Визначення енергоефективності термодинамічних циклів когенераційних машин комерційного призначення

Abstract

In many commercial enterprises, the implementation of cooling processes accounts for a significant part of its total energy consumption. To monitor the actual electricity consumption during the continuous ope­ration of refrigeration systems, methods of calculating energy efficiency have been formed and methodically substantiated. The main requirement for the method of energy analysis of such systems is its basis on the principles and laws of thermodynamics. The system boundary for comparing the efficiency of ref­rigeration and heat pump installations is the heat or refrigeration capacity and the operating temperature. The studying machine is intended for a trade enterprise with a wide range of products with two constant temperature levels of short-term storage. The corresponding refrigeration capacities differ in quantitative indicators, but are constant in time. Determination of efficiency indicators is carried out in the system boundaries of the thermodynamic cycle and design features of the machine elements. Type of analysis – comparison of energy efficiency and cycle dimensions of two or more machines with different working substances. Using reference cycles, numerical modeling of processes in a cogeneration machine with working substances R404A and CO₂ in a single operating mode was performed. Calculations were performed for six scheme-cyclic answers. The results of solving the "energy" problem are the actual conversion factor of the COP. The analysis showed low energy efficiency of one-stage cycles in the mode of the cogeneration machine with two boiling points, one of which is low-temperature. The highest efficiency is in machines that operate on a two-stage compression cycle with two evaporators and an expander in front of a high-temperature evaporator. The results of solving the "transport" problem are to determine the theoretical volumetric refrigeration capacity of compressors (cycle size). Comparative analysis of the results states that the size of the cycle with CO₂ is three times smaller than R404A. Recommendation for the future – a two-stage machine with two evaporators and an intermediate vessel with CO₂. After solving all the problems, the specified cycle has the best characteristics