Which solver type to use for coupled K-Epsilon and pipe flow model?

I have a heat exchanger model that I am solving with the CFD and pipe flow modules. I am unsure of which type of solver I should use. I have looked at the COMSOL example model 'heat exchanger plate' and it used a direct, fully coupled solver. However, that model was for a coupled laminar flow and pipe flow model. Should I use the same solver for my model? Or should I explore using other solvers?

Thanks,

Burns