Volume-19-Issue 2 (2022)
IJTEE, Volume-19, Issue 2 (2022) , PP 93 - 33
Published: 28 Dec 2022
by Mohamad Alsheikh, Abdelsalam Alkhalaileh, Isam Janajreh from Department of Mechanical Engineering, Khalifa University of Science and Technology, Abu Dhabi, UAE
Abstract: Optimizing the microclimate conditions has become a very significant demand by public, which led to numerous research in this field. In this study, the effect of different tree shapes and their influence on the microclimate conditions will be studied using computational fluid dynamics (CFD). A baseline geometry was designed with a set of boundaries conditions and its robustness is assessed via different mesh resolutions. Three different tree shapes with the same surface area (long-triangular, short-triangular, and round) were considered and compared. The flow field is governed by the two-dimensional, steady-state, multi-species, and non-isothermal Navier-Stokes equations. In all the tree model configurations, the trees were considered the source of moisture and lower temperature than the surrounding environment. This resulted in increase in the relative humidity of the incoming ambient air and reduction in its temperature. In this analysis the incoming air was considered to follow the common power law atmospheric boundary layer (u/Uinf=(y/Ho)1/7) with an inherited vertical strain rate. The presence of the trees created axial and exaggerated the vertical rate of strains. The results showed that long triangular tree shape had the biggest drop in temperatures with a value of DT= 4.15K (301K local value). It also resulted in a relative humidity value between 15% and 45% which is suitable for the human thermal comfort. read more... read less...
Keywords: Microclimate; CFD; Human thermal comfort; Tree-shape
IJTEE, Volume-19, Issue 2 (2022) , PP 87 - 92
Published: 27 Dec 2022
by Mubinul Islam, Md. Islam, Hemant Mittal, Saeed Alhassan from Khalifa University of Science and Technology, Abu Dhabi, UAE
Abstract: The use of agricultural waste for the production of activated carbon has gained popularity due to the high carbon content of the raw materials, improve sustainability of the product, and low cost. In this paper, activated carbon (DL-AC) was synthesized from discarded date palm leaves. The activation was done via chemical activation where KOH was used as the activating agent. The final product was characterized using XRD and SEM. The XRD results showed a loss in crystallinity due to the activation process whereas the SEM images showed improved porosity of the activated carbon. Water adsorption studies were carried out at 25 °C and the results were fitted to different isotherm models. The adsorption isotherm reported a maximum adsorption capacity of 0.109 gwat/gads at 0.66 p/po. The multilayer adsorption behavior is best explained using the GAB and FHH isotherm models. read more... read less...
Keywords: Activated carbon; Date palm leaves; Water adsorption
Assessment of Wind Speed and Power Density Using Weibull and Rayleigh Distributions at Turbat, Balochistan, Pakistan
IJTEE, Volume-19, Issue 2 (2022) , PP 77 - 85
Published: 27 Dec 2022
by Asif Jalal, Ussama Ali from Mechanical Engineering Department, University of Engineering and Technology Lahore, Pakistan
Abstract: The meager economic situation, indefinite energy crisis, industrial modernization, and hazardous contamination impulse the empiricist to transcend the attention on renewable energy resources in Pakistan. One of the most rapidly growing renewable energy sources is wind energy. The main goal of this research work is to examine the wind characteristics and wind potential at the site of Turbat, Balochistan, Pakistan. For this purpose, the measured hourly time series data was collected from the Pakistan Meteorological Department (CPDC, Karachi) for 21 months (Jan 2012 – Sep 2013). After evaluating the monthly average wind speed (> 4 m/s), the average value of most probable wind speed (3.83 m/s), the average value of wind speed carrying maximum energy (7.732 m/s), and the standard deviation of the data (1.699 – 3.306), the results are used to statistically evaluate the data by Weibull and Rayleigh distributions for the selected site. The monthly average value of wind power and energy densities of the selected site is 140.145 W/m2 and 101.775 kWh/m2, respectively. A comparison was made between the mean power potential of the site and the power potential assessed using the Weibull and Rayleigh distributions. It was revealed that the Weibull distribution depicted the data more accurately. This statement is further enriched by the assessment of the performance of both distributions with the RMSE, χ2, and R2 tests. read more... read less...
