We utilised Finite Element Method (FEM) to analyse the thermal behaviour of newly designed optical gas cell. we have investigated the impact of the gas pressure, design of the optical windows, thermal radiation and the flow regime inside the heat exchanger on the temperature gradient in the spectroscopic gas cells. Considering practical spectroscopic measurement conditions, the simulation covered wide ranges of pressure and temperature, from 1 mbar to 1000 mbar, and from 200 K to 400 K, respectively. The results of the FEM analysis highlight the significance of the design of optical windows, including the size and isolation, in maintaining gas thermodynamic stability and homogeneity. Moreover, the simulation demonstrates how temperature profiles vary in different conditions and how viscous dissipation in the heat exchanger fluid affects the gas temperature uniformity. Furthermore, the study emphasises the importance of the place where the temperature sensor is installed, for accurate temperature measurement. The findings of this research aim to provide valuable insights for the future design of optical gas cells.