There are three different repositories of solved examples in TEST. (i) The Daemons section of this Tutorial contains detailed hands-on instructions for selected examples. (ii) The visual examples found in the Slide Show, on the other hand, are screen shots of the daemons as a solution proceeds.  (iii) The Archive contains solved examples, complete with TEST-Codes, organized into fifteen chapters  in the tradition of existing text books. 

However, once you master the systematic approach that follows, you may never need to go back to a solved example. 

Three categories of 
daemons.

Evaluation of selected thermodynamic properties are typically done in the second chapter and later in chapter twelve or thirteen of most contemporary textbooks. TEST treats all materials (including mixtures and moist air) in a consistent manner with the state daemons found on the Daemons.States page. When we evaluate a state, say, at a turbine inlet, we evaluate the state at the inlet port at a given instant. It is assumed that the state  does not vary across the cross-section.  Such states are called a surface state in TEST. Similarly, when we say that a gas in a piston-cylinder device is at a particular state, it is assumed that the system is uniform so that a single state describes the entire system. This is called a volume state .

The rest of all thermodynamic problems involve a system and are handled starting with the Daemons.Systems page. Because of the range of systems encountered in thermodynamics, further classification of the system daemons is necessary.

Open or Closed?

d1. Open vs. Closed Daemons: A system that allows mass transfer across its boundary (tubes and pipes carrying flow in and/or out of the system) is called an open system. A closed system, on the other hand, does not allow any mass transfer.

Open and steady problems 
are abundant. 
 
 

d3. UnSteady Systems: In most thermodynamic problems involving unsteady systems, we are generally interested in what happens over a  finite period of time rather than an instant. During the period of interest, the system - open or closed -  goes from  a begin-state (b-state) to a finish-state (f-state) executing what is called  a process.  The governing equations are integrated between the two limits (b-state to f-state) producing the process equations which are, again, algebraic in nature.

Examples of open processes include charging and discharging. For such problems, all that is left to launch the daemon is to select a model for the working fluid, which is discussed in section-e.

Examples of closed processes are abundant,  and, like open-steady systems, require further classification.

Generic vs.
specific system - a division of convenience.

Specific topics on closed processes include: (i) Air-standard cycles such as the Otto Cycle, Diesel Cycle, Ericson Cycle etc., which execute a sequence of processes (strokes) on a closed mass of gas (Problems.Chapter08 ); (ii) HVAC (Problems. Chapter13); (ii) Combustion (Problems. Chapter14).

Specific topics on Open-Steady Systems include: (i)  Power cycles such as the Rankine Cycle, Brayton Cycle etc., where a series of open-steady devices are connected end-to-end ( Problems.Chapter08 and Problems.Chapter09); (ii) Refrigeration cycles (Problems.Chapter10); (iii) HVAC  (Problems. Chapter13); (iv) Combustion (Problems. Chapter14); (v) Gas dynamics  (Problems. Chapter15).

Closed-System:
Uniform or NonUniform?
 

d5. Closed Generic Processes - Uniform vs. NonUniform: A working substance is called uniform if the state (and, hence, composition) of the working substance do not change with location within the system at a given instant. Note that a uniform system must be made up of a pure substance (same chemical composition at all locations). 

Closed-System:

NonUniformMixed
vs.
NonUniformUnmixed
 
 
 
 
 
 

Open-System:
SingleFlow or
MultiFlow?
 

NonUniform systems have at least two identifiable uniform sub-systems. If the sub-systems are allowed to mix (for instance, a valve connecting two different gases in two tanks is opened), the system is called  non-uniform-mixed. On the other hand, if the subsystems do not mix (a hot block of copper dropped into a bucket of  water), the system is called  Non-uniform-unmixed . Once you classify a problem down to this level, you are ready to select the material model and launch the daemons.
 

d6. Open, Steady, Generic Systems - SingleFlow vs. MultiFlow: If an open system, also called an open device , has a single inlet and a single exit, it is called a single-flow device. Most open-steady problems  fall into this category. 

Open-System:

MultiflowMixed or
MultiFlowUnMixed?
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 

The last step:
Classify the working fluid
 

In Multi-flow systems, there must be multiple openings or ports at the system boundary resulting in more than one flow in and out of the system. If the flows remain separated as in a heat exchanger, such a system is called the multi-flow-unmixed device. On the other hand, if the flows are allowed to mix or separate, as in a mixing chamber or separation chamber, the system is called a multi-flow-mixed device. Once you classify a problem down to this level, you are ready to choose a model for the working fluids.

e. Classification of Working Substance: Having classified the system, all that remains to be done is to classify the working substance, the last step before launching a daemon. TEST divides all working substances into four categories. 

(i) Solids and liquids are in a single group because they are both characterized by constant specific heat and density. 

(ii) Gases are sub-divided into three categories:   Perfect gas is the simplest model with constant specific heats;  Ideal gas , which has a variable specific heat, is more accurate, especially if there is substantial temperature change in a problem;   Real gas is a generalized model based on the compressibility chart used mostly for gases under extreme pressure or very low temperature.  It should be kept in mind that the generality of the real gas model is achieved at the expense of accuracy.

(iii) Gas Mixture are sub-divided into mixtures of perfect, ideal or real gases. Moist Air , a mixture of dry air and water vapor, is also treated as a gas mixture. Dry air, a fixed  mixture of oxygen and nitrogen, is usually treated as a pure gas rather than a  gas mixture. 

Finally the (iv) Phase Change Model, which is based on saturated and super-heated tables is the most accurate of all models. Supercooled liquid is modeled as saturated liquid at the same temperature except for H2O*, which uses compressed liquid table for better accuracy. The "*" suffix is also used when a different reference value for enthalpy is used (Air vs. Air*, R-134 vs. R-134* etc.). The absolute value of enthalpy is different for Air and Air*, but the difference in enthalpy between two given states, which really counts, is identical for the two fluids. The refrigerants with a "%" suffix (R-401% for instance) are mixtures of pure fluids with a variable saturation pressure at a given temperature.