Wagner型通用蒸汽压方程优化算法研究

Modifications on Wagner’s Method of Fitting Equations to Vapor Pressure

针对Wagner型通用蒸汽压方程中优化算法(optimization algorithm by Setzmann and Wagner,OPTIM)存在容易早熟收敛和收敛速度慢的问题,提出一种改进优化算法,通过改变变异规则,增强原有算法跳出局部最优解的能力;采用新的控制参数,最大程度的保留遗传算法的优化结果,提高算法搜索效率。采用改进算法对R134a和新一代环保替代制冷剂R1234yf、R1336mzz(Z)的蒸汽压方程进行了优化计算,并与文献算法进行比较,结果表明:新算法在全局搜索能力、算法稳定性和计算效率方面均具有明显优势;优化得到了R1234yf和R1336mzz(Z)的Wagner型通用蒸汽压方程,通过分析发现项库中各项的重要性具有耦合关系,其中起主导作用的是第2项和第3项;5项通用方程和Wagner方程拟合2种替代工质的压力平均绝对相对偏差分别为0.1027%、0.1144%和0.0881%、0.1395%,前者较后者拟合精度分别提高了10.2%和36.8%。

Based on a comprehensive functional expression called "bank of terms",new vapor pressure equation was established with a method which was named the optimization algorithm by Setzmann and Wagner(optimization algorithm by Setzmann and Wagner,OPTIM).The OPTIM method yielded a complete optimization which included the length of the resulting correlation and the number of terms of certain forms.However,the starting combinations for the regression analysis could not be selected since no important term which appears the appropriate times exists at some conditions.Therefore,more computer time was required since the random selection should be repeated.Another disadvantage was that the final equation was not the real optimization one sometimes even the convergence criterion was satisfied.Modifications were presented in this work to improve the quality of the OPTIM method.New values were chosen for the control parameters for different optimization problems and the mutation process was modified as well.It was demonstrated in this work how the new procedure finds optimized structures of the vapor pressure equations for R134 a,R1234 yf and R1336 mzz(Z)-two new generation refrigerants with zero ozone deletion potential and very low global warming potential.The optimized structures of the vapor pressure equations were established for different number of equation terms with high efficiency and stability.The vapor pressure equations with various number of terms were analyzed based on the literature data and the most important terms were found to be the second and third terms of the bank.The average absolute relative pressure deviations of the experimental data from new equations with five terms and Wagner-type equation for R1234 yf and R1336 mzz(Z) are 0.1027%,0.1144% and 0.0881%,0.1395%,respectively.