Investigación

 

Heating load, COP, exergy loss rate, exergy output rate and ecological optimizations for a class of generalized irreversible universal heat pump cycles

 

Lingen Chen*, Huijun Feng, and Fengrui Sun

 

Postgraduate School, Naval University of Engineering, Wuhan 430033, P.R. China.

 

Recibido el 23 de febrero de 2010
Aceptado el 29 de junio de 2010

 

Abstract

The optimal performance of a class of generalized irreversible universal steady flow heat pump cycle model, which consists of two heat–absorbing branches, two heat–releasing branches and two irreversible adiabatic branches with the losses of heat–resistance, heat leakage and internal irreversibility is analyzed by using finite time thermodynamics. The analytical formulae about heating load, coefficient of performance (COP), exergy loss rate, exergy output rate and ecological function of the universal heat pump cycle are derived. Moreover, performance comparisons among maximum COP condition, a given exergy output rate condition and maximum ecological function condition are carried out by using numerical examples. It is shown that the ecological function objective is an excellent candidate objective with the ideal of an ecological and long–term goal. The effects of heat leakage and internal irreversibility on the cycle performance are discussed. The universal cycle model gives a unified description of seven heat pump cycles, and the results obtained include the performance characteristics of Brayton, Otto, Diesel, Atkinson, Dual, Miller and Carnot heat pump cycles with the losses of heat–resistance, heat leakage and internal irreversibility.

Keywords: Finite time thermodynamics; irreversible universal heat pump cycle; heating load; COP; exergy loss rate; exergy output rate; ecological function.

 

Resumen

Se analiza el funcionamiento óptimo de una clase de modelo universal irreversible generalizado del ciclo de una bomba térmica de flujo constante, que consiste en dos ramas de absorción térmica, dos ramas de liberación de calor y dos ramas adiabáticas irreversibles con pérdidas de resistencia al calor, de salida del calor y de irrevocabilidad interna, usando la termodinámica de tiempos finitos. Se obtienen las fórmulas analíticas de la carga de calor, del coeficiente del funcionamiento (CF), del índice de pérdida de exergía, del índice de salida de exergía, así como de la función ecológica del ciclo universal de la bomba de calor. Por otra parte, se compara el funcionamiento de la condición máxima del CF dada una condición de razón de salida de exergía con la condición del máximo de la función ecológica usando ejemplos numéricos. Se demuestra que el objetivo de la función ecológica es un excelente de candidato para el ideal de una meta ecológica y de largo plazo. Se discuten los efectos del escape de calor y de la irreversibilidad interna sobre el funcionamiento del ciclo. El modelo universal del ciclo da una descripción unificada de siete ciclos de la bomba de calor, y los resultados obtenidos incluyen las características de funcionamiento de los ciclos de Brayton, de Otto, Diesel, Atkinson, Dual, Miller y Carnot para bombas térmicas con pérdidas de la resistencia al calor, del escape de calor y de irreversibilidad interna.

Descriptores: Termodinámica de tiempos finitos; ciclo irreversible universal de bomba térmica; carga térmica; tasa de pérdida de exergía; tasa de salida de exergía; función ecológica.

 

PACS: 44.10.+i;44.40.+a

 

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Acknowledgments

This paper is supported by The National Natural Science Foundation of P.R. China (Project No. 10905093), the Program for New Century Excellent Talents in University of P.R. China (Project No. 20041006) and The Foundation for the Author of National Excellent Doctoral Dissertation of P.R. China (Project No. 200136). The authors wish to thank the reviewers for their careful, unbiased and constructive suggestions, which led to this revised manuscript.

 

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