3.4 Shape factor analysis
The comparison of AAE between AAG and AAGS shown in Table 1 can well reflect that the results of the model have been improved after we introduce the shape factor. The overall AAE of T c, P c andV c were 15.2451 K, 0.0824 MPa and 0.0104 L/kmol before the shape factor was added. The results were reduced by 41.84 %, 9.59 % and 6.73 % respectively after the introduction. The results show that the shape factor can effectively distinguish the error of compound shape calculation. The R 2 of the AAGS model with critical temperature is 0.0477 higher than that of the AAG model. Since R 2 of AAG model with critical volume is very high, the improvement effect of introducing shape factor is not obvious. Moreover, the AAE of the test set was reduced by 16.51-40.34 %, which proves that the introduction of the shape factor is effective compared with the AAG method.