The coating application of metals (especially in automotive and white goods sectors) is used in various fields to protect the metal against oxidation, corrosion, scratch, or high temperature to increase product lifetime. The most efficient technique in the coating application is powder coating where the powder is Epoxy-polyester. This process has three steps; surface pretreatment (washing), powder coating, and curing the coated metal. Metals may need to be dried and cured in ovens with 90°C and 200°C, respectively, for the required quality coating process. Burners are used as the heat source in the oven's heat exchangers. Due to high temperatures, the expanding heat exchanger is exposed to various thermal stresses. The stresses cause cracking and rupture problems. The regions where thermal stresses occur intensely are the surfaces with high-temperature differences. Various mass flow rates in the heat exchanger cause non-uniformity for how the energy to be transferred, thus non-uniform surface temperature distribution. In this study, a heat exchanger design provided by "ELECTRON – Sistem Teknik Makina" company has been studied. The mass flow rates in the heat transfer pipes (where the heat is mainly transferred) show deviations up to 75% from the ideal rate. With this study, deviations have been reduced to the level of ±10%. The results show that the maximum thermal stress on the heat exchanger was reduced by 24% with this improvement. In general, the uniform mass flow rates obtained in the heat transfer pipes provided a more homogeneous distribution of the surface temperatures, thus decreased thermal stresses.