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
Assessment of ultrasound assisted coalescence of water-in-crude oil emulsion: Influence of piezoelectric transducer material under batch and continuous conditions
IJTEE, Volume-19 , Issue 1 (2022), PP 47 - 54
Published: 26 Oct 2022
by Idowu Adeyemi, Mahmoud Meribout, Lyes Khezzar, Nabil Kharoua, Khalid AlHammadi from Department of Mechanical Engineering, Khalifa University of Science and Technology, P.O. Box 127788, Abu Dhabi, United Arab Emirates, Department of Electrical Engineering and Computer Science, Khalifa University of Science and Technology, P.O. Box 127788, Abu Dhabi, United Arab Emirates, and Department of Mechanical Engineering, Ecole Nationale Polytechnique de Constantine, Constantine, Algeria
Abstract: In this work, the potentiality of lead free ultrasound (US) materials towards crude oil emulsion demulsification was assessed. The assessment is crucial because of the detrimental environmental and health impacts of lead zirconate titanate, which is widely used for US coalescence presently. The production or utilization of lead zirconate titanate (PZT) results in the release of vaporized hazardous lead oxide (PbO) at elevated temperature or dissolution of poisonous lead into aqueous medium. Hence, the analysis of the effect of different piezoelectric material type (PZT, polyvinylidene fluoride (PVDF) and lithium niobate (LiNbO3)) on domain acoustic pressure distribution and the subsequent coalescence of binary droplets under batch conditions was conducted. The lead-free piezoelectric materials (PVDF and LiNbO3) were assessed with the PZT in order to determine their viability for droplet coalescence. The piezoelectric materials were subjected to mechanical oscillation under resonance in order to allow for optimum performance. Moreover, the US coalescence was examined under continuous flow conditions to determine coalescence behavior and performance during online emulsion treatment. The eigen-frequency analysis provided the resonance frequencies of 19.61, 26.04 and 57.80 kHz for PVDF, PZT and Lithium niobate, respectively. Moreover, the acoustic pressure in the emulsion domain varied in magnitude and distribution. The order of the coalescence time for the binary droplets followed the order PZT<PVDF<LiNbO3. Furthermore, increasing the flow velocities resulted in slight reduction in the coalescence time and energy consumed for the different piezoelectric materials evaluated. read more... read less...
Keywords: Piezoelectric transducer, Ultrasound, Coalescence, Demulsification, Lead free, Crude Oil Emulsion
IJTEE, Volume-19 , Issue 1 (2022), PP 29 - 45
Published: 26 Oct 2022
by Omar Ahmed Al-Mufti and Isam Janajreh from Department of Mechanical Engineering, Khalifa University of Science and Technology, Abu Dhabi, UAE
Abstract: Thermoacoustic is the science that studies the conversion of the heat into acoustical sound and vice versa. The conversion of heat to acoustic power is done through Thermoacoustic engine (TAE). This generated acoustic power can be converted to another and useful form such as mechanical or electrical energy. On the other hand, Thermoacoustic refrigerator (TAR) or heat pump is a device that uses acoustic sound to pump heat from a lower temperature reservoir. The most distinct feature of thermoacoustic systems is that they do not have moving parts, which makes them reliable. Thermoacoustic engine can recycle any source of waste heat and use sustainable heat like concentrated solar. Also, in contrast to conventional refrigeration methods, thermoacoustic refrigerator spares the usage of environmentally harmful gases that is daunting the centralized cooling industry. There is no doubt the thermoacoustic technology has been considered in various applications with some unspoken advancement. In this manuscript we intend to review the fundamentals of thermoacoustics and highlight their recent developments. Additionally, analytical simulation of thermoacoustic refrigerator will be discussed and validated against experimental published work. The goal is to reveal the effect of different parameters on the performance in an attempt to establish design guidelines for an improved technology metrics. The future prospects of thermoacoustic refrigeration are also presented at the end of this study. read more... read less...
Keywords: Thermoacoustic engine; Thermoacoustic refrigerator; Thermal and viscous penetration depth; Standing and traveling wave
IJTEE, Volume-19 , Issue 1 (2022), PP 23 - 28
Published: 19 Sep 2022
by M Mubashir Farid, Samia Sadaf, M Shahid Farooq, Ussama Ali from Department of Mechanical Engineering, University of Engineering and Technology Lahore, Pakistan
Abstract: This paper investigates the effect of nanofluids in a flat-tube heat exchanger on the heat transfer under the influence of constant heat flux using computational fluid dynamics (CFD) analysis. Two nanofluids: Titanium Oxide (TiO2)/water and Aluminum Oxide (Al2O3)/water were used with nanoparticles of diameter 10 nm. A two-phase approach with a mixture model is adopted in the CFD analysis. The heat transfer coefficient was evaluated at Reynolds number of 1750 utilizing various volume concentrations of nanoparticles (1%, 3%, 5%, and 7%). It was observed that an increase in the concentration of the nanoparticles resulted in an increase in the value of heat transfer coefficient. The results observed at 7% volume concentration, using two-phase approach, showed 5% and 8% enhancement in the heat transfer coefficient for TiO2/water and Al2O3/water, respectively, when compared with the results of single-phase technique. read more... read less...
