Ali Heydari

Numerical Analysis of a Small Size Baffled Shell-and-Tube Heat Exchanger Using Different Nano-Fluids

ABSTRACT In this study, numerical simulation was used to investigate the effect of adding different nano-particles into the fluid on the performance of a baffled shell-and-tube heat exchanger. A three-dimensional modeling approach was followed to analyze the effect of different nano-fluids, at various volume fractions, as applied in a baffled shell-and-tube heat exchanger. Once finished with validating the grid independency and results, we proceeded to obtain heat transfer rate, pressure drop, outlet shell temperature and exchanger effectiveness for different volume fractions and particle size of different nano-fluids. The studied nano-particles in the present work included Al2O3, CuO, Fe2O3, Cu, Fe, SiO2, and Au, with water and ethylene glycol employed as base fluids. With constant mass flow rate for all cases, the results indicated that, the addition of nano-particles had reduced the heat transfer coefficient, pressure drop and the rate of heat transfer through the shell, even though it had increased outlet shell temperature. In other words, considering a constant heat transfer rate, the presence of nano-fluids in a baffled shell-and-tube heat exchanger is likely to be associated with increased outlet shell temperature. Another consequence presents that using ethylene glycol as base fluid leads to higher effectiveness compared with water as a base fluid in exchanger.

A review of solar absorption cooling systems combined with various auxiliary energy devices

From both environmental and energy-saving points of view, solar heating and cooling systems have recently proven themselves in the commercial world as the environmentally friendly and sustainable energy systems which can replace the systems powered by conventional sources of energy such as fossil fuels and electricity. In the present paper, the research contributions conducted on solar absorption cooling systems, integrated with different auxiliary energy devices, are comprehensively reviewed and discussed. Also, various cooling systems integrated with solar technologies, i.e., flat-plate collector, evacuated tube collector, compound parabolic collector and parabolic trough collector, are reviewed. The survey and comparison are carried out in terms of some crucial parameters such as coefficient of performance, annual energy consumption and payback period. Further, this work briefly presents and discusses some possible opportunities for future works from the efficiency viewpoint.

Investigating the effect of connection type of a sintered porous fin through a channel on heat transfer and fluid flow

Extended surfaces represent one of practical approaches to enhance heat transfer. Based on the laws of conductive and convective heat transfer, an increase in the area across which the object is in contact with the fluid can increase heat transfer. Due to its special structure, porous media can be seen as suitable alternatives for extended surface applications. On this basis, this research investigates the effect of connection type of sintered porous fins on heat transfer and pressure drop in the fluid flow. Connection model of four- and six-contact sintered balls of constant dimensions was evaluated by means of CFD simulation in this research. To describe the problem further, surface analysis on the reference cube is presented. The results indicate that the six-contact model has more porosity than the four-contact in reference cube by 29.45%. It was further found that the six-contact model tends to increase convective heat transfer by 33%. Results of surface analysis show that the main reasons for the difference in heat transfer between the four- and six-contact models are porosity and the angle at which balls are arranged with another.