If you have access to Conjugate Heat Transfer V2.0, I strongly recommend to use this one to reduce the number of iteration to achieve convergence.
Checking the residuals is not enough to decide whether the simulation has converged or not. Please check this article to see how to check the convergence.
Some ways to accelerate the convergence of the current simulation:
Under the Numerics, increase the relaxation factors. 0.01 is small, which prevents residual oscillations but also increases the number of iterations. You can try with 0.1 or 0.3. If you observe high oscillations, keep the relaxation factors small then.
Under the Numerics, you will see the maximum and minimum range of density. Since you know the fluid type and possible temperature/pressure range, you might limit minimum and maximum density value here. This will help the solver to iterate to the right density value faster. As an example, air density will probably be somewhere between 0.6 and 1.2 kg/m3.
An additional recommendation with respect to the meshing strategy: Instead of using global mesh fineness, you can chose manual refinement strategy, where you can play with surface mesh size and boundary layers. This can help to reduce the mesh size, while doing mesh independence study effectively.