Fadi A. Ghaith

Nonlinear Finite Element Modeling of Charpy Impact Test

Finite element modeling of Charpy impact test was performed for a normalized carbon steel specimen based on plane strain geometry and bilinear isotropic hardening plasticity. As the suggested approach takes into account all aspects of nonlinearity such as geometric, material and contact nonlinearities, it may describe the conventional destructive impact test accurately with much less effort and cost. A failure criterion is assumed to be at 10 % of plastic strain based on the tensile experiment data. Impact energy was estimated at different testing temperatures. It was found that impact energy required for fracture of the selected steel specimen at room temperature (i.e. 25 °C) is to be 65.9 Joul. According to simulation results, it is found that the ductile to brittle transition temperature (DBTT) equals 0 °C. In order to validate the numerical model, a comparison study was established by comparing the numerical results with the corresponding experimental tests at the same conditions, which shows good match with maximum deviation of 5 % for all computer runs.

Thermal performance of parabolic trough collector for cooling applications in residential buildings in UAE

This paper addresses the potential of integrating Parabolic Trough Collectors (PTC) with a double-effect absorption chiller for the purpose of space cooling in residential buildings. The proposed model was designed such to provide a continuous cooling while in the absence of sun, the bio-mass heater was used as an auxiliary heating source. In this study, the thermal performance was investigated and a feasibility study was conducted in order to assess the system’s economic and environmental impacts. The obtained model was implemented on a case study represented by a four-floored residential building based in Dubai with a net cooling load requirement of 366 kW. The obtained results from the numerical simulation were analyzed to identify the optimum configuration in terms of feasibility and potential savings. It was found that a hybrid system with 40% solar contribution is the optimum solution compared to other alternatives. The proposed system achieved Annual Energy Consumption savings (AEC) of about 556061 kWh and a reduction by 69% in the annual operating costs. Moreover; the system reduced the Carbon-dioxide emissions by 344 tons/year. The payback period of the proposed system was found to be 2.42 years only.Copyright

Thermal Performance Enhancement of an Industrial Shell and Tube Heat Exchanger

This paper aims to enhance the thermal performance of an industrial shell-and-tube heat exchanger utilized for the purpose of cooling raw natural gas by means of mixture of Sales gas. The main objective of this work is to provide an optimum and reliable thermal design of a single-shelled finned tubes heat exchanger to replace the existing two- shell and tube heat exchanger due to the space limitations in the plant. A comprehensive thermal model was developed using the effectiveness-NTU method. The shell-side and tube-side overall heat transfer coefficient were determined using Bell-Delaware method and Dittus-Boelter correlation, respectively. The obtained results showed that the required area to provide a thermal duty of 1.4 MW is about 1132 m2 with tube-side and shell-side heat transfer coefficients of 950 W/m2K and 495 W/m2K, respectively. In order to verify the obtained results generated from the mathematical model, a numerical study was carried out using HTRI software which showed a good match in terms of the heat transfer area and the tube-side heat transfer coefficient.Copyright

Elastodynamic Modeling and Simulation of an Axially Accelerating Beam

This paper aims to develop an accurate nonlinear mathematical model which may describe the coupled in-plane motion of an axially accelerating beam. The Extended Hamilton’s Principle was utilized to derive the partial differential equations governing the motion of a simply supported beam. The set of the ordinary differential equations were obtained by means of the assumed mode method. The derived elastodynamic model took into account the geometric non-linearity, the time-dependent axial velocity and the coupling between the transverse and longitudinal vibrations. The developed equations were solved numerically using the Runge-Kutta method and the obtained results were presented in terms of the vibrational response graphs and the system natural frequencies. The system dynamic characteristics were explored with a major focus on the influence of the velocity, acceleration and the excitation force frequency. The obtained results showed that the natural frequency decreased significantly at high axial velocities. Also it was found that the system may exhibit unstable behavior at high accelerations.Copyright

Thermal Performance of Improved Inverted Trickle Solar Still

In this paper, the inverted trickle solar still was integrated with a flat plate collector and a basin still in order to improve the overall productivity. The flat-plate collector was used to pre-heat the saline water entering the inverted trickle solar still. Saline water flows at the backside of the inclined absorber plate on wire screen so that the water remains attached to the plate. Water evaporates from the plate and condenses in the lower compartment. The remaining non evaporated water and the condensed water on the back plate which has high temperature was collected and fed to the basin solar still. A comprehensive mathematical thermal model was developed to predict the productivity and to investigate the effects of several operating conditions on the overall productivity of the integrated system. Based on the performed parametric studies, the maximum mass flow rate of 0.002 kg/s was found to be optimum as it maximized both the efficiency and the productivity of the integrated solar still system. On the other hand, the obtained results at the optimum flow rate showed that the maximum overall productivity on a typical summer day (i.e. 1st of July) and a typical winter day (i.e. 1st of February) were 11.25 kg/day and 5.227 kg/day, respectively for Dubai weather conditions. This study revealed that the productivity of the proposed integrated inverted trickle solar still is almost doubled due to the incorporation of flat plate collector in comparison of the previous work posted in the literature.

Elastodynamic Modeling and Simulation of the AIRBUS A380 Wing

This paper addresses the dynamic modeling and simulation of the AIRBUS A380 wing. The governing equations of motion which describe the vibrational motion of the wing were derived using the extended Hamilton’s principle. The elastic wing structure is assumed to follow a Bernoulli-Euler cantilever beam clamped on the moving fuselage and carrying two Trent-900 engines on its span which were treated as lumped masses. The obtained equations of motion of the wing model were analyzed by means of the unconstrained modal analysis and the system natural frequencies were estimated. In order to verify the obtained results, the dynamic response was simulated using the Finite Element (FE) computational software by which the vibrational response was generated under several types of excitation. The obtained results showed good match between the natural frequencies extracted from the mathematical model and the corresponding ones generated by FE simulation. Also the developed computational model in this investigation was found successful in capturing the vibrational motions of a wide spectrum of relevant aerodynamic and unbalance loading conditions.Copyright