Variable speed liquid chiller drop-in modeling for predicting energy performance of R1234yf as low-GWP refrigerant

This paper presents a model for a variable-speed liquid chiller integrating a compressor model based on Buckingham π-theorem to accurately predict the system performance when R134a is replaced with R1234yf, using a wide range of data obtained from an experimental setup. Relevant variables such as temperature, pressure, mass and volumetric flow rates, compressor power consumption and rotation speed were measured at several positions along the refrigeration and secondary circuits and were used to validate the developed model. Model results show that cooling capacity and power consumption predicted values are in good agreement with experimental data, within ±5%, being slightly higher for the deviation obtained for R134a than for R1234yf. Moreover, model results indicate that R1234yf has a reduction of coefficient of performance (COP) compared with R134a (between 2 and 11.3%), and that R1234yf COP reduction is diminished at intermediate volumetric flow rate and higher inlet temperature for the evaporator secondary fluid, respectively. On the other hand, an environmental analysis based on TEWI (total equivalent warming impact) method showed that direct emissions are almost negligible for R1234yf. However, there are no environmental benefits in terms of indirect greenhouse gas emissions using R1234yf without system modifications (as for instance the addition of internal heat exchanger or R1234yf new design components), which are required to reduce the liquid chiller climate change contribution using it as low GWP alternative in comparison with the typically used R134a refrigerant

Experimental Local Loss Coefficients (Km) Of Some Common Fittings Used In Residential Hydraulic Networks

The loss coefficients values (Km) of hydraulic fittings produce energy losses that are related to the minor ones (hL) and are widely used in hydraulic network designs. In this work, through a loss bank, the most common fittings Km coefficients used in residential hydraulic installations in Colombia were found, such as 90° elbows, universal joints, reductions, and ball valves from ½ to 2 inches in diameter. Among the results found, it was evidenced that the smaller the diameter, the load losses, the velocity, and the loss coefficient increase. An analysis of variance (ANOVA) was performed to corroborate the results obtained and, in most cases, reliability greater than or equal to 90% was achieved

Chronic disease relapses: A cross-sectional study of the associated factors and socioeconomic inequalities during the COVID- 19 pandemic in Peru

Objectives To investigate the prevalence, associated factors and socioeconomic inequalities in chronic disease relapses (CDR) during 2020 in Peru. Methods A secondary analysis was made of the National Household Survey on Living Conditions and Poverty (ENAHO) 2020. Participants older than 18 years who suffered from a chronic disease and with information about the occurrence of a CDR in the last 4 weeks prior to the survey were included. Adjusted prevalence ratios (aPRs) were estimated to determine the associated factors. Socioeconomic inequality in CDR was estimated using concentration curves (CC) and the Erreygers concentration index (ECI). Results Data from 38,662 participants were analyzed; the prevalence of CDR in the last 4 weeks prior to the survey was 16.5% (95% CI: 15.8-17.2). Being female (aPR 1.29; 95% CI: 1.21- 1.37), with regards to being male; being 30-39 (aPR 1.22; 95% CI: 1.05-1.42), 40-49 (aPR 1.29; 95% CI: 1.12-1.48), 50-59 (aPR 1.60; 95% CI: 1.41-1.82), and 60 years or older (aPR 1.80; 95% CI: 1.58-2.04), compared to 18-29; reaching up to primary (aPR 1.18; 95% CI: 1.07-1.31), or secondary education (aPR 1.13; 95% CI: 1.02-1.24), in contrast to tertiary education; presenting some physical, psychological or cognitive limitation (aPR 1.33; 95% CI: 1.21-1.46), with respect to experiencing no limitations; and being affiliated to a health insurance (aPR 1.18; CI 95%: 1.09-1.29), opposed to not having health insurance; were associated with a higher probability of CDR. Residing in the natural region of the coastal area (aPR 0.83; 95% CI: 0.74-0.92) was associated with a lower probability of relapse compared to residing in the jungle area. In people with limitations and residents of the jungle areas, the prevalence of CDR was concentrated in those with higher per capita spending. Conclusions Approximately 1 in 6 Peruvians with chronic diseases had a relapse within the last 4 weeks prior to the survey of 2020 and certain geographic and sociodemographic factors were found to be associated with CDR. It was also found that a higher concentration of CDR was observed in the population with the highest per capita spending with some limitations, as well as in residents of the jungle, implying the need for appropriate policy interventions that address CDR with a special focus on these populations.Revisión por pare

