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Vakiloroaya V.,University of Technology, Sydney | Fakhar A.,University of Kashan | Samali B.,University of Technology, Sydney | Pishghadam K.,Giacomini Inc.
Journal of Renewable and Sustainable Energy | Year: 2013

This paper investigates and recommends design improvement for a central cooling plant to enhance the energy efficiency of the system. A storage tank together with an immersed heat exchanger is installed in the liquid line between the condenser and expansion valve to utilize the make-up water of the cooling tower. The heat exchanger uses the make-up water to reduce the refrigerant temperature leaving the condenser and thus enhance the refrigerant sub-cooling. For this purpose, an existing central cooling plant of a commercial building, located in a hot and dry climate region, is used for experimentation and data collection. The energy consumption and relevant data of the existing central cooling plant were acquired over the course of a typical week in summer. First, theoretical-empirical system models including mechanistic relations between components are developed. A numerical algorithm together with monitored data and mathematical model implemented on a transient system simulation tool is used to predict the performance of the new design under transient loads. The integrated simulation tool was validated by comparing predicted and measured power consumption of the central cooling plant. Comparison of the proposed system with existing cooling plant is included in this paper to demonstrate the advantages of our new configuration. Results show that about 9.7% in average and up to 14% power saving can be obtained by using our design while maintaining the comfort condition inside the building. © 2013 AIP Publishing LLC.


Vakiloroaya V.,University of Technology, Sydney | Samali B.,University of Technology, Sydney | Fakhar A.,University of Kashan | Pishghadam K.,Giacomini Inc.
Energy Conversion and Management | Year: 2014

Decreasing the energy consumption of heating, ventilation and air conditioning (HVAC) systems is becoming increasingly important due to rising cost of fossil fuels and environmental concerns. Therefore, finding novel ways to reduce energy consumption in buildings without compromising comfort and indoor air quality is an ongoing research challenge. One proven way of achieving energy efficiency in HVAC systems is to design systems that use novel configurations of existing system components. Each HVAC discipline has specific design requirements and each presents opportunities for energy savings. Energy efficient HVAC systems can be created by re-configuring traditional systems to make more strategic use of existing system parts. Recent research has demonstrated that a combination of existing air conditioning technologies can offer effective solutions for energy conservation and thermal comfort. This paper investigates and reviews the different technologies and approaches, and demonstrates their ability to improve the performance of HVAC systems in order to reduce energy consumption. For each strategy, a brief description is first presented and then by reviewing the previous studies, the influence of that method on the HVAC energy saving is investigated. Finally, a comparison study between these approaches is carried out. © 2013 Elsevier Ltd. All rights reserved.


Vakiloroaya V.,University of Technology, Sydney | Samali B.,University of Technology, Sydney | Fakhar A.,University of Kashan | Pishghadam K.,Giacomini Inc.
Building Simulation | Year: 2014

In this paper, the optimization-simulation approach is proposed to investigate energy saving potential of an air-cooled direct expansion rooftop package air conditioning system by refining the model of the HVAC system components and deriving optimal configuration for evaporator coil subject to technical constraints. In this method the frontal area of the evaporator coil is maintained as constant and the variation of other geometrical parameters on the thermal and economical performance of the system is investigated. An actual air-cooled rooftop package of a real-world commercial building in hot and dry climate conditions is used for experimental data collection. Both inputs and outputs are measured from the field monitoring in two summer weeks. Based on the mathematical models and using collected data, modules incorporating the proposed optimal redesign procedure were embedded in a transient simulation tool. A mixed heuristic- deterministic optimization algorithm was implemented in the transient tool to determine the synthesis and design variables that influence the cost and energy efficiency of each configuration. Available experimental results were compared to predicted results to validate the model. Afterwards, the computer model was used to predict how changes in cooling coil geometry would affect the building thermal comfort, the cost and energy consumption of the system. © 2013 Tsinghua University Press and Springer-Verlag Berlin Heidelberg.


Vakiloroaya V.,University of Technology, Sydney | Samali B.,University of Technology, Sydney | Pishghadam K.,Giacomini Inc.
Applied Thermal Engineering | Year: 2014

This paper addresses the energy saving significance of air-cooled direct expansion (DX) air conditioning systems using liquid pressure amplification (LPA) technology along with proposed theoretical-empirical models for the system components. This method utilizes a refrigerant pump in the liquid line to allow the system operation at lower condensing pressure. An actual DX rooftop package is used for data collection. The performance of the proposed method is simulated using transient simulation software. Simulation tool was validated by comparing predicted and measured power consumption of the rooftop package. Results show that up to 42% power savings can be obtained using this approach. © 2014 Elsevier Ltd. All rights reserved.


Vakiloroaya V.,University of Technology, Sydney | Samali B.,University of Technology, Sydney | Cuthbert S.,Green HVAC Solution Pty Ltd | Pishghadam K.,Giacomini Inc. | Eager D.,University of Technology, Sydney
Energy and Buildings | Year: 2014

The purpose of this study is to develop an optimization methodology for the detailed energy and cost effective design of a finned-tube condenser coil in order to enhance the system performance. Using this method, the frontal area of the condenser coil is maintained as constant, while other geometrical parameters of the thermal and economic performance of the system are varied and investigated. An existing air-cooled direct expansion (DX) rooftop package unit of a real-world commercial building is used for experimental data collection. First, the theoretical-empirical model for the system components is developed. Based on mathematical models and using collected data, a numerical algorithm is developed and embedded in a transient simulation tool. The integrated simulation tool is then validated by using the wide range of operating data obtained experimentally from the cooling plant during summer time. Furthermore, a mixed heuristic-deterministic optimization algorithm was implemented to determine the synthesis and design variables that influence the cost and energy efficiency of each configuration. Different new designs for condenser coil were then constructed to evaluate the potential of design improvements. Afterwards, the computer model was used to predict how changes in condenser coil geometry would affect the cost and energy consumption of the system. © 2014 Elsevier B.V.


Vakiloroaya V.,University of Technology, Sydney | Samali B.,University of Technology, Sydney | Pishghadam K.,Giacomini Inc.
Energy and Buildings | Year: 2014

This paper investigates and compares the energy saving potential of air-cooled vapor compression air conditioning systems by using liquid pressure amplification (LPA), evaporative-cooled condenser (ECC) and combined LPA and ECC strategies. The applicability, limitation and energy performance of these strategies are discussed. For the purpose of this study, an existing direct expansion rooftop package of a commercial building is used for experimentation and data collection. The system under investigation is extensively equipped with a number of instrumentation devices for data logging. Theoretical-empirical mathematical models for system components were developed first, while a numerical algorithm together with monitored data and a mathematical model implemented on a transient system simulation tool is used to predict the performance of each strategy under transient loads. The integrated simulation tool was validated by comparing predicted and measured power consumption of the rooftop package. Comparing between LPA and ECC methods shows that for the ambient temperatures less than 27 C the LPA is more effective method while for ambient temperature greater than 27 C the ECC system is more efficient. Our results also demonstrate average energy savings of 25.3%, 18.3% and 44.2%, respectively for LPA, ECC and combined LPA and ECC methods. © 2014 Elsevier B.V.

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