Biodegradable Chitosan Matrix Composite Reinforced with Titanium Dioxide for Biocidal Applications

Access to drinkable water is increasingly difficult in developing nations. According to the World Health Organization, more than 1.2 billion people lack access to this resource. The scientific community has risen to the challenge by developing innovating methods to purify water. In this context, a chitosan/titanium dioxide biocomposite represents an appealing, economically viable solution to remove oils, heavy metals, and pathogen colonies from contaminated waters. The present chapter reports the study of a chitosan film matrix impregnated with nanoparticles, which was capable of expressing antibacterial properties when exposed to UV light. Several techniques allowed characterizing the biocomposite uniformity, corroborating the crystal structure and assessing the bonding type of this biocomposite mixture. Antibacterial tests with Escherichia coli (Gram-negative) and Staphylococcus aureus (Gram-positive) were completed via growth curve analysis and the Kirby-Bauer technique. The results of this encompassing study revealed that bacterial growth was reduced by more than 50%. Optical microscopy, Fourier-transform infrared spectroscopy, and X-ray diffraction helped to characterize this biocomposite film. This chapter discusses how a novel and biodegradable film represents a better antibacterial material that is able to eliminate pathogens cost-effectively

A comprehensive study of two-stage vapor compression cycles with vapor-injection for heating applications, taking into account heat sink of finite capacity

[EN] This paper presents a comprehensive study of two-stage vapor compression cycles with vapor-injection for several refrigerants considering that the heat sink has a limited capacity. The key parameters of the cycle performance are identified and the influence of these parameters on the heating COP is analyzed. The optimum intermediate conditions of the cycle are evaluated using a general model of the cycle, considering two configurations (flash tank and economizer). Based on the optimization results, a correlation is proposed in order to estimate the optimum intermediate pressure, taking into account the temperature lift in the secondary fluid imposed by the application. The correlation uses cycle subcooling as an input, which is a novelty from the current correlations proposed in the literature. In addition, an optimum subcooling control strategy is proposed and finally, the influence of the size of the system components on the COP is studied.Fernando M. Tello-Oquendo acknowledges the financial support provided by the CONVOCATORIA ABIERTA 2013-SEGUNDA FASE program, which was funded by the SENESCYT (Secretaria de Educacion Superior, Ciencia, Tecnologia e Innovacion) (Grant no. 2015-AR37665) of Ecuador.Tello Oquendo, FM.; Navarro-Peris, E.; Gonzálvez-Maciá, J. (2018). A comprehensive study of two-stage vapor compression cycles with vapor-injection for heating applications, taking into account heat sink of finite capacity. International Journal of Refrigeration. 93:52-64. https://doi.org/10.1016/j.ijrefrig.2018.05.039S52649

Analysis of variable speed vapor injection scroll compressors working with several refrigerants: Empirical correlation for the characterization and optimization of the intermediate conditions

Vapor-injection scroll compressors (SCVI) are present in the market since many years. There are several studies in the literature dealing with their proper characterization and the development of correlation in order to estimate properly its intermediate working conditions. The main objective of these correlations is the prediction of the compressor behavior for any condition based on a reduced number of test. Derived from that a correlation would be better as less parameter it will require, as this will imply less number of test in order to determine it. Nowadays, variable speed SCVI are being installed more widely but not so much studies are available for these type of compressors. In this work, based on previous correlations obtained for constant speed SCVI, a correlation for variable SCVI has been obtained. In order to do that, a set of experimental calorimetric test has been conducted for different condensing and evaporating temperatures and 4 different compressor speeds. From these data, it has been possible to obtain a correlation depending in four parameters able to predict the intermediate conditions (pressure and temperature), the mass flow rates and the energy consumption with an error lower than 3%. The correlation has been checked with other sources of data available in the public literature obtaining similar deviations from the measured values. Finally and based on these results, the optimum intermediate operation conditions for an injection heat pump with an economizer has been determined in different external conditions. From the optimization process an improvement in COP up to 5% could be expected from the theoretical analysis

