Our new paper on heated wood seems to confirm our model for a phenomenon that remained unexplained for a few decades.
When a flat sample of medium density fibreboard (MDF) is exposed to radiant heat in an inert atmosphere, primary crack patterns suddenly start to appear over the entire surface before pyrolysis and any charring occurs. Contrary to common belief that crack formation is due to drying and shrinkage, it was demonstrated for square samples that this results from thermomechanical instability. In the present paper, new experimental data are presented for circular samples of the same MDF material. The sample was exposed to radiant heating at 20 or 50 kW/m2, and completely different crack patterns with independent eigenmodes were observed at the two heat fluxes. We show that the two patterns can be reproduced with a full 3‐D thermomechanical surface instability model of a hot layer adhered to an elastic colder foundation in an axisymmetric domain. Analytical and numerical solutions of a simplified 2‐D formulation of the same problem provide excellent qualitative agreement between observed and calculated patterns. Previous data for square samples, together with the results reported in the present paper for circular samples, confirm the validity of the model for qualitative predictions and indicate that further refinements can be made to improve its quantitative predictive capability.
A new paper on the energy efficiency of buildings (here, ice hockey halls) is now published!
Energy analysis in ice hockey arenas and analytical formula for the temperature profile in the ice pad with transient boundary conditions
The energy efficiency of ice hockey arenas is a central concern for the administrations, as these buildings are well known to consume a large amount of energy. Since they are composite, complex systems, solutions to such a problem can be approached from many different areas, from managerial to technological to more strictly scientific. In this paper we consider heat transfer processes in an ice hockey hall, during operating conditions, with a bottom-up approach based upon on-site measurements. Detailed heat flux, relative humidity and temperature data for the ice pad and the indoor air are used for a heat balance calculation in the steady-state regime, which quantifies the impact of each single heat source. We also solve the heat conduction equation for the ice pad in transient regime, and obtain a general analytical formula for the temperature profile that is suitable to practical applications. When applied to the resurfacing process for validation, it shows good agreement with an analogous numerical solution. Since our formula is given with implicit initial condition and boundary conditions, it can be used not only in ice hockey halls, but in a large variety of engineering applications.
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:
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):
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.
I have just published a new article entitled “Optimization of Radiators, Underfloor and Ceiling Heater Towards the Definition of a Reference Ideal Heater for Energy Efficient Buildings”. We discuss analytical methods for optimization of heating systems in residential buildings, providing a formal efficiency analysis and some specific optimal configurations.
Here I am using a simple analytical method that I have developed some time ago for a different topic (predicting hot water consumption in residential buildings).
You can view the article (with open access) and download it for free at the following address:
Heat emitters, as the primary devices used in space heating, cover a fundamental role in the energy efficient use of buildings. In the search for an optimized design, heating devices should be compared with a benchmark emitter with maximum heat emission efficiency. However, such an ideal heater still needs to be defined. In this paper we perform an analysis of heat transfer in a European reference room, considering surface effects of thermal radiation and computing the induced operative temperature (op.t.) both analytically and numerically. Our ideal heater is the one determining the highest op.t. By means of functional optimization, we analyse trends such as the variation of operative temperature with radiator panel dimensions, finding optimal configurations. To make our definitions as general as possible, we address panel radiators, convectors, underfloor (UFH) and ceiling heater. We obtain analytical formulas for the operative temperature induced by panel radiators and identify the 10-type as our ideal radiator, while the UFH provides the best performance overall. Regarding specifically UFH and ceiling heaters, we find optimal sizes providing maximum op.t. The analytical method and qualitative results reported in this paper can be generalized and adopted in most studies concerning the efficiency of different heat emitter types in building enclosures.
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: