Experimental and numerical studies of hybrid PCM embedded in plastering mortar for enhanced thermal behaviour of buildings

This paper proposes a methodology for improvement of energy efficiency in buildings through the innovative simultaneous incorporation of three distinct phase change materials (here termed as hybrid PCM) in plastering mortars for façade walls. The thermal performance of a hybrid PCM mortar was experimentally evaluated by comparing the behaviour of a prototype test cell (including hybrid PCM plastering mortar) subjected to realistic daily temperature profiles, with the behaviour of a similar prototype test cell, in which no PCM was added. A numerical simulation model was employed (using ANSYS-FLUENT) to validate the capacity of simulating temperature evolution within the prototype containing hybrid PCM, as well as to understand the contribution of hybrid PCM to energy efficiency. Incorporation of hybrid PCM into plastering mortars was found to have the potential to significantly reduce heating/cooling temperature demands for maintaining the interior temperature within comfort levels when compared to normal mortars (without PCM), or even mortars comprising a single type of PCM.

Utilização de modelos de simulação para a melhoria de um sistema de restauração: estudo de caso de uma cantina universitária

Dissertação de mestrado em Engenharia Industrial

Nonlinear behavior of gelatin networks reveals a hierarchical structure

We investigate the strain hardening behavior of various gelatin networks-namely physical gelatin gel, chemically cross-linked gelatin gel, and a hybrid gel made of a combination of the former two-under large shear deformations using the pre-stress, strain ramp, and large amplitude oscillations shear protocols. Further, the internal structures of physical gelatin gels and chemically cross-linked gelatin gels were characterized by small angle neutron scattering (SANS) to enable their internal structures to be correlated with their nonlinear rheology. The Kratky plots of SANS data demonstrate the presence of small cross-linked aggregates within the chemically cross-linked network whereas, in the physical gelatin gels, a relatively homogeneous structure is observed. Through model fitting to the scattering data, we were able to obtain structural parameters, such as the correlation length (ξ), the cross-sectional polymer chain radius (Rc) and the fractal dimension (df) of the gel networks. The fractal dimension df obtained from the SANS data of the physical and chemically cross-linked gels is 1.31 and 1.53, respectively. These values are in excellent agreement with the ones obtained from a generalized nonlinear elastic theory that has been used to fit the stress-strain curves. The chemical cross-linking that generates coils and aggregates hinders the free stretching of the triple helix bundles in the physical gels.

Tradição em continuidade: monitorização das estratégias bioclimáticas das Quintas no Nordeste Transmontano

In recent decades the vernacular architecture has been recognized as an important source of knowledge in the adaptation of construction to the climate and other specific local characteristics. However, the systematized information is still scarce to quantitatively understand the hydrothermal behaviour of bioclimatic strategies identified in previous surveys to this type of architecture. Using the farmsteads in the northeast region of Portugal as a case study, this article presents the results of hygrothermal monitoring carried out during the heating and cooling seasons. The data obtained enabled to verify and quantify the effective performance of the identified bioclimatic strategies, which are presented as opportunities for contemporary architecture.

Design of bio-based supramolecular structures through self-assembly of α-lactalbumin and lysozyme

Bovine α-lactalbumin (α-La) and lysozyme (Lys), two globular proteins with highly homologous tertiary structures and opposite isoelectric points, were used to produce bio-based supramolecular structures under various pH values (3, 7 and 11), temperatures (25, 50 and 75 °C) and times (15, 25 and 35 min) of heating. Isothermal titration calorimetry experiments showed protein interactions and demonstrated that structures were obtained from the mixture of α-La/Lys in molar ratio of 0.546. Structures were characterized in terms of morphology by transmission electron microscopy (TEM) and dynamic light scattering (DLS), conformational structure by circular dichroism and intrinsic fluorescence spectroscopy and stability by DLS. Results have shown that protein conformational structure and intermolecular interactions are controlled by the physicochemical conditions applied. The increase of heating temperature led to a significant decrease in size and polydispersity (PDI) of α-La–Lys supramolecular structures, while the increase of heating time, particularly at temperatures above 50 °C, promoted a significant increase in size and PDI. At pH 7 supramolecular structures were obtained at microscale – confirmed by optical microscopy – displaying also a high PDI (i.e. > 0.4). The minimum size and PDI (61 ± 2.3 nm and 0.14 ± 0.03, respectively) were produced at pH 11 for a heating treatment of 75 °C for 15 min, thus suggesting that these conditions could be considered as critical for supramolecular structure formation. Its size and morphology were confirmed by TEM showing a well-defined spherical form. Structures at these conditions showed to be stable at least for 30 or 90 days, when stored at 25 or 4 °C, respectively. Hence, α-La–Lys supramolecular structures showed properties that indicate that they are a promising delivery system for food and pharmaceutical applications.

