Eventos Anais de eventos
ENCIT 2022
19th Brazilian Congress of Thermal Sciences and Engineering
A comparative analysis of hypotheses in modeling a hybrid compression refrigeration cycle
Submission Author:
Allan Clemente , ES
Co-Authors:
Allan Clemente, Atilio Lourenço, José Joaquim Conceição Soares Santos, Rodrigo Guedes dos Santos
Presenter: Allan Clemente
doi://10.26678/ABCM.ENCIT2022.CIT22-0371
Abstract
The refrigeration technology market has seen the emergence of a solar hybrid air conditioning system, which uses thermal energy from solar radiation through vacuum glass tube thermal collectors. Such systems are proposed with the intention of saving energy by heating the refrigerant vapor to a constant volume after the fluid passes through the compressor, thus working together and supporting the compressor as long as solar heat is available. The temperature rise in the above-mentioned conditions gives an additional pressure rise, which supports the compressor driven by electromechanical energy conversion and thus reduces its electrical energy consumption. The electrical energy savings achieved by the hybrid system, when compared to the conventional vapor compression system, has been studied by some researchers recently, and these studies point to savings that can vary from 25% to up to 40% of electrical energy. consumed. The objective of this work is the theoretical thermodynamic analysis of this hybrid system, obtaining each thermodynamic state of the refrigerant, the cycle coefficient of performance (COP) and other information of interest. For that, two hypotheses will be approached for comparison. In the first one, an approach will be considered in which, during the passage of the fluid through the solar exchanger, the process occurs at a constant specific volume and this, added to the increase in temperature suffered by the gain of thermal energy, increases the pressure of the fluid during the passage. The second approach models the passage of refrigerant through the solar exchanger as a compressible flow process. From this, the inlet and outlet velocities of the heat exchanger become a crucial point, as they directly influence the thermodynamic states of the fluid, since when reaching the zone of velocities greater than that of sound in a flow with heat addition to the pressure tends to increase. In short, when heat is added in a supersonic compressible flow, the pressure increases, which becomes desirable for the analysis of the system in question, making the study revolve around the adjustment of such velocities and states. In addition, the article also aims to analyze and compare different working fluids in the cycle for each of the two hypotheses adopted for the modeling, thus comparing the response and results of each case.
Keywords
Evacuated Tube, Solar Collector, Electricity saving, Thermal compression, Compressible flow
