You can reduce the time taken for unsteady CHT simulations as follows: 1.If the flow and heat transfer are coupled (that is, your model includes temperature-dependent properties or buoyancy forces), you can first solve the flow equations before enabling energy. Once you have a converged flow-field solution, you can enable energy and solve the flow and energy equations simultaneously to complete the heat transfer simulation. 2.For transient CHT problems, particularly those with combustion, the dominant time-scales in the fluid and solid zones are often quite different. In most cases, it is desirable to have a larger time step in solid zones, while maintaining a smaller time step in fluid zones. This will increase the speed at which the solid heat transfer reaches steady-state without compromising the solution accuracy of the fluid flow. To accommodate this, you can specify a solid time step on the Run Calculation task page: Solution >Run Calculation Please see the attached resolution document for more details, including information on how the default time step is calculated. <\/p>\n