• Issue 1 (2023)

Analysis and Sensitivity Studies on Thermoacoustic Engine Stack Temperature Profile Development

IJTEE, Volume-20 , Issue 1 (2023), PP 35 - 39

Published: 12 Oct 2023

DOI: 10.5383/ijtee.20.01.006

by Timileyin Aworinde, Alfiya Simran, Isam Janajreh from Mechanical Engineering Department, Khalifa University of Science and Technology, Abu Dhabi, United Arab Emirates

Abstract: Thermoacoustic engines are devices that convert thermal energy to acoustic energy using the Stirling cycle principle. They have wide importance in refrigeration and power generation, therefore there has been intensified research in this area. High focus has particularly been on exploring ways to improve the efficiency of the thermoacoustic engine, the non- linearity of the temperature profile developed across the stack of the engine poses a hindrance to the efficiency of the engine because the thermal gradient across the stack greatly affects the performance of the engine. This work therefore investigates possible pathways for improving the linearity of the temperature gradient across the stack. Two methods of heating the engines are investigated, namely top heating and side heating. For the former the heat is supplied externally at the top of the resonator while in the latter is done internally at the sides of the stack. Different stack materials and fluid medium are also varied to observe their influence on the temperature gradient across the stack. The results of the conducted analysis show that the internal heating condition has a higher tendency to produce a linear temperature gradient across the stack compared to the top heating. The variation of stack materials shows that the linearity of the temperature gradient of the stack increases with the thermal conductivity of the stack materials as materials with very high thermal conductivities (e.g., diamond) produced a perfectly linear temperature gradient across the stack. For the fluid medium, it is also seen that the linearity of the temperature gradient across the stack improves with increase in specific heat and thermal conductivity of the fluid medium with helium giving the most linear gradient of all the medium investigated. read more... read less...

Keywords: Thermoacoustic engine, thermoacoustic refrigerator, stack heating, stack materials, CFD

Thermal Catalysis Effects of Ca(NO₃)₂, Mg(NO₃) ₂, KNO₃, and Fe(NO₃)₃ on Olive Mill Solid Waste

IJTEE, Volume-20 , Issue 1 (2023), PP 29 - 33

Published: 12 Oct 2023

DOI: 10.5383/ijtee.20.01.005

by Islam Alkahder and Reyad A. Shawabkeh from Chemical Engineering Department, University of Jordan, Amman, Jordan

Abstract: Thermogravimetric Analysis - Differential Scanning Calorimetry (TGA-DSC) was employed in this study to investigate the thermal characteristics of olive mill solid waste (OMSW) both alone and in conjunction with six different compositions of Ca(NO₃)₂, Mg(NO₃)₂, KNO₃, and Fe(NO₃)₃. Emphasis was placed on assessing the impact of these compositions on the thermal behavior and heat flow. The analyses of TGA–DSC for the seven samples, conducted at a 10 K/min heating rate, revealed that the thermal decomposition of the OMSW occurred in three stages corresponding to the removal of water, devolatilization, and the formation of bio-char. Particularly noteworthy was the observation of complete combustion events between approximately 155°C and 240°C for four samples with distinct compositions during TGA testing. These findings underscore the significant influence of nitrate salt compositions on the thermal behavior of OMSW. The insights derived from this study contribute to the optimization of waste-to-energy processes and the refinement of thermal treatment protocols for sustainable OMSW management. read more... read less...

Keywords: Thermogravimetric Analysis, Differential Scanning Calorimetry, Olive mill solid waste, Thermal behavior

Optimizing Gas Turbine Performance: Influence of Angle of Attack and Mist Cooling

IJTEE, Volume-20 , Issue 1 (2023), PP 21 - 28

Published: 12 Oct 2023

DOI: 10.5383/ijtee.20.01.004

by Omar Nasro, Said ELTurk, Isam Janajreh from Department of Mechanical Engineering, Khalifa University of Science and Technology, Abu Dhabi, UAE

Abstract: This work presents a comparative study of the flow over a gas turbine blade aimed at enhancing turbine performance. The study focuses on determining the optimal angle of attack of the fluid and implementing internal turbine blade cooling. Computational Fluid Dynamics (CFD) was employed under varying parameters, including fixed and rotating turbine blade conditions. Precise analysis of temperature and pressure coefficient distributions, as well as torque, enthalpy, thermodynamic power, flow velocity, and mass flow rate were conducted for each setup. Results indicate that the optimal flow attack angle is 60°. Subsequently, mist cooling was simulated as an internal cooling method at the optimum attack angle to examine its effect on blade temperature distribution. Simulation outcomes suggest that implementing mist cooling enhances temperature distribution over the blade and improves turbine performance. read more... read less...

