Optimization And Performance Research Of Waste Heat Generation For Organic Rankine Cycle

China possesses abundant industrial waste heat resources.There is huge space to develop the technology of recycling low-temperature waste heat,which has become a key part to promote energy conservation and emission reduction in China.Organic Rankine Cycle technology,featured the advantages of simple structure,high systematic efficiency,environmental friendliness and strong adaptability,can directly utilize low-boiling organic medium to absorb low-grade thermal energy for heat-work conversion.Therefore,applying ORC technology to recover low-temperature waste heat plays a significant role in achieving our country's goal of energy conservation and emission reduction.According to the organic Rankine cycle system driven by waste heat of industrial flue gas,this paper establishes the thermal performance model and economic model based on heat source parameters.Both thermodynamic performance and economy are taken into consideration to analyze performance of systems with different working fluids.The comparison between the system performance of internal heat recovery and non-heat recovery was made.The results show that using different evaluation indexes as optimization targets,the optimum result of operatin g conditions are different.The evaporation temperature optimized by the levelized electricity cost(LEC)is about 8-12? higher than the evaporation temperature optimized by the maximum net power.In the thermal performance,the performance of internal heat recovery system and non-heat recovery system is quite equivalent,but the economy of the internal heat recovery system is significantly worse than non-heat recovery system.In the whole,non-heat recovery system is better than internal heat recovery system.The influence of both superheat and pinch point temperature on the system thermal performance and economy has been studied.The LEC of each working fluid system under each working condition was calculated.Each system is optimized and the change regularities of parameter are analyzed.The results show that the change of pinch point temperature has opposite effects on the thermal performance and economy of the system.There is optimum pinch point temperature which makes the LEC minimum.Under the same exhaust gas temperature,the net power and investment cost of system improve with the increasing evaporation pressure.However,the rangeability is different.When the rangeability of investment cost is the same as net power,the system LEC reaches the minimum.The system performance under dry saturation remains better than overheating saturation.The final systematic optimization parameters with each working fluid have been screened.Through the analysis of change regularity,obtaining the ideal parameter range.Based on the optimization results of each working fluid system,analyze the variation tendency of the system performance under the circumstance that the temperature of the heat source fluctuates,study the sensitivity of each working fluid system to the temperature fluctuation of heat source.The results show that when heat source temperature reduces,the net power of each system decreases but LEC increases.When heat source temperature rises,the net power of each system increases and LEC decreases.Greater temperature fluctuation of heat source is,larger the deviation of LEC value from the design condition LEC is.Among them,the system which uses R123 as the working fluid has obvious advantages in system performance at high heat source temperature,but LEC rises rapidly when heat source temperature becomes low.