| The ORC provide a way to solve the world energy and environment problem.Also,as the main component of ORC,scroll expander has great significance to the whole system.The development of ORC has been precluded before due to few expander efficiency models and data.This paper mainly focused on efficiency parameters of scroll expander at output with studying and construction of the ORC prototype.This paper has fully carried out these tasks:(1)theoretical analysis:determined a relation of efficiency between scroll compressor and scroll expander based on the performance of thermodynamics;(2)model validation:examined this theoretical relationship and compared with experimental results.By using these relations determined isentropic efficiency and volumetric efficiency under various conditions;(3)empirical model:this paper also presented an optimization model of efficiency as a function of expansion ratio after performing test;(4)ORC simulation analysis:using EES as the simulation platform,respectively for R123,R124,R152a with the condensation temperature of 30 ? to 50 ? and the pressure ratio ranged from 2 to 7.5.(5)Test prototype construction:using R123 as the working fluid,designed ORC heat engine,and participated in the selection and construction of the prototype.The results are as follows:(1)The isentropic efficiency and volumetric efficiency of the scroll expander have a good correlation with the efficiency parameters of the front scroll compressor.When the expansion ratio ranged from 2 to 7.5,the efficiency value of the scroll compressor in the corresponding pressure parameter could be used as the efficiency parameter of the scroll expander.The error is less than 5%.(2)Studed the efficiency and found:(a)the isentropic efficiency reached a maximum of 70.82%at a condensation temperature of 50 ? and an expansion ratio of 2.5;(b)at a condensing temperature of 45 ?,expansion ratio of 2,the volumn efficiency was max at 95/8%.(c)when the expansion ratio rangedfrom 2 to 4,the scroll expander performanced best,at this time the highest entropy efficiency ranged from 60%to 70%,the volume efficiency was over 80%.(d)when increased the expansion ratio,the entropy efficiency of the scroll expander increases first and then decreases,and the volumetric efficiency decreases continuously.With the increase of the condensing temperature,the entropy efficiency and the volumetric efficiency all show the first increase and then decreased.(3)The entropy efficiency and volumetric efficiency of the scroll expander coud be expressed as the regression curves with the expansion ratio as the parameters.The error between the calculated and experimental values is less than 5%.(4)Using the empirical model to simulate the ORC system,the following conclusions were obtained:(a)the netpower generation,cycle thermal efficiency and isentropic efficiency increased fist and then decresed as the condensation tempratuere increased;(b)the optimum expansion ratio is higher than the peak of the isentropic efficiency,and the optimal expansion ratio of the different working fluid was different.Increasing the expansion ratio leads to a greater increase in the proportion of total loss in the system,(c)The cycle thermal efficiency and efficiency of R123 and R124 system decreased with the increase of superheat degree.The cycle efficiency of R152 system increased first and then decreased with the increase of superheat degree.When the superheat degree is 5 K,the thermal efficiency and efficiency reached the maximum,respectively 7.43%and 43.42%.(5)According to the simulation results,designed and constructed of the ORC prototype.This study is very meaningful to the design and application for ORC. |
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