Abstract: A stirred tank is one of the most key process equipment for the synthesis of energy compounds. It is highly required for the flow and heat transfer performance of the stirred tank, due to the harsh synthetic reaction with the exothermic heat. Therefore, the spiral tube is frequently used to enhance the heat transfer in the stirred tank. Different types of blades can also play a decisive role in the flow fields inside the stirred tank. This study aims to explore the flow and heat transfer behavior of the internal spiral tube in the stirred tank with the four-pitched blade-Rushton impeller. The standard k-ε turbulence model and wall functions were also adopted for the numerical simulation. Typical axial and radial flow blades were selected to form the four-pitched blade-Rushton impeller. A systematic investigation was also made to clarify the influence of the rotational speeds on the flow and heat transfer performance of the internally immersed spiral tube inside the stirred tank. The fluid flow and heat transfer were determined using similarity criteria and multiple reference frames. The general applicability of the simulation was obtained for the flow distribution, turbulence kinetic energy pattern, and stirrer power in the stirred tank. The similarity criterion was used to reduce the calculation volume for the high efficiency of the model. The maximum deviation of 3.75% was achieved to simulate the internal immersed spiral tube in the stirred tank, compared with the prototype. The high accuracy was verified for the Froude similarity criterion during the simulation. The rotational speed increased the fluid turbulent kinetic energy, indicating little influence on the formation of the axial circulation. The optimal model achieved a 20% enhancement in the Nusselt number, demonstrating the superior performance of the structural modifications. The higher the rotational speed was, the higher the mixing and diffusion efficiency in the tank were. According to the velocity observation line graph, the axial velocity was symmetrically distributed about the central axis x=0. The radial and tangential velocities were centrally symmetric about x=0. Each velocity component also increased with the increase of rotational speed. The peak axial velocity in the tank increased by approximately 68.93% with the rotational speeds ranging from 30 to 90 r/min. As such, the axial circulation efficiency was improved inside the stirred tank. The maximum scope of peak velocity was 24.3%~33.33% at 15 r/min. At the same time, the extra-tube convection heat transfer coefficient increased by 64.66%, the magnitude of which in the tube basically remained unchanged with the change of rotational speed. There was a constant amplitude of the fluid flow inside the spiral tube, indicating a stable structure. The higher the rotational speed was, the greater the resistance of the paddles was. The power also increased by 27.09 times with the rotational speeds ranging from 30 to 90 r/min. The power numbers remained consistent across different rotational speeds. The convective heat transfer was fitted to compare for the mixer optimization. Furthermore, the power number exhibited a low sensitivity to the Reynolds number under identical impeller configurations. The maximum deviation of 0.58% was achieved in the combined impeller, indicating the Reynolds number suitable for the power characteristics.