New characterization methodology for vapor-injection scroll compressors

[EN] This paper presents a characterization methodology for vapor-injection scroll compressors (SCVI). An SCVI was characterized in a modified calorimetric test bench, which is able to control the intermediate pressure and the injection superheat independently. Based on the characterization results, the injection mass flow rate was correlated with the intermediate pressure through a linear expression, and a modified AHRI polynomial was proposed to estimate the compressor power input. The correlations were used in a simple model to predict the intermediate conditions of the SCVI installed in a heat pump prototype with an economizer. The deviations obtained for the evaporator mass flow rate, injection mass flow rate, intermediate pressure, and compressor power input were lower than 5% in all cases. The proposed methodology allows evaluating SCVI in a wide range of operating conditions, being only dependent on compressor characteristics and totally independent of the system in which it is installed.Fernando M. Tello-Oquendo acknowledges the financial support provided by the "CONVOCATORIA ABIERTA 2013-SEGUNDA EASE" program, which was funded by the SENESCYT ("Secretaria Nacional de Educacion Superior, Ciencia, Tecnologia e Innovacion") (Grant No. 2015-AR37665) of Ecuador.Tello-Oquendo, FM.; Navarro-Peris, E.; Gonzálvez-Maciá, J. (2017). New characterization methodology for vapor-injection scroll compressors. International Journal of Refrigeration. 74:528-539. https://doi.org/10.1016/j.ijrefrig.2016.11.019S5285397

A Methodology for Characterization of Vapor-injection Compressors

Vapor-injection compressor technology is being used in refrigeration systems and heat pumps working at large differences between evaporating and condensing temperatures. However, there are no published standards for the characterization of this kind of compressors. Calorimetric benches are widely used to characterize compressors, nevertheless, the calorimetric benches, as known, cannot be used directly to characterize vapor-injection compressors, since the refrigerant conditions at the injection port are defined by the injecting temperature and the intermediate pressure. In addition, these intermediate conditions depend critically on the way in which the injection is performed (economizer, flash tank, liquid injection, etc.). Therefore, the characterization process of this type of compressors is more complex. In this paper, a methodology for characterizing vapor-injection compressors is proposed. The method allows measurement of vapor-injection compressors in a typical calorimetric test bench after implementing some minor modifications in order to incorporate the injection line. With these modifications, the system is capable of independently controlling the intermediate pressure and the injection temperature. The proposed methodology has been evaluated with a vapor-injection scroll compressor (of 17.1 m3/h) using R407C as a refrigerant. The measurement results and the performance parameters of the vapor-injection scroll compressor are presented. A simple correlation to estimate the injection mass flow rate as a function of the intermediate pressure has been found, that can be used to correlate the experimental results with high accuracy for several operating conditions. The advantages of the proposed methodology are the better control of the intermediate compression conditions and the possibility of testing vapor-injection compressors in a wide range of operating conditions

Comparison of the performance of a vapor-injection scroll compressor and a two-stage scroll compressor working with high pressure ratios

[EN] This paper presents a comparative analysis of the performance of a vapor-injection scroll compressor (SCVI) and a two-stage scroll compressor (TSSC) working with high pressure ratios in heat pump applications. Semi-empirical models of the compressors are implemented. The models are adjusted with experimental data obtained in a calorimetric test bench. The optimum displacement ratio (DR) is analyzed considering two criteria, COP maximization, and discharge temperature minimization. Once defined the optimum DR, a systematic comparison of the compressors is performed in terms of compressor efficiencies, heating capacity, COP, and discharge temperature. Finally, the intermediate pressure is optimized for a high-temperature water heating application, taking into account heat sink of finite capacity. Results show that the optimum DR of TSSC is around 0.58 and the COP is 6% larger than that the SCVI at the nominal point. Considering a wide range of operating conditions, the SCVI presents better efficiency and COP for pressure ratios below 5. For higher-pressure ratios, the TSSC presents better performance and achieves lower discharge temperature. The heating capacity of the TSSC can be improved by 7% by varying the swept volume of the high-stage compressor compared with the SCVI, with a minimum effect on the COP and on the discharge temperature from the optimum conditions.Fernando M. Tello-Oquendo acknowledges the financial support provided by the CONVOCATORIA ABIERTA 2013-SEGUNDA FASE program, which was funded by the SENESCYT (Secretaría de Educación Superior, Ciencia, Tecnología e Innovación) (Grant No. 2015-AR37665) of Ecuador. The authors would like to acknowledge Emerson Commercial and Residential Solutions for the given support to obtain the experimental data of scroll compressors and testing. In addition, the authors acknowledge the Spanish MINISTERIO DE ECONOMIA Y COMPETITIVIDAD , through the project ref-ENE2017-83665-C2-1-P Maximización de la eficiencia y minimización del impacto ambiental de bombas de calor para la descarbonización de la calefacción/ACS en los edificios de consumo casi nulo for the given support.Tello-Oquendo, FM.; Navarro-Peris, E.; Gonzálvez-Maciá, J. (2019). Comparison of the performance of a vapor-injection scroll compressor and a two-stage scroll compressor working with high pressure ratios. Applied Thermal Engineering. 160:1-15. https://doi.org/10.1016/j.applthermaleng.2019.114023S11516

