Eventos Anais de eventos
ENCIT 2022
19th Brazilian Congress of Thermal Sciences and Engineering
MODELING A DIRECT-EXPANSION SOLAR ASSISTED HEAT PUMP CONDENSER WITH EMPHASIS ON CONVECTIVE HEAT TRANSFER COEFFICIENTS
Submission Author:
Sara Isabel de Melo Resende , MG
Co-Authors:
Sara Isabel de Melo Resende, Hélio Augusto Goulart Diniz, Ivana de Fátima Braga, Ralney Faria, Raphael Nunes Nunes de Oliveira
Presenter: Sara Isabel de Melo Resende
doi://10.26678/ABCM.ENCIT2022.CIT22-0721
Abstract
Used in several areas of engineering either for heating or cooling, heat exchangers are equipment responsible for the process of the heat exchange between fluids. In this process, knowledge of the convective heat transfer coefficients is very important. The objective of this work is to dimension the coaxial condenser of a Direct-Expansion Solar Assisted Heat Pump (DX-SAHP) used for domestic water heating, emphasizing the methodology used to determine the convective heat transfer coefficient in the single-phase regions – desuperheating and subcooling – and in the two-phase region – condensation – of the heat exchanger. In the single-phase regions, the quality of the refrigerant fluid does not change, therefore the correlation of Gnielinski was used. In these regions, it was considered that the temperature varies linearly over the heat exchanger. However, in the two-phase region, the quality variation must be considered, so the Shah correlation was adopted. The quality was assumed to vary linearly during the fluid condensation. The three control volumes were divided into 100 parts and the convective heat transfer coefficient for each one was determined using an arithmetic average. For the thermal load and pressure conditions considered in this work, the condenser were dimensioned in length of 9.6 m and the propane convective heat transfer coefficients found for the desuperheating, condensation and subcooling regions were 333.9 W/m²-K, 1209.8 W/m²-K and 334.2 W /m²-K, respectively. For the water, the heat transfer coefficient is almost constant in the three regions at about 715.3 W/m²-K.
Keywords
Refrigeration, condenser, convective heat transfer coefficient, Heat transfer
