albeit much thinner than the fully developed turbulent pipe flow further downstream. Using the same Reynolds number and diameter ratio, scalar transfer simulations were also undertaken in the SPE with Prandtl numbers of Pr = 0.71, 5, 10, 100 and 200. An applied scalar flux was used to heat the expanded pipe wall. The LES results are in agreement with experimental Nusselt numbers from Baughn et al. (1984) for Pr = 0.71. The disturbed turbulent flow enhances the scalar transfer and this is the result of down wash events transporting low (cold) scalar from the inlet pipe to the near-wall of the expanded pipe. This cools the heated wall and enhances localized scalar transfer downstream of the expansion. A diffusive sublayer still exists in the reattachment region within the viscous sublayer for Prandtl numbers greater than unity. As the Prandtl number increases the diffusivity decreases relative to viscosity and near-wall scalar transfer enhancement decreases as the diffusion time-scales increase.