Thermodynamic Study On Nuclear Closed Brayton/Ammonia Combined Cycle

With the development of the world economy, the total energy consumption increases steadily. The consumption of the energy, especially fossil energy resources, causes and accelerates the occurrence of many environmental problems. Nuclear energy is a clean, efficient energy source that plays an important role in current energy demand. Because of its inherent safety, the high temperature gas-cooled reactor(HTGR) has attracted many attentions of the researchers. To ensure the high efficiency of nuclear power plant, reasonable thermodynamic cycle should be used. Despite of the higher efficiency of HTGR, a large amount of waste heat is discharged from the pre-cooler of the nuclear closed Brayton cycle,and the temperature of this waste heat is lower than 150??In this temperature range, Goswami cycle and Kalina cycle are two effective ways to utilize the waste heat.In this paper, a combined cycle, in which a combined power/cooling cogeneration cycle is combined with the nuclear closed Brayton cycle, is proposed to recover and utilize the waste heat rejected from the pre-cooler of the closed Brayton cycle. The detailed thermodynamic and economic analyses are carried out for the combined cycle. The effects of several important parameters, such as the absorber pressure, the turbine inlet pressure, the turbine inlet temperature, the ammonia mass fraction, and the ambient temperature, are investigated. The combined cycle performance is also optimized based on a multi-objective function. The results indicate that the power output and thermal efficiency of the combined cycle are increased with the increases in the turbine inlet temperature and ammonia mass fraction. Comparing with the closed Brayton cycle, the maximum power output and thermal efficiency increase by 2.7% and 2.81%, respectively. It is also found that LEC and payback period increase with the decreases in absorber pressure and turbine inlet temperature. The minimum LEC and payback period of the combined cycle are 0.0706USD/(kWh) and 5.02 years, respectively, and are 0.7% and 0.3% lower than those of the closed Brayton cycle, respectively.In this paper, the comparisons of the thermodynamic performance and economic performance between Kalina cycle and the Goswami cycles are carried out. The results indicate that in the same conditions, the power output of Kalina cycle is higher than that of Goswami cycle, but the thermal efficiency of Kalina cycle is lower than that of Goswami cycle; the system LEC and payback period of Kalina cycle are lower than those of Goswami cycle. When the waste heat source temperature is higher than 380 K, the Kalina cycle is a better choice. If the power plant need cooling capacity, and the waste heat source temperature is lower than 380 K, Goswami cycle is better.