Keywords: Turbine Blades, Turbine Cooling, Gas Turbine, Internal Cooling, Mist Cooling, CFD

Single plate analysis of thermoacoustic refrigerator

IJTEE, Volume-20 , Issue 1 (2023), PP 13 - 19

Published: 07 Feb 2023

DOI: 10.5383/ijtee.20.01.003

by Omar Al-Mufti and Isam Janajreh from Department of Mechanical Engineering, Khalifa University of Science and Technology, Abu Dhabi, UAE

Abstract: 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 with no to low maintenance. TAR can be driven using thermoacoustic engine (TAE) in which the later can be sustainably operated utilizing waste heat or concentrated solar. Also, in contrary to conventional refrigeration methods, TARs do not use environmentally harmful gasses. In this work, a high-fidelity localized model is developed to simulate the flow in a standing wave (straight tabular) thermoacoustic refrigerator. In this localized analysis a subsection domain that runs through two stack halves and stretches nearly 1.5 stack length at each side is considered. The acoustic waves were simulated using oscillating walls at the two domain limits at a given resonance frequency. The model compared favorably to previous experimental and numerical findings. The analysis was done for drive ratios in range of 0.28% to 2%. A 3.2 oC temperature difference is produced at the 2% drive ratio compared to 0.5 oC at the 0.28% ratio. Higher difference can be achieved at higher drive ratio and also larger stack length. read more... read less...

Keywords: Numerical modeling, Thermoacoustic, Refrigerator, Drive ratio, CFD

Thermal Comfort Analysis of Wind Tower Greenhouse Integration System using Ansys

IJTEE, Volume-20 , Issue 1 (2023), PP 07 - 12

Published: 07 Feb 2023

DOI: 10.5383/ijtee.20.01.002

by Sameer Khan, Ruqiya Abdullah Farah, Isam Janajreh from Department of Mechanical Engineering, Khalifa University of Science and Technology, Abu Dhabi, United Arab Emirates

Abstract: Increasing urbanization, a shortage of arable land, and climate change-related weather extremes are some of the challenges facing the production of global food and agriculture due to the estimated global population of 9.6 billion by 2050. As a result, improvements in greenhouse technology and modifications pushed science-based solutions for optimal plant production in all seasons worldwide by adjusting internal climate growing factors. By using passive technology coupled with evaporation cooling from wind towers, significant amounts of energy can be saved, reducing the emissions of greenhouse gases. In this study, the effect of wind tower greenhouse integration on the micro-climatic conditions inside the greenhouse is modeled and simulated. The model is governed by the non-isothermal Navier-Stokes flow in heat, viscous and turbulent flow regimes. The effect of various parameters such as airflow velocity, relative humidity, and temperature in the greenhouse is studied as well as the effect of mist flow rate, and the position of the injector in the wind tower. The results show the optimal design of the greenhouse wind tower integrated system based on the desired temperature and relative humidity within the greenhouse. The final model selected was the flat slope geometry greenhouse with a temperature value of 29.839792°C and relative humidity of 68.34%. read more... read less...

Keywords: Ansys, Evaporative Cooling, Greenhouse, Wind tower

Experimental Study on the Effect of Water as a Working Fluid in Aluminium Heat Pipes

IJTEE, Volume-20 , Issue 1 (2023), PP 01 - 05

Published: 07 Feb 2023

DOI: 10.5383/ijtee.20.01.001

by Salman Hemayet Uddin, Md. Islam, Firas Jarrar, Isam Janajreh from Department of Mechanical Engineering, Khalifa University, Abu Dhabi, United Arab Emirates

Abstract: Thermal management of machines and electronic devices is a matter of high importance. Cooling of electronics becomes much more sensitive in applications related to space because of the difficult constraints and environment. The weight and size are very important parameters as well as the efficiency of the cooling method and heat pipes are considered a very suitable option because of its passive operation and light weight. Different working fluids can be used in a heat pipe but the compatibility of the casing material with the working fluid is a very important parameter. Water aluminum heat pipes are not a common option because they react at temperatures starting from 294 K. In this research the effect of water in the degradation of the performance of aluminum heat pipes is studied. A suitable operation range for the heat load is considered. It is found that at higher loads, the performance of the heat pipe decreased but with the addition of nano particles the performance was compensated by a large measure. read more... read less...

Keywords: Aluminum water heat pipe, Grooved Heat pipe, Hydrogen formation in heat pipe, Nanoparticles