Journal of Infrastructure Systems

In this paper, the effect of using a phase-change material (PCM) on the storage capacity of a conventional solar storage system was carried out. This was obtained by using encapsulated spheres that contain paraffin wax as PCM; this enables the control of the quantity of the PCM. The quantity of the solar energy stored was indicated by the rise in both inlet and outlet water temperatures of the collectors used in the system. Hourly storage temperatures were recorded during the charging of the system. The maximum increase in water temperature was recorded when the volume flow rate of the water was found to be $4\mathrm{L}/\min$; this value was used throughout the work to study the enhancement of thermal energy storage using PCM. It was found that the amount of energy stored increases with the quantity of phase-change material, with a percent increase in the inlet and outlet water temperatures of 8 and 9%, respectively.

Genetic algorithms (GAs) can be the tool of choice especially for optimizing combinatorial and complex problems in transport and infrastructure systems such as traffic signal control, pavement rehabilitation and design, and transit service scheduling. This paper presents an overview of different techniques to improve performance of GAs, with particular emphasis on parallel GAs (PGAs). Results are presented from applications of a simple GA (SGA) and a migration PGAs on a traffic control problem, a benchmark GA–difficult, and benchmark GA–easy problem. For all problems, savings in computation resources were realized when PGA was used. Advantages of PGAs are more pronounced for complex and difficult (deceptive) problems. On a difficult problem tested in this research, a PGA with four subpopulations was 7 times more efficient than a serial one, and a PGA with eight subpopulations was more than 18 times more efficient. With smaller and less complex problems, the impact of parallelism is less dramatic when the computation resources are limited. Use of parallel GAs does not reduce the importance of seeking efficient problem-specific operators and parameter values, but does magnify the effectiveness of such choices and increase the range of options available. The advantages PGAs offer mean more efficient and faster optimization for many applications in civil infrastructure design, operating management, and maintenance projects.

Three artificial neural network models [feedforward, Elman, and nonlinear autoregressive exogenous (NARX)] were used to find the performance of two flat-plate collectors operating under Jordanian climate. One collector used water as a working fluid, while the other used fuel oil as a working fluid. Previously obtained experimental data on the performance of solar collectors were used to train the neural network. Density of fluid, input temperature, output temperature, ambient temperature, and solar radiation were used as input parameters in the input layer of the network while the efficiency of the flat-plate solar collector was in the output layer. It was found that the artificial neural network technique may be used to estimate the efficiency of the flat-plate collector with excellent accuracy. The obtained results showed that the multilayer feedforward model with five inputs has the best ability to estimate the required performance, while the other models, the feedforward, NARX, and Elman networks, have the lowest ability to estimate it. Furthermore, using the sensitivity analysis, it was found that the NARX and Elman models have the least ability to estimate the solar collector’s thermal efficiency, while the feedforward model with the input parameters of density, $T_{\text{out}}$, $T_{\text{in}}$, $T_{\text{amb}}$, and $G_t$, has the best performance in both training and validation period.

An artificial neural network (ANN) model was developed to study the heat transfer analysis in an unglazed flat-plate solar collector with air passing behind the absorbing plate. The construction of the solar air collector included the absorber plate, the structural layer under the plate, the air channel, and the back insulation layer. The mean inside temperature at each surface of the solar collector and the heat added to the airflow were estimated by a nonlinear autoregressive exogenous (NARX) model. The obtained results were verified against the mathematical calculation that was used to find the aforementioned values by the optimization technique. It was found that the NARX model may be used to estimate the mean inside temperature at each surface of the flat-plate collector with excellent accuracy with a coefficient of determination of 0.99997. The advantages of the ANN model compared to the conventional testing methods are speed, simplicity, and the capacity of the ANN to learn from examples.

A theoretical analysis was performed to study the attenuation of a heat wave through two composite walls. Each wall was made of three homogenous layers in addition to an insulation layer, all of which were made of local materials. One way to attenuate this heat wave was to apply insulation inside the wall. In this work, an artificial neural network (ANN) was developed to study the effect of insulation materials on a building wall through a four-layered wall. The layer material type, the layer thickness, and the inside and outside temperature were used in the input layer of the network, whereas the temperature distribution was in the output layer of the network. Data that were obtained from previous experiments were used to train the neural network. It was found that the algorithm used (Levenberg-Marquardt) was very much capable of estimating the temperature distribution within each of the four-layered walls with excellent accuracy.

The analysis of numerous cases of failure in shell structures has shown it occurs at stresses lower than the design stresses. The origin of these failures has been attributable to flaws or cracks. To determine which size of crack is admissible, one must study how the structural strength is affected by cracks. In this paper, the analysis is done using a finite-element program developed by the authors. The stress intensity factor, $K$, of the shell structure is calculated and compared with that of the theoretical one, and excellent results were achieved, as shown in the figures and tables of the results. The load-carrying capacity of cracked shell structures were also evaluated and compared with that of the uncracked shell structures’ capacity to determine the crack size that is admissible. The results obtained were also compared with that of theoretical solutions, and excellent results were achieved, as shown in the figures. The elements used in this program are eight-nodes shell elements, six-nodes singular triangular shell elements, and eight-nodes transition singular shell element, all elements with a 5 degree of freedom per node.