Wide Area RTK: a satellite navigation system based on precise real-time ionospheric modelling

The Wide Area Real Time Kinematic (WARTK) is an augmentation system concept for multi-frequency users based on precise real-time ionospheric modeling. It is able to provide a high accuracy and integrity GNSS positioning service over continental areas using the infrastructure of a network of permanent ground monitor stations, such as the European Geostationary Navigation Overlay Service (EGNOS) network of Ranging and Integrity Monitoring Stations (RIMS) in Europe. In this way, it allows an additional benefit to be obtained from these reference stations, that is, the network has the potential to support two independent systems: a satellite-based augmentation system, such as EGNOS, and a high-precision positioning service, based on WARTK. Indeed, thanks to the accuracy of the ionospheric corrections provided, WARTK users have available in real-time an extra constraint per satellite between the carrier phase ambiguities, which helps solve them quickly. Once such ambiguities have been solved, the GNSS user obtains navigation accurate to within 20 cm at the 95th percentile (about 10 cm RMS). Moreover, this precise positioning is achieved in a few minutes (with two frequency signals) or in a single epoch, after initial convergence of the tropospheric delay (with three frequency signals), even up to hundreds of kilometers away from the nearest reference station. While previous WARTK research has been devoted to implementing the concept and assessing its feasibility, considering in particular the accuracy achievable, the work reported in this paper focused on consolidating the results by analyzing a large and representative data set, and on deeper analysis of the integrity issue. It was carried out in the context of the Multi-constellation Regional System (MRS) project, within the European Space Agency GNSS Evolution Programme, with the aim of designing a high accuracy service for GPS and/or Galileo. Three months of actual data, from more than 25 permanent GPS stations in Europe, have been processed (some of them as a roving user), for high-, mid- and low-solar cycle conditions (in 2002, 2004 and 2006 respectively). In addition, several ionospheric storms occurred during the selected periods, with Dst values reaching up to −150 nT. Results based on these data show that user domain integrity was maintained for baselines of up to 400 km. At the 95th percentile, the daily horizontal and vertical position errors were 20 and 30 cm, respectively, and the corresponding protection levels were about 1 and 2 m. The convergence time was around 5 minutes with actual GPS constellation data. The benefits of using a multi-constellation system were also studied, with simulated GPS and three-frequency Galileo data, showing that it is possible to reduce the convergence time to a few seconds.Postprint (published version

Valorization of Caesalpinia coriaria Fruit Waste to Enhance the Ruminal Mitigation of Greenhouse Gases Production

La editorial tiene los derechos de autor y le solicito a hacer visibles la fecha técnica del artículo.The use of fruits waste from tanniniferous trees represents a new technology that aims to solve or mitigate greenhouse gases emission, and to increase the production of food of animal origin in an ecofriendly manner. This study aims to evaluate the production of methane and carbon dioxide, degradability by in vitro ruminal fermentation in goats diet supplemented with nuts (Caesalpinia coriaria Jacq. Willd.) for adoption by livestock farmers. Condensed tannins (CT) of C. coriaria inclusion rates were 0 (CT0 or control, no CT), 1.5 (CT1.5), 3.0 (CT3), 4.5 (CT4.5) and 6.0% (CT6) of the total mixed ration. All CT treatments reduced (linear, quadratic and cubic; P = 0.001) CH4, CO2 and H2 gases, and had some increasing effect on total biogas production. However, CT3 reduced greenhouse gases and had the highest biogas production. Addition of tannins from cascalote fruit waste (C. coriaria Jacq. Willd.) to goats diet at CT3 level reduced methane production, improved fermentation and ruminal degradability in vitro and has potential to be used as ecofriendly feed or feed additive

