Closed Steady Systems - TEST Tutorial

(The Closed Steady daemon is a stand-alone daemon that does not require any state evaluation. )

States	Closed Process		Open Steady
Open Process	Closed Cycle	Open Cycles	States-II
HVAC	Combustion	Equilibrium	Gas Dynamics

(Each section above is divided into two sub-sections - Manual and Applications.)
	Applications

(Detailed cycle analysis is covered in Closed and Open Cycles pages.)

Daemons>Closed Steady> Manual

A Closed Steady system is a
closed system operating at steady state.

Generally, cycles executed by a heat engine, refrigerator or heat pump can be treated under this category for overall performance analysis.

If the internal details of the cycles are unimportant, a closed steady analysis is usually adequate.

a. Closed and Steady Systems: In the Approach section, we have discussed in details the questions that need to be answered to completely classify a problem. As you read the problem description you define the system at hand (somewhat subjectively) by drawing an imaginary boundary around the object of interest. If there is no mass transfer across the boundary, the system is closed . For a steady system the snapshot of the system taken with the state camera (discussed in the States page) remains frozen even though the system may exchange heat and work with its surroundings. Problems involving such systems are called Closed and Steady .

At first thought, examples of such systems appear to be trivial systems that remain at the same state due to lack of any action. But all closed systems with a frozen state are not necessarily devoid of any action. For instance, there may be a continuous heat and work transfer with the surroundings. In the case of a heat engine, a conceptual closed system operating on a continuous basis produces work at the expense of heat, with the heat transfer taking place between the system and two thermal reservoirs at two different temperatures. Refrigerator or heat pump constitute similar practical examples of Closed Steady systems. As long as the internal details of a heat engine or a refrigeration (or heat pump) cycle are unimportant, the overall analysis can be based on the closed and steady assumptions.

In general, such engines, refrigerators or heat pumps are implemented either by connecting a series of steady-state devices back to back to form a loop, or having a piston-cylinder device execute a series of processes (involving heat and work transfer only) forming a cycle. While it is easy to understand that a closed loop of steady devices will form a closed steady system, one may question how a system executing a sequence of unsteady processes can constitute a steady cycle, especially when the system steps through a series of drastically different states within a single cycle. The answer lies in averaging the cycle over a time of interest that is much larger than the cycle period. If the exposure time of the state camera is large enough, the picture of the system will assume an average constant state validating the steady state assumption.

These daemons appear under the branch Daemons. Systems. Closed. SteadyState on the TEST-Map.

When the internal details of the Cycles are important, more specialized branches such as the Daemons. Systems. Open. SteadyState. Specific. Cycles or the Daemons. Systems. Closed. Process. Specific. Cycles page should be visited.

Choose the type of the cycle, enter the known variables and Calculate the unknowns.

b. The Analysis Panel: The Analysis Panel for a closed and steady system daemon is shown in Fig. 1.

Unlike most other system daemons, the States panel is absent here. On the analysis panel, you select the type of cycles, enter the known variables and Calculate the rest.
second law efficiency eta_ii, are calculated (see Fig. 2).

As with any other daemon, moving the pointer slowly over a variables brings up its definition and its relation to other variables on the Message Panel at the bottom margin of the daemon.

Change a variable and Calculate.

c. Parametric Studies: Once a cycle problem is set up, it is relatively simple to evaluate the effect of changing one or more variables on the problem.

Because of the simple nature of the relationship among the cycle variables, the daemon does not support use of algebraic expressions and does not generate TEST-Codes.

You will find a number of uniform and mixing examples on the Applications page, Slide Show and the Archive.

(Each section above is divided into two sub-sections - Manual and Applications.)
	Applications