A review of recent advancements of variable refrigerant flow air-conditioning systems

Wan, Hanlong; Cao, Tao; Hwang, Yunho; Oh, Saikee

doi:10.1016/j.applthermaleng.2019.114893

Cited by 47 publications

(22 citation statements)

References 109 publications

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“…A key aspect of the condenser fan speed optimization is the VCS modeling, which can be separated into black box and component-based [9]. While black box models use a set of data to characterize the system, component-based models consider physical aspects for describing each component of the system.…”

Section: Optimization Of the Condenser Fan Speed Controlmentioning

confidence: 99%

“…Furthermore, component-based models can be subdivided regarding the heat exchanger modeling into empirical, distributed, moving boundary, and hybrid or lumped models [10,11]. An overview of steady-state VCS modeling is given by Wan et al [9] and Zhang et al [12]. The VCS models are usually assessed on the basis of the prediction accuracy of the coefficient of performance (COP).…”

Section: Optimization Of the Condenser Fan Speed Controlmentioning

confidence: 99%

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Model-Based Condenser Fan Speed Optimization of Vapor Compression Systems

Angermeier

Karcher

2020

Energies

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Vapor compression systems (VCS) cover a wide range of applications and consume large amounts of energy. In this context, previous research identified the optimization of the condenser fans speed as a promising measure to improve the energy efficiency of VCS. The present paper introduces a steady-state modeling approach of an air-cooled VCS to predict the ideal condenser fan speed. The model consists of a hybrid characterization of the main components of a VCS and the optimization problem is formulated as minimizing the total energy consumption by respectively adjusting the condenser fan and compressor speed. In contrast to optimization strategies found in the literature, the proposed model does not relay on algorithms, but provides a single optimization term to predict the ideal fan speed. A detailed experimental validation demonstrates the feasibility of the model approach and further suggests that the ideal condenser fan speed can be calculated with sufficient precision, assuming constant evaporating pressure, compressor efficiency, subcooling, and superheating, respectively. In addition, a control strategy based on the developed model is presented, which is able to drive the VCS to its optimal operation. Therefore, the study provides a crucial input for set-point optimization and steady-state modeling of air-cooled vapor compression systems.

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Section: Optimization Of the Condenser Fan Speed Controlmentioning

confidence: 99%

Section: Optimization Of the Condenser Fan Speed Controlmentioning

confidence: 99%

Model-Based Condenser Fan Speed Optimization of Vapor Compression Systems

Angermeier

Karcher

2020

Energies

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“…It is essential to select the most appropriate air conditioning system so that it can be used efficiently during its life cycle, keeping in mind that the energy sources are becoming scarcer around the world. One of the approaches that is worth considering is the usage of variable refrigerant flow systems (VRF) [5]. The indoor units of the air conditioning system in Qatar consists of constant air volume (CAV) and variable air volume (VAV).…”

Section: Introductionmentioning

confidence: 99%

“…The electronic expansion valve (EEV) plays an important role in regulating the refrigerant flow rate through the heat exchanger of the indoor unit, while the inverter-driven variable speed compressors allow for a larger modulation capacity considering part load factors in the VRF systems. The VRF system allows each IU to be controlled independently and does not lose too much energy through ductwork like conventional systems [5]. Such VRF systems have been used widely in Japan since the 1980s and in the U.S. since 2002 [5].…”

Section: Introductionmentioning

confidence: 99%

Comparison between Variable and Constant Refrigerant Flow Air Conditioning Systems in Arid Climate: Life Cycle Cost Analysis and Energy Savings

Atallah

Tarlochan

2021

Sustainability

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All over the world, there is a call to encourage sustainable energy thinking and implementation. There is an urgent need to consider sustainable solutions in any design projects that are able to reduce energy consumption. In the heating, ventilation, and air conditioning field, the rise of the variable refrigerant flow systems has made big progress. This study presents a life cycle cost analysis to evaluate the economic feasibility of constant refrigerant flow (CRF), and in particular, the conventional ducted unit air conditioning system and the variable refrigerant flow (VRF) system by using detailed cooling load profiles, as well as initial, operating, and maintenance costs. Two operating hours scenarios are utilized and the present worth value technique for life cycle cost analysis is applied to an existing office building located in Qatar, which can be conditioned by CRF and VRF systems. The results indicate that, although the initial cost of the VRF system is higher than that of the CRF system by 23%, the present worth cost of the VRF system is much lower than that of the CRF system at the end of the lifetime due to lower operating costs. There is also a significant energy saving of 27% by using VRF compared to the CRF. The implementation of these results on a national scale will promote the use of sustainable energy technologies such as the VRF system.

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“…Compressors are widely applied in commercial and residential air-conditioning, refrigeration and heat pump applications because they offer continuous control, low noise level, reduced vibration, low start current. The initial high-speed operation of the compressor can quickly control the temperature and obtain better performance coefficient (COP) than conventional on/off control [1]- [3]. To define the best control strategy and improve the efficiency of refrigeration systems, it is necessary to develop a simple and accurate model of the compressor, which plays an important role in the refrigerant system.…”

Section: Introductionmentioning

confidence: 99%

A Hybrid Steady-State Compressor Model for Real-Time Applications in Performance Monitoring, Control and Optimization

et al. 2021

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In this study, a hybrid steady-state compressor model is proposed that can be used in the realtime performance monitoring, control and optimization of the vapor compression cycle. In the proposed model, first, a detailed analysis of the mass flow rate is presented, which is based on the volumetric efficiency concept and the assumption of a polytropic compression process. Then, discharge temperature of the refrigerant and power consumption of the compressor are also investigated. Three semiempirical models are constructed respectively. Further, to tune the unknown empirical parameters of the models, a social learning particle swarm optimization (SLPSO) algorithm is developed by using the real-time experimental data. An experimental apparatus of a refrigerant system is tested to validate the proposed models. The experimental results demonstrate that the proposed models accurately predict the performance of real-time operating compressors. Meanwhile, the models identified by the SLPSO algorithm are more accurate than those identified by the traditional least-squares method.INDEX TERMS Compressor, hybrid modeling, control, parameter identifications, social learning particle swarm optimization.

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A review of recent advancements of variable refrigerant flow air-conditioning systems

Cited by 47 publications

References 109 publications

Model-Based Condenser Fan Speed Optimization of Vapor Compression Systems

Model-Based Condenser Fan Speed Optimization of Vapor Compression Systems

Comparison between Variable and Constant Refrigerant Flow Air Conditioning Systems in Arid Climate: Life Cycle Cost Analysis and Energy Savings

A Hybrid Steady-State Compressor Model for Real-Time Applications in Performance Monitoring, Control and Optimization

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