Theoretical study of the heat pump performance for simultaneous production of space heating and domestic hot water

Nowadays, one of the most important challenges in the residential sector is the efficiency improvement of the equipment and systems used for space heating (SH) and domestic hot water (DHW) production. The main objective is to reduce the consumption of fossil fuels and CO2 emissions in these applications. In this context, heat pumps are an effective technology as an alternative to boilers for SH and DHW production. However, the SH demand has a different temperature level than the DWH demand. Generally, the SH demand has a variable temperature level that depends on the type of distribution system (type of building) and the different climate conditions, while the DHW demand requires the storage of hot water at a temperature above 60 °C to prevent the presence of legionella. On the other hand, the performance of heat pumps deteriorates when working with high condensing temperatures. This paper presents a theoretical study of the performance of an air-to-water heat pump for simultaneous SH and DHW production, where the use of a desuperheater for DHW production and the condenser for SH production are analyzed. The study shows the optimization of the desuperheater capacity for a given SH demand. The performance of the heat pump is analyzed in terms of the COP and the capacities of the condenser and desuperheater. In addition, the heat pump performance was compared with the performance of two heat pumps (SH and DHW) for the same capacity in terms of compressor swept volume and heat exchanger sizes

Aggression, Impulsivity and Suicidal Behavior in Depressive Disorders: A Comparison Study between New York City (US), Madrid (Spain) and Florence (Italy)

The association of aggression and impulsivity with suicidal behavior (SB) in depression may vary across countries. This study aimed (i) to compare aggression and impulsivity levels, measured with the Brown-Goodwin Scale (BGS) and the Barratt Impulsivity Scale (BIS), respectively, between New York City (NYC) (US), Madrid (Spain) and Florence (Italy) (ANOVA); and (ii) to investigate between-site differences in the association of aggression and impulsivity with previous SB (binary logistic regression). Aggression scores were higher in NYC, followed by Florence and Madrid. Impulsivity levels were higher in Florence than in Madrid or NYC. Aggression and impulsivity scores were higher in suicide attempters than in non-attempters in NYC and in Madrid. SB was associated with aggression in NYC (OR 1.12, 95% CI 1.07–1.16; p p = 0.032). Impulsivity was linked with SB in NYC (OR 1.01, 95% CI 1.00–1.02; p p < 0.001). The higher suicide rates in NYC, compared to Madrid or Florence, may be, in part, explained by these cross-cultural differences in the contribution of aggression-impulsivity to SB, which should be considered by future research on SB prevention

Analysis of the Corrosion Resistance of Bronze to Aluminium (ASTM B 824) in a Corrosive Environment Controlled with an Artificial Seawater Solution

