When a system is at steady state,the snapshot of the system taken with a state-camera does not change with time (read the Tutorial.Navigation page.) The total  mass, energy and entropy of the system remain constant, that is, their time derivates are zero.

Other than simple systems such as a light bulb, a gear box, a wall, etc. (see animations in VT, sections 2.E and 2.F), closed steady analysis can be useful in overall analysis of heat engines, refrigerators, and heat pumps. The icon on the left will launch the closed steady daemon. Of course, for detailed analysis involving components or processes of a cycle, specialized daemons located in Systems..Specifc branch should be used.

If the global image (state) changes with time, the system is called unsteady. Furthermore, if the instantaneous rate of change of any property (rate of change of temperature, for instance) is of interest, the problem is called a transient unsteady problem.

The state daemons can be used to evaluate neighboring states from which time rate of change can be calculated in the I/O panel. Currently, there is no dedicated daemon for transient analysis (hence no icon on the left column) since transient problems are rare in thermodynamics.

Most unsteady problems involve a process - transition of the system from a beginning-state (b-state) to a final-state (f-state). The balance equations (see below) , therefore, can be integrated over the process, resulting in algebraic equations.

Examples of closed processes include heating a cup of coffee, compressing a gas in a piston-cylinder assembly, mixing between two substances in a closed chamber, etc. Animations in VT, section 5.A-C, illustrate several closed processes.