Efect of heat transfer law on the finite-time exergoeconomic performance of a Carnot refrigerator

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The Carnot engine proposed in 1824 operates on reversible process principles. As a consequence, this hypothetical engine produces the maximum possible work for a given heat source and sink temperatures, but generates zero power because it has to operate at an infinitely slow pace. Its thermodynamic efficiency, which has long been used as the standard against which all real engine efficiencies are measured, is unrealistically high. In 1975 did Curzon and Ahlborn pioneered an analysis that accounts for the irreversibilities of finite-time heat transfer to and from the engine. Such an endoreversible engine can generate useful power. Because of external irreversibilities, its efficiency at maximum power, which is termed the “finite-time thermodynamic efficiency”, is less than that of the Carnot efficiency. Since finite-time thermodynamics was first advanced in 1975, many authors have studied the effect of irreversibilities on the performance of thermodynamic processes and cycles. Some detailed literature surveys of finite-time thermodynamics were given by Sieniutycz and Salamon and Chen et al.

Some authors have assessed the effect of finite-rates of heat transfer on the performance of irreversible refrigerators.

The objective functions in finite-time thermodynamics are often pure thermodynamic parameters including power, efficiency, entropy production, effectiveness, cooling load, specific cooling load, COP and loss of exergy.

Salamon and Nitzan viewed the operation of the endoreversible heat engine as a production process with work as its output. They carried out the economic optimization of the heat engine with the maximum profit as the objective function.

A relatively new method that combines exergy with conventional concepts from long-run engineering economic optimization to evaluate and optimize the design and performance of energy systems is exergoeconomic (or thermoeconomic) analysis. Some detailed literature surveys of the exergoeconomics were given by Sieniutycz and Salamon and Tsatsaronis. Salamon and Nitzan’s work combined the endoreversible model with exergoeconomic analysis. We termed it as finite-time exergoeconomic analysis to distinguish it from the endoreversible analysis with pure thermodynamic objectives and the exergoeconomic analysis with long-run economic optimization. Similarly, we termed the performance bound at maximum profit as finite-time exergoeconomic performance bound to distinguish it from the finite-time thermodynamic performance bound at maximum thermodynamic output. Based on the work for heat engines, such a method has been extended to Newton’s Law two-heat-reservoir refrigerator and heat pump, and the three-heatreservoir refrigerator and heat pump by Chen et al.

 

 

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Enviado por Martín Vasquez