Performance Research On Combined Power And Refrigeration Cycle And Key Components

Energy plays an increasingly important role in the progress of human civilization.However,traditional energy sources such as the heavy use of coal,oil,and natural gas has caused serious environmental pollution problems,and also made the problem of uneven energy distribution more significant.Compared with traditional energy sources,emerging energy sources represented by solar energy,wind energy,and industrial waste heat are widely distributed and sustainable,and are gradually receiving attention.Organic Rankine Cycle(ORC)technology is an important technology in the use of low and medium temperature thermal energy.The distributed multi-generation system with ORC technology as the core can not only realize the cascade utilization of energy and improve the energy utilization efficiency of the entire system,but also provide users with multiple energy forms to meet the multiple needs of users.As a result,cogeneration technology has drawn more attention,and ejectors are often used in such systems.The ejector is a simple,inexpensive,and easy-to-maintain pressurized,vacuum,and hybrid component of a thermodynamic system.The reasonable combination of the ejector and the organic Rankine cycle can improve the overall performance of the organic Rankine cycle-jet refrigeration system.Therefore,this article will study the spray power and refrigeration system and key components to optimize the performance of the system and components,thereby enhancing the system’s application potential.The paper focuses on the design of the ejector,the optimization of the power and refrigeration system,and the design of the system and component test bench.The following research work has been carried out:1.The latest advances in a structural improvement of existing ejectors are reviewed from three perspectives: design,simulation,and refrigeration applications.The mathematical model used in the optimization and improvement of the structure of the ejector is summarized.From the two aspects of geometric characteristics and rheological characteristics,the simulation study of the improved structure of the ejector is summarized,and the nozzle outlet position,needle position and mixing The influence of structural parameters such as the length of the chamber on the performance of the ejector;Finally,the representative experimental research of the structure-optimized ejector in the field of refrigeration is also summarized.At the same time,based on the results of the system’s thermodynamic analysis and the ejector structure improvement method,the design work of traditional and structurally optimized ejectors was completed.2.The thermodynamic performance of the non-azeotropic working fluid spray power and refrigeration system was studied by the simulation method.The cyclic thermodynamic properties of organic working fluids at medium and high-temperature heat sources(623.15 K,673.15 K)and evaporation temperatures(400-450 K)were studied.The effects of parameters such as evaporation temperature,heat source temperature,and working fluid composition on system performance when working cooling is used for the system using mixed working fluid are analyzed.3.Based on the analysis of the influence of parameters such as heat source temperature,steam turbine outlet pressure,and working fluid composition on the performance of components and systems,the efficiency of the ejector is defined.From the perspective of the input heat value of the ejector,the power saved by the ejector,the reduced value of the network of the system,and the cooling capacity,the influence of the introduction of the ejector into the system was discussed.4.Starting from the requirements of the key research and development plan,the output of power and refrigeration system should reach 30 k W and the thermal efficiency should reach 30 %,and the system design work should be carried out.Based on the design results,the selection or design of four heat exchangers,throttles,pumps,ejectors,separators and steam turbines was carried out,and an experimental system was successfully established.Based on the above research work,the following main conclusions are drawn:1.Ejector design.(1)The adjustable ejector can adapt to a larger operating range and more complex operating conditions and has gradually become the main direction of ejector research.However,the existing design method still uses the traditional ejector method.The research framework of robotics needs to be expanded,and the core physical models and mathematical tools need to be updated accordingly.The existing experimental research mainly focuses on the effect of NXP on the performance of the ejector,and the experimental research on the effects of the nozzle throat size,the angle of the diffusion chamber and the mixing chamber on the performance is to be performed.(2)Simulation studies of adjustable ejectors include studies of dimensional parameters and internal flow characteristics.Among them,k-ω-sst and Realizable k-εmodels are in good agreement with experimental results.The use of a spindle can effectively eliminate shock waves and improve the performance of the injector.As research progresses,the integration of variant lines and adjustable ejectors will receive more attention.(3)The type of working fluid has an important impact on system performance.Many scholars have analyzed the performance of traditional ejectors using pure working fluids and mixed working fluids.However,research on variant lines and adjustable ejectors rarely involves mixed working fluids.Moreover,the existing research mainly conducted the influence of the mixed working fluid mass fraction on the load change,and the flow characteristics of the mixed working fluid inside the ejector have not yet been discussed.2.Combined power and refrigeration cycle performance at medium and high-temperature heat source and evaporation temperature.(1)There are certain conditions for temperature slip and component migration in the mixed working fluid,which can improve the thermal efficiency of the system.For example,a)when the benzene component is >0.5;Only when the temperature is>423.15 K does the efficiency increase.(2)Increasing the temperature of the heat source can increase the efficiency of radon.Radon losses account for the largest proportion of evaporators,condensers,and turbines.The improvement of system performance is closely related to the performance of these three devices.(3)By adjusting the composition of the mixture,the output of work cooling can be changed to achieve the purpose of automatically adjusting the output of work cooling.3.Research on combined power and refrigeration cycle based on ejector performance.(1)When the heat source temperature is 423.15 K,the evaporation temperature is363.15 K,the turbine outlet pressure is 1.53 MPa,and the mass fraction of R134 a is30 %,the maximum COP and ejection rate are 0.18 and 0.23,respectively.(2)The heat source temperature is 423.15 K,the evaporation temperature is363.15 K,and the mass fraction of R134 a is 50 %.Due to the introduction of the ejector,the network reduction is 21.18 k W,which is far less than the 28.85 k W savings and 110.42 k W cooling capacity.(3)Ejector efficiency is defined to analyze ejector performance.As the turbine outlet pressure increases,the ejection rate,ejector efficiency,cooling capacity,and COP all increase.In a cogeneration system,when the heat source temperature is423.15 K,the mass fraction of R134 a is 20 %,the evaporation temperature is 368.15 K,and the turbine outlet pressure is 1.277 MPa,the ejector efficiency is up to21.89 %.4.Design of combined power and refrigeration cycle and ejector experiment system.Based on the requirements of the project,the experimental system was researched,and the performance of the system and the ejector was tested.The system has good power and cooling output.