Theoretical Analysis And Experimental Study Of Low Temperature Screw Expander Generation System

China is rich in waste heat. If the waste heat is effectively recovered and used,the energy efficiency of conventional energy utilization can be significantly improved,and the contradiction between development and energy can be eased. There aremainly three ways for waste heat utilization: heat transfer, heat pump and powergeneration system. Currently, due to the advantages of organic Rankine cycle powergeneration technology which can reduce the discharge temperature of waste heat andcan use waste heat energy and other low-grade heat source as much as possible, moreattention are paid on organic Rankine cycle. This study focuses on the organicRankine cycle power generation system used for renewable energy andnon-renewable low-grade waste heat resources below85, theoretical analysis andexperimental research are carried out.In previous theory research process, the studies on organic Rankine cycle powergeneration system were mainly focused on theoretical physical properties andtemperature of working fluid. But in actual production process, due to the forms anddiversity of heat sources, the parameter of working fluid is largely affected by theinternal parameters of the external environment, and it is not the fundamental keyfactors which affect the low temperature waste heat power generation technology.Therefore, in this paper, the variable parameters of flow rate and temperature of heatsources were simulated to analyze the factors which impact low temperature wasteheat power generation technology. The effects of working fluid on low-temperaturepower generation technology were analyzed by selecting the pure and mixtures ofworking fluid.Under support of the national “973” project, a screw expander generation systemwith power generation capacity of10kW was built up based on the original test bed.From the preliminary simulations and experiments, the working fluid mass flow ratewas demonstrated to be a key factor that can improve the generation power. As thescrew expander is volume expander, when the rotational speed is constant, the volumeflow rate of the vapor of working fluid through screw expander is constant. Therefore,to generate more power, the vapor density should be as large as possible, thussaturated vapor is more suitable for screw expander than superheated vapor. The experimental device of “preheater+evaporator” was designed, and the powergeneration efficiency was improved effectively in the system. During theexperimental, process each component was calculated for the generation system. Thecorrectness and feasibility were verified by analysis the10kW experiment system. Onthis basis, a100kW power generation system was established for exhaust steam heatrecovery project in Shanxi and the reliability was proved after a long time operationperiod.To optimize the performance of low-temperature generation system operation,study on transmission ratio of10kW system was carried out, and the result shows thatthere is an optimum transmission ratio corresponding to different heat sourcetemperature making the low-temperature generation maximum power. With thisconclusion, a simulation model and organic Rankine cycle test bed was built. Theload on the screw expander was changed from generator to “torque tester+electricbrake”. The theory of that optimum speed screw expander corresponding to thedifferent heat temperature was confirmed through experimental analysis of the torquetest bed. The accuracy of simulation model was also validated by experimental studies,which laid a solid experimental and theoretical basis for the further development andoptimization of organic Rankine cycle generation system.