This paper presents the analysis of corrosion resistance of bronzes to aluminum in a controlled corrosive environment. Three alloys were studied CuAl4.5; CuAl7,1 and CuAl10,1 (ASTM B824), whose chemical composition was evaluated by spectrometry (OES). To determine its metal phases, chemical attacks were carried out with FeCl3, HCl in 95% Ethanol and FeCl3, HCl, CrO3 in distilled water. The microstructures obtained were characterized by metallography using two microscopes, an optical and a scanning electron (SEM) and the phases obtained were compared. Subsequently, electrochemical corrosion tests were performed on each alloy. The electrolyte used in the tests was artificial seawater (ASTM D1141) with a pH of 10 ± 0.3. Then, the corrosion products were characterized by EDS and SEM. Once the identification phase was over, the products were removed with a 50% HCl solution. Corrosive attack damage in each microstructural matrix was identified and corrosion rates for each alloy were evaluated. Finally, the corrosion rate data were correlated with the Al and Sn percentages of the alloy. The results show that the higher the increase in aluminum, the lower the corrosion rate, for a maximum limit of Al = 10.11%; Sn = 0.13%; CR = 5,170 mpy; In addition, it was shown that these alloys are effective for marine environments with high salinity. The correlation can be used to estimate the corrosion rate for different pH of the electrolytic medium of any type of ferrous or non-ferrous alloy whose variables are dependent on its chemical composition. Keywords: corrosion, alloy, metallography, microstructure, spectrometry, electrochemistry. Resumen Este artículo presenta el análisis la resistencia a la corrosión de bronces al aluminio en un ambiente corrosivo controlado. Se estudiaron tres aleaciones CuAl4,5; CuAl7,1 y CuAl10,1 (ASTM B824), cuya composición química fue evaluada por espectrometría (OES). Para determinar sus fases metálicas se realizaron ataques químicos con FeCl3, HCl en Etanol al 95% y FeCl3, HCl, CrO3 en agua destilada. Las microestructuras obtenidas se caracterizaron mediante metalografía empleando dos microscopios, un óptico y un electrónico de barrido (SEM) y se compararon las fases obtenidas. Posteriormente, se realizaron ensayos de corrosión electroquímica a cada aleación. El electrolito utilizado en los ensayos fue agua de mar artificial (ASTM D1141) con un pH 10±0.3. Sucesivamente, se caracterizaron los productos de la corrosión mediante microscopia SEM. Una vez terminada la fase de identificación, se removieron los productos con una solución al 50% HCl. Los daños del ataque corrosivo en cada matriz microestructural fueron identificados y las tasas de corrosión para cada aleación fueron evaluadas. Finalmente, se correlacionaron los datos de tasas de corrosión con los porcentajes de Al y Sn de la aleación. Los resultados muestran que a mayor aumento de aluminio existe una menor tasa de corrosión, para un límite máximo de Al=10,11%; Sn=0.13%; CR=5,170 mpy; además, se demostró que estas aleaciones son eficaces para ambientes marinos con alta salinidad. La correlación puede ser utilizada para estimar la tasa de corrosión para diferentes pH del medio electrolítico de cualquier tipo de aleación ferrosa o no ferrosa cuyas variables sean dependientes de su composición química. Palabras claves: corrosión, aleación, metalografía, microestructura, espectrometría, electroquímica

Profile of Volatile Organic Compounds (VOCs) from Cold-Processed and Heat-Treated Virgin Coconut Oil (VCO) Samples

Virgin coconut oil (VCO) can be prepared with or without heat. Fermentation and centrifuge processes can be done without the use of heat (cold process), while expelling involves heat due to friction. Volatile organic compounds (VOCs) from VCO samples prepared using these three methods were collected using solid phase microextraction (SPME) and analyzed using gas chromatography–mass spectrometry (GC-MS). Twenty-seven VCO samples from nine VCO producers were analyzed. The VOCs from refined, bleached, and deodorized coconut oil (RBDCO) were also obtained for comparison. Fourteen compounds were found to be common in more than 80% of the VCO samples analyzed. These included: Acetic acid; C6, C8, C10, C12, and C14 fatty acids, and their corresponding delta-lactones; and C8, C10 and C12 ethyl carboxylates. Fourteen minor VOCs were likewise detected which can be grouped into five types: Carboxylic acids (formic acid, butanoic acid, benzoic acid, and pentadecanoic acid), ketones (acetoin, 2-heptanone), an alcohol (ethanol), aldehydes (acetaldehyde, hexanal, benzaldehyde), esters (ethyl acetate, methyl tetradecanoate), and hydrocarbons (n-hexane and toluene). Five pyrazines were detected in expeller VCO. Various hydrocarbons from C5 to C14 were noted to be higher in old RBDCO and VCO samples. There were variations in the VOCs within each VCO process as each producer used different processing times, temperatures, and drying procedures. Principal components analysis (PCA) was able to group the samples according to the process used, but there were overlaps which may be due to variations in the specific procedures used by the manufacturers. These results may help VCO manufacturers control their production processes