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Parametric analysis based on energy and exergy balances of a condensing boiler
Rubén Arévalo-Ramírez,Javier Aros-Taglioni 대한기계학회 2023 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.37 No.3
Condensing boilers are highly efficient equipment increasingly used to heat water for heating or industrial use, characterized by taking advantage of the residual heat of the combustion gases, including the condensation latent heat of water vapor. The present work analyzes important aspects to optimize the design and operation of this type of equipment from the energy and exergy point of view, specifically, the effect that changes in fuel, water inlet temperature (20-70 °C), excess air used in combustion (5-100 %) and relative humidity of the air (10-100 %), have on their energy and exergy efficiencies. For this purpose, the energy and exergy balance equations for the reactive and heat exchange processes that occur within it were implemented and solved using the computational program engineering equation solver (EES). The model was validated by comparing its results with the efficiency curve of a commercial condensing boiler model. The results show an important effect of the fuel type on the operating ranges in condensing and non-condensing modes and on the energy efficiency values, finding that the technology is widely justified when used with natural gas, and not so much with the other fuels analyzed. Likewise, a favorable effect of the reduction of excess air for combustion on energy efficiency can be seen, which is why it is advisable to operate this equipment with the least possible amount of air that guarantees good combustion. On the other hand, exergy efficiency has the highest values using natural gas, and benefits from a higher water return temperature and lower excess air. The greatest irreversibilities are found in the main coil and the combustion chamber.
Jose I. Martínez-Quesada,Javier E. Anaya-Ayala,Santiago Mier y Terán-Ellis,Montserrat Miranda-Ramírez,Luis H. Arzola,Christopher Ruben-Castillo,Juan C. Aramburo,Jesus M. de los Ríos,Carlos A. Hinojosa 대한혈관외과학회 2022 Vascular Specialist International Vol.38 No.2
Chronic limb-threatening ischemia is rarely associated with previous traumatic injury. We present a case of a 28-year-old male with progressive digit ulcers, a weak pulse, cyanosis, and a cold limb. Eight months prior, he had a motorcycle accident resulting in a right clavicle fracture and brachial plexus injury. Computed tomography angiography revealed occlusion of the right subclavian artery near a surgically implanted reduction plate. The patient underwent an open subclavianbrachial bypass with a reversed saphenous vein graft. His postoperative recovery was uneventful. After 3 months, he had a euthermic right hand with a palpable pulse and his ulcers had completely healed. This case reinforces the need for patients with a neurological deficit in the upper extremity caused by blunt trauma to undergo thorough vascular examination to identify potential arterial injury and compromised perfusion.
Ricardo Casas Carrillo,Ofelia Begovich Mendoza,Antonio Ramírez Treviño,Javier Ruiz León 제어·로봇·시스템학회 2021 International Journal of Control, Automation, and Vol.19 No.11
This work is concerned with a structural characterization of the diagnosability property in Timed Continuous Petri Nets (TCPNs) systems under infinite server semantics. Regarding this problem, three novel results are presented. The first one is the introduction of structural sufficient conditions for diagnosability in TCPNs, which are based on the concepts of relative degree, system distinguishability, and parameter identification. To this aim, the concept of a simple directed path from other works is extended to diagnosable directed paths. These new paths include attribution-places, pre-join-places and post-join-places, which allows to deal with multiple non-concurrent tokens-leak faults, and enlarging the class of systems that can be analyzed. Based on these structural conditions, a novel methodology to place a reduced number of sensors that guarantees the net diagnosability is proposed. Finally, a diagnoser based on a modified Differential Evolution algorithm is presented, which introduces individual searching sets in orthogonal spaces to diagnose (detect, locate, and identify) faults when an error is detected, avoiding the use of a bank of diagnosers of other approaches. The effectiveness and applicability of the main results are illustrated through an illustrative example.
José Antonio Silva-Guzmán,Raúl Rodríguez Anda,Francisco Javier Fuentes-Talavera,Ricardo Manríquez-González,María Guadalupe Lomelí-Ramírez 한국섬유공학회 2018 Fibers and polymers Vol.19 No.9
Currently, greater environmental awareness promotes research and development advances in biodegradable materials; they represent an alternative that decreases the environmental impact caused by traditional synthetic plastics. This study consists of the development and characterization of thermoplastic corn starch-based composites, reinforced with barley straw particles made by thermal compression. The study materials were prepared by using three particle concentrations (5, 10, and 15 %), while the matrix (0 %) was used as a reference. A mechanical evaluation of all samples was carried out, as well as that of their water absorption properties. They were also characterized by scanning electron microscopy (SEM), infrared spectroscopy (FTIR), X-ray diffraction (XRD), and flammability tests. The inclusion of straw in the thermoplastic matrix increased water absorption and quickened carbon formation, although it also increased its tensile strength (7 MPa) and the Young’s modulus of activity (MOE) (420 MPa) with a 15 % reinforcement. The FTIR analysis highlights the presence of a carbonyl signal (1720 cm-1) caused by a thermal breakdown (caramelization) linked to barley particles. Moreover, X-ray diffraction demonstrated a VA-type crystallinity pattern (anhydrous) within the biocomposites and an increase of the crystallinity index, through incorporating barley particles in the thermoplastic corn starch-based matrix.
José Arnold González-Garrido,José Rubén García-Sánchez,Carlos Javier López-Victorio,Adelma Escobar-Ramírez,Ivonne María Olivares-Corichi 한국영양학회 2023 Nutrition Research and Practice Vol.17 No.2
BACKGROUND/OBJECTIVES: Cocoa consumption is associated with health benefits due to its high content of polyphenols. However, the effects of short-term cocoa consumption remain unclear. We aimed to determine the effects generated by cocoa consumption (for 7 days) in young adults in normoweight and class II obesity. SUBJECTS/METHODS: Before-and-after study was carried out in normoweight (NW) (n = 15) and class II obesity (CIIO) (n = 15) young adults. The NW and CIIO participants consumed 25 and 39 g of cocoa, respectively, per day for 7 days. The effect of cocoa consumption was evaluated on the lipid profile, insulin resistance (IR), and inflammation. Oxidative damage was also examined by assessing the biomarkers of oxidative damage in plasma. In addition, recombinant human insulin was incubated with blood obtained from the participants, and the molecular damage to the hormone was analyzed. RESULTS: Cocoa consumption resulted in decreased low-density lipoprotein-cholesterol in both groups (P = 0.04), while the total cholesterol, high-density lipoprotein cholesterol, and triglycerides were maintained at the recommended levels. Initially, IR was detected in the CIIO group (homeostasis model assessment [HOMA] = 4.78 ± 0.4), which is associated with molecular damage to insulin. Interestingly, intervention with cocoa resulted in improved IR (HOMA = 3.14 ± 0.31) (P = 0.0018) as well as molecular damage to insulin. Finally, cocoa consumption significant decreased the arginase activity (P = 0.0249) in the CIIO group; this is a critical enzymatic activity in the inflammatory process associated with obesity. CONCLUSIONS: The short-term consumption of cocoa improves the lipid profile, exerts antiinflammatory effects, and protects against oxidative damage. Results of this study indicate that cocoa consumption can potentially improve IR and restore a healthy redox status.