Journal of Engineering

This paper presents an experimental study conducted to enhance the thermal performance of a double-pass solar air heater (SAH) using phase change material (PCM) for thermal storage at the climatic conditions of Baghdad city, Iraq. The double-pass solar air heater integrated with a thermal storage system was manufactured and tested to ensure that the air heating was reserved after the absence of the sun. The rectangular cavity filled with paraffin wax was used as latent heat storage and incorporated into the lower channel of the solar air heater. Experiments were carried out to evaluate the charging and discharging characteristics of two similarly designed solar air collectors with and without using phase change material at a constant air mass flow rate of 0.0375 kg/sec. The parameters that affect the thermal performance of the SAH with and without the PCMs presented by solar radiation, the difference in air temperature, outlet air temperature, instantaneous thermal efficiency, and daily efficiency are evaluated. The experimental results show that when using the PCM, the temperature of the outlet air was enhanced and increased over the ambient temperature by 1.5 - 6.5°C after sunset for a 5-hour period. It was found that the instantaneous thermal efficiency of the heater using thermal storage exceeds 100% after sunset, due to a large amount of heat stored in the paraffin wax that has been released during the discharge process. Also, it was found that the daily efficiency of the double-pass SAH integrated with and without thermal energy storage unit was 56% and 47%, respectively.

Roofs in Iraqi houses are typically made of concrete panels, which have poor thermal properties. This study explores the use of materials with low thermal conductivity and high specific heat to improve the thermal properties of concrete panels, thereby enhancing indoor room temperature. A Mathcad program based on a mathematical model employing complex Fourier series was built for a single-room building. The model input data included ambient temperature, solar radiation, and sol-air temperature, treated as periodic functions of time. The room construction remained constant, except for the roof properties, which were varied based on improved mixing ratios. The results showed that using a concrete panel with components (cement, sand, coarse aggregate, wood ash, and Alabaster aggregates) in a ratio of 1:1:2:1:1 and three plastic layers (denoted as roof No.4) provided the best improvement in thermal performance. The thermal conductivity was reduced by 42%, and the specific heat increased by 41.2% compared to the traditional concrete panel mixing ratio (denoted as roof No.1). The mechanical properties also met the Iraqi standards No. 1107 on 2002.

In this paper, an experimental analysis of conventional air-cooled and microchannel condensers in automotive vapor compression refrigeration cycle concerning heat transfer coefficient and energy using R134a as a refrigerant was presented. The performance of two condensers and cycles tested regarding ambient temperature which it was varied from 40°C to 65°C, while the indoor temperature and load have been set to be 23°C and 2200 W respectively. Results showed that the microchannel condenser has 224% and 77% higher refrigerant side and air side heat transfer coefficient respectively than the coefficients of the conventional condenser. Thus, the COP, in case of using the microchannel condenser, was found to be 20% higher than that of the conventional cycle. Also, the microchannel condenser has a 50% smaller volume than the conventional. Therefore, it provides more space in the car engine container occupied with other components.

In this study, experimental tests were conducted to explain the effect of insulation and water level on the yield output of a linear basin, single slope solar still. The tests were performed from May to August 2017 in Mosul City, Iraq. The experimental results showed that the yield output of the still increased by 20.785% and 19.864% when using thermal insulation at 4 cm and 5 cm, respectively. Conversely, the yield output decreased by 15.134% as the water level increased from 4 cm to 5 cm with the presence of insulation, and by 14.147% without it. The study concluded that insulation and water level play important roles in the process of passive solar desalination, and that the desalination process has significant value at night and cannot be ignored.

The aim of this work is to enhance the mechanical properties of the glass ionomer cement (GIC) used in dental materials by adding Zirconium Oxide (ZrO2) in both micro and nano particles. GIC was mixed with 3, 5, and 7 wt% of both ZrO2 micro and nanoparticles separately. Compressive strength (CS), biaxial flexural strength (BFS), Vickers Microhardness (VH), and wear rate losses (WR) were investigated. The maximum compression strength was 122.31 MPa with 5 wt% ZrO2 micro particles, while 3 wt% nanoparticles gave the highest microhardness and biaxial flexural strength of 88.8 VHN and 35.79 MPa, respectively. The minimum wear rate losses were 3.776 µg/m with 7 wt% ZrO2 nanoparticles. GIC containing ZrO2 micro and nanoparticles is a promising restorative material with improved mechanical properties except for wear rate losses.

