Our paper discussing the usage of geothermal energy for heating buildings is now published. You can download the full version from the publisher at the following webpage:
https://www.mdpi.com/1996-1073/12/5/770
Advertisements
Physics
Our paper “A combined analytical model for increasing the accuracy of heat emission predictions in rooms heated by radiators” is now published on the Journal of Building Engineering. Here is the link to the pdf (free download for the next 50 days):
https://www.sciencedirect.com/science/article/pii/S235271021831413X?dgcid=author
Abstract:
The efficiency of heat emitters plays an important role in the improvement of building energy performance, especially in the context of system and product comparison. In particular, it can be directly related to thermal comfort via the operative temperature that is effectively sensed by the users.
For the first time in the literature, in this paper we develop a combined analytical model for room and radiator that computes directly the heat output required to maintain a specific operative temperature. The total heat balance of the enclosure is used to accurately quantify and compare the heat emission losses of different radiator types via an analytical calculation of the operative temperature. This determines the efficiency of a selection of panel radiators with different surface temperature, radiation fraction and number of panels, which were tested in a chamber conforming to the EN 442-2 standard.
Additionally, we assess the related annual energy consumption in different climates by carrying out annual simulations in old (without heat recovery) and new (with heat recovery) building types located in Tallinn, Estonia and Strasbourg, France. In the new building we find a similar performance for all the radiators. In the old building however, one radiator outperforms the other two with up to 1.38% lower annual energy consumption, due to smaller rear losses and higher thermal comfort provided by the larger front panel surface.
Cheers!
You might already know that I’m very fond of philosophy. I loved it immediately, as soon as I started my studies in high school in Italy, back in the 90s. I certainly refer to it in my daily life, more or less explicitly; after all, my entire Quantum Prana concept is based on the interaction between Eastern and Western traditions.
Interestingly enough though, sometimes it happens that you don’t see a tangible outcome of your studies for a long period of time. Perhaps, even for over two decades.
And in fact, here it is! A paper entitled “Epistemological Explanation of Lean Construction” that I wrote together with my colleagues at Aalto University, Finland and at the University of Huddersfield, UK.
My contribution consists of a short review and comparison of the classical epistemology of Plato and Aristotle. I then explain how their differences got enhanced through the centuries, until the debate between the Rationalists (René Descartes, Baruch Spinoza, and Gottfried Wilhelm Leibniz) and the British Empiricists (John Locke, George Berkeley, and David Hume), commenting also on their role in cosmology.
I then move forward by shortly analyzing some features of the epistemology of Edmund Husserl and Martin Heidegger, in relation with tacit knowledge and Japanese philosophy.
At this webpage you can read our paper for free or download it in PDF:
https://ascelibrary.org/doi/10.1061/%28ASCE%29CO.1943-7862.0001597
My article on reheating and gravitino production in MSSM inflation is now published in The European Physical Journal C. It is a full access publication, if you are interested you can find it here:
https://link.springer.com/article/10.1140/epjc/s10052-017-5269-8
Abstract
In the framework of MSSM inflation, matter and gravitino production are here investigated through the decay of the fields which are coupled to the udd inflaton, a gauge-invariant combination of squarks. After the end of inflation, the flat direction oscillates about the minimum of its potential, losing at each oscillation about 56% of its energy into bursts of gauge/gaugino and scalar quanta when crossing the origin. These particles then acquire a large inflaton VEV-induced mass and decay perturbatively into the MSSM quanta and gravitinos, transferring the inflaton energy very efficiently via instant preheating. Regarding thermalization, we show that the MSSM degrees of freedom thermalize very quickly, yet not immediately by virtue of the large vacuum expectation value of the inflaton, which breaks the SU(3)C×U(1)YSU(3)C×U(1)Y symmetry into a residual U(1). The energy transfer to the MSSM quanta is very efficient, since full thermalization is achieved after only O(40)O(40) complete oscillations. The udd inflaton thus provides an extremely efficient reheating of the Universe, with a temperature Treh=O(108GeV)Treh=O(108GeV), which allows for instance several mechanisms of baryogenesis. We also compute the gravitino number density from the perturbative decay of the flat direction and of the SUSY multiplet. We find that the gravitinos are produced in negligible amount and satisfy cosmological bounds such as the Big Bang nucleosynthesis (BBN) and dark matter (DM) constraints.
Here is my newest paper!