Keywords: Flat tube, Heat transfer coefficient, Two-phase approach, Nanofluids
IJTEE, Volume-19 , Issue 1 (2022), PP 15 - 22
Published: 19 Sep 2022
by Muna AlQaydi, Md Islam, Isam Janajreh from Khalifa University of Science and Technology, Abu Dhabi, UAE
Abstract: Atmospheric water harvesting (AWH) is used to address the current scarcity of fresh water. Sorption-based AWH technology using desiccant coated heat exchanger (DCHE) could enable a good water supply in arid regions since sorbents can grab moisture from arid environment and then release water once it is thermally generated. Recent developments focus on novel adsorbents with high sorption capacity at low humidity and low regeneration temperature. However, a thermodynamic analysis on overall system to predict the best operating parameters and how it affects system efficiency has not been studied. In this study, we investigated the energy and heat transfer properties of desiccant-coated heat exchanger. A one-dimensional mathematical model is developed to predict the performance of a DCHE system which uses super-porous hydrogel (SPH) made of N-isopropylacrylamide (NIPAM) as a desiccant material. The effects of inlet temperature, inlet humidity ratio, air mass flow rate, and cold side temperature brought by using thermo-electric cooling (TEC) on the amount of water collected, COP, and second law efficiency of the system were analyzed. The results suggest that the rate of water production and COP of the system increased as the temperature and humidity of the air increased. It emerged that increasing airflow increases water intake and COP due to the improved heat transfer through the system. However, rising cold side temperature of TEC decreases water production rate and COP while it improves second law efficiency because of reduced heat transfer and entropy generation. The obtained results show that water harvesting using the proposed system with thermoelectric cooling device and solar energy is feasible. read more... read less...
Keywords: Cooling Load, Air-Conditioning, Desiccant coated heat exchanger, Atmospheric water collection
IJTEE, Volume-19 , Issue 1 (2022), PP 07 - 13
Published: 19 Sep 2022
by Ussama Ali, Ayoola Brimmo, Md Islam, Isam Janajreh from Department of Mechanical Engineering, Khalifa University of Science and Technology, Abu Dhabi, UAE and Department of Mechanical Engineering, University of Engineering and Technology, Lahore, 54890, Pakistan
Abstract: Two-dimensional low Reynolds number flow (Re = 100) over a transversely oscillating circular cylinder placed in a uniform stream is numerically investigated in this work using the commercial software Ansys/Fluent. The forced transverse oscillations of the cylinder are carried out to mimic the specific cases of flow-induced vibrations. The frequency ratio is varied between 0 – 2, where 0 corresponds to stationary cylinder. The layering technique of dynamic mesh is employed to incorporate the cylinder motion. The unsteady flow simulations are performed to solve for URANS. The parameters studied are the coefficients of lift and drag, vortex shedding frequency, and the vortex shedding patterns. The results reveal that the cylinder oscillation induces modulation in the lift and drag coefficients in terms of their frequency and amplitude. The lock-in occurs at frequency ratio of 1 where the frequency of cylinder oscillation matches with the natural vortex shedding frequency of the cylinder. Maximum average drag coefficient is observed at the lock-in condition however the lift coefficient is found to increase with the frequency ratio. The 2S vortex shedding pattern is observed in the vorticity contours for all the cases studied. read more... read less...
Keywords: Forced transverse oscillations, Unsteady flow, Lift and drag coefficients, Vortex shedding pattern
IJTEE, Volume-19 , Issue 1 (2022), PP 01 - 05
Published: 19 Sep 2022
by Ahmad Hasan, Md Islam, Isam Janajreh from Khalifa University of Science and Technology, Abu Dhabi, UAE
Abstract: UAE’s climate is considered one of the hottest and humid regions in the world, making air conditioning systems essential in each house nearly all year long. Air-conditioning systems consume most of the buildings’ electricity and that comes at a hefty energy cost. Therefore, any serious improvements in this technology in reducing the needed cooling load will lead to economical gain. Different parameters affect the cooling load of a building including the type of air conditioning system (centralized or decentralized units), the outdoor temperature and humidity, and the orientation of the building. Proper building orientation in Malaysia lead to 7.9% cooling load saving. The aim of this work is to study the effect of building orientation located in UAE on the cooling load. A single room is considered as the baseline building and TRNSYS software is used to calculate its cooling load when oriented to north, west, north–west, and south. The ASHRAE Standard 55 is adopted where the zone temperature ranges between 20°C – 25°C, and the relative humidity between and 40 – 60%. The study concludes that when the room is oriented to north–west the cooling load was at the minimum of 2627 Ton-hr. Whereas the maximum cooling load occurs when the room was oriented to west at 3161 Ton-hr. This led to nearly 17% cooling load saving. Therefore, it is recommended to orient buildings facing the north–west direction in the UAE. read more... read less...
Keywords: Cooling Load, Building Orientation, Air-Conditioning