Energy and Exergy Analysis and Optimization of a Heat Sink Collector Equipped with Rotational Obstacles

In this paper, the forced convection flow in a heat sink collector equipped with stationary and rotational obstacles is studied numerically. Three-dimensional governing equations are solved by control volume approach based on the SIMPLE algorithm and k.. turbulence model. Reynolds numbers are considered in the laminar-turbulent range of 50 < Re < 12,000. The optimization was carried out by variation of related parameters. It is concluded that using heat sink, instead of a customary instrument, increases the outlet temperature from the collector and exergy efficiency due to longer installing of the fluid inside the collector. Also, it is realized that using the stationary and rotational obstacles enhance the outlet fluid temperature (about 2.5°C), energy efficiency and exergy efficiency. Nevertheless, using the rotational obstacles is more effective than the stationary obstacles. While the trend of exergy efficiency variation with effective parameters is increasing, applying the obstacles precipitates the efficiency increment (from 4% to 5.3%). In addition, for the case that the trend of exergy efficiency variation by changing these parameters is decreasing, the decreasing trend gets slow. There is a unique mass flow rate (0.005 kg/s) that the exergy efficiency gets a maximum value and for the higher mass flow rates, the efficiency decreases slightly and then remains unchanged.