Biodiesel is considered as a sustainable alternative to diesel fuel, as it can be utilized in current internal combustion (IC) diesel engine without any modification. It is transesterified from the combination of methanol or ethanol and triglycerides to form monoalkyl ester under the presence of catalyst. In this work, a newly designed continuous tubular reactor is modeled using coupled reactive flow. The model is based on Navier-Stokes, three-dimensional (3D), multiple-fluid species, turbulent internal flow for reactive and nonreactive flow. In particular, this work entails a nonreactive flow to estimate the total residence time and pressure drop in a newly developed tubular reactor assembly. The residence time in the new reactor found to be nearly an order of magnitude larger than the length-based transfer time under reasonable pressure drop. With the intent of developing a robust numerical model, a parametric study of the reactive flow was conducted. The simulation accounts to the different reaction temperatures and reactants molar ratios. The results demonstrated that higher conversion and product yield is achieved at higher temperature and prior to reaching boiling of the alcohol; whereas a lower product is achieved at higher alchol:oil ratios. The latter result is due to departing from the stoichiometric state (dilution of the flow) and to the reverse reaction.

An available inverted trickle solar still was rebuilt, and its performance was tested at different conditions of solar radiation, feedwater flow rate, and natural convection existence. The still was designed to desalinate water of high salinity by flowing it on the back side of an absorber plate with the help of a layer of jute attached to that side of the plate. The still produces three types of water: saline, intermediate, and condensate. Enhancements were made on the current still to improve its performance. The main improvement made was increasing the size of the heat exchanger to its possible maximum to study its effect on the still’s performance. Also, other improvements were made to the still, such as increasing the contact between the absorber plate and the jute under it and increasing the sealing tightness to prevent internal and external leakage of water. The study was carried out for 5 days from 9:00 a.m. to 5:00 p.m. Data were measured for solar radiation, temperatures on several parts of the still, and flow rates of inlet and outlet water. Tap water was tested for 4 days on different flow rates and natural convection conditions, and brackish water was tested in the fifth day. It was found that the still’s productivity increased by 15%, reaching $2.55\mathrm{L}/\text{day}{\mathrm{m}}^2$ of fresh water, with an average salinity of 60 ppm. The main advantage of the still is that it provides another product from the so-called intermediate header, which is approximately twice the productivity of the condensate header. It is a product of reduced salinity such that if brackish water has a 12,000-ppm salinity, for example, the intermediate product would be approximately 9,000 ppm at a productivity of approximately $5.53\mathrm{L}/\text{day}{\mathrm{m}}^2$. In addition, the still’s daily efficiency increased by 8.6% relative to that of previous work to reach 23.7%.

The effectiveness of mixing aluminum residue and recycled asphalt pavement materials (RAPs) with silty clay soil on the soil’s physical properties was discussed. The mixing material that is used enhances the silty clay soil’s volume changes and bearing capacity and reduces settlement. Different percentages of aluminum and asphalts by weight, ranging from 2 to 10% in increments of 2%, were used to determine the enhancement in soil properties gained using these materials. Physical and mechanical testing was carried out according to applicable ASTM and AASHTO testing methods. Soil mixtures of various ratios were studied in the laboratory to note the enhancements in the swelling behavior, shear strength parameters, Atterberg’s limits, optimum moisture content, and corresponding maximum dry density. Moreover, this investigation also included evaluation of the bearing capacity of subgrade material. The results of this investigation showed that the addition of aluminum residue and recycled asphalt materials to a silty clay soil with proper compaction would lead to an increase in the bearing capacity and dry density. In addition, an increase in the unconfined shear strength and a decrease in swelling and the shrinkage potential of the silty clay soil were also observed.

In this paper, transmission lines overload alleviation for the Sudan National Grid has been performed. Resizing the transmission system components is not suitable during the operation. On the contrary, in that case, alleviation of the overloads by generation rescheduling is suitable and effective. Decreasing the generation station output relieves transmission line overload, but to maintain the power equilibrium, the output of other generation stations must be increased, making sure no additional transmission lines are being overloaded. A simple, efficient, fast, and accurate technique for the alleviation of line overloads by corrective generation rescheduling and load shedding is applied to alleviate the overloads. The method ensures that alleviation of the existing violations does not create any new violations. The load shedding is used as a last choice in cases when generation rescheduling has not completely alleviated the overloads. An overload that cannot be relieved by only rescheduling the generation is always due to weaknesses in the system design. The method gives good results for alleviating line overloads in cases of the most severe contingencies.

The palm oil industry in countries such as Malaysia, Indonesia, and Colombia has been aggressively expanding over the years. Inevitably, the production of palm oil from fresh fruit bunches has generated solid waste, such as oil palm shell (OPS). Such exploitation of OPS when utilized as coarse aggregate in concrete can reduce the reliance of the local construction industry on the use of natural stone aggregates, which are depleting quantitatively. When and if huge amount of OPS can be effectively used, it will not only be a green solution but also a great advantage to both the local palm oil industry and the construction business. Particularly to highlight in typical modern buildings made of reinforced concrete, slab panels consume the most concrete compared to the rest of structural components because they occupy a large space in the floor. Precast floor panels cast with concrete made with OPS can comply with the Industrialized Building System (IBS) because they are innovative, involving the precast system. This paper reports the structural performance of precast floor panels made with OPS concrete under two-line load (TLL), both at the early age of 28 days and a later age of 400 days. Panels tested at an early age failed in a brittle manner, whereas the others, at the later age, failed in a flexural behavior. Results based on parameters, such as service and ultimate load capacity, moment capacity, deflection, cracking characteristics, and ductility, also revealed that the panels performed generally better at a later age compared to an early age.