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...

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In this paper, performance analysis of a hybrid photovoltaic-thermal (PV/T) greenhouse air heater and dryer has been carried out. Analytical expressions have been developed for • greenhouse air temperature, instantaneous and overall energy and exergy efficiencies for without load and • instantaneous exergy efficiency with load under forced mode operation. An experimental validation has been car...

In this paper, an attempt has been made to obtain nonsensitive solutions in the multi-objective optimization of a photovoltaic/thermal (PV/T) air collector. The selected objective functions are overall energy efficiency and exergy efficiency. Improved thermal, electrical and exergy models are used to calculate the thermal and electrical parameters, overall energy efficiency, exergy components a...

The performance and design criteria of air powered multistage turbines are studied thermodynamically in this paper. In-house code is developed in the C++ environment and the characteristics of four-stage turbines with inter-heating are analyzed in terms of maximum thermal efficiency, maximum exergy efficiency and maximum work output over the inlet temperature range of 293 K–793 K with inlet pre...

Cascaded thermal storage, consisting of multiple Phase Change Materials (PCMs) with different melting temperatures, has been proposed to solve the problem of poor heat transfer caused by unavoidable decrease of temperature differences during heat exchange process. This paper conducts a theoretical study of the overall thermal performance for a cascaded thermal storage system. Both heat transfer...

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...

Metal Foam-enhanced Cascaded Thermal Energy Storage (MF-CTES) has been proposed to solve the problem of poor heat transfer during heat exchange process, which is caused by unavoidable decrease of temperature differences. This paper conducts a theoretical study examining the overall thermal performance of STES (Single-stage Thermal Energy Storage), CTES (Cascaded Thermal Energy Storage) and MF-C...

Tubular solar thermal receivers suitable for central towers are modelled using energy and exergy analysis, in a way that allows individual inspection of the the irreversibilities associated with the various receiver heat transfer processes occurring. The model was used to compare the behaviour of four working fluids: molten salt (NaNO3/KNO3), liquid sodium metal, supercritical carbon dioxide, a...

In this work, energy and exergy analyses are carried out for a combined cycle consisting of an organic Rankine cycle (ORC) and a liquefied natural gas (LNG) Rankine cycle for the recovery of low-grade heat sources and LNG cold energy. The effects of the turbine inlet pressure and the working fluid on the system performance are theoretically investigated. A modified temperature-enthalpy diagram ...