Keywords: Wind energy; Weibull distribution; Rayleigh distribution; Wind energy density; Turbat, Pakistan
The Numerical Analysis of the Suppression of Flow-Induced Vibrations using Slits at the Laminar Regime
IJTEE, Volume-19, Issue 2 (2022) , PP 69 - 76
Published: 27 Dec 2022
by Anas Ghannam, Mohammad Belal and Isam Janajreh from Department of Mechanical Engineering, Khalifa University of Science and Technology, P.O. Box 127788, Abu Dhabi, United Arab Emirates
Abstract: The flow over a cylinder is responsible for stimulating vibrations on circular cylinders due to the flow separation and periodic vortex shedding at the downstream area of the cylinder near the wake. Significant damage and fatigue failure transpire when the vortex shedding frequency coincides with the structure's natural frequency, leading to a severe financial and human catastrophe. Therefore, this paper aims to establish a passive control method suppressing the flow induced vibrations (FIVs) by incorporating parallel slits with different sizing examined at various mounting conditions. read more... read less...
Keywords: Flow induced vibrations, Slits, Laminar, Passive flow control
IJTEE, Volume-19, Issue 2 (2022) , PP 63 - 68
Published: 27 Dec 2022
by Mohammad Islayem, Mohammed Tarnini, Isam Janajreh from Department of Mechanical Engineering, Khalifa University of Science and Technology, Abu Dhabi, UAE
Abstract: Hyperloop is forecasted to be the future transportation system for medium distance range. It consists of levitated pods traveling inside a reduced pressure tunnel/tube near the transonic speed. The flow around the pod is limited to Mach speed to avoid the choking and shockwaves formation that can cause damages and destabilization of the pod and the tube. The most crucial parameter in the hyperloop traveling system is the aerodynamic drag. In this study, numerical flow simulation of compressible steady air flow has been done on the hyperloop pod traveling inside the low-pressure tunnel environment. Two-dimensional axisymmetric simulations were carried out to assess the flow and aerodynamic forces exerted on the pods under varying speed (25 to 350 m/s) and separation distance (10.75, 21.5, 43, 86 m) between two pods. For all the cases, Mach number =1 flow speed is reached at a value between 150 to 200 m/s and the shockwaves start appearing on the 2nd pod at a value between 200 to 250 m/s. Results show that shockwave appeared at the 1st pod at separation distance of 86 m and speed 350 m/s. Overall, the pressure drag has more impact on the total drag than the friction drag especially at the 2nd pod. The total drag obtained at the 1st pod in a multiple pod model is less than the total drag in a single pod model, while it is higher at the 2nd pod when compared with a single pod model. read more... read less...
Keywords: Hyperloop, Multiple pods, Steady flow, Drag coefficients
IJTEE, Volume-19, Issue 2 (2022) , PP 55 - 62
Published: 27 Dec 2022
by António Costa, Rui Pitarma from Polytechnic Institute of Guarda, Guarda, Portugal
Abstract: Wood is a crucial component of the green economy of the 21st Century. From house construction to innovative daily applications and products, wood is one of the most sustainable resources. However, as a natural material, it suffers deterioration with time. Infrared thermography may provide an excellent potential for detecting internal damage. Although the prices of infrared cameras have dropped recently, getting the best value for money and choosing the right camera for wood inspection is a significant challenge. Before choosing an infrared camera, the operator needs to consider several parameters, such as the temperature range, spectral range, thermal sensitivity, resolution, spatial resolution, accuracy, optics and focus, to make an informed decision. This study aims to evaluate the performance of two infrared cameras, a high-end model and a mid-range model, in visual wood damage detection. For this purpose, samples of different wood species with induced damage were observed using active thermography. Our results suggest that, for technical purposes such as qualitative studies, resolution and thermal sensitivity may be more important parameters than accuracy. The results achieved are an important contribution when deciding which infrared camera to purchase. read more... read less...
Keywords: Infrared Cameras, Thermal Sensitivity, Resolution, Accuracy, Performance, Wood Damage Detection