Functional Design of the mCCHP-RES System

Nicolae Badea, Alexandra Epureanu, Emil Ceanga, Marian Barbu and Sergiu Caraman

Abstract In order to be shown in detail, the design process algorithm (see Fig. 2 in Chapter “Structural Design of the mCCHP-RES System”) was divided into two stages, namely structural design and functional design. In Chapter “Structural Design of the mCCHP-RES System” was presented the first stage while in this chapter is presented the second. Then, in Chapter “Experimental Case Study” it is shown a concrete example. Here, the functional design was divided into five steps and to each step has been devoted a paragraph. Regarding the contents of steps, this is as following: In the first step (described in Sect. 2.1) the acceptable structural models resulted from the structural design stage, are completed with all the com­plementary components (such as recirculation pumps, expansion tanks, heat exchangers etc.), this way becoming the functional models of the system. After that all the components, main or complementary, are dimensioned taking into account both the energetic consumptions of the residence and the internal energetic con­sumptions of the system. The next two steps (described in Sects. 3 and 4) consist in establishing the operation and control strategy of the system, based on which then the system dynamics is analyzed numerically. Simulation and analysis of the system operation highlights the system performance in critical moments (such as the coldest/hottest day of the year, for example), in case of each functional model. The step described in Sect. 5 consists in designing the monitoring and control sub­system, which includes choosing the field equipments, design of the connection

N. Badea (H) • A. Epureanu • E. Ceanga • M. Barbu • S. Caraman “Dunarea de Jos” University of Galati, Galati, Romania e-mail: nicolae. badea@ugal. ro

A. Epureanu

e-mail: alexandru. epureanu@ugal. ro E. Ceanga

e-mail: emil. ceanga@ugal. ro M. Barbu

e-mail: marian. barbu@ugal. ro S. Caraman

e-mail: sergiu. caraman@ugal. ro © Springer-Verlag London 2015

N. Badea (ed.), Design for Micro-Combined Cooling, Heating and Power Systems, Green Energy and Technology, DOI 10.1007/978-1-4471-6254-4_6

devices of these equipments to the data acquisition system, design of the monitoring software of the whole system, as well as designing the numerical controllers of the thermal and electric control loops. The last step (described in Sect. 8) consists in designing the system interfaces. Finally, the system designer has at his disposal several functional models, each with advantages and disadvantages, and, on this basis, can make the best decision.

1 Introduction

Nicolae Badea and Alexandru Epureanu

Conceptually, the functional design is the second stage of the design process (see Fig. 2 in Chap. “Structural Design of the mCCHP-RES System”) and consists in: (a) conversion of the system structural model (that is the result of first stage) in func­tional model of the system, (b) adding of an incorporated control subsystem, and (c) drafting the manufacturing documentation of system (that is the result of the second stage). During the functional design, the completion, customization, and analysis of the system model takes place so that the description of the system gets to be suffi­ciently detailed that it becomes possible to elaborate the manufacturing documen­tation. In other words, the starting point of the functional design is the structural models resulting in the structural design stage, and the output is a complete description of mCCHP system, based on which the customer can realize it.

Unlike the closed-ended approach, where the functional design has as input only one structural model, in case of open-ended approach (the case presented here), at input there are several structural models all of which being considered acceptable. Therefore, in this case, all structural models will be transformed into functional models, following that the customer will select one of them. For the selected model, the manufacturing documentation of the mCCHP system will be prepared. Practically, the functional design means undertaking the following actions:

• Supplementing the structural model with complementary components required for a system to work, thus this becoming the functional scheme of mCCHP system.

• Sizing of both the basic components and the complementary, thereby under­standing the setting of the technical characteristics of components (such as the installed power of a supplier or consumer, the electric capacity of battery, the diameter of pipes through which circulate the thermal fluid, or the diameter of electrical wires, for example), on the one hand, and determining ofthe operating parameters of components (such as the operating time of a supplier, the pres­sure, flow, and temperature of the fluid flowing through a pipe, the amount of energy supplied daily by the PV/ST panel, for example), on the other hand. This way the functional scheme becomes the functional model of mCCHP system.

• Analysis of the system dynamics (by numerical simulation of the functional model operation, for example).

• Design of the control subsystem, including all components of this subsystem, both hard (the set of sensors for monitoring, for example) and soft ones (the numerical controller, for example), followed by incorporation of the entire control subsystem in the functional model of mCCHP system.

Algorithmically, the functional design consists of the following steps:

1. Functional modeling of the system,

2. Elaboration of the operation and control strategies,

3. Analysis of the system dynamics,

4. Design of the control subsystem, and

5. Design of the system interfaces.

In the following, the functional design algorithm is presented in detail. Each paragraph is dedicated to one of the steps above.

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