the mechanical aspect of entropy-exergy relationship, together with the thermal aspect usually consid-ered, leads to an extended formulation of physical exergy based on both maximum useful work and maximum useful heat that are the outcome of available energy of a thermodynamic system. this approach suggests that a mechanical entropy can be studied, in addition to the already used thermal entrop...

In this paper, a comparison of exergetic models between two hot air engines (a Gamma type Stirling prototype having a maximum output mechanical power of 500 W and an Ericsson hot air engine with a maximum power of 300 W) is made. Referring to previous energetic analyses, exergetic models are set up in order to quantify the exergy destruction and efficiencies in each type of engine. The repartit...

Of evaporative cooling or energy recovery potential in HVAC, the conventional thermodynamic analysis is based on the enthalpy of moist air. In fact, the available energy of moist air is its exergy and the available energy saving potential ought to be the exergy. Isoexergic lines on psychometric charts associated with different ambient states persuade us that exergy and enthalpy are completely i...

The current method used for calculating societal aggregated exergy efficiencies is reviewed. Cooling is introduced as an end-use category; conversion efficiencies for heating processes are obtained for each energy carrier; and electricity shares per end-use are retrieved for each sector, improving the accuracy of the estimated values of aggregated exergy efficiencies. We show that: (1) cooling ...

Energy and exergy concepts come from thermodynamics laws and are applicable to all fields of science and engineering. This study considers numerical simulations of combustion of hydrogen with air in a constant pressure environment and exergy terms according to first and second laws analysis using homemade code. Chemical kinetic model includes 20 reactions and 9 species.  At the first stage of p...

The paper reviews various representations of exergy and exergy losses in energy systems going from simple heat exchanger (heat transfer, dissipation and embedded exergy) to the exergy of full energy systems from fossil or non fossil resources (including the diffusion exergy). The systems shown include shell in tube heat exchangers, thermal power cycles, cogeneration, heat pump direct heating sy...

The paper presents a comparison of various CHP system configurations, such as Vapour Turbine, Gas Turbine, Internal Combustion Engine, External Combustion Engine (Stirling, Ericsson), when different thermodynamic criteria are considered, namely the first law efficiency and exergy efficiency. Thermodynamic optimization of these systems is performed intending to maximize the exergy, when various ...

The present article is dedicated for evaluating the power generation sub-sector in terms of energetic and exergetic aspects. In this regard, energy and exergy utilization efficiencies during the period 1989-2006 are assessed based on real data obtained from main generators in Jordan. Sectoral energy and exergy analyses are conducted to study the variations of energy and exergy efficiencies for ...

The evaluation of ecosystem health is a fundamental process for conducting effective ecosystem management. Ecological exergy is used primarily to summarize the complex dynamics of lotic ecosystems. In this study, we characterized the functional aspects of lotic ecosystems based on the exergy and specific exergy from headwaters to downstream regions in the river’s dimensions (i.e., river width a...

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