A new heat transfer correlation for high temperature helium on the shell side of a helically coiled tube heat exchanger was derived with the use of computational fluid dynamics (CFD) tools. The use of suitable heat transfer correlations has an impact on the evaluation of performance of a heat exchanger in relation to the requirements for a sufficient heat transfer surface, which relates to material cost requirements; therefore, it is of high importance. A numerical model was validated with data measured using the helium cooler, which is part of an experimental channel located at the Research Center Řež (CVR) in the Czech Republic. The numerical model used for obtaining the heat transfer correlation assumes a constant heat flux on the wall of the helical coil. In total, 72 cases with varying inlet temperatures, velocities, and heat fluxes were simulated to obtain the heat transfer correlation. Furthermore, the effects of the flow rectifier within the channel regarding the heat transfer coefficient and pressure loss were discussed.