Development and characterization of lipid-based nanosystems for controlled release of bioactive compounds

Tese de Doutoramento em Engenharia Química e Biológica.

Análise custo-benefício da integração de painéis solares térmicos na reabilitação de um edifício

Dissertação de mestrado integrado em Engenharia Civil

Thermal technologies in food processing

[Excerpt] Introduction: Thermal processing is probably the most important process in food industry that has been used since prehistoric times, when it was discovered that heat enhanced the palatability and the life of the heat-treated food. Thermal processing comprehends the heating of foods at a defined temperature for a certain length of time. However, in some foods, the high thermotolerance of certain enzymes and microorganisms, their physical properties (e.g.,highviscosity),ortheircomponents(e.g.,solidfractions) require the application of extreme heat treatments that not only are energy intensive, but also will adversely affect the nutritional and organoleptic properties of the food. Technologies such as ohmic heating, dielectric heating (which includes microwave heating and radiofrequency heating), inductive heating, and infrared heating are available to replace, or complement, the traditional heat-dependent technologies (heating through superheated steam, hot air, hot water, or other hot liquid, being the heating achieved either through direct contact with those agents – mostly superheated steam – or through contact with a hot surface which is in turn heated by such agents). Given that the “traditional” heatdependent technologies are thoroughly described in the literature, this text will be mainly devoted to the so-called “novel” thermal technologies. (...)

Incorporation of hybrid phase change materials in plastering mortars for increased energy efficiency in buildings

Tese de Doutoramento em Engenharia Civil.

Combustion of alternative biomass fuels in a domestic boiler and in a large-scale furnace

Programa Doutoral em Engenharia Mecânica.

Influence of skeletal muscle mass on ventilatory and hemodynamic variables during exercise in patients with chronic heart failure

OBJECTIVE: To assess the influence of skeletal muscle mass on ventilatory and hemodynamic variables during exercise in patients with chronic heart failure (CHF). METHODS: Twenty-five male patients underwent maximum cardiopulmonary exercise testing on a treadmill with a ramp protocol and measurement of the skeletal muscle mass of their thighs by using magnetic resonance imaging. The clinically stable, noncachectic patients were assessed and compared with 14 healthy individuals (S) paired by age and body mass index, who underwent the same examinations. RESULTS: Similar values of skeletal muscle mass were found in both groups (CHF group: 3863 ± 874 g; S group: 3743 ± 540 g; p = 0.32). Significant correlations of oxygen consumption in the anaerobic threshold (CHF: r = 0.39; P= 0.02 and S: r = 0.14; P = 0.31) and of oxygen pulse also in the anaerobic threshold (CHF: r = 0.49; P = 0.01 and S: r =0.12; P = 0.36) were found only in the group of patients with chronic heart failure. CONCLUSION: The results obtained indicate that skeletal muscle mass may influence the capacity of patients with CHF to withstand submaximal effort, due to limitations in their physical condition, even maintaining a value similar to that of healthy individuals. This suggests qualitative changes in the musculature.

An investigation into the temperature distribution resulting from cutting of compact bone using a reciprocating bone saw

Surgical procedures such as osteotomy and hip replacement involve the cutting of bone with the aid of various manual and powered cutting instruments including manual and powered bone saws. The basic mechanics of bone sawing processes are consistent with most other material sawing processes such as for wood or metal. Frictional rubbing between the blade of the saw and the bone results in the generation of localised heating of the cut bone. Research studies have been carried out which consider the design of the bone saw which deals with specifics of the saw teeth geometry and research which examines the effect of drilling operations on heating of the bone has shown that elevated temperatures will occur from frictional overheating. This overheating in localised areas is known to have an impact on the rate of healing of the bone post operation and the sharpness life of the blade. The purpose of this study was to measure the temperature at three zones at fixed intervals of 3mm, 6mm, and 9mm away from the cutting zone. It should be noted that it was the first time that this measurement technique was used to measure the temperature gradient through the bone specimen thereby establishing the extent to which clinicians are experiencing thermal injury during sawing of bone while using a reciprocating saw. The effect of various cutting feed rate on temperature elevation was also investigated in this research. The results showed that there will be a region of bone at least 9mm either side of the cutting blade experiencing thermal injury as temperatures in this region exceeded the threshold temperature of 44°C for necrosis (cell death).

