How to model Natural Convection model in ANSYS

[CondensedMatter]

I have a thermal model of a rubber hose that houses a heat-generating device. There is a stagnent fluid inside the hose and around the heat generating device, and outer hose wall is held at a constant temperature. So far I have assumed only conductive heat transfer but in reality the fluid will begin a natural convection cycle inside the hose.

I have all the material properties I need.

My objective is to obtain the temperature distribution without writing line code.

Help on any level is greatly appreciated!