Work

Study of the Maximum Pressures in an Evaporator of a Direct Expansion Heat Pump Using R744 Assisted by Solar Energy

Year: 2025

Type: article

Abstract: Replacing electric water heaters with heat pumps significantly lowers energy consumption and greenhouse gas emissions. Among the refrigerants considered, carbon dioxide (CO2 or R744) has attracted considerable attention from refrigeration specialists. However, the high operating pressures of R744 can exceed safe limits when heat pump components are exposed to intense solar radiation and elevated temperatures. This study develops a mathematical model for the evaporator of a Direct Expansion Solar-Assisted Heat Pump (DX-SAHP) to analyze pressure behavior when the system is inactive but subjected to solar radiation. The model also examines how these pressures affect component integrity, accounting for the mass of R744 trapped inside the evaporator. Meteorological data from Brazil’s four regions, provided by INMET, were used in the simulations. Simulations were conducted using information from five different cities and up to 10 years of climate data. Results show that for a refrigerant mass fraction of 12%, the maximum pressure reached approximately 122 bar, compared to the manufacturer’s specified limit of 132 bar for the evaporator tubes.

Source: Processes

DOI: 10.3390/pr14010103

Authors: Jéssica C. C. M. Silva, Tiago F. Paulino, Luiz Machado, Willian M. Duarte

Institutions: Universidade Federal de Minas Gerais, Federal Center for Technological Education of Minas Gerais

Language: English

Topic: Refrigeration and Air Conditioning Technologies

Subfield: Mechanical Engineering

Field: Engineering

Domain: Physical Sciences

SDGs: Affordable and clean energy, Climate action

Open Access status: gold

Estimated APC paid: $2,896