Maximum water quality path entropy for water distribution systems

This paper investigated optimization of two objectives function include the total amount of heat transfer between two mediums and the total cost of shell and tube heat exchanger. The study was carried out for k-type heat exchanger of the cryogenic unit of gas condensates by multiple objective particle swarm optimization. Six decision variables including pipe pitch ratio, pipe diameter, pipe number, pipe length, baffle cut ratio, and baffle distance ratio were taking into account to conduct this simulation-based research. The results of mathematical modeling confirmed the actual results (data collected from the evaporator unit of the Tehran refinery’s absorption chiller). The optimization results revealed that the two objective functions of heat transfer rate and the total cost were in contradiction with each other. The results of the sensitivity analysis showed that with change in the pitch ratio from 1.25 to 2, the amount of heat transfer was reduced from 420 to 390 kW about 7.8%. Moreover, these variations caused reduction in cost function from 24,500 to 23,500 $, less than 1%. On the other hand, an increase in pipe length from 3 to 12 meters, the heat transfer rate raised from 365 to 415 kW by 13.7%, while the cost increased from 20,000$ to 24500$ about 22%.

Charge and discharge behavior of elemental sulfur in isochoric high temperature thermal energy storage systems

The objective of this study was to demonstrate a real-time chlorine decay with enhancement of simulation program (EPANET 2.0) developed for drinking water supply networks. Periodically samples, two runs/week at various time intervals, were tested at (20) locations in water distribution system of Mosul University and analyzed in site with chlorinator instrument. First the system hydraulic model (EPANET) was used with the entire pipe and junction data which was obtained from university’s records, while chlorine decay coefficients (both bulk and wall) were used from previous literatures and some model runs. A value of the bulk decay coefficient of (-1.0 d-1) was chosen, as for the wall decay coefficient, it was set to zero. The study demonstrated that most of the highly water consumption nodes have a residual chlorine concentration within (0.25 -1.2) mg/l. Moreover, the simulation program shows that from (12 – 5 A.M) chlorine concentration has nil values .However, due to the lack of maintenance works in both storage tank and piping network, about 93% of the reaction rates of the chlorine were happened in, so it is recommended to add an adequate dosing of chlorine with appropriate mixing in the high elevated tank. KEYWORDS: simulation, chlorine decay, water quality, distribution networks, EPANET

Mixing of arsenic-rich groundwater and surface water in drinking water distribution systems: Implications for contaminants, disinfection byproducts and organic components

A novel input-output model of water quality in water distribution systems is presented as a particle (water parcel) backtracking algorithm (PBA). The PBA is a simpler and more efficient version of that described by Zierolf et. al. in 1998 and is extended to allow storage tanks and multiple water sources and quality inputs. For simplicity the algorithm details are described for networks with a single water quality input at the water source, and the necessary extensions to allow multiple water sources and quality inputs are described separately. The PBA provides information that is not available using traditional simulation approaches: the various paths that water takes between a particular input source and output node, and their associated time delays and impact on output node water quality. Such information constitutes a complete description of the input-output behavior under typical assumptions of first-order chemical decay or production reactions. Thus the output behavior can be calculated for any source quality input, and the explicit mathematical form of the input-output behavior is useful information for certain applications such as feedback control. More generally, the PBA is a tool to understand flow-path-dependent water quality processes in distribution systems, since those paths and their characteristics are made explicit and thus available for analysis. The potential utility of input-output analysis is illustrated by several examples.

Placing fixed water quality monitoring stations in a water distribution system can greatly improve the security of the system via prompt detection of poor water quality. In the event that a harmful substance is injected into a water distribution system, large populations can be put at risk of exposure to the contaminant. Promptly detecting the presence of a contaminant will reduce the number of people put at risk of exposure. However, to protect against a wide variety of possible contaminants, a water quality monitoring station will need to identify contamination via recognition of anomalous changes in a suite of surrogate water quality indicators (chlorine, pH, etc.). This work attempts to place water quality monitoring stations within the water distribution at locations that best detect contamination events via surrogate water quality signals. Networks of water quality monitoring stations are designed to minimize the population affected prior to contamination event detection, and simultaneously minimize the expected number of false positive detections, under uncertain water quality conditions. Solutions generated in this study are compared to solutions designed via classical detection methods. Results show the sensor networks designed without consideration to detection via surrogate water quality parameters have higher false positive detection rates.

