Analysis Of The Influence Of T-junction Separator On The Performance Of Component Adjustable Thermal Cycle

The composition adjustment organic Rankine cycle（composition adjustment organic Rankine cycle,CA-ORC）based on the method of three-dimensional cycle construction with zeotropic mixture as working fluid has higher energy utilization efficiency for low and medium grade energy than the traditional organic Rankine cycle system.The separator,as a key component,plays a role of component regulation in the composition adjustment thermal cycle.The T-junction,which has simple structure and low cost has been proposed to be applied in the CA-ORC system.Considering the influence of T-unction on the separation of two-phase fluid and the change of internal pressure,a mathematical model of the CA-ORC with T-junction as separator is established.The results show that the first law of thermodynamics efficiency and second law of thermodynamics efficiency of the system is the highest when R123/Toluene（0.9/0.1）is used as the working fluid and the inlet quality of the separator,which are 10.95%and 38.16%respectively.The effects of mass flow rate of working fluid(0.5 kg·s^-1～1.3 kg·s^-1),evaporation temperature（310 K～335 K）and condensation temperature（295 K～325 K）on thermodynamic performance parameters of CA-ORC system with and without local pressure drop are investigated and compared.The results show that compared with the CA-ORC system without local pressure drop,the system net output work and the first thermodynamic efficiency of the CA-ORC system with local pressure drop are decreasing,but it has less irreversible exergic loss.When mass flow rate of working fluid is 1.0 kg·s^-1,evaporation temperature is 335 K and condensation temperature is295 K,the CA-ORC system with local pressure drop has the best thermodynamic performance,the first law of thermodynamics efficiency and second law of thermodynamics efficiency of the system are 10.61%and 36.91%,respectively.As the CA-ORC system with local pressure drop considered has smaller irreversible exergic loss,the proportion of net output work and irreversible exergic loss generated in each process in the system are compared with the CA-ORC system without local pressure drop.The results show that when the heat exchanger and the heat/cold source have a good match,the net output power of the CA-ORC system considering the local pressure drop is higher than that of the system without considering the pressure drop.When evaporation temperature is 335 K,condensation temperature is 293.15 K,the net output power ratio of CA-ORC system considering local pressure drop is50.27%.In order to improve the net output power of CA-ORC system considering local pressure drop and optimize the system structure,the phase separation efficiency of two-phase organic working fluid in double T-unctions is studied.The results show that the reduction of inlet mass flow rate,inlet quality and branch diameter ratio can improve the separation efficiency of double T-unctions.The maximum phase separation efficiency of gas is obtained when the distance is 2.0 m.Although the double T-unctions has higher phase separation efficiency than the single T-junction,it still cannot effectively optimize the structure of the CA-ORC system and reduce the system components.