I have a shell and tube heat exchanger at lab. I want to find its (tube length) with shell-and-tube calculations, and I don't know the overall heat transfer coefficient. How can I
![Entropy | Free Full-Text | Numerical Analysis on Natural Convection Heat Transfer in a Single Circular Fin-Tube Heat Exchanger (Part 2): Correlations for Limiting Cases Entropy | Free Full-Text | Numerical Analysis on Natural Convection Heat Transfer in a Single Circular Fin-Tube Heat Exchanger (Part 2): Correlations for Limiting Cases](https://pub.mdpi-res.com/entropy/entropy-22-00358/article_deploy/html/images/entropy-22-00358-g001.png?1585815048)
Entropy | Free Full-Text | Numerical Analysis on Natural Convection Heat Transfer in a Single Circular Fin-Tube Heat Exchanger (Part 2): Correlations for Limiting Cases
![thermodynamics - Why do people use the outer area of the inner pipe for overall heat transfer coefficients in heat exchangers? - Physics Stack Exchange thermodynamics - Why do people use the outer area of the inner pipe for overall heat transfer coefficients in heat exchangers? - Physics Stack Exchange](https://i.stack.imgur.com/VgBjt.png)