Distribución de los niveles de concentración de COVs en el aire ambiente y su relación con la altitud en la Isla de Tenerife

Ponencia presentada en: 1er Encuentro sobre Meteorología y Atmósfera de Canarias, celebrado en el Puerto de la Cruz, los días 12,13 y 14 de noviembre de 2003. El encuentro estuvo organizado por el Centro Meteorológico Territorial en Canarias Occidental, con la colaboración del Observatorio Atmosférico de Izaña y del Grupo de Física de la Atmósfera de la Facultad de Física (Universidad de La Laguna

VO2peak and Watt exercise testing: arm crank vs cycle ergometry

INTRODUCTION: Multiple sclerosis is a disease of the central nervous system that primarily affects the strength and functional capacity of the lower extremities. PURPOSE: The objectives of the present study were evaluate VO2peak and the power output (W) during a leg and an arm test performance in relapsing-remitting multiple sclerosis (MS) versus healthy people (HP). METHODS: Twelve women (age 45.8 ± 11.8 yr) with MS (EDSS 3.3 ± 1.8) and twelve women (age 45.6 ± 10.7 yr) HP were included in this study. They underwent two incremental exercise tests on an electromechanical braked arm crank ergometer and on an electromagnetic braked leg cycling ergometer separately. A computerized gas analysis system collected and analyzed gas exchange during the two kinds of testing. The statistical analysis was determined with the Wilcoxon test. RESULTS: First, VO2peak (21.5 ± 5.9 vs. 30.5 ± 4.8 ml·kg·min-1, p = 0.001) y W (84.5 ± 30.1 vs. 141.0 ± 13.7, Watt, p =0.0001) during cycle ergometer test were significantly lower in MS compared with HP. Similarly, the VO2peak in MS during arm crank was significantly lower (16.7 ± 5.4 vs. 23.4 ± 5.1 ml·kg·min-1, p = 0.023) compared with HP. However, the power generated by the arm was not different between the groups. CONCLUSION: The patients with MS during leg ergometer test showed a lower VO2peak. In the same sense, the patients with MS showed lower VO2peak in the test performed with the arms. Interestingly, the power generated with arms was similar in the two groups. These results indicate, that the patients with MS reflect a greater affectation to produce high loads of physical work with legs but not with arms. Further research is suggested where both the lower and upper extremities are involved to improve the processes of rehabilitation in MS

Adhesion mechanisms of Actinobacillus pleuropneumoniae to the porcine respiratory system and biofilm formation

Actinobacillus pleuropneumoniae is a Gram-negative bacterium and the causative agent of porcine pleuropneumonia, a highly contagious disease of pigs characterised by fibrinohaemorrhagic necrotising pneumonia. Although it has been well controlled in some developed countries, outbreaks can occur in pigs of all ages in contact with asymptomatic carriers, leading to significant economic losses to the swine industry due to the high morbidity and mortality rates. Adhesion is a critical step in the colonisation of the swine respiratory tract and the pathogenesis of the porcine pleuropneumonia; however, a literature review of this process is not available to date. Therefore, this review aims to provide information regarding the molecules that have been described in the adhesion of A. pleuropneumoniae to cells and tissues of the porcine respiratory tract. Since adhesion is the first step in biofilm formation, we included a section to describe the genes involved in this process; some of these genes could participate directly or indirectly in the adhesion of A. pleuropneumoniae to the porcine respiratory system. Although the role of biofilms in porcine pleuropneumonia is still not clear, these molecules could be considered in the future as candidates for vaccine development