A Model of Thermal Energy Storage According to the Convention of Bond Graphs (Bg) and State Equations (Se)

Abstract

The main advantage of the use of the Bond Graphs method and State Equations for modeling energy systems with a complex structure (marine power plants, hybrid vehicles, etc.)

Causality in Models of Thermal Processes in Ship Engine Rooms with the Use of Bond Graph (BG) Method

“…Doubts arise when creating BG models of thermal processes, especially regarding the new elements introduced into these models as a dual battery [1,27] (2-port) or the modeling of thermal processes using so-called "pseudo Bond Graphs" [1,3,8,10,26,27]. In [2,3] a new method of modeling thermal processes has been presented using only elements introduced in the basic BG theory form modeling of mechanical, hydraulic and electrical processes. In these works the analysis of causality was deliberately not used since according to the theory proposed in separate models of thermal processes, there was no possibility of a conflict of causality [3].…”

“…In [2] it was found that the Energy storing models of thermal processes, as in the basic theory, should be in the form of a graph (bond) with a single node (1-port). The concept of an energy transducer has been introduced [2,3] (fig.…”

“…In general theory of thermodynamics and heat exchange there are physical concepts that could justify the introduction of such a distribution of energy converters. Introduced in [2] energy converters must comply only with the basic theory of the BG relationship (1) of the net amount of energy flow in any multiple node (multiports), in which the n graphs (bonds). When modeling the extracted thermal processes, the available literature does not provide a specified example where a conflict of causality would be shown.…”

“…When modeling the extracted thermal processes, the available literature does not provide a specified example where a conflict of causality would be shown. Numerous examples of creating equations of state based on the BG model in [2,3] showed that the determination of causality can only serve to illustrate the flow of energy. However, the need for analysis of causality exists only when the systems are modeled, in which the nest thermal processes taking place relate to processes of different physical nature such as the mechanical or electrical one.…”

“…As shown in [2] the thermal processes, there is only one type of energy storage accumulator wherein the state variable characterizing is the temperature of the kinetic energy of the molecules. There is no physical evidence to assign two kinds of causality to heat accumulators just as it has been, for example, in the mechanical processes, namely integral and differential causality.…”