**3. Conclusions**

Analyzing the papers contributed to the Special Issue, 'Numerical Heat Transfer and Fluid Flow', one can say that all papers are applied to specific engineering problems. All papers are encountered in fluid dynamics in machines, electronic packaging, chemical processes, and other related areas of mechanical engineering.

The majority of the papers dealt with simulations. For this reason, the papers presented physical models, which include major assumptions, physical properties of the flowing medium, boundary, and initial conditions, and also mathematical models. Mathematical models were formulated using conservation laws, such as the continuity, N-S, and energy equations. Using the boundary and initial conditions, the authors formulated the set of equations and solved them numerically, taking into account the convergence criteria and ensuring a grid-independent solution. Part of the models have been validated in full, while part have been validated in the limited scale. Some papers presented their own experimental data.

Through these approaches, the readers can find a variety of physical and mathematical models and can gain a better understanding of phenomena in the specific engineering applications of heat transfer and/or fluid flow, including interpretation of computed and measured results.

**Funding:** This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors.
