This can be done by finding the component in the Class Browser and looking at it in the Text View:
Navigate to Modelica -> Thermal -> HeatTransfer -> Components and double-click on Convection.
Then go to
Modelica Text View by pressing Cmd+3 (OS X) / Ctrl+3 (Windows) or by clicking the Modelica Text View icon.
The equations are listed under
equation: dT=solid.T - fluid.T;
solid.Q_flow=Q_flow;
fluid.Q_flow=-Q_flow;
Q_flow=Gc*dT;
