JOURNAL OF ENERGY RESOURCES TECHNOLOGY-TRANSACTIONS OF THE ASME

An existing air-cooled binary geothermal pow er plans in northern Nevada is studied. The current performance of the plant is analyzed with an emphasis on the effects of seasonal climate changes. Two potential sites have been identified to improve the performance of the plant. Northern Nevada has a dry climate, particularly in hot summer months, and the temperature of cooling air can be decreased considerably by evaporative cooling. When the air temperature is decreased to the wet-bulb temperature, the decrease in the condenser temperature is determined to increase the power output by up to 29 percent The required amount of water for this case is calculated to be about 200, 000 tons per yr. Several parametric studies are performed by simulating the operation of the plant with an equation solver with built-in thermophysical property functions. It is determined that the net power output of the plant can be increased by 2.8 pe,cent by optimizing the maximum pressure in the cycle. Also, replacing the existing working fluid isobutane by other commonly toed binary fluids such as butane, R-114, isopentane, and pentane do not produce as much of an improvement in the plant performance as operating with isobutane at the optimum maximum pressure. Therefore, isobutane appears to be the best choice for this power plant

Effect of obstacles on thermal stratification in hot water storage tanks

Effect of using different obstacles on thermal stratification in a cylindrical hot water tank is analyzed numerically. The numerical method is validated using both experimental and numerical results. Temperature distributions within the tank for 12 different obstacles are obtained. The results indicate that placing obstacle in the tank provides better thermal stratification compared to the no obstacle case. The obstacle types having gap in the center appear to have better thermal stratification than those having gap near the tank wall. The obstacles numbered 7 and 11 represent better obstacle shapes and configurations for thermal stratification among the considered cases and consequently the tanks with these obstacles can supply hot water at higher temperatures. Other obstacle types have little effect on improving thermal stratification in the tank. Further comparisons of obstacles 7 and 11 in terms of the temperatures of hot water supply indicate that the obstacle 11 provides the best thermal stratification in the tank among all the considered cases. (c) 2005 Published by Elsevier Ltd