Hollow fiber membrane permeators have gained widespread acceptance for a variety of applications, including gas separation. This study presents our efforts to develop an appropriate methodology and mathematical modelling for the analysis of the transport properties and separation performance in hollow fiber membrane permeators with asymmetric structure. A relatively simplified model, developed based on ideal conditions, provides the opportunity for having a quick and overall prediction of the separation performance; while a comprehensive model developed by incorporation of non-ideal conditions enables a more accurate prediction of the membrane performance. The real gas behaviour, temperature, pressure, and concentration dependence of gas viscosity, as well as pressure changes on both sides of hollow fibers, concentration polarization, temperature change due to permeation, and temperature dependence of permeance are considered non-ideal parameters in development of the model. The integrated models with associated parameters in the form of differential equations are coded in MATLAB and solved as initial value problem using appropriate numerical methods. The validity of the developed models is examined, indicating close agreement between predictions and the experimental data provided in literature. The proposed methodology and developed models provide valuable opportunities for researchers in designing appropriate hollow fiber membrane permeators and processes for practical gas separation applications.