Analysis The Effect of Inlet Duct and Transition Zone Angle Variations on Flow Characteristics and Heat Transfer on Vertical Type Heat Recovery Steam Generator

The components that determine the shape of the flow in Heat Recovery Steam Generator (HRSG) are the inlet duct and the transition zone. After passing through the inlet duct, flue gas is expected to have uniform axial velocity and temperature distribution, with the aim of optimizing pressure drop and reducing residual gas turbulence due to its high velocity. Turbulence can cause uneven flow temperature because there is heat concentrated at a certain point so that it can reduce heat transfer that occurs between flue gas and steam. Thus, an effort is needed so that the flow coming out of the inlet duct has a uniform flow profile and temperature distribution. In this study, researchers will conduct a numerical study in the form of a 2-dimensional simulation using Computational fluid dynamics (CFD) regarding the effect of angle variations on the vertical type HRSG inlet and transition zone on the flow and heat transfer characteristics. Variations of inlet duct angle ($\beta$) and transition zone angle $(\mathrm{c}x)$ in this study there are 5 variations, variation 1 $(\alpha=35^{\circ},\ \beta=15^{\circ})$, variation 2 $(\alpha=35^{\circ},\ \beta=25^{\circ})$, variation 3 $(\alpha=35,\ \beta=30^{\circ})$, variation 4 $(\alpha=30^{\circ},\ \beta=25^{\circ})$, variation 5 $(\alpha=45^{\circ},\beta=25^{\circ})$. From the simulation results it can be known that inlet duct angle and transition zone affect the flow and heat transfer of gas flue in vertical type HRSG, the greater the angle of $\mathrm{c}x$ cause the flow separation, the greater the angle of $\beta$ cause the velocity of gas flue flow to be faster. In this simulation, variation 2 $(\alpha=35^{\circ},\ \beta=25^{\circ})$ had the best flow velocity and distribution with an average gas flue velocity of 4.27 m/s, while the highest total heat transfer also occurred at a variation of 2 ($\alpha$=3$5^{\circ},\ \beta$=25°) with a total heat transfer of190.2057 MW.