Vol 5 - Issue 2

Entropy: Thermodynamics – Energy – Environment – Economy

List of Articles

The much-needed energy transition brings special focus on fuel cell micro-combined Heat and Power (mCHP or micro-CHP) systems for residential uses, one of which is a Solid Oxide Fuel Cell (SOFC), fed by natural gas, designed to provide continuously 1.5 kWel with an associated amazingly high expected Low heating Value (LHV) electrical efficiency of 60%. This power output can be modulated as desired down to 500 Wel and heat can also be recovered to partially contribute to the heat demand of the household. This system has been installed in a laboratory environment and has been specifically instrumented in order to evaluate its performance with different thermal loads and electrical output power settings. In this paper, focus is brought on the resulting thermal output and efficiencies, both thermal and electrical, which have also been modelled with great goodness of fit. With several electrical power outputs between the 500-1500 Wel range, this study shows total High Heating Value (HHV) total efficiencies up to 88-89% at minimal return temperatures (around 20°C) in the heat recovery circuit. Maximum LHV electrical efficiency has been found to be equal to 57% at nominal output power (regardless of the thermal loads), which is close to the manufacturer’s target of 60%.

This article is dedicated to the analysis of the magnetic induction effects on the iron loss and the equivalent diagrams elements of a ferromagnetic domain subjected to this induction by using a parallelepipedic ferromagnetic domain subjected to a uniaxial magnetic flux. Induction B produced by an interdependent known source with the domain causes the domain saturation. This domain increases its consumption and sees the decrease of the resistances and the reactances values of its equivalent diagrams vis-a-vis the induction producing source. The increase in the iron loss and the reduction in the passive elements values of the equivalent diagrams are confirmed by the reduction in the resistivity and the permeability of the domain in Voltage Model where elements RL are in parallel as in Current Model where elements RL are in series. This phenomenon is visible during the duality parallel-series checking of the domain equivalent diagrams vis-a-vis the inductive source.

Bioeconomics is a new approach to the relationship between the economy and the environment developed by N. Georgescu-Roegen (1906-1994), a great economist of the 20th century who was also a mathematician, philosopher and historian of science. The economy, as a sub-system of the biosphere, is understood in a global ecological context. It is also inseparable from the historical dimension of the development of societies, given the limited access to a stock of resources (energy and matter) taken from the environment. The ultimate aim of this original approach is to reconcile economic development with ecological constraints and to lead the economy towards sufficiency.

The so-called “water vapor pump” cycle is defined by the selective recycling of the water vapor carried by the combustion products at the outlet of the thermal machine by exchange of mass and heat between the exiting combustion products and the incoming atmospheric air. With hydrogen fuel, this form of wet combustion is capable of very high energy and ecological performance. In this context, we present here the Hydrometric Combustion Diagram (HCD) of hydrogen and apply this tool to anticipate the energy performance of this new fuel whose PCS exceeds its PCI by 18%. These expectations also concern the case of gas turbines in the case of wet combustion which, moreover, are, a priori, highly consuming additional water. The formation of atmospheric water plumes, the "cost" of its elimination, the possible residual pollution due to NOx are also presented, this concerning the use of hydrogen fuel in all thermal combustion machines, including in fuel cells. All applications combined and in a cogeneration context, wet combustion, of which the so-called “water vapor pump” cycle is part, increases the dew point temperature of the combustion products by approximately 10°C and promotes useful energy recovery. approaching 100% of the higher calorific value of the fuel (100% of the PCS). What is to be emphasized with hydrogen fuel.

The exponential growth in the use of digital technology is forcing changes in the engineering of material and energy transformation processes, not only in terms of training, but also in terms of inventions of various origins, to revitalize this discipline, which is subject to strong environmental constraints. This near-breakthrough situation needs to be translated into greater creativity before we can achieve breakthrough or incremental innovations. To achieve this objective, it is sometimes useful to bring together two normally disjoint fields to generate ideas that are robust enough to be applied. This article discusses this method, based on biomimicry. Can taking advantage of nature’s ingenuity foster the emergence of anthropocentric inventions and thus accelerate innovation in the field of process engineering? This is the question posed by the authors in their quest to illustrate the opportunities and advantages of such an approach, as well as its current limitations.

A look at the curricula of many French engineering schools reveals that their global vision is reflected in educational categories geared towards theoretical, rational and deterministic generalist learning, with a focus on the main application targets. Links with industry are developed in large part through internships, which broaden the somewhat closed vision provided by their school. This situation has its roots in history, with the need to master mathematical models to design structures, weapons, bridges, factories, material and energy transformation processes, and so on. What we are witnessing is the decline of technological eras from coal to electricity to electronics, with an increasingly constrained environment and demands for ever more sophisticated devices, with ever shorter life spans, in a changing social context. The question posed in this reflection is to analyze whether the impact of the major trends we have just mentioned is likely to call into question, at least in part, the fundamentals of current training courses. What we are showing is the importance of rigorous concepts, which must nevertheless be extended in different ways to other fields, promoting creativity, imagination and agility to bring the engineer’s work closer to the social demand for new needs. For the time being, the authors see this as a flexible/adaptive approach that should encourage creative modes on the part of students, the mastery of doubt, interdisciplinarity and the management of complexity in the development of industrial processes.

The analysis of very irregular processes is often based on the search for a trend, an average curve representing the general course of the observed phenomenon. If each people is more or less capable of drawing such a curve freehand, in an intuitive way, its objective determination is very delicate. The method of moving averages being one of the most used in the search for trends, we propose here to study some properties of these moving averages (essentially mean and variance, or standard deviation). We then show that they can be used to detect characteristic observation windows, leading to structural trends of the analyzed signal. The notion of tau-average (trend obtained by a moving average with a variable window) is also re-examined.