IJTEE, Volume-20 , Issue 1 (2023), PP 13 - 19
Published: 07 Feb 2023
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
IJTEE, Volume-20 , Issue 1 (2023), PP 07 - 12
Published: 07 Feb 2023
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
IJTEE, Volume-20 , Issue 1 (2023), PP 01 - 05
Published: 07 Feb 2023
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