“Thermomechanical generation of fissure patterns on the surface of heated circular wood samples”
https://arxiv.org/abs/1709.03546
We discuss the observation of primary crack patterns on the surface of heated medium density fiberboard (MDF) round samples in inert atmosphere. A constant heat flux irradiates the wood surface, and the primary cracks seem to appear instantaneously at a temperature below the pyrolysis point, \textit{before} any actual charring. Such fissures were originally believed to form mainly by the action of physicochemical processes; on the contrary, we show here that below the pyrolysis temperatures this occurs by means of thermomechanical surface instability. The crack patterns can indeed be explained qualitatively by the simultaneous thermal expansion and softening of the hot surface layer, which is restrained by the colder wood beneath. This generates membrane compressive stresses leading to surface instability. Physically, this is a consequence of the thermomechanical properties of wood, which is a natural thermoplastic. In this paper, the macro-crack topology is reproduced by a full 3D thermomechanical instability model. We obtain the patterns by solving the according eigenvalue problem numerically, by Finite Element Method (FEM). We also formulate the model in 2D, assuming a circular soft thin plate bonded to an elastic foundation, and solve it both analytically and numerically. Finally, we compare our results with analogous crack patterns appearing on the surface of square samples, which we discussed in a previous study. We conclude that very different pattern symmetries (orthotropic, isotropic and circular) might be explained by the same model of thermomechanical surface instability.
My paper on thermomechanical processes of charring wood is now published in Combustion And Flame. Here you can download the pdf for free for 50 days, if you are interested 🙂
In our study we develop a model for explaining the crack patterns which are formed on the wood surface when this is exposed to intense heat. It was believed for decades that such cracks are created by physicochemical processes like shrinkage, with impossibility to obtain an analytical model predicting their topology. On the contrary, we show that if one assumes the origin to be thermomechanical, the according analytical model can produce formulas which can describe and predict the crack patterns with an excellent agreement with the observations.
Here is the abstract:
In the assessment of wood charring, it was believed for a long time that physicochemical processes were responsible for the creation of cracking patterns on the charring wood surface. This implied no possibility to rigorously explain the crack topology. In this paper we show instead that below the pyrolysis temperatures, a primary global macro-crack pattern is already completely established by means of a thermomechanical instability phenomenon. First we report experimental observations of the crack patterns on orthotropic (wood) and isotropic (Medium Density Fibreboard) materials in inert atmosphere. Then we solve the 3D thermomechanical buckling problem numerically by using the Finite Element Method, and show that the different crack topologies can be explained qualitatively by the simultaneous thermal expansion and softening, taking into account the directional dependence of the elastic properties. Finally, we formulate a 2D model for a soft layer bonded to an elastic substrate, and find an equation predicting the inter-crack distance in the main crack-pattern for the orthotropic case. We also derive a formula for the critical thermal stress above which the plane surface will wrinkle and buckle. The results can be used for finding new ways to prevent or delay the crack formation, leading to improved fire safety of wood-based products.
I am now working with my colleagues on some developments of the model.
Thermal greetings to everybody!
Andrea /QP
Greetings!
My paper on theoretical modelling of daily hot water consumption in residential buildings is now published in Energy And Buildings. Here follows the abstract:
—
We consider Domestic Hot Water (DHW) consumption hourly data for Finnish apartments in November and August. Using datasets obtained in a previous work, we formulate a bottom-up model to quantify correlations in the consumption patterns, which are discerned by a different number of occupants for both weekday (WD) and weekend (WE). The analytical formulas thus obtained describe accurately the hourly consumption of any specific dataset. In particular, we can generate the consumption curves for unknown datasets and derive quantitatively the correlations between occupant groups and different seasons. We explain this procedure into details, define the key variables of the model and validate it against the measurements. Our quantitative results are immediately applicable to simulation tools for energy investigations and sizing of heating systems in Finland or areas with similar occupant behavior. More generally, the analytical, inductive method here introduced could be adapted to DHW studies concerning other geographic areas as well. We also argue that this simple, yet effective formalism might also be extended to other engineering contexts that are not strictly related to energy consumption. For example, the main idea could be developed and adapted to those disciplines where understanding dataset correlations constitutes an important investigation tool.
—
Analytical modelling and prediction formulas for domestic hot water consumption in residential Finnish apartments. Available from: https://www.researchgate.net/publication/309672534_Analytical_modelling_and_prediction_formulas_for_domestic_hot_water_consumption_in_residential_Finnish_apartments.
I will present these results in August, at the 7th International Symposium on Energy in Manchester: http://energy7.nscj.co.uk/
Energetic cheers!
Andrea /QP
