J.L. Míguez

Fuel lignocellulosic briquettes, die design and products study

Briquetting of biomass can be done through various techniques. The present work describes the process of designing a taper die and its optimisation for use in a hydraulic machine. The application of an experimental design technique, and the later statistical analysis of the results is presented, applied to a laboratory hydraulic press densification process of lignocellulosic biomass. The most appropriate experiment type is determined for a first set of experiments; calculating, among other things: minimum number of tests to carry out to obtain binding conclusions, most influential factors, and search paths to improve fuel quality. Another experiment type is determined for a second set of experiments, taking account of the most influential factors [1, 3] (pressure, temperature and moisture content), and also the number of tests to carry out considering the improvement of density and friability. Finally, an approximation study of the best product allows conclusions to be reached on product behaviour beyond the experimental design range factors.

The Influence of Phase Change Materials on the Properties of Self-Compacting Concrete

The aim of this paper is to research new thermally-efficient concrete walls, analyzing the mechanical behavior of a self-compacting concrete to manufacture an uncoated solid structural panel, with the incorporation of a micro-encapsulated phase change material as additive. Different dosages are tested and mechanical properties of the product obtained from the molding of concrete specimens are evaluated, testing mechanical compressive strength, slump flow, and density. The results reveal the optimum percentage of additive in the mixture that enables compliance with the technical specifications required by the product to be manufactured. A test is also performed for measuring the thermal conductivity for the optimal sample obtained and it evidences the reduction thereof.

Experimental study on thermal conductivity of self-compacting concrete with recycled aggregate

The research focuses on the use of recycled aggregate (RA), from waste pieces generated during production in precast plants for self-compacting concrete (SCC) manufactured with a double sustainable goal: recycle manufacturing waste (consumption) and improvement of the thermal properties of the manufactured product (energy efficiency). For this purpose, a mechanical study to ensure technical feasibility of the concrete obtained has been conducted, as well as a thermal analysis of recycled SCC specimens of 50 N/mm2 resistance, with different RA doses (0%, 20%, 50% and 100%). The main parameters that characterize a SCC in both states, fresh (slump-flow) and hard (compressive strength), have been tested; also, a qualitative analysis of the thermal conductivity using infrared thermography (IRT) and quantitative analysis with heat flow meter at three temperatures 20 °C, 25 °C and 30 °C have been performed. The results suggest the existence of two different thermal behaviors: concretes with 0% and 20% of RA, and on the other hand concretes with 50% and 100% of RA. It has also demonstrated the validity of the IRT as sampling technique in estimating the thermal behavior of materials having reduced range of variation in parameters.

Potential effect of uncertainty on the GRG interpretation

Purpose – The purpose of this paper is to propose an interpretation of the grey relational grade taking into account its variation range on the basis of the error propagation theory.Design/methodology/approach – The paper uses error propagation theory to calculate the uncertainty of the grey relational grade, exploring how errors are propagated through the sequential operations of the grey relational analysis.Findings – The non‐consideration of the error associated to the measurement of the experimental data that is transferred to the grey relational grade may have a potential effect on the interpretation of the grey relational rank. Data uncertainty quantification provides information about how well measurement fits to the value of the measured quantity and determines its validity. Therefore, this might lead one to consider that some sequences are less attractive than other lower‐ranked ones.Practical implications – The combination of the grey and error propagation theories is a tool to choose the most a...

On the Behavior of Different PCMs in a Hot Water Storage Tank against Thermal Demands

Advantages, such as thermal storage improvement, are found when using PCMs (Phase Change Materials) in storage tanks. The inclusion of three different types of materials in a 60 𝓁 test tank is studied. Two test methodologies were developed, and four tests were performed following each methodology. A thermal analysis is performed to check the thermal properties of each PCM. The distributions of the water temperatures inside the test tanks are evaluated by installing four Pt-100 sensors at different heights. A temperature recovery is observed after exposing the test tank to an energy demand. An energetic analysis that takes into account the energy due to the water temperature, the energy due to the PCM and the thermal loss to the ambient environment is also presented. The percentage of each PCM that remains in the liquid state after the energy demand is obtained.