One of the critical public safety roles for water distribution systems (WDS) is suppression of urban fire events. Previous studies have investigated WDS rehabilitation for mitigation of potential fire events with a major focus on improving fire flows by pipe enlargement. However, pipe enlargement can cause water quality problems and place public health at risk during normal operational periods. Thus a novel approach is required to effectively address the conflicting goals of the WDS: reliable delivery of water during normal as well as emergency conditions, meeting water quality standards, and finding cost-effective design and rehabilitation options. In this study an evolutionary computation-based multi-objective optimization-simulation framework is developed to design effective mitigation strategies for urban fire events for water distribution systems with three objectives: (1) minimizing fire damages, (2) minimizing water quality deficiencies, and (3) minimizing the cost of mitigation. An elitist non-dominated sorting genetic algorithm (NSGA-II) is modified by incorporating an evolution strategy (ES) to address difficulties for heuristic algorithms posed by WDS problems. Implementation of this methodology generates Pareto-optimal solution surfaces that express the trade-off relationship between fire damage, water quality, and least cost objectives. Thus, the method provides decision makers with the flexibility to choose a mitigation plan for urban fire events best suited for their circumstances. Each Paretooptimal solution comprises a set of pipes to be enlarged to achieve increased fire flow and the corresponding diameters of these pipes. The algorithm is illustrated with several test functions. The Micropolis virtual city is then used to demonstrate the application of the proposed methodology to a complex WDS.

Pipe Failure Prediction in Water Distribution Systems Considering Static and Dynamic Factors

Hybrid Photovoltaic Thermal (PV/T) systems are energy-generation systems that transform thermal irradiance into both electrical and thermal energy at the same time. Hybrid photovoltaic thermal systems consist of a photovoltaic panel connected to a thermal collector. The main objective of this paper is to find the optimal operating conditions that can be controlled to decrease the photovoltaic panel temperature in order to improve the electrical and thermal performance of PV/T systems. In this work, we proposed the 3D numerical model that is implemented within the COMSOL Multiphysics program to study the PV/T system. The experimental input data being used in this research study reflects a typical Algerian area with semi-humid climate conditions. We study the effect of water velocity, pipe length, diameter, thickness and inlet fluid temperature on the electrical and thermal performance using the design of experiments (DOE) method. Further, the analysis of variance (ANOVA) is used to identify which of these effects impact the most the photovoltaic thermal and electrical efficiencies, the response surface methodology (RSM) is employed to describe how these effects are interacting. Based on ANOVA analysis, the following factors are reported to be important: water velocity, pipe diameter, pipe length and the inlet fluid temperature. Further, there is a significant interactions between water velocity, pipe length and pipe diameter. Among the operating conditions being calculated using the RSM, the optimal one is found when water velocity, pipe length, pipe diameter, pipe thickness and inlet water temperature have the following values, 0.05 m/s, 7.27 m, 0.01 m, 0.0008 m and 10°C, respectively. The corresponding thermal, electrical and overall efficiency were found around 80.73%, 12.87% and 93.60%, respectively. The proposed simulation model provides a reliable framework to study, improve and predict PV/T systems performance whilst ensuring low computational time.

In the present study, CFD-based parametric analysis is carried out to optimise the parameters affecting the temperature drop and heat transfer rate achieved from earth air tunnel heat exchanger (EATHE) system. ANSYS FLUENT 15.0 is used for CFD analysis, and k-ε model and energy equation were considered to define the turbulence and heat transfer phenomena. For a straight EATHE system configuration, four design and operating parameters, i.e., diameter of the pipe (A), length of pipe (B), inlet air velocity (C), and inlet air temperature (D), are considered at four different levels in Taguchi method. The Taguchi method is used to obtain maximum air temperature drop and heat transfer rate. The best combination of parameters for achieving a maximum drop in air temperature is A1B4C1D4 and that for obtaining maximum total heat transfer rate is A4B4C4D4. Statistical analysis reveals the percentage contribution of different factors for air temperature drop in the following order: inlet air temperature (57.80%), diameter of pipe (20.66%), length of pipe (12.03%), and air velocity (9.51%), while, for heat transfer rate, pipe diameter (53.28%), inlet air temperature (30.87%), air velocity (9.40%), and length of pipe (6.45%).

To sustain water quality in water distribution system (WDS), disinfectant generally chlorine is boosted to water distribution system. However, the concentration of chlorine should be limited to acceptable scope. The upper bound of the scope is set for preventing the occurrence of disinfectant byproduct, which is harmful to human health. The lower bound of the scope is set for controlling the growth of microorganism as well as reducing the cost. As such, the optimization model was applied to solve the water quality issue in WDS. However, in WDS, chlorine decays and varies with time and space, affected by pipe material, temperature, pH value, and chlorine injection. Therefore, in this paper, an inexact [Formula: see text] fuzzy chance-constrained programming (IMFCCP) model was proposed to optimize the chlorine injection to maintain chlorine in WDS at an acceptable level with consideration of uncertainty in water quality simulation. The results indicated that the upper bounds, the lower bounds, and intervals of the injection mass increased with preference parameter λ, which means that the results are more unreliable with higher preference parameter λ. However, the effect of reliability level ζ on the injection mass is determined by the relationship between the preference parameter λ and reliability level ζ. In case of [Formula: see text], the effect is not more significant than the case of [Formula: see text]. The results can help managers determine the injection strategy under uncertainty.

