Endoreversible Trigeneration Cycle Design Based on Finite Physical Dimensions Thermodynamics

Dumitrascu Gheorghe,Feidt Michel,Popescu Aristotel,Grigorean Stefan

doi:10.3390/en12163165

Abstract

This paper focuses on the finite physical dimensions thermodynamics (FPDT)-based design of combined endoreversible power and refrigeration cycles (CCHP). Four operating schemes were analyzed, one for the summer season and three for the winter season. These basic CCHP cycles should define the reference ones, having the maximum possible energy and exergy efficiencies considering real restrictive conditions. The FPDT design is an entropic approach because it defines and uses the dependences between the reference entropy and the control operational parameters characterizing the external energy interactions of CCHP subsystems. The FPDT introduces a generalization of CCHP systems design, due to the particular influences of entropy variations of the working fluids substituted with influences of four operational finite dimensions control parameters, i.e., two mean log temperature differences between the working fluids and external heat sources and two dimensionless thermal conductance inventories. Two useful energy interactions, power and cooling rate, were used as operational restrictive conditions. It was assumed that there are consumers required for the supplied heating rates depending on the energy operating scheme. The FPDT modeling evaluates main thermodynamic and heat transfer performances. The FPDT model presented in this paper is a general one, applicable to all endoreversible trigeneration cycles.

Highlights

The thermodynamic design and optimization of simple or complex thermal systems might be performed through the below methods. Equilibrium thermodynamics (ET) involves the reversible Carnot cycle and Carnot energy efficiency.Besides, they developed the methods of optimization of real cycles by using mean thermodynamic temperature, exergy, and irreversible entropy generation concepts
The use of the Carnot cycle does not take into account the time, respectively it has maximum–maximorum energy efficiency but zero power because it asks infinitesimal temperature differences, i.e., infinite time to fulfill the heat transfers between the working fluid and external heat reservoirs
The possible value ranges of ∆TH and of ∆TR were determined based on two extra restrictive conditions, energy efficiency of engine and COP of refrigeration machine, respectively, close to the maximum possible values obtained by the finite physical dimensions thermodynamics (FPDT) numerical results of the endoreversible trigeneration subsystem

Summary

Introduction

Equilibrium thermodynamics (ET) involves the reversible Carnot cycle and Carnot energy efficiency They developed the methods of optimization of real cycles by using mean thermodynamic temperature, exergy, and irreversible entropy generation concepts. These additional concepts can evaluate the irreversibility of real cycles by comparison with the Carnot one. The use of the Carnot cycle does not take into account the time, respectively it has maximum–maximorum energy efficiency but zero power because it asks infinitesimal temperature differences, i.e., infinite time to fulfill the heat transfers between the working fluid and external heat reservoirs. FTT considers the externally irreversible Carnot cycle that requires finite time to complete the heat transfers between the working fluid and external heat reservoirs. The main drawback of approaches based on FTT is the fact that it cannot be Energies 2019, 12, 3165; doi:10.3390/en12163165 www.mdpi.com/journal/energies applied entirely for non-Carnot irreversible cycles, see for instance [1], where they concluded:

Methods

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Discussion

Conclusion