Análise comparativa e modelo de simulação de um climatizador veicular com condensadores a R1234yf/água e R134a/ar

• Ano de defesa: 2023
• Autor(a) principal: Renato Arruda de Oliveira
• Tipo de documento: Dissertação
• Tipo de acesso: Acesso aberto
• Idioma: por
• Instituição de defesa: Universidade Federal de Minas Gerais; Brasil; ENG - DEPARTAMENTO DE ENGENHARIA MECÂNICA; Programa de Pós-Graduação em Engenharia Mecanica; UFMG
• Palavras-chave em Português: Ar condicionado veicular; R1234yf; R134a; Condesador a ar; Condensador a água.; Engenharia mecânica; Condensação; Ar condicionado; Bombas de calor; Refrigeração
• Link de acesso: http://hdl.handle.net/1843/54877

Due to recurrent crises in the energy sector and the earth global warming, car manufacturers and researchers have been accelerating the search for more efficient vehicle air conditioning systems (VACS) and more friendly to the environment. In addition, due to the impacts of Covid-19 in the world, must VACS operates with higher rates of the air renewal in cabins of cars, buses, subways and others roads and rains modes of public transport. Almost all VACS operate with the fluid R134a as refrigerant, of high GWP (Global Warming Potential), and with a condenser at air. In this context, the objective of this work is to comparatively study the operations of a conventional LCA system and an alternative system with water cooled condenser and the ecofluid R1234yf. To establish the corresponding comparative analysis, mathematical models were developed for the two systems. A methodology from the literature was also used to estimate the thermal load in the cabin of a car in order to support the mathematical models of the two VACS. The results of the comparative study revealed that the (Coefficient of Performance) of the VACS at R1234yf/water was 9.4% higher than the value of the VACS at R134a/air. The temperature of R1234yf at the system compressor discharge was 17.5C below the R134a correspondent temperature, so a longer useful life for this equipment. On the other hand, the water temperature at the condenser outlet was 39C, a value well above the average temperature of 31.8C at the air outlet conventional condenser. Two solutions were proposed to promote water cooling of return to the condenser. The most plausible proposal was to use the condenser at air to reduce the temperature of the hot water leaving the condenser at R1234yf/water. Due to the greater weight of the new condenser and the incorporation of a water pump and the heat exchanger to promote the cooling of this liquid, a mass increase of 961 g was observed. However, this value is negligible compared to the total mass of the car, passagers, and luggage. Thus, the small weight gain of the VACS does not cause major negative impacts on the car weight/power ratio.