Structural Analysis And Working Fluid Selection On The Combined Heat And Cold Energy Power Generation System

Energy is the foundation of the national economy,the exploitation and utilization of energy in domestic is relatively backward.Therefore,we are facing a severe energy shortage and environmental pollution problems.It is an effective method to build the organic Rankine cycle power generation system to solve the energy shortage problems which combined the low-grade thermal energy and liquefied natural gas cold.However,there is little research on the basic theory and low boiling point working fluid selection mechanism.Therefore,the main research of this paper focus on the structural analysis and working fluid selection on the combined heat and cold energy power generation system.The main research contents are as follows:Subentry established the common low boiling point organic refrigerant selection mechanism,which taking the comprehensive consideration on the power generation system of heat source temperature,cold source temperature,environmental friendliness and thermal conductivity of working fluid,et al.Based on the principle of working fluid selection mechanism,ten kinds of organic matter are selected as the power generation system candidate working fluid,such as Butane,Isobutene,Propane,R134a,R152a,R227ea,R245fa,R1234ze,R32 and R125,which from the eighty two commonly used organic refrigerant.The influence of evaporation temperature,turbine inlet temperature and condensation temperature on the thermodynamic performance of subcritical basic organic Rankine cycle was analyzed.The results show that increasing the evaporation temperature and turbine inlet temperature,reducing the condensing temperature can raise the system power output and exergy efficiency effectively.Under the constant heat source temperature,the increase of turbine inlet temperature has litter helpful to system thermal efficiency.More than 50%of system exergy losses occur in condenser,improving the evaporative temperature,decreasing the turbine inlet temperature and condensing temperature can reduce this part irreversible loss.The key parameters influence of complex organic Rankine cycle and two-stage parallel organic Rankine cycle are simulated and compared with basic organic Rankine cycle.The results show that adding the regenerator has no effect on system power output and thermal efficiency,but it can reduce the condenser irreversible loss effectively.We set a reheater can improving the system net power output and turbine outlet dryness effectively.Simultaneously,there is an optimal reheat value to get the best system exergy efficiency.The liquefied natural gas cold energy can be cascade utilization in the two-stage parallel organic Rankine cycle.In this way,the irreversible loss can be reduced in the condenser.The combination of propane and butane is the optimal working fluid for two-stage parallel organic Rankine cycle which exergy efficiency reaches 33.18%.The particle swarm optimization was used to optimize the performance parameters in the simple organic Rankine cycle,complex organic Rankine cycle and two-stage parallel organic Rankine cycle.The results show that the complex organic Rankine cycle can reduce the evaporation temperature of optimal efficiency correspongd to the basic organic Rankine cycle.Therefore,the minimum condensing pressure has a significant effect on the best working fluid selection,the optimum working fluid may be distinguish under the different condensing pressure.Adopting the exergy efficiency as the evaluation index,propane is determined as the best working fluid on conbined low temperature heat and liquied natural gas power generation system which efficiency reaches 39.44%.