Exhaust Emissions from Diesel, LPG, and Gasoline Low-power Engines

Abstract In a way similar to the automotive industry, outboard emissions limits are being constantly revised, which strongly effects the development of the new engines and their compliance. During the last ten years, conventional two-stroke outboard engines, which are used for fishing and recreational boats, have thus been replaced by four-stroke engines or direct-injection two-stroke engines. The objective of this article is to compare various outboard engines and the technical solutions developed for the reduction of exhaust emissions, with special emphasis being placed on the low-power gasoline and diesel outboard engine range. A gasoline outboard engine was also transformed to allow the use of liquefied petroleum gas (LPG) and showed that this technique could be an alternative solution for the future emission limit compliance.

Contribution of Renewable Energy Sources to Electricity Production in Galicia (Spain)

The use of renewable energy offers a decrease in external energy dependence; a boost to local and regional component manufacturing industries; promotion of regional engineering; increased R&D, decrease in impact of electricity production and transformation; increase in the level of services for the rural population; creation of employment, etc. To achieve these benefits, a series of actions are required, among which the following are particularly important: creation of a suitable climate for performing R&D; training of technicians in design, production, and maintenance of equipment; motivation for establishing a new market; proper financing; fostering of appropriate technologies; practical demonstration of results; etc. This article reviews the progress made in the Autonomous Community of Galicia in terms of the introduction of renewable energy technologies (RETs) and examines the possibility of meeting a target of 90% coverage (practical electrical self-sufficiency) by 2010.

Design and monitoring of a micro-cogeneration system: A wide practice proposed for engineering education

Learning by doing is essential in engineering education, along with topics such as systems automation and control and energy efficiency. This article presents work including all of these different topics. A micro‐cogeneration facility located at the University of Vigo is studied. The experimental plant is automated after detecting the most important variables and actuations. A system responsible for the control, supervision, and monitoring of the system was developed using the programming software LabVIEW. All of these processes are explained in depth here. Finally, a complete practice experience is proposed for the next course of the Master of Thermal Engineering programme taught at the University of Vigo. Different tasks are included: the study of the operating principle of a micro‐cogeneration system, the analysis of measurement devices and actuators for the automation of an experimental facility, LabVIEW programming, and interaction with the integrated system. The effectiveness of the proposed methodology will be evaluated through a five‐point Likert‐type scale survey.

Integration of the free software GenOpt for a thermal engineering course

Information and communications technologies (ICT) are being used in engineering fields due to multiple advantages that motivate their introduction in university teaching. A course on thermal engineering has been taught for the past 3 years as part of the industrial engineering degree at the University of Vigo. Energy savings and efficiency are common issues. In a practical classroom, one example is the energy simulations of buildings. These tools can be used to simplify the realization of control strategies for different building HVAC systems, which, in most cases, results in an important reduction in the buildings energy consumption over its lifetime. In this paper, the feasibility of using the free software GenOpt for simulation practice and as a tool for teaching and learning inside and outside the classroom is analyzed. These results, together with an analysis of the study plan of the industrial engineering degree at the University of Vigo, allow for the development of new teaching and learning methodologies as well as their implementation in energy simulation practice.

Automating, monitoring, and control of an ICE based micro-CCHP system using LabVIEW and Android

A methodology to automate and control a small-scale combined heat and power system (micro-CHP) is proposed. The contribution of this design is to extend the original plant toward micro-CHP system modeling, thus allowing flexible and efficient system through graphical programming. The automation involves the synthesized system analysis; thereby, human intervention is reduced. It builds on LabVIEW™ software that takes the model architecture to monitor and control de plant. Measured signals and parameters (SQL database) managed by LabVIEW™ are used to issue remote control communication. An Android application was developed to communicate with the database. The integration methodology of automation, monitoring and control energy variables in real-time may be extended to study failures and possible improvements on micro-CHP systems.