Terminology 

Taking into consideration modern tendencies of simulation the real world, from our point of view, can be presented in the form of four main components: channels, ports (streams), objects and structures. Currently, such terminology is not a standard; therefore those who are interested can appeal to the well-known books. Taking into account that this work is not a monograph, but only the author’s conception about simulation we will write only about this conception.

During the development of the program MODEN we used both terminology that is used in energetics and taken from programming, automation and object-oriented design. We understand, that potential user of our program can be frightened off, firstly, by unusual terminology, and, secondly, by given material. Therefore we make to you in advance our apologies. But if you know terminology of the subject you know 50% of the subject. Will you believe it or check it?

The energy system structure that is made according to the organizational principle is presented in the fig. 3.1. We will begin the study with the main notion of a program - object.

Object is an element of the lowest level of a power system which can be both consumer, and energy source. If we claim, that "heating coil" is an object, and then we understand that we are not interested in the device itself i.e. in elements it consists of. If we will decide to examine “heating coil” more deeply we will discuss such objects, as tube and shell side, calling them objects. In this case “heating coil” turns into the structure.

Structure is one of the elements of the power system that consists of objects and exists under its certain laws and also has its own material embodiment. Very often structure includes the other structures. There are energy connections between the objects. Such connections represent concrete type of energy flows. It is clear, that connection (stream) of a certain type cannot be brought into intentionally taken object. Thus, “heating coil” will not take compressed air. The notion of port is used to show what kind of streams can be taken in by the object.

Port is an element in the enclosure of the object through which the stream passes from the environment. Each port can take only one type (sort) of stream. Ports of the object are marked. Thus the object "heating coil" has four ports. Ports 1 and 2 are used for the heating medium - water passing and ports 3 and 4 are used for the heating medium - air passing (it is clear, that marks are fixed by the user).

Each stream is characterized by a number of parameters that are used as channels in the program.

Channel is the smallest element that is used in a model construction. If we take such stream as water it can be characterized by the following parameters: temperature, mass flow rate, pressure, specific heat, etc. If at simulation we use any stream it does not mean yet, that we should work with all its channels. All depends on those tasks that . . .

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