Particulate erosion is a major concern in slurry handling unit of a thermal power plant. The pipe bends are the most erosion affected element of a pipeline unit thus, a cost-effective method to reduce pipeline erosion is highly desirable. This work aims to suggest the optimal pipe bend design to minimize the particulate erosion by analyzing the erosion wear in geometrically different pipe bends for bottom ash slurry flow by using Computational Fluid Dynamics code FLUENT. A Three-dimensional simulation study of erosion wear is carried out by implementing Euler-Lagrange modeling along with the standard k-ε turbulence model to solve the complex multi-phase flow. Pipe bends of different bending angle (30°, 45°, 60°, and 90°), diameter (50 to 250 mm) and bending ratio (r/D = 1 to 2.5) are evaluated at different flow condition. The wear location gets shifted to the upper section of the bend and its magnitude is significantly reduced with the increase in pipe diameter and bending angle. The dynamics of multiphase slurry through different bends is analyzed to understand the complex wear phenomenon. The simulation result shows good agreement with the published findings. Finally, a least erosion affected pipe bend profile is suggested for slurry transport unit.

Experiments which test the concentration and molecular weight dependence of turbulent pipe flow drag reduction for random coiling polymers in dilute solutions show correlations with concentration to the one‐half power and molecular weight to the 0.8 power for good solvents. This result is not consistent with a model of extension of single1 molecules, but could be related to the increase in bulk viscosity of interacting molecules after some extension. In this work, measurements for very low amounts of drag reduction for rigid rod molecules arc reported, and the effect of tube diameter on the amount of drag reduction is examined for fiexible rod molecules. No diameter effect is observed for the rigid rods, but an increase in drag reduction with increase in pipe diameter is found for the flexible polyeleetrolytes. In all cases, the volume occupied by spheres which circumscribe the molecules is greater than the actual volume when drag reduction is found. The results indicate that combined effects of individual molecule stretching and molecular interactions are present in drag reduction for random coiling or flexible rod molecules.

Two-phase flow in horizontal and inclined pipelines can cause significant practical operating problems. When slugs flow in a horizontal pipeline that contains sections of different inclinations they undergo a change of length and slug flow characteristics as the slug move from section to section. In addition, slugs can be generated at low elbows, dissipate at top elbows and shrink or grow in length as they travel along the pipe. A mathematical model and a computer program were developed to simulate these phenomena. The model was based on the sink/source concept at the pipeline connections. A connection between two pipeline sections of different slopes was conveniently called elbow. An elbow accumulates liquid as a sink, and releases liquid as a source. The sink/source has a characteristic capacity of its own. This capacity is positive if the liquid can indeed be accumulated at the elbow or negative if the liquid is actually drained away from the elbow. This type of treatment effectively isolates the flow upstream from an elbow from that downstream, while still allowing flow interactions between two detailed pipeline sections. The hydrodynamic flow model was also used to calculate the film liquid holdup in horizontal and inclined pipelines. The model can successfully predict the liquid film holdup if the liquid film height is assumed to be uniform through the gas pocket. Many other models were used to calculate all the needed parameters to perform the sink/source model. The overall effect of horizontal and inclined pipelines on slug flow depends on the operating flow rates and pipeline configurations. For special case of near constant slug frequency corresponding to moderately high superficial liquid and gas velocities, this effect was found to be small. The changes in the film characteristics between two adjacent pipeline sections were found to be mostly responsible for the pseudo-slug generation, slug growth and dissipation in the downstream pipeline sections. The film liquid holdup decreased with increasing pipe diameter. The unit slug length increased at the upstream inclined pipes and decreased at the downstream inclined pipes with increasing pipe diameter. The possibility of pseudo-slug generation was increased at large pipe diameters even at high sink capacities. At low sink capacities, no pseudo-slugs were generated at high superficial velocities. The slug flow characteristics were more affected by low superficial gas and liquid velocities, large pipe diameters and shallow pipeline inclinations.

Both measurement and parameters uncertainties affect a parameter estimation process. To date measurement uncertainties have been considered during water quality parameter estimation in the water distribution systems (WDS). User defined parameter uncertainties have been avoided. It is known that some parameters in the distribution systems can be uncertain. For example, demand affects both the WDS hydraulics and water quality and is one of the most uncertain parameters. This paper considered nodal demand and temporal demand factor as the uncertain parameters when estimating wall decay coefficients of the water quality model. To account uncertainties in demand parameters hydraulic and water quality simulation model, EPANET was run in Monte Carlo Simulation (MCS) with predefined coefficients of variation for the uncertain parameters. Measurement uncertainties were added then with the mean concentration to create observed data. A meta-heuristic search technique, the Shuffled Frog Leaping Algorithm (SFLA) coupled with EPANET was used then to calibrate the wall decay parameters. Results show that parameters uncertainties can be as important as measurement uncertainties. Measurement uncertainty does not compensate parameters' uncertainties rather it increases the prediction errors.