Net pay is one of the most important parameters used in determining the initial oil in place of a reservoir. It can be delineated through the use of limiting values of the petrophysical properties of the reservoir, known as cutoffs. This paper provides an insight into the application of the regression line method in estimating porosity, clay volume, and water saturation cutoff values in the Mishrif reservoir/Missan oil fields. The study included 29 wells distributed in seven oilfields: Halfaya, Buzurgan, Dujaila, Noor, Fauqi, Amara, and Kumait. The Mishrif formation was divided into three main units: MA, MB, and MC. The methods were applied to each unit of the Mishrif formation individually and as one unit. The division of the Mishrif formation into subunits led to a great improvement in the accuracy of the porosity-permeability correlations. The results indicated that the regression lines method of defining cutoffs gives unrealistic values with the common assumption of permeability cutoff = 0.1 md. Another assumption for permeability cutoff = 1 md was made, chosen due to lithology and hydrocarbon type (limestone and oil, respectively). This assumption led to more realistic and higher porosity cutoff and smaller water saturation and clay volume cutoff values using the two types of regression lines.

In this research, an enhancement in lubricating, rheological, and filtration properties of unweighted water-based mud is fundamentally investigated using XC polymer NPs with 0.2gm, 0.5gm, 1gm, 2gm, and 4gm concentrations. Bentonite, that had been used in the preparation of unweighted water-based mud, was characterized using XRF-1800 Sequential X-ray Fluorescence Spectrometer, XRD-6100/7000 X-ray Diffractometer, and Malvern Mastersizer 2000 particle size analyzer, respectively. Lubricating, rheology and filtration properties of unweighted water-based mud were measured at room temperature (35°C) using OFITE EP and Lubricity Tester, OFITE Model 900 Viscometer, and OFITE Low-Pressure Filter Press, respectively. XC Polymer NPs show a good enhancement in lubricating, rheology and filtration properties of unweighted water-based mud. The effect of XC Polymer NPs on lubricating properties was denoted at 4gm concentration, where the reduction percentage in COF was 30%. An increase in PV, YP, AV, gel strength of unweighted water-based mud was obtained due to the addition of XC Polymer NPs at concentrations up to 4gm. A reduction in filtrate volume and mud cake thickness of unweighted water-based mud was obtained due to the addition of XC Polymer NPs at 2gm and 4gm concentrations, the best result was obtained with using 4gm concentration, the reduction percentage of filtrate volume was 20.7% and mud cake thickness was 41%.

This paper proposes a new structure of the hybrid neural controller based on the identification model for nonlinear systems. The goal of this work is to employ the structure of the Modified Elman Neural Network (MENN) model into the NARMA-L2 structure instead of the Multi-Layer Perceptron (MLP) model in order to construct a new hybrid neural structure that can be used as an identifier model and a nonlinear controller for the SISO linear or nonlinear systems. Weight parameters of the hybrid neural structure with its serial-parallel configuration are adapted by using the Back Propagation learning algorithm. The ability of the proposed hybrid neural structure for nonlinear systems has achieved fast learning with a minimum number of epochs, a minimum number of neurons in the hybrid network, high accuracy in the output without oscillation response, as well as a useful model for a one-step-ahead prediction controller for the nonlinear CSTR system used in the MATLAB simulation.

This work is concerned with the design and performance evaluation of a shell and double concentric tubes heat exchanger using Solid Works and ANSYS (Computational Fluid Dynamics). The computational fluid dynamics technique, which is a computer-based analysis, is used to simulate the heat exchanger involving fluid flow and heat transfer. CFD resolves the entire heat exchanger in discrete elements to find temperature gradients, pressure distribution, and velocity vectors. The RNG k-ε model of turbulence is used to determine accurate results from CFD. The heat exchanger design for this work consisted of a shell and eight double concentric tubes. The number of inlets and outlets for all the fluids passing through the heat exchanger are three each. A comparison was made between the numerical and experimental results, and it was found that the percentage error for the hot oil outlet temperature was 6.8%, and the percentage error for the cold water outlet temperature was -21%.

Theoretical trends have appeared which posed the concept of biological structures in contemporary architecture. This concept spread through the emergence of architectural production that reflects and indicates the nature of construction structures based on the ideas and principles of biological structures in biological science. Despite the emergence of many architectural proposals that tried to explain the concept in the field of architecture, it has not been dealt with in depth and not given a comprehensive definition. Therefore, there was a need to search for the concept and its beginning in the biological field as a general framework down to the field of architecture for the purpose of reducing the limits of their search framework. Through a cognitive survey for the appearance of biological structures in architectural production, previous studies were found to discover the knowledge gap and identify the research problem, which states the presence of cognitive deficiencies demonstrating the nature of biological structures in contemporary architecture in general and in the work of architect Caltrava specifically. The goal of the research was to build a conceptual framework illustrating the nature of biological structures in contemporary architecture in general and in the work of architect Caltrava specifically. This need requested a theoretical framework drawn from a set of architectural studies. Two main vocabularies (simulated biological, biological structures properties) were applied to three projects by Caltrava, then the search results were subtracted to reach final conclusions and recommendations.