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8. Evaluation of optimal subcooling in subcritical heat pump systems

Author

Universitat Politècnica de València. Departamento de Termodinámica Aplicada - Departament de Termodinàmica Aplicada, Ministerio de Economía y Competitividad, European Commission, Pitarch, Miquel, Hervas-Blasco, Estefanía, Navarro-Peris, Emilio, Gonzálvez-Maciá, José, Corberán, José M., Universitat Politècnica de València. Departamento de Termodinámica Aplicada - Departament de Termodinàmica Aplicada, Ministerio de Economía y Competitividad, European Commission, Pitarch, Miquel, Hervas-Blasco, Estefanía, Navarro-Peris, Emilio, Gonzálvez-Maciá, José, and Corberán, José M.

Abstract

[EN] The performance of a transcritical cycle is highly dependent on the rejection pressure. The optimal rejection pressure depends mainly on the inlet and outlet temperatures at the heat sink (secondary fluid). For the subcritical cycles, recent studies have demonstrated that the performance of these systems depends significantly on the degree of subcooling and its optimal value varies depending on the application. This paper presents a general methodology to calculate the optimal subcooling depending on the boundary conditions. The refrigerants R290, R134a, R1234yf and R32 are analyzed. Exergy analysis is used in order to see the subcooling effect at condenser and expansion valve independently. The optimal subcooling strongly depends on the temperature lift at the secondary fluid, and it is found when two pinch points are given in the condenser, one at the condenser outlet and another one inside the condenser (at the refrigerant dew point).

Published
2017

9. Experimental study of a heat pump with high subcooling in the condenser for sanitary hot water production.

Author

Pitarch, Miquel, Navarro-Peris, Emilio, Gonzálvez-Maciá, José, and Corberán, José M.

Subjects
*HEAT pumps, *THERMODYNAMICS, *DYNAMICS, *ENERGY consumption, *RENEWABLE energy sources
Abstract

The use of heat pumps in order to produce sanitary hot water have been demonstrated as a very efficient alternative to traditional boilers. Nevertheless, the high water temperature lift (usually from 10°C to 60°C) involved in this application has conditioned the type of used solutions. In order to overcome it, transcritical cycles have been considered as the most suitable solution. The current article analyzes a new heat pump prototype able to enhance the heat pump efficiency using a subcritical cycle. The proposed prototype is able to control the system subcooling and make it capable to work at different subcoolings in the condenser. That kind of mechanism has demonstrated its capability to increase the efficiency of the heat pump. The obtained results have shown that coefficient of performance depends strongly on subcooling. In nominal condition (inlet/outlet water temperature at evaporator is 20°C/15°C and the water inlet/outlet temperature in the heat sink is 10°C and 60°C), the optimal subcooling is 42 K with a heating coefficient of performance of 5.35, which is about 25% higher than the same cycle working without subcooling. [ABSTRACT FROM PUBLISHER]

Published
2018
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10. Cartes de poblament valencianes modernes : (segles XVI-XVIII)

Author

AAVV and AAVV

Abstract

Aquest és el primer volum d'una obra que, de manera novedosa, edita exhaustivament les cartes de població valencianes dels segles XVI-XVIII. Les cartes pobles són els documents que utilitzà el poder feudal (monarquia, noblesa laica i eclesiàstica) per a dirigir els processos de repoblament i colonització. Durant el temps de les conquestes medievals de les terres d'Al-Àndalus foren un instrument usual en el marc del que anomenem la repoblació dels segles XII al XIV, i el mateix tornà a passar en un episodi crucial i traumàtic com l'expulsió dels moriscos valencians al principi del segle XVII. Però cal tenir en compte que també foren utilitzades per la noblesa o la corona al llarg dels segles en processos més locals de fundació de noves viles i localitats, de la posada en explotació de zones no cultivades fins aleshores i, en general, per regular o modificar les condicions de poblament dels vassalls d'una senyoria concreta.

Published
2016

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