Marco Cartesegna

Thermodynamic analysis of elastic systems

Abstract The purpose of this paper is firstly a general analysis of piezoelectric elastic systems with constant volume, to which one can apply an equation of the kind f ( L , Φ , q , T )=0 with three independent variables. Subsequently, one deals with a more detailed analysis of elastic systems without piezoelectric effects with two independent variables in an equation of the kind f ( L , Φ , T )=0 analogous to the relation f ( p , v , T )=0 that is valid for fluid systems. In addition, a system with variable volume and, thus, depending on four independent state functions is synthetically examined.

Thermodynamic analysis of heat transformers employing thermal sources and sinks of finite capacity

The problem of using low-level energies is a general one, in the light of the amount of thermal waste in numerous sectors. It is important both in the utilization of new energy sources available in thermal form (e.g., low enthalpy geothermal and solar energies) and in large-size works. Upgrading low-level energy can be achieved either by means of absorption and resorption cycles or by heat transformers or by their combinations. In this paper, after a definition of heat transformers, all the types of existing or thermodynamically possible heat transformers are considered by means of a suitable diagram; besides, the relative entropy production and the exergy efficiency, defined in another paper, are determined for various of the above devices operating with thermal sources and sinks of finite capacity. In addition, a new absorption heat transformer cycle using a partially miscible mixture is synthetically described.

The measurement of interface velocity in solid–liquid slugging fluidised beds

Abstract A new experimental apparatus based on conductivity measurements has been developed to measure liquid and solid phase volume fractions in fluidised suspensions. The device provides a measurement of the instantaneous values of volume fractions: this characteristic has been used here to estimate the velocity at which voidage discontinuities travel in a solid–liquid slugging fluidised suspension. The proposed method is based on the analysis of the rate of change of the electrical signal collected from various sensors placed along the fluidising column. The present work has verified the applicability of the new algorithm; measured voidage discontinuity velocities (i.e. the velocity of the interface separating dense and lean regions in the slugging suspensions) are reported and discussed in the light of existing fluid dynamic theories on the behaviour of such suspensions.

Thermodynamic analysis of fluids with the possible presence of chemical reactions

Abstract Chemically reacting systems with three independent state functions are systematically examined with a mathematical tool with some differences from the usual one. The thermodynamic relations for the usual fluids depending upon two state functions are obtained as a particular case in the absence of the chemical state function. Fluids which obey the relation (V=KVf(p/T)), formally similar to Curies law for magnetic systems, are also investigated. Quasi-static irreversible processes with uniform intensive properties are considered.

Energy Efficiency: Technical Feasibility, Compatibility, Energy Balance

The definition of strategies for improving energy performance of historical buildings compares instances of different nature. Among the variety of techniques and technologies available on the market or under scientific development, must be selected those considered more compatible and less invasive with the architectural features to be preserved. The text, specifically focused on the feasibility study on the monumental historical complex of the Albergo dei Poveri in Genoa, provides an assessment of the advantages, in terms of energy gains, which may be obtained by applying some passive techniques. It is also investigated the possibility to insert this building and its surroundings in a grid net, through cogeneration (n. 2 gas micro-turbines) and insertion of photovoltaic glass on the roofs of the greenhouses in the green valley, in order to balance energy production with energy needs or to connect to a net system.

Thermal Behaviour and Energy Demand

The chapter describes the first part of a feasibility study aimed at improving the thermal behaviour of the monumental historical complex of the Albergo dei Poveri in Genoa, chosen as a case study. The general masterplan for the complete recovery of the building primarily involves the definition of new uses (university pole for humanities), compatible with its architectural characters. A second phase consists in the calculation of transmittance values of transmittance of external walls and other dispersing elements, especially at the level of the top floor. According to these kinds of data (new uses and thermal behaviour) are then calculated the energy needs, thermal power for heating and sanitary water, electricity for illumination, other equipment, and cooling of several rooms. As a result of this first stage is a reliable calculation of the total energy requirement needed for the complete reuse of the building.

Complex Energy Systems Exploiting Solar Energy and Natural Gas Vaporization

The fossil fuel reserves are limited. In addition, usable energy supply has a considerable impact on the environment, even if some effects, which are usually alleged, are far from being fully established. Natural gas is often found in remote locations far from developed industrial nations. Where possible, the gas is transported by pipeline to the end user. However, where oceans separate the gas source and the user, or there are other difficulties, the only viable way to transport the gas is to convert it into liquid natural gas (LNG) and to convey it using insulated LNG tankers. This paper outlines the results of an examination of a complex system, employing solar energy, for the production of electrical energy and the vaporization and superheating of LNG. It is to be remarked that, differently from the usual combined systems, both the thermal source and the thermal sink are exergy sources.Copyright