Article

# “Performance Representation of Variable-speed Compressor for Inverter Air Conditioners Based on Experimental Data

Department of Building Science, Tsinghua University, Beijing, 100084, China
(Impact Factor: 2.24). 12/2004; 27(8):805-815. DOI: 10.1016/j.ijrefrig.2004.02.008

ABSTRACT

Variable speed control of compressors is one of the best methods to regulate the capacity of heat pumps and air conditioners. An analysis is conducted for modeling the variable speed compressor for simulation of inverter air conditioner and heat pump. Having scattered the real operation performance of inverter compressor into infinite operation performance of constant speed compressor, the map-based method is utilized to fit the performance curves of inverter compressor. The model is built at the basic frequency and the map condition as the second-order function of condensation temperature and evaporation temperature. Then it is corrected by the compressor frequency as the second-order function of frequency and by the actual operating condition as the actual specific volume of the suction gas. This method is used to set up simulation models of three different compressors. Compared with the data provided by the compressor manufacturers, the average relative errors are less than 2, 3 and 4% for refrigerant mass flow rate, compressor power input and coefficient of performance (COP), respectively. This model of variable speed compressor is suitable for the simulation of inverter air conditioner and heat pump systems. Based on the experimental data and simulation model, the frequency at zero mass flow rate and power input at zero frequency are discussed and the relation between COP and compressor frequency is analyzed.

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• "These models are however highly nonlinear, require a large number of state variables and are thus too complex for incorporation in an optimal control formulation. An alternative is to represent the heat pump characteristics by polynomial fits based on experimental data (see e.g., Gayeski 2010, Shao et al. 2004). This approach has been adopted here. "
##### Article: Multi-objective optimal control of an air-to-water heat pump for residential heating
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ABSTRACT: The current study investigates the optimal operation of an air-to-water heat pump system. To this end, the control problem is formulated as a classic optimal control or dynamic optimization problem. As conflicting objectives arise, namely, minimizing energy cost while maximizing thermal comfort, the optimization problem is tackled from a multi-objective optimization perspective. The adopted system model incorporates the building dynamics and the heat pump characteristics. Because of the state-dependency of the coefficient of performance (COP), the optimal control problem (OCP) is nonlinear. If the COP is approximated by a constant value, the OCP becomes convex, which is easier to solve. The current study investigates how this approximation affects the control performance. The optimal control problems are solved using the freely available Automatic Control And Dynamic Optimization toolkit ACADO. It is found that the lower the weighting factor for thermal discomfort is, the higher the discrepancy is between the nonlinear and convex OCP formulations. For a weighting factor resulting in a quadratic mean difference of 0.5°C between the zone temperature and its reference temperature, the difference in electricity cost amounts to 4% for a first scenario with fixed electricity price, and up to 6% for a second scenario with a day and night variation in electricity price.
Building Simulation 09/2012; 5(3). DOI:10.1007/s12273-012-0061-z · 1.03 Impact Factor
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• "A number of studies has been conducted on the coefficient of performance (COP) of ACs. Shao et al. pointed out that the COP of an inverter AC is highly influenced by its compressor frequency (Shao et al. 2004). Yu and Chan found that the highest COP of air-cooled centrifugal chillers occurs at a part load ratio of 0.71-0.84 "
##### Conference Paper: Development of energy performance comparison method for residential electric appliances

10th IEA Heat Pump Conference, Tokyo, Japan; 01/2011
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##### Article: Optimisation des performances non nominales des pompes à chaleur réversibles pour le secteur tertiaire
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ABSTRACT: L'optimisation des performances non nominales des pompes à chaleur réversibles contribue à la réduction des consommations énergétiques du secteur tertiaire. Une modélisation thermodynamique détaillée d'une pompe à chaleur destinée au secteur tertiaire (compresseur, condenseur, détendeur, évaporateur) en régime non nominal est réalisée. Le modèle de pompe à chaleur validé par expérimentation en laboratoire et in-situ est couplé à un modèle de calcul des besoins thermiques de bâtiment afin d'évaluer les performances saisonnières de la PAC et d'améliorer la conception en fonction de ce critère. Des voies d'optimisation des performances saisonnières sont évaluées suivant deux axes principaux : -Optimum du point de vue local : optimisation par rapport à une courbe de besoins donnée ; interviennent la régulation de puissance, la conception orientée mode chaud ou orientée mode froid. Ces simulations sont réalisées sur un bâtiment tertiaire de type neuf ou existant. Une étude de sensibilité des résultats au climat du lieu d'installation est également réalisée. -Optimum du point de vue industriel : par l'intégration de composants innovants à fort enjeu concurrentiel pour un bon positionnement vis-à-vis de l'étiquetage européen des systèmes de climatisation. Les améliorations de performance sont complétées par une étude technico-économique, basée sur la décomposition des coûts de la PAC selon ses principaux composants. On détermine finalement le temps de retour de la machine optimisée en fonction du type de bâtiment et du climat.
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