Search results for "Thermoeconomic"

On the reliability of thermoeconomic diagnosis of fouled evaporators: assessing the influence of geometries, operating conditions and reference state

2015

Thermoeconomic diagnosis of refrigeration systems is a pioneeristic approach, which has been proven to achieve good performances (under favorable conditions) for the detection of specific faults such as condenser and evaporator fouling and compressor valve leakage. In this paper the sensitivity of performance in detecting fouled Direct Expansion (DX) coils is investigated; the examined parameters are the temperature and relative humidity of coil inlet air and the sensible/latent heat ratio of the coil (varied by considering different numbers of rows). As the thermoeconomic model requires splitting the specific exergy of cooling air into “mechanical”, “thermal” and “chemical” fractions, and …

SETUP OF VIRTUAL EXPERIMENTS AND CRITICAL ANALYSIS OF CONVENTIONAL THERMOECONOMIC DIAGNOSIS OF MULTIPLE FAULTS IN AIR-CONDENSED ROOFTOP SYSTEMS

2012

The diagnosis of soft faults in vapor compression cooling systems is a crucial activity, since malfunctions may provoke heavy degradation in plant performance and increase the power consumption for space cooling. Among the various Faults Detection and Diagnosis techniques developed over the last two decades, thermoeconomic diagnosis has been playing only a marginal role due to the difficulties encountered when applying the conventional thermoeconomic approaches to vapor compression refrigeration plants. In this paper a critical analysis on capabilities and limits of thermoeconomic diagnosis of refrigeration systems is proposed. The reference plant assumed for this study is a 116 kWc air-con…

Formation structure of optimality by thermoeconomics: disassembling thermodynamic and external influences in energy systems’ design

2009

In this paper an original thermoeconomic approach for the optimization of complex energy systems is presented, based on a revitalized concept of “scope”, and therefore indicated as Scope Oriented Thermoeconomics (SOT). In plants including dissipative components, it allows to formulate non-arbitrary allocation criteria as concerns marginal costs; consequently, the optimization process is disassembled to recognize the Formation Structure of Optimality, i.e. the specific influences of thermodynamic and economic parameters in the path toward the optimal design. The method is applied to a very didascalic example, that is the optimization of the condensation temperature in a vapour compression ch…

INNOVATIVE APPLICATIONS OF EXERGY ANALYSIS AND THERMOECONOMICS IN CHEMICAL, THERMAL AND COOLING ENERGY CONVERSION SYSTEMS

Since 70s, the world has been becoming more and more concerned about energy and environmental issues. The need of meeting the current energy demand by guaranteeing the ability of future generation to satisfy theirs have been pushing research not only to exploit alternative energy sources such as renewable energies, but also to improve the efficiency of energy conversion systems. To this regard, developing systems that use efficiently energy is of paramount importance especially in those countries which rely on non-renewable energy sources such as oil, natural gas, and coal. In fact, the reduction of energy consumption will lead not only to the saving of unrestorable and limited energy resou…

Advanced energetics of a Multiple-Effects-Evaporation (MEE) desalination plant. Part II: Potential of the cost formation process and prospects for en…

2010

This paper represents the 2nd part of a paper in two parts. In part I a 2nd Principle analysis of a Multiple- Effects-Evaporation (MEE) process has been proposed. In this Part II perspectives for process improvement will be investigated, along two distinct research lines: the thermoeconomics-aided optimization of a new system and the increase of thermal efficiency for existing systems by a pinch-based plant retrofit. As concerns the first research line, a detailed productive structure for the plant stage (i.e. effect) examined in Part I is presented; the cost formation structure is then used to improve a simplified optimization process, revealing capable to properly reflect the interactions…

Optimal design of cogeneration plants for seawater desalination

2004

Multi-stage flash (MSF) and reverse osmosis (RO) are the most common techniques for seawater desalination. A significant difference between these methodologies consists of their different energy requirements, i.e., thermal energy for MSF and mechanical energy for RO plants. The presence of both desalination systems (MSF and RO) appears to be suitable for cogeneration plants. The reject heat from the power cycle can feed an MSF section, while some power feeds the RO section and the MSF auxiliary equipment; the rest is sold to the grid. A criterion for the optimal design of such tri-functional cogeneration plants is proposed, based on exergo-economics and on profit maximization. In particular…

Criteri e metodi per l'ottimizzazione di sistemi di poligenerazione di piccola e media taglia - Criteria and methodologies for the optimization of sm…

2011

L'Unione Europea ha individuato nella produzione combinata di energia elettrica e calore una delle tecnologie ad alta efficienza di maggior interesse, fissando per il 2010 il target del 18% della produzione elettrica totale dell'Unione da sistemi cogenerativi (COM/97/0514). Dati recenti rivelano la non attualità di tale target (al 2005 si è raggiunto il 12% di penetrazione); rimane tuttavia evidente la volontà, esistente sia a livello comunitario che in molti Stati Membri, di perseguire la via della promozione della poligenerazione. Le ragioni di questo interesse sono evidenti: l'elevata efficienza di conversione garantita dal recupero dei cascami termici di un ciclo diretto consente, a par…

Critical analysis of conventional thermoeconomic approaches to the diagnosis of multiple faults in air conditioning units: Capabilities, drawbacks an…

2013

Abstract Faults diagnosis in air conditioning systems is a crucial activity, since malfunctions may induce heavy degradation of performance. Among the available techniques, thermoeconomic diagnosis has played a marginal role due to the difficulties encountered when applying the methodology to refrigeration plants. In this paper a critical analysis on capabilities and limits of thermoeconomic diagnosis is proposed. The reference plant is a 120 kWc air-cooled air conditioning system; a simulator is used to evaluate thermodynamic data under normal and faulty conditions, setting up “virtual experiments” to simulate each fault. Five malfunctions are imposed, either individually or simultaneously…

Assessing the Robustness of Thermoeconomic Diagnosis of Fouled Evaporators: Sensitivity Analysis of the Exergetic Performance of Direct Expansion Coi…

2016

Thermoeconomic diagnosis of refrigeration systems is a pioneering approach to the diagnosis of malfunctions, which has been recently proven to achieve good performances for the detection of specific faults. Being an exergy-based diagnostic technique, its performance is influenced by the trends of exergy functions in the “design” and “abnormal” conditions. In this paper the sensitivity of performance of thermoeconomic diagnosis in detecting a fouled direct expansion coil and quantifying the additional consumption it induces is investigated; this fault is critical due to the simultaneous air cooling and dehumidification occurring in the coil, that induce variations in both the chemical and th…

A novel solar-geothermal trigeneration system integrating water desalination: Design, dynamic simulation and economic assessment

2016

Abstract In this paper, an innovative solar-geothermal polygeneration system is investigated. The system supplies a small community with electricity, desalinated water and space heating and cooling through a district network. The hybrid multi-purpose plant, based on an Organic Rankine Cycle (ORC) supplied by medium-enthalpy geothermal energy and by solar energy; this latter is provided by Parabolic Trough Collectors (PTC). The geothermal brine is first used to drive the ORC loop, then to provide space heating at around 85÷90 °C (in the winter), or cooling (in the summer, by means of a single-effect absorption chiller). Finally, the geothermal brine drives a Multi-Effect Distillation (MED) s…