Energy-efficient HVAC systems: Simulation–empirical modelling and gradient optimization

Vakiloroaya, Vahid; Ha, Q.P.; Samali, Bijan

doi:10.1016/j.autcon.2012.12.006

Cited by 40 publications

(21 citation statements)

References 22 publications

(20 reference statements)

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“…As a result, many previous studies have investigated the influence of various technologies on the compressor performance to enhance the operating and energy efficiency of vapour compression refrigeration systems [5]. However, compared with a water-cooled air conditioning system, air-cooled cycles are less energy-efficient.…”

Section: Introductionmentioning

confidence: 99%

Energy-Efficient Air-Cooled DX Air-Conditioning Systems with Liquid Pressure Amplification

Vakiloroaya¹,

Ha²

2014

Proceedings of the International Symposium on Automation and Robotics in Construction (IAARC)

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-The objective of this study is to explore an optimal strategy on energy consumption for a direct expansion (DX) air-conditioning system by using a refrigerant pump in the liquid line to allow the system to operate at a lower condensing pressure. An existing DX rooftop package of a commercial building located in a hot and dry climate zone is used for data collection. The theoretical-empirical modelling approach is used to obtain system model, from which the proposed strategy is formulated. A numerical algorithm is developed to analyse the system transient performance, using an iterative loop. As a minimum pressure differential is required across the expansion device, liquid pressure amplification (LPA) devices can be used on DX systems that operate with fixed head pressure control. They can be fitted to new or existing systems. Results show that the LPA approach is more effective when the ambient temperature is falling, with electricity saving around 25.3% in average.

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Section: Introductionmentioning

confidence: 99%

Energy-Efficient Air-Cooled DX Air-Conditioning Systems with Liquid Pressure Amplification

Vakiloroaya¹,

Ha²

2014

Proceedings of the International Symposium on Automation and Robotics in Construction (IAARC)

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“…Component-wise mathematical models are coded into the fully integrated visual interface known as TRNSYS simulation studio using FORTRAN for the validation purpose, combining the simulation 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 13 prediction and experimental monitoring approach, as adopted in [5]. Under the real world condition, there are many factors that influence on the system.…”

Section: Simulation-experimental Validationmentioning

confidence: 99%

Modeling and experimental validation of a solar-assisted direct expansion air conditioning system

Vakiloroaya

Skibniewski

2013

Energy and Buildings

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Continuous increase in global electricity consumption, environmental hazards of pollution and depletion of fossil fuel resources have brought about a paradigm shift in the development of ecofriendly and energy-efficient technologies. This paper reports on an experimental study to investigate the inherent operational characteristics of a new direct-expansion air conditioning system combined with a vacuum solar collector. Mathematical models of the system components are firstly derived and then validated against experimental results. To investigate the potential of energy savings, the hybrid solar-assisted air-conditioner is installed and extensively equipped with a number of sensors and instrumentation devices, for experimentation and data collection. The influence on the system energy usage of the average water temperature, storage tank size and room set-point temperature are then analyzed. Once the air-conditioned room has achieved its desired temperature, the compressor turns off while the cooling process still continues until the refrigerant pressure no longer maintains the desired temperature. The advantages of the proposed hybrid system rest with the fact that the compressor can remain off in a longer period by heat impartation into the refrigerant via the water storage tank. Results show an average monthly energy saving of about between 25% and 42%. AbstractContinuous increase in global electricity consumption, environmental hazards of pollution and depletion of fossil fuel resources have brought about a paradigm shift in the development of ecofriendly and energy-efficient technologies. This paper reports on an experimental study to investigate the inherent operational characteristics of a new direct-expansion air conditioning system combined with a vacuum solar collector. Mathematical models of the system components are firstly derived and then validated against experimental results. To investigate the potential of energy savings, the hybrid solar-assisted air-conditioner is installed and extensively equipped with a number of sensors and instrumentation devices, for experimentation and data collection. The influence on the system energy usage of the average water temperature, storage tank size and room set-point temperature are then analyzed. Once the air-conditioned room has achieved its desired temperature, the compressor turns off while the cooling process still continues until the refrigerant pressure no longer maintains the desired temperature. The advantages of the proposed hybrid system rest with the fact that the compressor can remain off in a longer period by heat impartation into the refrigerant via the water storage tank. Results show an average monthly energy saving of about between 25% and 42%.Keywords: energy saving, solar-assisted air conditioner, modeling, experimental validation, performance prediction. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47...

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“…Therefore, the optimum set-points for the refrigerant temperature entering the condenser should lower the refrigerant temperature leaving the condenser and, in turn, increase system overall COP. In principle, a proper control strategy for the refrigerant temperature entering the condenser can lead to more energy-efficient operations [Vakiloroaya et al, 2013]. To achieve this, an appropriate modification should be applied to adapt the plant with changing operational conditions caused by a transient cooling load and varying ambient conditions.…”

Section: Introductionmentioning

confidence: 99%

Development of a New Energy-Efficient Hybrid Solar-Assisted Air Conditioning System

Vakiloroaya¹,

Ismail²,

Ha³

2013

Proceedings of the 30th International Symposium on Automation and Robotics in Construction and Mining (ISARC 2013): Building Th

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The paper aims at developing a hybrid solar-assisted air conditioner system for performance enhancement and energy efficiency improvement. To increase sub-cooling of the refrigerant at partial loads, we propose a new discharge bypass line together with an inline solenoid valve, installed after the compressor to regulate the mass flow rate of the refrigerant vapour passing through a hot water storage tank. For control design, a lumped parameter model is first developed to describe the dynamics of the system in an explicit form of input-output relationship. The system has been fully-instrumented to examine its performance under different operation conditions. The system model is then validated by extensive experimental tests. The predictions from the models exhibit a good coincidence with experimental results, judging by an RMS error less than 15%. Based on the obtained dynamic model, a linear quadratic regulator (LQR) is applied to optimize a cost function of the output errors and control efforts. The key challenge is to regulate the refrigerant temperature entering the condenser by controlling the valve opening. The design approach is then tested in a transient simulation tool to predict the system performance in transient conditions. The experimental results obtained from implementation with PLC demonstrate that the proposed system delivers higher system efficiency owing to the higher refrigeration effect in the direct expansion evaporator. Thus, the novel development is promising for improvement of energy efficiency, enhancement of the system performance while fulfilling the cooling demand. Consequently, between 25 and 43% of monthly electricity can be saved on average.

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Energy-efficient HVAC systems: Simulation–empirical modelling and gradient optimization

Cited by 40 publications

References 22 publications

Energy-Efficient Air-Cooled DX Air-Conditioning Systems with Liquid Pressure Amplification

Energy-Efficient Air-Cooled DX Air-Conditioning Systems with Liquid Pressure Amplification

Modeling and experimental validation of a solar-assisted direct expansion air conditioning system

Development of a New Energy-Efficient Hybrid Solar-Assisted Air Conditioning System

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