Evaluation of R448A and R450A as Low-GWP alternatives for R404A and R134a using a micro-fin tubes evaporator model

[EN] When retrofitting new refrigerants in an existing vapour compression system, their adaptation to the heat exchangers is a major concern. R450A and R448A are commercial non-flammable mixtures with low GWP developed to replace the HFCs R134a and R404A, fluids with high GWP values. In this work the evaporator performance is evaluated through a shell-and-microfin tube evaporator model using R450A, R448A, R134a and R404A. The accuracy of the model is first studied considering different recently developed micro-fin tube correlations for flow boiling phenomena. The model is validated using experimental data from tests carried out in a fully monitored vapour compression plant at different refrigeration operating conditions. The main predicted operational parameters such as evaporating pressure, UArp, and cooling capacity, when compared with experimental data, fit within 10% using the Akhavan-Behabadi et al. correlation for flow boiling. Results show that R450A and R404A are the refrigerants in which the model fits better, even though R448A and R134a predictions are also accurate. (C) 2015 Elsevier Ltd. All rights reserved.The authors thankfully acknowledge "Ministerio de Educacion, Cultura y Deporte" (Grant number FPU12/02841) for supporting this work through "Becas y Contratos de Formacion de Profesorado Universitario del Programa Nacional de Formacion de Recursos Humanos de Investigacion del ejercicio 2012". Finally the linguistic support of Irene I. Elias-Miranda is appreciated.Mendoza Miranda, JM.; Mota-Babiloni, A.; Navarro Esbri, J. (2016). Evaluation of R448A and R450A as Low-GWP alternatives for R404A and R134a using a micro-fin tubes evaporator model. Applied Thermal Engineering. 98:330-339. https://doi.org/10.1016/j.applthermaleng.2015.12.064S3303399

A review of refrigerant R1234ze(E) recent investigations

[EN] Climate change is demonstrated through global surface temperatures increase in the last century. To stop this phenomenon, new regulations that ban or tax greenhouse gas fluids (HFC among them) have been approved. In the medium term, only low-GWP refrigerants will be permitted in developed countries. HFO fluids and most used HFCs as refrigerants in HVACR systems possess similar thermophysical properties. Among them, one of the most promising is R1234ze(E). This refrigerant presents good environmental properties and can be used in most of HVACR applications, pure or mixed with HFC or natural refrigerants (mainly CO2). This paper collects the most relevant research about R1234ze(E) thermophysical and compatibility properties, heat transfer and pressure drop characteristics, and vapor compression system performance; separating those works that consider R1234ze(E) pure or blended. Once the available literature is analyzed, it can be concluded that pure R1234ze(E) is a good option only in new HVACR systems. Nevertheless, if it is combined with other refrigerants, the final GWP value is also considerably reduced, maintaining efficiency parameters at levels that allow them to replace R134a, R404A or R410A in existing systems with minor modifications.The authors thankfully acknowledge the “Ministerio de Educación, Cultura y Deporte” (Grant Number FPU12/02841) for supporting this work through “Becas y Contratos de Formación de Profesorado Universitario del Programa Nacional de Formación de Recursos Humanos de Investigación del ejercicio 2012”.Mota-Babiloni, A.; Navarro-Esbrí, J.; Molés, F.; Barragán Cervera, Á.; Peris, B.; Verdú Martín, GJ. (2016). A review of refrigerant R1234ze(E) recent investigations. Applied Thermal Engineering. 95:211-222. https://doi.org/10.1016/j.applthermaleng.2015.09.055S2112229