A comparative study in two secondary schools aimed at improving their energy management: Archbishop McHale College Tuam, Coláiste Cholmcille Indreabhánn

Climate change is a crisis that is going to affect all of our lives in the future. Ireland is expected to have increased storms and rain throughout the country. This will affect our lives greatly unless we do something to change it. In an attempt to try and reduce the impacts of climate change, countries across the world met to address the problem. The meeting became known as the Kyoto Protocol. The Kyoto protocol set out objectives for each developed country to achieve with regards to carbon emissions to the same levels as 1990 levels. Due to the economy in Ireland being at a low point in 1990, Ireland was given a target of 13% carbon emissions above 1990 levels. In order to meet targets Ireland produced two energy papers, the green paper and the white paper. The green paper identified drivers for energy management and control; they were security of energy supply, economic competitiveness and environmental protection. The white paper produced targets in which we should aim to achieve to try and address the green papers drivers. Within the targets was the plan to reduce energy consumption in the public sector by 33% by 2020 through energy conservation measures. Schools are part of the public sector that has targets to reduce its energy consumption. To help to achieve targets in schools initiatives have been developed by the government for schools. Energy audits should be performed in order to identify areas where the schools can improve their current trends and show where they can invest in the future to save money and reduce the schools overall environmental footprint. Grants are available for the schools for insulation through the energy efficiency scheme and for renewable energy technologies through the ReHeat scheme. The promotion of energy efficient programs in schools can have a positive effect for students to have an understanding. The Display Energy Certificate is a legal document that can be used to understand how each school is performing from an energy perspective. It can help schools to understand why they need to change their current energy management structure. By improving the energy management of the schools they then improve the performance on the Display Energy Certificate. Schools should use these tools wisely and take advantage of the grants available which can in the short to long term help them to save money and reduce their carbon footprint.

Analysis of energy management in GMIT

Energy management is the process of monitoring, controlling and conserving energy in a building or organisation. The main reasons for this are for cost purposes and benefit to the environment. Through various techniques and solutions for lighting, heating, office equipment, the building fabric etc along with a change in people’s attitudes there can be a substantial saving in the amount spent on energy. A good example o f energy waste in GMIT is the lighting situation in the library. All the lights are switched on all day on even in places where that is adequate daylighting, which is a big waste o f energy. Also the lights for book shelves are left on. Surely all these books won’t be searched for all at the one time. It would make much more sense to have local switches that the users can control when they are searching for a particular book. Heating controls for the older parts o f the college are badly needed. A room like 834 needs a TRV to prevent it from overheating as temperatures often reach the high twenties due to the heat from the radiators, computers, solar gains and heat from users o f the room. Also in the old part o f the college it is missing vital insulation, along with not being air tight due to the era when it was built. Pumped bonded bead insulation and sealant around services and gaps can greatly improve the thermal performance o f the building and help achieve a higher BER cert. GMIT should also look at the possibility o f installing a CHP plant to meet the base heating loads. It would meet the requirement o f running 4500 hours a year and would receive some financial support from the Accelerated Capital Allowance. I f people’s attitudes are changed through energy awareness campaigns and a few changes made for more energy efficient equipment, substantial savings can be made in the energy expenditure.

The design and development of heat extraction technologies for the utilisation of compost thermal energy

A composting Heat Extraction Unit (HEU) was designed to utilise waste heat from decaying organic matter for a variety of heating application The aim was to construct an insulated small scale, sealed, organic matter filled container. In this vessel a process fluid within embedded pipes would absorb thermal energy from the hot compost and transport it to an external heat exchanger. Experiments were conducted on the constituent parts and the final design comprised of a 2046 litre container insulated with polyurethane foam and kingspan with two arrays of qualpex piping embedded in the compost to extract heat. The thermal energy was used in horticultural trials by heating polytunnels using a radiator system during a winter/spring period. The compost derived energy was compared with conventional and renewable energy in the form of an electric fan heater and solar panel. The compost derived energy was able to raise polytunnel temperatures to 2-3°C above the control, with the solar panel contributing no thermal energy during the winter trial and the electric heater the most efficient maintaining temperature at its preset temperature of 10°C. Plants that were cultivated as performance indicators showed no significant difference in growth rates between the heat sources. A follow on experiment conducted using special growing mats for distributing compost thermal energy directly under the plants (Radish, Cabbage, Spinach and Lettuce) displayed more successful growth patterns than those in the control. The compost HEU was also used for more traditional space heating and hot water heating applications. A test space was successfully heated over two trials with varying insulation levels. Maximum internal temperature increases of 7°C and 13°C were recorded for building U-values of 1.6 and 0.53 W/m2K respectively using the HEU. The HEU successfully heated a 60 litre hot water cylinder for 32 days with maximum water temperature increases of 36.5°C recorded. Total energy recovered from the 435 Kg of compost within the HEU during the polytunnel growth trial was 76 kWh which is 3 kWh/day for the 25 days when the HEU was activated. With a mean coefficient of performance level of 6.8 calculated for the HEU the technology is energy efficient. Therefore the compost HEU developed here could be a useful renewable energy technology particularly for small scale rural dwellers and growers with access to significant quantities of organic matter