The primary goal of this work was to investigate the influence of the sampling rate for the surrogate generation. Sampling was desired to be of a homogenous type, which may be disturbed by exploitation-based methods. As a result, we only considered exploration-based methods in our current methodology workflow. In the future, to further enhance sampling efficiency, the exploration in sampling the global design space should be well balanced with the exploitation in sampling the nonlinear/complex local areas. Another work that can be done is to determine better termination criteria: we tried to stop the algorithm when the MSE difference between two consecutive iterations approached 0, or the slope approached 0, but the fluctuation of MSE values always existed for the case study of GTL or PSA, which made the tolerance value for termination hard to set. One solution could be to apply feature selection techniques (i.e., automatically adjust input variables) to improve fitting performance and reduce its fluctuation during sequential sampling. (3) Ideal gas law is applied for the state of the gas phase.