Optimisation of indirect heaters in gas pressure-reducing stations is one of the main goals in countries with high natural gas reserves. This paper mainly aims to optimise the 3D-heat exchanger, considering the tubes with rotating, Elliptical, Half -circular, Square, Rectangular, and Triangular cross sections in three different torsional angles. The simulation is conducted by commercial software with high accuracy with an experimental validation model. The simulation result indicates that the creation of turbulence in the pipe path at torsional cross-sections will increase fluid temperature. After comparing the six designs and selecting the elliptical tube as the best model, the simulation continues for different torsion angles (3600, 7200 and 10800 angles) to further optimise the heat exchanger. Outputs illustrate that 3600 twisted elliptical tube has the highest temperature variations with the lowest pressure drop changes by increasing the path length compared to other torsions.