Yazar "Cheema, Taqi Ahmad" seçeneğine göre listele

Listeleniyor 1 - 2 / 2
  • [ X ]
    Öğe
    Hydrothermal Investigation of the Performance of Microchannel Heat Sink with Ribs Employed on Side Walls
    (Walter De Gruyter Gmbh, 2021) Ahmad, Faraz; Cheema, Taqi Ahmad; Khan, Amjid; Mohib-Ur-Rehman, Muhammad; Yildizhan, Hasan
    In the present study, conjugate heat transfer and fluid flow performance of microchannel heat sink has been investigated using dimensionless parameters. Novel ribs of four different types are introduced on the side walls of channel, which include trapezoidal ribs, rectangular ribs, hydrofoil ribs, and elliptical ribs. The performance evaluation has been conducted by comparing friction factor (f), Nusselt number (Nu), fluid bulk temperature (T-f), wall shear stress (tau), field synergy number (Fc), irreversible heat loss (Q(d)), and Bejan number (Be) in a Reynolds number, ranging from Re = 100 to Re = 1000. The results revealed that the addition of these novel ribs are helpful in improving the overall thermal and hydraulic performance of microchannel heat sink. From the results of Bejan number, it has been revealed that more than 96 % of losses are because of heat transfer. However, at low Reynolds number, the frictional losses can be neglected, because of very low fluid velocity. Moreover, it has been revealed that synergetic relation between velocity and temperature gradient becomes weaker at higher Reynolds number. Furthermore, it is clear from this study that elliptical ribs performed better in thermal aspects, whereas hydrofoil ribs performed better at hydrodynamic aspects.
  • [ X ]
    Öğe
    The effect of the intermediate fluid-flow rate on the system performance in the closed circuit applications of the solar collector
    (Serbian Society of Heat Transfer Engineers, 2021) Yildizhan, Hasan; Cheema, Taqi Ahmad; Sivrioglu, Mecit
    Solar collector water heating system use solar thermal energy to provide hot water for domestic and industrial use. These systems are operated either as open-loop or closed-loop flow circuit. The former loop systems are not recommended for the cold climates having water freezing problem. Although previous studies on solar collectors have used closed-loop operation with water as the working fluid. However, it must have high boiling and low freezing points for the colder regions and thus arises the need for antifreeze mixtures of water. Another solution the same problem is the use of heat transfer oil as intermediate working fluids. In the present study, the energy and exergy analysis of a boiler supported vacuum tube solar collector system working with closed-loop in different working fluid-flow rates have been performed and evaluated. Heat transfer oil has been used as an intermediate working fluid in the closed loop system at different flow rates of 0.277 kg/s, 0.383 kg/s, and 0.494 kg/s. The results show that the collector temperature difference as well as the outlet temperature decrease. However, the collector inlet temperature increases by increasing the flow rate. Moreover, with the increase in flow rate, it was ascertained that the energy and exergy efficiency of the system and the collectors increase. The main finding of the present study is that the intermediate fluid used in the closed-circuit operation of the solar collectors has a direct effect on the energy and exergy efficiency of the system. © 2021 Society of Thermal Engineers of Serbia Published by the Vin?a Institute of Nuclear Sciences, Belgrade, Serbia. This is an open access article distributed under the CC BY-NC-ND 4.0 terms and conditions