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ENCIT 2020
18th Brazilian Congress of Thermal Sciences and Engineering
EXPERIMENTAL STUDY AND MASS CHARGE SIMULATION MODEL IN A DIRECT EXPANSION SOLAR ASSISTED HEAT PUMP CHARGED WITH CO2
Submission Author:
Gleberson Marques Humia , MG
Co-Authors:
Gleberson Marques Humia, Willian Moreira Duarte, Juan Jose Garcia Pabon, Sabrina Nogueira Rabelo, Tiago de Freitas Paulino, Luiz Machado
Presenter: Gleberson Marques Humia
doi://10.26678/ABCM.ENCIT2020.CIT20-0207
Abstract
The present work is a theoretical/experimental study about the fluid mass charge in a direct expansion solar assisted heat pump (DX-SAHP), for the supply of domestic hot water. The heat pump operates in the transcritical cycle, with carbon dioxide as the refrigerant. CO2 is a natural fluid that has an ozone depletion potential (ODP) equal to zero and a global warming potential (GWP) equal to one. For the heat pump to operate with high-energy efficiency, it is essential to know the CO2 mass charge to be used under various conditions of insolation. The effects of solar radiation changes were analyzed in 48 experimental points, evaluated under three different conditions of mass. The results were compared with a simulation model that used eight void fraction correlations for the two-phase flow of the solar evaporator. To estimate the amount of mass in each part of the heat pump, the phenomena of heat transfer and head loss were considered in the model, both in the evaporator and in the gas cooler, as well as the conditions of the fluid in the supercritical region. The best results for mass prediction were obtained by the correlations of Hughmark and Filimonov, with an average error in absolute terms of 5.53% and 6.03% respectively. Considering a tolerance margin of ± 2%, the Hughmark correlation generated a total accuracy of 27.1% of the predictions against 14.6% achieved by the correlations of Zivi, Premoli and Filimonov. All the correlations tested were 100% correct for a tolerance of ± 18%.
Keywords
heat pump, CO2, void fraction, Fluid mass charge, Simulation Model
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