Examinando por Autor "Palomar-Torres, Amalia"
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Ítem Convective drying of mango stone for use as biomass.(ELSEVIER, 2023-06) Gómez-de la Cruz, Francisco J.; Palomar-Torres, Amalia; Pérez-Latorre, Francisco J.; Cruz-Peragón, FernandoMango stone is an interesting biomass by-product with a considerable net calorific value. Mango production has significantly risen in the last few years, meaning that mango waste has increased as well. However, mango stone has a moisture content of about 60% (wet basis) and it is very important to dry the samples for using them in electrical and thermal energy production. In this paper, the main parameters involved in the mass transfer during drying are determined. Drying was carried out in a convective dryer through a set of experiments based on five drying air temperatures (100ºC, 125ºC, 150ºC, 175ºC and 200ºC) and three air velocities (1 m/s, 2 m/s and 3 m/s). Drying times ranged between 2 and 23 hours. The drying rate was calculated from the Gaussian model whose values ranged from 1.5·10-6 to 6.3·10-4 s-1. Effective diffusivity was obtained as an overall parameter in the mass diffusion for each test. These values were found between 0.71·10-9 and 13.6·10-9 m2/s. The activation energy was calculated from the Arrhenius law for each test, made at different air velocities. These values were 36.7, 32.2 and 32.1 kJ/mol for 1, 2 and 3 m/s, respectively. This study provides information for future works on design, optimization and numerical simulation models in convective dryers for standard mango stone pieces according to industrial drying conditions.Ítem Energy and exergy analysis during drying in rotary dryers from Finite Control Volumes: applications to the drying of olive stone(ELSEVIER, 2022-01) Gómez-de la Cruz, Francisco J.; Palomar-Torres, Amalia; Palomar-Carnicero, José M.; Cruz-Peragón, FernandoNowadays, the design, control and development of rotary dryers are based on the study of the complete equipment. Rotary dryers are treated as a black box where only inlet and outlet parameters are known. This implies the need to know the main interactions of mass, energy and exergy throughout the trommel to help improve the drying process. In this paper, we carried out an analysis of energy and exergy during drying of olive stone from finites control volumes in an experimental rotary dryer. Mass, energy and exergy balances are applied to each control volume in the drying air. The design of experiments is based on three initial drying air temperatures (210ºC, 180ºC and 150ºC) and three drying air flows (576 kg/h, 425 kg/h and 280 kg/h), with a by-product mass flow of 40 kg/h and a rotational speed of 5.5 rpm. The results indicated that olive stone moisture content was reduced to less than half in the first third of the trommel where a big thermal shock is produced due to the interaction between the by-product and the drying air flow at high moisture contents and high temperatures, respectively. This fact led to the highest exergy destruction values, thereby diminishing the flow exergies for the following control volumes. Heat losses were considerable in all equipment, especially in the first two control volumes. Furthermore, drying process was analyzed from the energetic, exergetic and drying efficiencies and the unit energy consumption.Ítem The effect of HDPE and LDPE pyrolytic oils on cavitation formation in a common-rail diesel injector(Elsevier, 2022-12-15) Lešnik, Luka; Palomar-Torres, Amalia; Torres-Jiménez, Eloísa; Mata, Carmen; Volmajer Valh, Julija; Kevorkijan, Luka; Biluš, IgnacijoPlastic production and usage increase every year due to its practicality, adaptability, and low-cost production. The problem with plastic arises when it becomes waste and needs to be treated. Most of the plastic we use is produced from petrochemical material that can be used in resource recovery processes like pyrolysis to produce various materials. One of the pyrolysis process products is pyrolytic oil, whose properties are similar to conventional fuels. Minor differences in fuel properties can influence the injection process, in-nozzle flow condition, spray formation and break-up, the combustion process, etc. The presented paper aims to study the influence of pyrolytic oil‘s properties on cavitation formation in the injection nozzle of a common-rail injector. First, the pyrolytic oils were obtained from waste high- and low-density polyethylene using a pyrolysis reactor. Afterwards, the oils were characterized and implemented in the AVL FIRE computation program for studying their influence on cavitation formation in the injection nozzle hole. The obtained results indicate slight differences in fuel properties that influence cavitation formation and spread in the injection hole, which further influence conditions at the exit of the injection hole. The lower lower viscosity of pyrolytic oils influences lower friction in the fuel nozzle flow. The lower density and viscosity of pyrolytic oils promotes cavitation formation, advance time of it appearance at injection hole exit and influence the shorter presence of cavitation in the needle closing phase.